Security: add lsm hooks for checking permissions on eBPF objects

PATCH In review Chenbo Feng 7 participants 15 messages Aug 31, 2017 – Sep 7, 2017

Subsystems (6)

Networking Network drivers BPF SELinux security module +2 more subsystems

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Chenbo Feng

author

2017-08-31 20:56 UTC #0 lore raw

cover Security: add lsm hooks for checking permissions on eBPF objects

From: Chenbo Feng <[email protected]>

Much like files and sockets, eBPF objects are accessed, controlled, and shared via a file descriptor (FD). Unlike files and sockets, the existing mechanism for eBPF object access control is very limited. Currently there are two options for granting accessing to eBPF operations: grant access to all processes, or only CAP_SYS_ADMIN processes. The CAP_SYS_ADMIN-only mode is not ideal because most users do not have this capability and granting a user CAP_SYS_ADMIN grants too many other security-sensitive permissions. It also unnecessarily allows all CAP_SYS_ADMIN processes access to eBPF functionality. Allowing all processes to access to eBPF objects is also undesirable since it has potential to allow unprivileged processes to consume kernel memory, and opens up attack surface to the kernel.

Adding LSM hooks maintains the status quo for systems which do not use an LSM, preserving compatibility with userspace, while allowing security modules to choose how best to handle permissions on eBPF objects. Here is a possible use case for the lsm hooks with selinux module:

The network-control daemon (netd) creates and loads an eBPF object for network packet filtering and analysis. It passes the object FD to an unprivileged network monitor app (netmonitor), which is not allowed to create, modify or load eBPF objects, but is allowed to read the traffic stats from the object.

Selinux could use these hooks to grant the following permissions:
allow netd self:bpf { create modify read?};
allow netmonitor netd:bpf read;

In this patch series, 5 security hooks is added to the eBPF syscall implementations to do permissions checks. The LSM hooks introduced to eBPF maps and programs can be summarized as follows:

Bpf_map_create: check for the ability of creating eBPF maps.
Bpf_map_modify: check the ability of update and delete eBPF map
entries.
Bpf_map_read: check the ability of lookup map element as well as
get map keys.
Bpf_post_create: initialize the security struct inside struct
bpf_map
Bpf_prog_load: check the ability for loading the eBPF program.

In order to store the ownership and security information about eBPF maps, a security field pointer is added to the struct bpf_map. And a simple implementation of selinux check on these hooks is added in selinux subsystem.

Chenbo Feng (3):
security: bpf: Add eBPF LSM hooks to security module
security: bpf: Add eBPF LSM hooks and security field to eBPF map
selinux: bpf: Implement the selinux checks for eBPF object

 include/linux/bpf.h                 |  3 +++
 include/linux/lsm_hooks.h           | 41 ++++++++++++++++++++++++++++
 include/linux/security.h            | 36 +++++++++++++++++++++++++
 kernel/bpf/syscall.c                | 28 +++++++++++++++++++
 security/security.c                 | 28 +++++++++++++++++++
 security/selinux/hooks.c            | 54 +++++++++++++++++++++++++++++++++++++
 security/selinux/include/classmap.h |  2 ++
 security/selinux/include/objsec.h   |  4 +++
 8 files changed, 196 insertions(+)

--
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Chenbo Feng

author

2017-08-31 20:56 UTC #1 lore raw

PATCH 1/3 security: bpf: Add eBPF LSM hooks to security module

From: Chenbo Feng <[email protected]>

Introduce 5 LSM hooks to provide finer granularity controls on eBPF related operations including create eBPF maps, modify and read eBPF maps content and load eBPF programs to the kernel. Hooks use the new security pointer inside the eBPF map struct to store the owner's security information and the different security modules can perform different checks based on the information stored inside the security field.

Signed-off-by Chenbo Feng <[email protected]>

---
 include/linux/lsm_hooks.h | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/security.h  | 36 ++++++++++++++++++++++++++++++++++++
 security/security.c       | 28 ++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+)

include/linux/lsm_hooks.h +41 -0

index ce02f76a6188..3aaf9a08a983 100644
@@ -1353,6 +1353,32 @@
  *	@inode we wish to get the security context of.
  *	@ctx is a pointer in which to place the allocated security context.
  *	@ctxlen points to the place to put the length of @ctx.
+ *
+ * Security hooks for using the eBPF maps and programs functionalities through
+ * eBPF syscalls.
+ *
+ * @bpf_map_create:
+ *	Check permissions prior to creating a new bpf map.
+ *	Return 0 if the permission is granted.
+ *
+ * @bpf_map_modify:
+ *	Check permission prior to insert, update and delete map content.
+ *	@map pointer to the struct bpf_map that contains map information.
+ *	Return 0 if the permission is granted.
+ *
+ * @bpf_map_read:
+ *	Check permission prior to read a bpf map content.
+ *	@map pointer to the struct bpf_map that contains map information.
+ *	Return 0 if the permission is granted.
+ *
+ * @bpf_prog_load:
+ *	Check permission prior to load eBPF program.
+ *	Return 0 if the permission is granted.
+ *
+ * @bpf_post_create:
+ *	Initialize the bpf object security field inside struct bpf_maps and
+ *	it is used for future security checks.
+ *
  */
 union security_list_options {
 	int (*binder_set_context_mgr)(struct task_struct *mgr);

@@ -1685,6 +1711,14 @@ union security_list_options {
 				struct audit_context *actx);
 	void (*audit_rule_free)(void *lsmrule);
 #endif /* CONFIG_AUDIT */
+
+#ifdef CONFIG_BPF_SYSCALL
+	int (*bpf_map_create)(void);
+	int (*bpf_map_read)(struct bpf_map *map);
+	int (*bpf_map_modify)(struct bpf_map *map);
+	int (*bpf_prog_load)(void);
+	int (*bpf_post_create)(struct bpf_map *map);
+#endif /* CONFIG_BPF_SYSCALL */
 };
 
 struct security_hook_heads {

@@ -1905,6 +1939,13 @@ struct security_hook_heads {
 	struct list_head audit_rule_match;
 	struct list_head audit_rule_free;
 #endif /* CONFIG_AUDIT */
+#ifdef CONFIG_BPF_SYSCALL
+	struct list_head bpf_map_create;
+	struct list_head bpf_map_read;
+	struct list_head bpf_map_modify;
+	struct list_head bpf_prog_load;
+	struct list_head bpf_post_create;
+#endif /* CONFIG_BPF_SYSCALL */
 } __randomize_layout;
 
 /*

include/linux/security.h +36 -0

index 458e24bea2d4..0656a4f74d14 100644
@@ -31,6 +31,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
+#include <linux/bpf.h>
 
 struct linux_binprm;
 struct cred;

@@ -1735,6 +1736,41 @@ static inline void securityfs_remove(struct dentry *dentry)
 
 #endif
 
+#ifdef CONFIG_BPF_SYSCALL
+#ifdef CONFIG_SECURITY
+int security_map_create(void);
+int security_map_modify(struct bpf_map *map);
+int security_map_read(struct bpf_map *map);
+int security_prog_load(void);
+int security_post_create(struct bpf_map *map);
+#else
+static inline int security_map_create(void)
+{
+	return 0;
+}
+
+static inline int security_map_read(struct bpf_map *map)
+{
+	return 0;
+}
+
+static inline int security_map_modify(struct bpf_map *map)
+{
+	return 0;
+}
+
+static inline int security_prog_load(void)
+{
+	return 0;
+}
+
+static inline int security_post_create(struct bpf_map *map)
+{
+	return 0;
+}
+#endif /* CONFIG_SECURITY */
+#endif /* CONFIG_BPF_SYSCALL */
+
 #ifdef CONFIG_SECURITY
 
 static inline char *alloc_secdata(void)

security/security.c +28 -0

index 55b5997e4b72..02272f93a89e 100644
@@ -12,6 +12,7 @@
  *	(at your option) any later version.
  */
 
+#include <linux/bpf.h>
 #include <linux/capability.h>
 #include <linux/dcache.h>
 #include <linux/module.h>

@@ -1708,3 +1709,30 @@ int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule,
 				actx);
 }
 #endif /* CONFIG_AUDIT */
+
+#ifdef CONFIG_BPF_SYSCALL
+int security_map_create(void)
+{
+	return call_int_hook(bpf_map_create, 0);
+}
+
+int security_map_modify(struct bpf_map *map)
+{
+	return call_int_hook(bpf_map_modify, 0, map);
+}
+
+int security_map_read(struct bpf_map *map)
+{
+	return call_int_hook(bpf_map_read, 0, map);
+}
+
+int security_prog_load(void)
+{
+	return call_int_hook(bpf_prog_load, 0);
+}
+
+int security_post_create(struct bpf_map *map)
+{
+	return call_int_hook(bpf_post_create, 0, map);
+}
+#endif /* CONFIG_BPF_SYSCALL */

Signature · 6 lines

2.14.1.581.gf28d330327-goog

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Stephen Smalley

2017-09-01 12:50 UTC #2 lore raw

Re: [PATCH 1/3] security: bpf: Add eBPF LSM hooks to security module

Quoted 132 lines · Chenbo Feng

From: Chenbo Feng <[email protected]>
Introduce 5 LSM hooks to provide finer granularity controls on eBPF related operations including create eBPF maps, modify and read eBPF maps
content and load eBPF programs to the kernel. Hooks use the new security
pointer inside the eBPF map struct to store the owner's security information and the different security modules can perform different checks based on the information stored inside the security field.
Signed-off-by Chenbo Feng <[email protected]>
---
?include/linux/lsm_hooks.h | 41
+++++++++++++++++++++++++++++++++++++++++
?include/linux/security.h??| 36 ++++++++++++++++++++++++++++++++++++ ?security/security.c???????| 28 ++++++++++++++++++++++++++++ ?3 files changed, 105 insertions(+)
include/linux/lsm_hooks.h +0 -0
index ce02f76a6188..3aaf9a08a983 100644
@@ -1353,6 +1353,32 @@
? * @inode we wish to get the security context of.
? * @ctx is a pointer in which to place the allocated security
context.
? * @ctxlen points to the place to put the length of @ctx.
+ *
+ * Security hooks for using the eBPF maps and programs functionalities through
+ * eBPF syscalls.
+ *
+ * @bpf_map_create:
+ * Check permissions prior to creating a new bpf map.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_map_modify:
+ * Check permission prior to insert, update and delete map
content.
+ * @map pointer to the struct bpf_map that contains map
information.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_map_read:
+ * Check permission prior to read a bpf map content.
+ * @map pointer to the struct bpf_map that contains map
information.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_prog_load:
+ * Check permission prior to load eBPF program.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_post_create:
+ * Initialize the bpf object security field inside struct
bpf_maps and
+ * it is used for future security checks.
+ *
? */
?union security_list_options {
? int (*binder_set_context_mgr)(struct task_struct *mgr);
include/linux/lsm_hooks.h +0 -0
@@ -1685,6 +1711,14 @@ union security_list_options {
 ?				struct audit_context *actx);
 ?	void (*audit_rule_free)(void *lsmrule);
?#endif /* CONFIG_AUDIT */
include/linux/lsm_hooks.h +8 -0
+
+#ifdef CONFIG_BPF_SYSCALL
+	int (*bpf_map_create)(void);
+	int (*bpf_map_read)(struct bpf_map *map);
+	int (*bpf_map_modify)(struct bpf_map *map);
+	int (*bpf_prog_load)(void);
+	int (*bpf_post_create)(struct bpf_map *map);
+#endif /* CONFIG_BPF_SYSCALL */
?};
?
?struct security_hook_heads {
include/linux/lsm_hooks.h +0 -0
@@ -1905,6 +1939,13 @@ struct security_hook_heads {
 ?	struct list_head audit_rule_match;
 ?	struct list_head audit_rule_free;
?#endif /* CONFIG_AUDIT */
include/linux/lsm_hooks.h +7 -0
+#ifdef CONFIG_BPF_SYSCALL
+	struct list_head bpf_map_create;
+	struct list_head bpf_map_read;
+	struct list_head bpf_map_modify;
+	struct list_head bpf_prog_load;
+	struct list_head bpf_post_create;
+#endif /* CONFIG_BPF_SYSCALL */
?} __randomize_layout;
?
?/*
include/linux/security.h +0 -0
index 458e24bea2d4..0656a4f74d14 100644
@@ -31,6 +31,7 @@
?#include <linux/string.h>
?#include <linux/mm.h>
?#include <linux/fs.h>
+#include <linux/bpf.h>
?
?struct linux_binprm;
?struct cred;
include/linux/security.h +0 -0
@@ -1735,6 +1736,41 @@ static inline void securityfs_remove(struct
 dentry *dentry)
?
?#endif
?
include/linux/security.h +24 -0
+#ifdef CONFIG_BPF_SYSCALL
+#ifdef CONFIG_SECURITY
+int security_map_create(void);
+int security_map_modify(struct bpf_map *map);
+int security_map_read(struct bpf_map *map);
+int security_prog_load(void);
+int security_post_create(struct bpf_map *map);
+#else
+static inline int security_map_create(void)
+{
+	return 0;
+}
+
+static inline int security_map_read(struct bpf_map *map)
+{
+	return 0;
+}
+
+static inline int security_map_modify(struct bpf_map *map)
+{
+	return 0;
+}
+
+static inline int security_prog_load(void)

include/linux/security.h static inline void securityfs_remove(struct dentry *dentry) · line 1772

Quoted 10 lines

include/linux/security.h +10 -0

+{
+	return 0;
+}
+
+static inline int security_post_create(struct bpf_map *map)
+{
+	return 0;
+}
+#endif /* CONFIG_SECURITY */
+#endif /* CONFIG_BPF_SYSCALL */

These should be named consistently with the ones in lsm_hooks.h and should unambiguously indicate that these are hooks for bpf objects/operations, i.e. security_bpf_map_create(), security_bpf_map_read(), etc.

Do you need this level of granularity?

Could you coalesce the map_create() and post_map_create() hooks into one hook and just unwind the create in that case?

Why do you label bpf maps but not bpf progs? Should we be controlling the ability to attach/detach a bpf prog (partly controlled by CAP_NET_ADMIN, but also somewhat broad in scope and doesn't allow control based on who created the prog)?

Should there be a top-level security_bpf_use() hook and permission check that limits ability to use bpf() at all?

Quoted 38 lines

+
?#ifdef CONFIG_SECURITY
?
?static inline char *alloc_secdata(void)
security/security.c +0 -0
index 55b5997e4b72..02272f93a89e 100644
@@ -12,6 +12,7 @@
? * (at your option) any later version.
? */
?
+#include <linux/bpf.h>
?#include <linux/capability.h>
?#include <linux/dcache.h>
?#include <linux/module.h>
security/security.c +0 -0
@@ -1708,3 +1709,30 @@ int security_audit_rule_match(u32 secid, u32
 field, u32 op, void *lsmrule,
 ?				actx);
 ?}
?#endif /* CONFIG_AUDIT */
security/security.c +17 -0
+
+#ifdef CONFIG_BPF_SYSCALL
+int security_map_create(void)
+{
+	return call_int_hook(bpf_map_create, 0);
+}
+
+int security_map_modify(struct bpf_map *map)
+{
+	return call_int_hook(bpf_map_modify, 0, map);
+}
+
+int security_map_read(struct bpf_map *map)
+{
+	return call_int_hook(bpf_map_read, 0, map);
+}
+

security/security.c int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule, · line 1738

Quoted 10 lines

security/security.c +10 -0

+int security_prog_load(void)
+{
+	return call_int_hook(bpf_prog_load, 0);
+}
+
+int security_post_create(struct bpf_map *map)
+{
+	return call_int_hook(bpf_post_create, 0, map);
+}
+#endif /* CONFIG_BPF_SYSCALL */

Chenbo Feng

2017-09-05 22:24 UTC #3 lore raw

Re: [PATCH 1/3] security: bpf: Add eBPF LSM hooks to security module

Quoted 140 lines · Stephen Smalley

Quoted 139 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce 5 LSM hooks to provide finer granularity controls on eBPF related operations including create eBPF maps, modify and read eBPF maps
content and load eBPF programs to the kernel. Hooks use the new security
pointer inside the eBPF map struct to store the owner's security information and the different security modules can perform different checks based on the information stored inside the security field.
Signed-off-by Chenbo Feng <[email protected]>
---
 include/linux/lsm_hooks.h | 41
+++++++++++++++++++++++++++++++++++++++++
 include/linux/security.h  | 36 ++++++++++++++++++++++++++++++++++++
 security/security.c       | 28 ++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+)
include/linux/lsm_hooks.h +0 -0
index ce02f76a6188..3aaf9a08a983 100644
@@ -1353,6 +1353,32 @@
  *   @inode we wish to get the security context of.
  *   @ctx is a pointer in which to place the allocated security
context.
* @ctxlen points to the place to put the length of @ctx.
+ *
+ * Security hooks for using the eBPF maps and programs functionalities through
+ * eBPF syscalls.
+ *
+ * @bpf_map_create:
+ * Check permissions prior to creating a new bpf map.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_map_modify:
+ * Check permission prior to insert, update and delete map
content.
+ * @map pointer to the struct bpf_map that contains map
information.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_map_read:
+ * Check permission prior to read a bpf map content.
+ * @map pointer to the struct bpf_map that contains map
information.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_prog_load:
+ * Check permission prior to load eBPF program.
+ * Return 0 if the permission is granted.
+ *
+ * @bpf_post_create:
+ * Initialize the bpf object security field inside struct
bpf_maps and
+ * it is used for future security checks.
+ *
*/
 union security_list_options {
      int (*binder_set_context_mgr)(struct task_struct *mgr);
include/linux/lsm_hooks.h +15 -0
@@ -1685,6 +1711,14 @@ union security_list_options {
                              struct audit_context *actx);
      void (*audit_rule_free)(void *lsmrule);
 #endif /* CONFIG_AUDIT */
+
+#ifdef CONFIG_BPF_SYSCALL
+     int (*bpf_map_create)(void);
+     int (*bpf_map_read)(struct bpf_map *map);
+     int (*bpf_map_modify)(struct bpf_map *map);
+     int (*bpf_prog_load)(void);
+     int (*bpf_post_create)(struct bpf_map *map);
+#endif /* CONFIG_BPF_SYSCALL */
 };
 
 struct security_hook_heads {
@@ -1905,6 +1939,13 @@ struct security_hook_heads {
      struct list_head audit_rule_match;
      struct list_head audit_rule_free;
 #endif /* CONFIG_AUDIT */
+#ifdef CONFIG_BPF_SYSCALL
+     struct list_head bpf_map_create;
+     struct list_head bpf_map_read;
+     struct list_head bpf_map_modify;
+     struct list_head bpf_prog_load;
+     struct list_head bpf_post_create;
+#endif /* CONFIG_BPF_SYSCALL */
 } __randomize_layout;
 
 /*
include/linux/security.h +32 -0
index 458e24bea2d4..0656a4f74d14 100644
@@ -31,6 +31,7 @@
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
+#include <linux/bpf.h>
 
 struct linux_binprm;
 struct cred;
@@ -1735,6 +1736,41 @@ static inline void securityfs_remove(struct
 dentry *dentry)
 
 #endif
 
+#ifdef CONFIG_BPF_SYSCALL
+#ifdef CONFIG_SECURITY
+int security_map_create(void);
+int security_map_modify(struct bpf_map *map);
+int security_map_read(struct bpf_map *map);
+int security_prog_load(void);
+int security_post_create(struct bpf_map *map);
+#else
+static inline int security_map_create(void)
+{
+     return 0;
+}
+
+static inline int security_map_read(struct bpf_map *map)
+{
+     return 0;
+}
+
+static inline int security_map_modify(struct bpf_map *map)
+{
+     return 0;
+}
+
+static inline int security_prog_load(void)
+{
+     return 0;
+}
+
+static inline int security_post_create(struct bpf_map *map)
+{
+     return 0;

Quoted 9 lines

include/linux/security.h static inline void securityfs_remove(struct dentry *dentry) · line 1772
Quoted 3 lines
include/linux/security.h +3 -0
+}
+#endif /* CONFIG_SECURITY */
+#endif /* CONFIG_BPF_SYSCALL */
These should be named consistently with the ones in lsm_hooks.h and should unambiguously indicate that these are hooks for bpf objects/operations, i.e. security_bpf_map_create(), security_bpf_map_read(), etc.

Thanks for pointing out, will fix this.

Quoted 2 lines

Do you need this level of granularity?

The cover letter of this patch series described a possible use cases of these lsm hooks and this level of granularity would be ideal to reach that goal. We can also implement two hooks such as bpf_obj_create and bpf_obj_use to restrict the creation and using when get the bpf fd from kernel. But that will be less powerful and flexible.

Quoted 3 lines

Could you coalesce the map_create() and post_map_create() hooks into one hook and just unwind the create in that case?

Okay, I will take a look on how to fix this.

Quoted 8 lines

Why do you label bpf maps but not bpf progs? Should we be controlling the ability to attach/detach a bpf prog (partly controlled by CAP_NET_ADMIN, but also somewhat broad in scope and doesn't allow control based on who created the prog)?
Should there be a top-level security_bpf_use() hook and permission check that limits ability to use bpf() at all?

This could be useful but having additional lsm hooks check when reading and write to eBPF maps may cause performance issue. Instead maybe we could have a hook for creating eBPF object and retrieve object fd to restrict the access.

Quoted 40 lines

include/linux/security.h +1 -0

+
 #ifdef CONFIG_SECURITY

static inline char *alloc_secdata(void)

security/security.c +20 -0

index 55b5997e4b72..02272f93a89e 100644
@@ -12,6 +12,7 @@
  *   (at your option) any later version.
  */
 
+#include <linux/bpf.h>
 #include <linux/capability.h>
 #include <linux/dcache.h>
 #include <linux/module.h>

@@ -1708,3 +1709,30 @@ int security_audit_rule_match(u32 secid, u32
 field, u32 op, void *lsmrule,
                              actx);
 }
 #endif /* CONFIG_AUDIT */
+
+#ifdef CONFIG_BPF_SYSCALL
+int security_map_create(void)
+{
+     return call_int_hook(bpf_map_create, 0);
+}
+
+int security_map_modify(struct bpf_map *map)
+{
+     return call_int_hook(bpf_map_modify, 0, map);
+}
+
+int security_map_read(struct bpf_map *map)
+{
+     return call_int_hook(bpf_map_read, 0, map);
+}
+
+int security_prog_load(void)
+{

Quoted 8 lines

security/security.c int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule, · line 1738
Quoted 8 lines
security/security.c +8 -0
+     return call_int_hook(bpf_prog_load, 0);
+}
+
+int security_post_create(struct bpf_map *map)
+{
+     return call_int_hook(bpf_post_create, 0, map);
+}
+#endif /* CONFIG_BPF_SYSCALL */

Stephen Smalley

2017-09-07 12:32 UTC #4 lore raw

Re: [PATCH 1/3] security: bpf: Add eBPF LSM hooks to security module

Quoted 170 lines · Chenbo Feng via Selinux

Quoted 146 lines · Stephen Smalley
Quoted 145 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce 5 LSM hooks to provide finer granularity controls on eBPF
related operations including create eBPF maps, modify and read eBPF
maps
content and load eBPF programs to the kernel. Hooks use the new security
pointer inside the eBPF map struct to store the owner's security information and the different security modules can perform different
checks based on the information stored inside the security field.
Signed-off-by Chenbo Feng <[email protected]>
---
?include/linux/lsm_hooks.h | 41
+++++++++++++++++++++++++++++++++++++++++
?include/linux/security.h??| 36
++++++++++++++++++++++++++++++++++++
?security/security.c???????| 28 ++++++++++++++++++++++++++++ ?3 files changed, 105 insertions(+)
include/linux/lsm_hooks.h +0 -0
index ce02f76a6188..3aaf9a08a983 100644
@@ -1353,6 +1353,32 @@
? *???@inode we wish to get the security context of.
? *???@ctx is a pointer in which to place the allocated security context.
? *???@ctxlen points to the place to put the length of @ctx.
+ *
+ * Security hooks for using the eBPF maps and programs functionalities through
+ * eBPF syscalls.
+ *
+ * @bpf_map_create:
+ *???Check permissions prior to creating a new bpf map.
+ *???Return 0 if the permission is granted.
+ *
+ * @bpf_map_modify:
+ *???Check permission prior to insert, update and delete map content.
+ *???@map pointer to the struct bpf_map that contains map information.
+ *???Return 0 if the permission is granted.
+ *
+ * @bpf_map_read:
+ *???Check permission prior to read a bpf map content.
+ *???@map pointer to the struct bpf_map that contains map information.
+ *???Return 0 if the permission is granted.
+ *
+ * @bpf_prog_load:
+ *???Check permission prior to load eBPF program.
+ *???Return 0 if the permission is granted.
+ *
+ * @bpf_post_create:
+ *???Initialize the bpf object security field inside struct bpf_maps and
+ *???it is used for future security checks.
+ *
? */
?union security_list_options {
??????int (*binder_set_context_mgr)(struct task_struct *mgr);
include/linux/lsm_hooks.h +0 -0
@@ -1685,6 +1711,14 @@ union security_list_options {
 ??????????????????????????????struct audit_context *actx);
 ??????void (*audit_rule_free)(void *lsmrule);
?#endif /* CONFIG_AUDIT */
include/linux/lsm_hooks.h +8 -0
+
+#ifdef CONFIG_BPF_SYSCALL
+?????int (*bpf_map_create)(void);
+?????int (*bpf_map_read)(struct bpf_map *map);
+?????int (*bpf_map_modify)(struct bpf_map *map);
+?????int (*bpf_prog_load)(void);
+?????int (*bpf_post_create)(struct bpf_map *map);
+#endif /* CONFIG_BPF_SYSCALL */
?};
?struct security_hook_heads {
include/linux/lsm_hooks.h +0 -0
@@ -1905,6 +1939,13 @@ struct security_hook_heads {
 ??????struct list_head audit_rule_match;
 ??????struct list_head audit_rule_free;
?#endif /* CONFIG_AUDIT */
include/linux/lsm_hooks.h +7 -0
+#ifdef CONFIG_BPF_SYSCALL
+?????struct list_head bpf_map_create;
+?????struct list_head bpf_map_read;
+?????struct list_head bpf_map_modify;
+?????struct list_head bpf_prog_load;
+?????struct list_head bpf_post_create;
+#endif /* CONFIG_BPF_SYSCALL */
?} __randomize_layout;
?/*
include/linux/security.h +0 -0
index 458e24bea2d4..0656a4f74d14 100644
@@ -31,6 +31,7 @@
?#include <linux/string.h>
?#include <linux/mm.h>
?#include <linux/fs.h>
+#include <linux/bpf.h>
?struct linux_binprm;
?struct cred;
include/linux/security.h +0 -0
@@ -1735,6 +1736,41 @@ static inline void
securityfs_remove(struct
dentry *dentry)
?#endif
include/linux/security.h +31 -0
+#ifdef CONFIG_BPF_SYSCALL
+#ifdef CONFIG_SECURITY
+int security_map_create(void);
+int security_map_modify(struct bpf_map *map);
+int security_map_read(struct bpf_map *map);
+int security_prog_load(void);
+int security_post_create(struct bpf_map *map);
+#else
+static inline int security_map_create(void)
+{
+?????return 0;
+}
+
+static inline int security_map_read(struct bpf_map *map)
+{
+?????return 0;
+}
+
+static inline int security_map_modify(struct bpf_map *map)
+{
+?????return 0;
+}
+
+static inline int security_prog_load(void)
+{
+?????return 0;
+}
+
+static inline int security_post_create(struct bpf_map *map)
+{
+?????return 0;
Quoted 9 lines
include/linux/security.h static inline void securityfs_remove(struct dentry *dentry) · line 1772
Quoted 3 lines
include/linux/security.h +3 -0
+}
+#endif /* CONFIG_SECURITY */
+#endif /* CONFIG_BPF_SYSCALL */
These should be named consistently with the ones in lsm_hooks.h and should unambiguously indicate that these are hooks for bpf objects/operations, i.e. security_bpf_map_create(), security_bpf_map_read(), etc.
Thanks for pointing out, will fix this.
Quoted 2 lines
Do you need this level of granularity?
The cover letter of this patch series described a possible use cases of
these lsm hooks and this level of granularity would be ideal to reach that
goal. We can also implement two hooks such as bpf_obj_create and bpf_obj_use to restrict the creation and using when get the bpf fd from
kernel. But that will be less powerful and flexible.

Quoted 6 lines

Quoted 4 lines
Could you coalesce the map_create() and post_map_create() hooks into
one hook and just unwind the create in that case?
Okay, I will take a look on how to fix this.

Also, what you called security_post_create() would normally be called something like security_bpf_alloc_security(), and would have a corresponding security_bpf_free_security() hook too. However, whether or not you still need this security field and hook at all is unclear to me, given the direction the discussion has gone.

Quoted 57 lines

Quoted 9 lines
Why do you label bpf maps but not bpf progs???Should we be controlling
the ability to attach/detach a bpf prog (partly controlled by CAP_NET_ADMIN, but also somewhat broad in scope and doesn't allow control based on who created the prog)?
Should there be a top-level security_bpf_use() hook and permission check that limits ability to use bpf() at all?
This could be useful but having additional lsm hooks check when reading
and write to eBPF maps may cause performance issue. Instead maybe we could have a hook for creating eBPF object and retrieve object fd to restrict
the access.
Quoted 41 lines
Quoted 41 lines
+
?#ifdef CONFIG_SECURITY
?static inline char *alloc_secdata(void)
security/security.c +0 -0
index 55b5997e4b72..02272f93a89e 100644
@@ -12,6 +12,7 @@
? *???(at your option) any later version.
? */
+#include <linux/bpf.h>
?#include <linux/capability.h>
?#include <linux/dcache.h>
?#include <linux/module.h>
security/security.c +0 -0
@@ -1708,3 +1709,30 @@ int security_audit_rule_match(u32 secid,
u32
field, u32 op, void *lsmrule,
??????????????????????????????actx);
?}
?#endif /* CONFIG_AUDIT */
security/security.c +19 -0
+
+#ifdef CONFIG_BPF_SYSCALL
+int security_map_create(void)
+{
+?????return call_int_hook(bpf_map_create, 0);
+}
+
+int security_map_modify(struct bpf_map *map)
+{
+?????return call_int_hook(bpf_map_modify, 0, map);
+}
+
+int security_map_read(struct bpf_map *map)
+{
+?????return call_int_hook(bpf_map_read, 0, map);
+}
+
+int security_prog_load(void)
+{

Quoted 8 lines

Quoted 8 lines
security/security.c int security_audit_rule_match(u32 secid, u32 field, u32 op, void *lsmrule, · line 1738
Quoted 8 lines
+?????return call_int_hook(bpf_prog_load, 0);
security/security.c +7 -0
+}
+
+int security_post_create(struct bpf_map *map)
+{
+?????return call_int_hook(bpf_post_create, 0, map);
+}
+#endif /* CONFIG_BPF_SYSCALL */

Chenbo Feng

author

2017-08-31 20:56 UTC #5 lore raw

PATCH 2/3 security: bpf: Add eBPF LSM hooks and security field to eBPF map

In reply to Chenbo Feng

From: Chenbo Feng <[email protected]>

Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.

Signed-off-by Chenbo Feng <[email protected]>

---
 include/linux/bpf.h  |  3 +++
 kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

include/linux/bpf.h +3 -0

index b69e7a5869ff..ca3e6ff7091d 100644
@@ -53,6 +53,9 @@ struct bpf_map {
 	struct work_struct work;
 	atomic_t usercnt;
 	struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
 };
 
 /* function argument constraints */

kernel/bpf/syscall.c +28 -0

index 045646da97cc..b15580bcf3b1 100644
@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		return -EINVAL;
 
+	err = security_map_create();
+	if (err)
+		return -EACCES;
+
 	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
 	map = find_and_alloc_map(attr);
 	if (IS_ERR(map))

@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		goto free_map_nouncharge;
 
+	err = security_post_create(map);
+	if (err < 0)
+		goto free_map;
+
 	err = bpf_map_alloc_id(map);
 	if (err)
 		goto free_map;

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	if (ukey) {
 		key = memdup_user(ukey, map->key_size);
 		if (IS_ERR(key)) {

@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_PROG_LOAD))
 		return -EINVAL;
 
+	err = security_prog_load();
+	if (err)
+		return -EACCES;
+
 	if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
 		return -EINVAL;

Signature · 6 lines

2.14.1.581.gf28d330327-goog

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Mimi Zohar

2017-08-31 21:17 UTC #6 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

Quoted 34 lines · Chenbo Feng

From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>
---
 include/linux/bpf.h  |  3 +++
 kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
include/linux/bpf.h +3 -0
index b69e7a5869ff..ca3e6ff7091d 100644
@@ -53,6 +53,9 @@ struct bpf_map {
 	struct work_struct work;
 	atomic_t usercnt;
 	struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
 };
 
 /* function argument constraints */
kernel/bpf/syscall.c +0 -0
index 045646da97cc..b15580bcf3b1 100644

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 284

Quoted 6 lines

kernel/bpf/syscall.c +3 -0

@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		return -EINVAL;
 
+	err = security_map_create();
+	if (err)
+		return -EACCES;

Any reason not to just return err?

Mimi

Quoted 60 lines

kernel/bpf/syscall.c +21 -0

+
 	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
 	map = find_and_alloc_map(attr);
 	if (IS_ERR(map))

@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
 	if (err)
 		goto free_map_nouncharge;
 
+	err = security_post_create(map);
+	if (err < 0)
+		goto free_map;
+
 	err = bpf_map_alloc_id(map);
 	if (err)
 		goto free_map;

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	if (ukey) {
 		key = memdup_user(ukey, map->key_size);
 		if (IS_ERR(key)) {

kernel/bpf/syscall.c static int bpf_prog_load(union bpf_attr *attr) · line 968

Quoted 10 lines

kernel/bpf/syscall.c +4 -0

@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (CHECK_ATTR(BPF_PROG_LOAD))
 		return -EINVAL;
 
+	err = security_prog_load();
+	if (err)
+		return -EACCES;
+
 	if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
 		return -EINVAL;

Chenbo Feng

2017-08-31 22:17 UTC #7 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

Quoted 38 lines · Mimi Zohar

Quoted 37 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>
---
 include/linux/bpf.h  |  3 +++
 kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)
include/linux/bpf.h +3 -0
index b69e7a5869ff..ca3e6ff7091d 100644
@@ -53,6 +53,9 @@ struct bpf_map {
      struct work_struct work;
      atomic_t usercnt;
      struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+     void *security;
+#endif
 };
 
 /* function argument constraints */
kernel/bpf/syscall.c +0 -0
index 045646da97cc..b15580bcf3b1 100644
@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
      if (err)
              return -EINVAL;
 

Quoted 8 lines

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 284
Quoted 3 lines
kernel/bpf/syscall.c +3 -0
+     err = security_map_create();
+     if (err)
+             return -EACCES;
Any reason not to just return err?
Mimi

Nope... return err might be better. I will fix this in next version.

Thanks
Chenbo

Quoted 63 lines

kernel/bpf/syscall.c +21 -0

+
      /* find map type and init map: hashtable vs rbtree vs bloom vs ... */
      map = find_and_alloc_map(attr);
      if (IS_ERR(map))

@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
      if (err)
              goto free_map_nouncharge;
 
+     err = security_post_create(map);
+     if (err < 0)
+             goto free_map;
+
      err = bpf_map_alloc_id(map);
      if (err)
              goto free_map;

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_read(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_modify(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);

@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_modify(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);

@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_read(map);
+     if (err)
+             return -EACCES;
+
      if (ukey) {
              key = memdup_user(ukey, map->key_size);
              if (IS_ERR(key)) {

@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
      if (CHECK_ATTR(BPF_PROG_LOAD))
              return -EINVAL;

Quoted 8 lines

kernel/bpf/syscall.c static int bpf_prog_load(union bpf_attr *attr) · line 968

Quoted 7 lines

kernel/bpf/syscall.c +4 -0

+     err = security_prog_load();
+     if (err)
+             return -EACCES;
+
      if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
              return -EINVAL;

Daniel Borkmann

maintainer

2017-08-31 22:38 UTC #8 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

In reply to Chenbo Feng

Quoted 10 lines · Chenbo Feng

From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>

Against which tree is this by the way, net-next? There are changes here which require a rebase of your set.

Quoted 24 lines

---
  include/linux/bpf.h  |  3 +++
  kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
  2 files changed, 31 insertions(+)

include/linux/bpf.h +3 -0

index b69e7a5869ff..ca3e6ff7091d 100644
@@ -53,6 +53,9 @@ struct bpf_map {
  	struct work_struct work;
  	atomic_t usercnt;
  	struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+	void *security;
+#endif
  };
 
  /* function argument constraints */

kernel/bpf/syscall.c +0 -0

index 045646da97cc..b15580bcf3b1 100644

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 282

Quoted 4 lines

kernel/bpf/syscall.c +1 -0

@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
  	if (err)
  		return -EINVAL;
 
+	err = security_map_create();

Seems a bit limited to me, don't you want to be able to also differentiate between different map types? Same goes for security_prog_load() wrt prog types, no?

Quoted 7 lines

kernel/bpf/syscall.c +3 -0

+	if (err)
+		return -EACCES;
+
  	/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
  	map = find_and_alloc_map(attr);
  	if (IS_ERR(map))

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 301

Quoted 7 lines

kernel/bpf/syscall.c +4 -0

@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
  	if (err)
  		goto free_map_nouncharge;
 
+	err = security_post_create(map);
+	if (err < 0)
+		goto free_map;
+

So the hook you implement in patch 3/3 does:

+static int selinux_bpf_post_create(struct bpf_map *map) +{
+ struct bpf_security_struct *bpfsec;
+
+ bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
+ if (!bpfsec)
+ return -ENOMEM;
+
+ bpfsec->sid = current_sid();
+ map->security = bpfsec;
+
+ return 0;
+}

Where do you kfree() bpfsec when the map gets released normally or in error path?

kernel/bpf/syscall.c static int map_lookup_elem(union bpf_attr *attr) · line 423

Quoted 10 lines

kernel/bpf/syscall.c +3 -0

  	err = bpf_map_alloc_id(map);
  	if (err)
  		goto free_map;

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
  	if (IS_ERR(map))
  		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;

How about actually dropping ref?

kernel/bpf/syscall.c static int map_update_elem(union bpf_attr *attr) · line 507

Quoted 11 lines

kernel/bpf/syscall.c +4 -0

+
  	key = memdup_user(ukey, map->key_size);
  	if (IS_ERR(key)) {
  		err = PTR_ERR(key);

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
  	if (IS_ERR(map))
  		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;

Ditto ...

kernel/bpf/syscall.c static int map_delete_elem(union bpf_attr *attr) · line 594

Quoted 10 lines

kernel/bpf/syscall.c +3 -0

  	key = memdup_user(ukey, map->key_size);
  	if (IS_ERR(key)) {
  		err = PTR_ERR(key);

@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
  	if (IS_ERR(map))
  		return PTR_ERR(map);
 
+	err = security_map_modify(map);
+	if (err)
+		return -EACCES;

Ditto ...

kernel/bpf/syscall.c static int map_get_next_key(union bpf_attr *attr) · line 641

Quoted 10 lines

kernel/bpf/syscall.c +3 -0

  	key = memdup_user(ukey, map->key_size);
  	if (IS_ERR(key)) {
  		err = PTR_ERR(key);

@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
  	if (IS_ERR(map))
  		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;

And once again here ... :(

Quoted 5 lines

kernel/bpf/syscall.c +0 -0

  	if (ukey) {
  		key = memdup_user(ukey, map->key_size);
  		if (IS_ERR(key)) {

kernel/bpf/syscall.c static int bpf_prog_load(union bpf_attr *attr) · line 968

Quoted 10 lines

kernel/bpf/syscall.c +4 -0

@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
  	if (CHECK_ATTR(BPF_PROG_LOAD))
  		return -EINVAL;
 
+	err = security_prog_load();
+	if (err)
+		return -EACCES;
+
  	if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
  		return -EINVAL;

Chenbo Feng

2017-09-01 00:29 UTC #9 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

Quoted 11 lines · Daniel Borkmann

Quoted 10 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.

Quoted 6 lines

Quoted 1 line
Signed-off-by Chenbo Feng <[email protected]>
Against which tree is this by the way, net-next? There are changes here which require a rebase of your set.

This patch series is rebased on security subsystem since patch 1/3 is a patch for
security system I assume. But I am not sure where this specific patch should go in.
If I should submit this one to net-next, I will rebase it against net-next and submit again.

Quoted 27 lines

---
  include/linux/bpf.h  |  3 +++
  kernel/bpf/syscall.c | 28 ++++++++++++++++++++++++++++
  2 files changed, 31 insertions(+)

include/linux/bpf.h +3 -0

index b69e7a5869ff..ca3e6ff7091d 100644
@@ -53,6 +53,9 @@ struct bpf_map {
        struct work_struct work;
        atomic_t usercnt;
        struct bpf_map *inner_map_meta;
+#ifdef CONFIG_SECURITY
+       void *security;
+#endif
  };
 
  /* function argument constraints */

kernel/bpf/syscall.c +0 -0

index 045646da97cc..b15580bcf3b1 100644
@@ -279,6 +279,10 @@ static int map_create(union bpf_attr *attr)
        if (err)
                return -EINVAL;

Quoted 7 lines

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 282
Quoted 1 line
kernel/bpf/syscall.c +1 -0
+       err = security_map_create();
Seems a bit limited to me, don't you want to be able to also differentiate between different map types? Same goes for security_prog_load() wrt prog types, no?

I don't want to introduce extra complexity into it if not necessary. so I only included the
thing needed for the selinux implementation for now. But I agree that the map and program type information could be useful when people developing more complex security checks. I will add a union bpf_attr *attr pointer into the security hook functions
for future needs.

Quoted 33 lines

Quoted 8 lines

kernel/bpf/syscall.c +3 -0

+       if (err)
+               return -EACCES;
+
        /* find map type and init map: hashtable vs rbtree vs bloom vs ...
 */
        map = find_and_alloc_map(attr);

        if (IS_ERR(map))

kernel/bpf/syscall.c static int map_create(union bpf_attr *attr) · line 301

Quoted 7 lines

kernel/bpf/syscall.c +4 -0

@@ -291,6 +295,10 @@ static int map_create(union bpf_attr *attr)
        if (err)
                goto free_map_nouncharge;
 
+       err = security_post_create(map);
+       if (err < 0)
+               goto free_map;
+

So the hook you implement in patch 3/3 does:

(quoted diff) +13 -0

+static int selinux_bpf_post_create(struct bpf_map *map)
+{
+       struct bpf_security_struct *bpfsec;
+
+       bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
+       if (!bpfsec)
+               return -ENOMEM;
+
+       bpfsec->sid = current_sid();
+       map->security = bpfsec;
+
+       return 0;
+}

Quoted 3 lines

Where do you kfree() bpfsec when the map gets released normally or in error path?

Will add it in next version. Thanks for point it out.

Quoted 7 lines

kernel/bpf/syscall.c +0 -0

        err = bpf_map_alloc_id(map);
        if (err)
                goto free_map;

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
        if (IS_ERR(map))
                return PTR_ERR(map);

Quoted 7 lines

kernel/bpf/syscall.c static int map_lookup_elem(union bpf_attr *attr) · line 423
Quoted 3 lines
kernel/bpf/syscall.c +3 -0
+       err = security_map_read(map);
+       if (err)
+               return -EACCES;
How about actually dropping ref?

May bad, thanks again.

Quoted 51 lines

kernel/bpf/syscall.c static int map_update_elem(union bpf_attr *attr) · line 507

Quoted 11 lines

kernel/bpf/syscall.c +4 -0

+
        key = memdup_user(ukey, map->key_size);
        if (IS_ERR(key)) {
                err = PTR_ERR(key);

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
        if (IS_ERR(map))
                return PTR_ERR(map);
 
+       err = security_map_modify(map);
+       if (err)
+               return -EACCES;

Ditto ...

kernel/bpf/syscall.c static int map_delete_elem(union bpf_attr *attr) · line 594

Quoted 10 lines

kernel/bpf/syscall.c +3 -0

        key = memdup_user(ukey, map->key_size);
        if (IS_ERR(key)) {
                err = PTR_ERR(key);

@@ -573,6 +589,10 @@ static int map_delete_elem(union bpf_attr *attr)
        if (IS_ERR(map))
                return PTR_ERR(map);
 
+       err = security_map_modify(map);
+       if (err)
+               return -EACCES;

Ditto ...

kernel/bpf/syscall.c static int map_get_next_key(union bpf_attr *attr) · line 641

Quoted 10 lines

kernel/bpf/syscall.c +3 -0

        key = memdup_user(ukey, map->key_size);
        if (IS_ERR(key)) {
                err = PTR_ERR(key);

@@ -616,6 +636,10 @@ static int map_get_next_key(union bpf_attr *attr)
        if (IS_ERR(map))
                return PTR_ERR(map);
 
+       err = security_map_read(map);
+       if (err)
+               return -EACCES;

And once again here ... :(

Quoted 7 lines

kernel/bpf/syscall.c +0 -0

        if (ukey) {
                key = memdup_user(ukey, map->key_size);
                if (IS_ERR(key)) {

@@ -935,6 +959,10 @@ static int bpf_prog_load(union bpf_attr *attr)
        if (CHECK_ATTR(BPF_PROG_LOAD))
                return -EINVAL;

Quoted 9 lines

kernel/bpf/syscall.c static int bpf_prog_load(union bpf_attr *attr) · line 968

Quoted 8 lines

kernel/bpf/syscall.c +4 -0

+       err = security_prog_load();
+       if (err)
+               return -EACCES;
+
        if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
                return -EINVAL;

Alexei Starovoitov

2017-09-01 02:05 UTC #10 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

In reply to Chenbo Feng

Quoted 10 lines · Chenbo Feng

From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>

...

Quoted 12 lines

kernel/bpf/syscall.c +4 -0

@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_read(map);
+	if (err)
+		return -EACCES;
+
 	key = memdup_user(ukey, map->key_size);
 	if (IS_ERR(key)) {
 		err = PTR_ERR(key);

kernel/bpf/syscall.c static int map_update_elem(union bpf_attr *attr) · line 505

Quoted 4 lines

kernel/bpf/syscall.c +1 -0

@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
 	if (IS_ERR(map))
 		return PTR_ERR(map);
 
+	err = security_map_modify(map);

I don't feel these extra hooks are really thought through. With such hook you'll disallow map_update for given map. That's it. The key/values etc won't be used in such security decision. In such case you don't need such hooks in update/lookup at all. Only in map_creation and object_get calls where FD can be received. In other words I suggest to follow standard unix practices:
Do permissions checks in open() and allow read/write() if FD is valid. Same here. Do permission checks in prog_load/map_create/obj_pin/get and that will be enough to jail bpf subsystem.
bpf cmds that need to be fast (like lookup and update) should not have security hooks.

Jeffrey Vander Stoep

2017-09-01 05:50 UTC #11 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

Quoted 29 lines · Alexei Starovoitov

Quoted 10 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>
...
Quoted 15 lines
kernel/bpf/syscall.c +4 -0
@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_read(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);
@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 

Quoted 14 lines

Review static int map_update_elem(union bpf_attr *attr) · line 505
Quoted 1 line
(quoted diff) +1 -0
+     err = security_map_modify(map);
I don't feel these extra hooks are really thought through. With such hook you'll disallow map_update for given map. That's it. The key/values etc won't be used in such security decision. In such case you don't need such hooks in update/lookup at all. Only in map_creation and object_get calls where FD can be received. In other words I suggest to follow standard unix practices:
Do permissions checks in open() and allow read/write() if FD is valid. Same here. Do permission checks in prog_load/map_create/obj_pin/get and that will be enough to jail bpf subsystem.
bpf cmds that need to be fast (like lookup and update) should not have security hooks.

I do think we want to distinguish between read/write (or read/modify) for these objects. Essentially, we want to implement the example described in patch 0/3 where eBPF objects can be passed to less privileged processes which can read, but not modify the map. What would be the best way to do this? Add a mode field to the bpf_map struct?
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Chenbo Feng

2017-09-05 21:59 UTC #12 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

In reply to Alexei Starovoitov

Quoted 29 lines · Alexei Starovoitov

Quoted 10 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>
...
Quoted 15 lines
kernel/bpf/syscall.c +4 -0
@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_read(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);
@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 

Quoted 14 lines

Review static int map_update_elem(union bpf_attr *attr) · line 505
Quoted 1 line
(quoted diff) +1 -0
+     err = security_map_modify(map);
I don't feel these extra hooks are really thought through. With such hook you'll disallow map_update for given map. That's it. The key/values etc won't be used in such security decision. In such case you don't need such hooks in update/lookup at all. Only in map_creation and object_get calls where FD can be received. In other words I suggest to follow standard unix practices:
Do permissions checks in open() and allow read/write() if FD is valid. Same here. Do permission checks in prog_load/map_create/obj_pin/get and that will be enough to jail bpf subsystem.
bpf cmds that need to be fast (like lookup and update) should not have security hooks.

Thanks for pointing out this. I agree we should only do checks on creating and passing
the object from one processes to another. And if we can still distinguish the read/write operation
when obtaining the file fd, that would be great. But that may require us to add a new mode
field into bpf_map struct and change the attribute struct when doing the bpf syscall. How do you
think about this approach? Or we can do simple checks for bpf_obj_create and bpf_obj_use when
creating the object and passing the object respectively but this solution cannot distinguish map modify and
read.
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Alexei Starovoitov

2017-09-06 00:39 UTC #13 lore raw

Re: [PATCH 2/3] security: bpf: Add eBPF LSM hooks and security field to eBPF map

Quoted 45 lines · Chenbo Feng

Quoted 29 lines · Alexei Starovoitov
Quoted 10 lines · Chenbo Feng
From: Chenbo Feng <[email protected]>
Introduce a pointer into struct bpf_map to hold the security information about the map. The actual security struct varies based on the security models implemented. Place the LSM hooks before each of the unrestricted eBPF operations, the map_update_elem and map_delete_elem operations are checked by security_map_modify. The map_lookup_elem and map_get_next_key operations are checked by securtiy_map_read.
Signed-off-by Chenbo Feng <[email protected]>
...
Quoted 15 lines
kernel/bpf/syscall.c +4 -0
@@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
+     err = security_map_read(map);
+     if (err)
+             return -EACCES;
+
      key = memdup_user(ukey, map->key_size);
      if (IS_ERR(key)) {
              err = PTR_ERR(key);
@@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
      if (IS_ERR(map))
              return PTR_ERR(map);
 
Quoted 14 lines
Review static int map_update_elem(union bpf_attr *attr) · line 505
Quoted 1 line
(quoted diff) +1 -0
+     err = security_map_modify(map);
I don't feel these extra hooks are really thought through. With such hook you'll disallow map_update for given map. That's it. The key/values etc won't be used in such security decision. In such case you don't need such hooks in update/lookup at all. Only in map_creation and object_get calls where FD can be received. In other words I suggest to follow standard unix practices:
Do permissions checks in open() and allow read/write() if FD is valid. Same here. Do permission checks in prog_load/map_create/obj_pin/get and that will be enough to jail bpf subsystem.
bpf cmds that need to be fast (like lookup and update) should not have security hooks.

Quoted 13 lines

Thanks for pointing out this. I agree we should only do checks on creating and passing
the object from one processes to another. And if we can still distinguish the read/write operation
when obtaining the file fd, that would be great. But that may require us to add a new mode
field into bpf_map struct and change the attribute struct when doing the bpf syscall. How do you
think about this approach? Or we can do simple checks for bpf_obj_create and bpf_obj_use when
creating the object and passing the object respectively but this solution cannot distinguish map modify and
read.

iirc the idea to have read only maps was brought up in the past (unfortunately no one took a stab at implementing it), but imo that's better then relying on lsm to provide such restriction and more secure, since even if you disable map_update via lsm, the user can craft a program just to udpate the map from it. For bpffs we already test for inode_permission(inode, MAY_WRITE); during BPF_OBJ_GET command and we can extend this facility further. Also we can allow dropping 'write' permissions from the map (internally implemented via flag in struct bpf_map), so update/delete operations won't be allowed.
This flag will be checked by syscall during map_update/delete and by the verifier if such read-only map is used by the program being loaded, so map_update/helpers won't be allowed in such program.
Would also be good to support read-only programs as well (progs that are read-only from kernel state point of view) They won't be able to modify packets, maps, etc.

Chenbo Feng

author

2017-08-31 20:56 UTC #14 lore raw

PATCH 3/3 selinux: bpf: Implement the selinux checks for eBPF object

In reply to Chenbo Feng

From: Chenbo Feng <[email protected]>

Introduce 5 new selinux checks for eBPF object related operations. The check is based on the ownership information of eBPF maps and the capability of creating eBPF object.

Signed-off-by Chenbo Feng <[email protected]>

---
 security/selinux/hooks.c            | 54 +++++++++++++++++++++++++++++++++++++
 security/selinux/include/classmap.h |  2 ++
 security/selinux/include/objsec.h   |  4 +++
 3 files changed, 60 insertions(+)

security/selinux/hooks.c +54 -0

index 33fd061305c4..39ad7d9f335d 100644
@@ -85,6 +85,7 @@
 #include <linux/export.h>
 #include <linux/msg.h>
 #include <linux/shm.h>
+#include <linux/bpf.h>
 
 #include "avc.h"
 #include "objsec.h"

@@ -6245,6 +6246,52 @@ static void selinux_ib_free_security(void *ib_sec)
 }
 #endif
 
+#ifdef CONFIG_BPF_SYSCALL
+static int selinux_bpf_map_create(void)
+{
+	u32 sid = current_sid();
+
+	return avc_has_perm(sid, sid, SECCLASS_BPF, BPF__MAP_CREATE, NULL);
+}
+
+static int selinux_bpf_map_modify(struct bpf_map *map)
+{
+	struct bpf_security_struct *bpfsec = map->security;
+
+	return avc_has_perm(current_sid(), bpfsec->sid, SECCLASS_BPF,
+			    BPF__MAP_MODIFY, NULL);
+}
+
+static int selinux_bpf_map_read(struct bpf_map *map)
+{
+	struct bpf_security_struct *bpfsec = map->security;
+
+	return avc_has_perm(current_sid(), bpfsec->sid, SECCLASS_BPF,
+			    BPF__MAP_READ, NULL);
+}
+
+static int selinux_bpf_prog_load(void)
+{
+	u32 sid = current_sid();
+
+	return avc_has_perm(sid, sid, SECCLASS_BPF, BPF__PROG_LOAD, NULL);
+}
+
+static int selinux_bpf_post_create(struct bpf_map *map)
+{
+	struct bpf_security_struct *bpfsec;
+
+	bpfsec = kzalloc(sizeof(*bpfsec), GFP_KERNEL);
+	if (!bpfsec)
+		return -ENOMEM;
+
+	bpfsec->sid = current_sid();
+	map->security = bpfsec;
+
+	return 0;
+}
+#endif
+
 static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(binder_set_context_mgr, selinux_binder_set_context_mgr),
 	LSM_HOOK_INIT(binder_transaction, selinux_binder_transaction),

@@ -6465,6 +6512,13 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(audit_rule_match, selinux_audit_rule_match),
 	LSM_HOOK_INIT(audit_rule_free, selinux_audit_rule_free),
 #endif
+#ifdef CONFIG_BPF_SYSCALL
+	LSM_HOOK_INIT(bpf_map_create, selinux_bpf_map_create),
+	LSM_HOOK_INIT(bpf_map_modify, selinux_bpf_map_modify),
+	LSM_HOOK_INIT(bpf_map_read, selinux_bpf_map_read),
+	LSM_HOOK_INIT(bpf_prog_load, selinux_bpf_prog_load),
+	LSM_HOOK_INIT(bpf_post_create, selinux_bpf_post_create),
+#endif
 };
 
 static __init int selinux_init(void)

security/selinux/include/classmap.h +2 -0

index b9fe3434b036..83c880fb17b4 100644
@@ -235,6 +235,8 @@ struct security_class_mapping secclass_map[] = {
 	  { "access", NULL } },
 	{ "infiniband_endport",
 	  { "manage_subnet", NULL } },
+	{ "bpf",
+	  {"map_create", "map_modify", "map_read", "prog_load" } },
 	{ NULL }
   };

security/selinux/include/objsec.h +4 -0

index 6ebc61e370ff..ba564f662b0d 100644
@@ -150,6 +150,10 @@ struct pkey_security_struct {
 	u32	sid;	/* SID of pkey */
 };
 
+struct bpf_security_struct {
+	u32 sid;	/*SID of bpf obj creater*/
+};
+
 extern unsigned int selinux_checkreqprot;
 
 #endif /* _SELINUX_OBJSEC_H_ */

Signature · 6 lines

2.14.1.581.gf28d330327-goog

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