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audit: address ANOM_LINK excess records

RFC PATCH Applied Richard Guy Briggs 4 participants 23 messages Feb 14, 2018 – Mar 12, 2018

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VFS Audit

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Richard Guy Briggs

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#0 lore raw

cover audit: address ANOM_LINK excess records

Audit link denied events were being unexpectedly produced in a disjoint way when audit was disabled, and when they were expected, there were duplicate PATH records. This patchset addresses both issues for symlinks and hardlinks.

This was introduced with

	commit b24a30a7305418ff138ff51776fc555ec57c011a
	("audit: fix event coverage of AUDIT_ANOM_LINK")
	commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
	("fs: add link restriction audit reporting")

Here are the resulting events:

symlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:21.635:238) : proctitle=cat my-passwd
type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=1 name=/tmp/my-passwd inode=17618 dev=00:27 mode=link,777 ouid=rgb ogid=rgb rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0
type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=0 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0
type=CWD msg=audit(02/14/2018 04:40:21.635:238) : cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:21.635:238) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c a1=0x7ffc6c1acdda
a2=O_RDONLY a3=0x0 items=2 ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm=
cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=ANOM_LINK msg=audit(02/14/2018 04:40:21.635:238) : op=follow_link ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=roo
t sgid=root fsgid=root tty=ttyS0 ses=1 comm=cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no
----
hardlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:25.373:239) : proctitle=ln test test-ln
type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=1 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0
type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=0 name=test inode=17619 dev=00:27 mode=file,700 ouid=root ogid=root rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0
type=CWD msg=audit(02/14/2018 04:40:25.373:239) : cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:25.373:239) : arch=x86_64 syscall=linkat success=no exit=EPERM(Operation not permitted) a0=0xffffff9c a1=0x7fffe6c3f628 a2=0xffffff9c a3=0x7fffe6c3f62d items=2 ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:25.373:239) : op=linkat ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

The remaining problem is how to address this when syscall logging is disabled since it needs a parent path record and/or a CWD record to complete it. It could also use a proctitle record too. In fact, it looks like we need a way to have multiple auxiliary records to support an arbitrary record. Comments please.

See: https://github.com/linux-audit/audit-kernel/issues/21
See also: https://github.com/linux-audit/audit-kernel/issues/51

Richard Guy Briggs (4):
audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
audit: link denied should not directly generate PATH record
audit: add refused symlink to audit_names
audit: add parent of refused symlink to audit_names

 fs/namei.c     | 10 ++++++++++
 kernel/audit.c | 13 ++-----------
 2 files changed, 12 insertions(+), 11 deletions(-)
Signature · 1 line
1.8.3.1
author
#1 lore raw

RFC PATCH 1/4 audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +3 -0
index 227db99..4c3fd24 100644
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
 	struct audit_buffer *ab;
 	struct audit_names *name;
 
+	if (!audit_enabled || audit_dummy_context())
+		return;
+
 	name = kzalloc(sizeof(*name), GFP_NOFS);
 	if (!name)
 		return;
Signature · 1 line
1.8.3.1
#2 lore raw

Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Quoted 14 lines · Richard Guy Briggs

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +0 -0
index 227db99..4c3fd24 100644

kernel/audit.c void audit_log_link_denied(const char *operation, const struct path *link) · line 2269

Quoted 9 lines
kernel/audit.c +3 -0
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
        struct audit_buffer *ab;
        struct audit_names *name;
 
+       if (!audit_enabled || audit_dummy_context())
+               return;
+
        name = kzalloc(sizeof(*name), GFP_NOFS);
        if (!name)
                return;

Doesn't this means errors here would be silent if audit isn't enabled? I don't that; sysadmins should see this notification regardless of the audit state...

-Kees

Signature · 2 lines
Kees Cook
Pixel Security
author
#3 lore raw

Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Quoted 18 lines · Kees Cook
Quoted 17 lines · Richard Guy Briggs

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +0 -0
index 227db99..4c3fd24 100644
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
        struct audit_buffer *ab;
        struct audit_names *name;
Quoted 10 lines

kernel/audit.c void audit_log_link_denied(const char *operation, const struct path *link) · line 2269

Quoted 6 lines
kernel/audit.c +3 -0
+       if (!audit_enabled || audit_dummy_context())
+               return;
+
        name = kzalloc(sizeof(*name), GFP_NOFS);
        if (!name)
                return;

Doesn't this means errors here would be silent if audit isn't enabled? I don't that; sysadmins should see this notification regardless of the audit state...

This is a user error and not a system error, so I would think if system auditing is disabled, they don't care about this kind of error.

Steve?

Quoted 1 line

-Kees

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

#4 lore raw

Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Quoted 30 lines · Richard Guy Briggs
Quoted 18 lines · Kees Cook
Quoted 17 lines · Richard Guy Briggs

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +0 -0
index 227db99..4c3fd24 100644
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
        struct audit_buffer *ab;
        struct audit_names *name;
Quoted 10 lines

kernel/audit.c void audit_log_link_denied(const char *operation, const struct path *link) · line 2269

Quoted 6 lines
kernel/audit.c +3 -0
+       if (!audit_enabled || audit_dummy_context())
+               return;
+
        name = kzalloc(sizeof(*name), GFP_NOFS);
        if (!name)
                return;

Doesn't this means errors here would be silent if audit isn't enabled? I don't that; sysadmins should see this notification regardless of the audit state...

Quoted 2 lines

This is a user error and not a system error, so I would think if system auditing is disabled, they don't care about this kind of error.

It could indicate an attack attempt...

-Kees

Quoted 13 lines

Steve?

Quoted 1 line

-Kees

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

Signature · 2 lines
Kees Cook
Pixel Security
maintainer
#5 lore raw

Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Quoted 31 lines · Kees Cook
Quoted 30 lines · Richard Guy Briggs
Quoted 28 lines · Kees Cook
Quoted 14 lines · Richard Guy Briggs

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +0 -0
index 227db99..4c3fd24 100644

kernel/audit.c void audit_log_link_denied(const char *operation, const struct path *link) · line 2269

Quoted 9 lines
kernel/audit.c +3 -0
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
        struct audit_buffer *ab;
        struct audit_names *name;
 
+       if (!audit_enabled || audit_dummy_context())
+               return;
+
        name = kzalloc(sizeof(*name), GFP_NOFS);
        if (!name)
                return;

Doesn't this means errors here would be silent if audit isn't enabled? I don't that; sysadmins should see this notification regardless of the audit state...

Quoted 4 lines
Quoted 2 lines

This is a user error and not a system error, so I would think if system auditing is disabled, they don't care about this kind of error.

It could indicate an attack attempt...

We get beat up by several folks when we emit audit records with audit disabled, and they have a very valid point.

I'm not arguing that the information isn't useful, I'm arguing that if you are interested in the sort of information that audit provides you should enable audit. :)

Signature · 2 lines
paul moore
www.paul-moore.com
maintainer
#6 lore raw

Re: [RFC PATCH ghak21 1/4] audit: make ANOM_LINK obey audit_enabled and audit_dummy_context

Quoted 35 lines · Paul Moore
Quoted 34 lines · Kees Cook
Quoted 32 lines · Richard Guy Briggs
Quoted 18 lines · Kees Cook
Quoted 17 lines · Richard Guy Briggs

Audit link denied events emit disjointed records when audit is disabled. No records should be emitted when audit is disabled.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 3 +++
 1 file changed, 3 insertions(+)
kernel/audit.c +0 -0
index 227db99..4c3fd24 100644
@@ -2261,6 +2261,9 @@ void audit_log_link_denied(const char *operation, const struct path *link)
        struct audit_buffer *ab;
        struct audit_names *name;
Quoted 10 lines

kernel/audit.c void audit_log_link_denied(const char *operation, const struct path *link) · line 2269

Quoted 6 lines
kernel/audit.c +3 -0
+       if (!audit_enabled || audit_dummy_context())
+               return;
+
        name = kzalloc(sizeof(*name), GFP_NOFS);
        if (!name)
                return;

Doesn't this means errors here would be silent if audit isn't enabled? I don't that; sysadmins should see this notification regardless of the audit state...

This is a user error and not a system error, so I would think if system auditing is disabled, they don't care about this kind of error.

Quoted 8 lines
Quoted 1 line

It could indicate an attack attempt...

We get beat up by several folks when we emit audit records with audit disabled, and they have a very valid point.

I'm not arguing that the information isn't useful, I'm arguing that if you are interested in the sort of information that audit provides you should enable audit. :)

FYI, merged into audit/next.

Signature · 2 lines
paul moore
www.paul-moore.com
author
#7 lore raw

RFC PATCH 2/4 audit: link denied should not directly generate PATH record

In reply to Richard Guy Briggs

Audit link denied events generate duplicate PATH records which disagree in different ways from symlink and hardlink denials. audit_log_link_denied() should not directly generate PATH records.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)
kernel/audit.c +1 -13
index 4c3fd24..683b249 100644
@@ -2259,31 +2259,19 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 void audit_log_link_denied(const char *operation, const struct path *link)
 {
 	struct audit_buffer *ab;
-	struct audit_names *name;
 
 	if (!audit_enabled || audit_dummy_context())
 		return;
 
-	name = kzalloc(sizeof(*name), GFP_NOFS);
-	if (!name)
-		return;
-
 	/* Generate AUDIT_ANOM_LINK with subject, operation, outcome. */
 	ab = audit_log_start(current->audit_context, GFP_KERNEL,
 			     AUDIT_ANOM_LINK);
 	if (!ab)
-		goto out;
+		return;
 	audit_log_format(ab, "op=%s", operation);
 	audit_log_task_info(ab, current);
 	audit_log_format(ab, " res=0");
 	audit_log_end(ab);
-
-	/* Generate AUDIT_PATH record with object. */
-	name->type = AUDIT_TYPE_NORMAL;
-	audit_copy_inode(name, link->dentry, d_backing_inode(link->dentry));
-	audit_log_name(current->audit_context, name, link, 0, NULL);
-out:
-	kfree(name);
 }
 
 /**
Signature · 1 line
1.8.3.1
maintainer Applied
#8 lore raw

Re: [RFC PATCH ghak21 2/4] audit: link denied should not directly generate PATH record

Quoted 9 lines · Richard Guy Briggs

Audit link denied events generate duplicate PATH records which disagree in different ways from symlink and hardlink denials. audit_log_link_denied() should not directly generate PATH records.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

Merged, thanks.

Quoted 40 lines
kernel/audit.c +1 -14
index 4c3fd24..683b249 100644
@@ -2259,31 +2259,19 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 void audit_log_link_denied(const char *operation, const struct path *link)
 {
        struct audit_buffer *ab;
-       struct audit_names *name;
 
        if (!audit_enabled || audit_dummy_context())
                return;
 
-       name = kzalloc(sizeof(*name), GFP_NOFS);
-       if (!name)
-               return;
-
        /* Generate AUDIT_ANOM_LINK with subject, operation, outcome. */
        ab = audit_log_start(current->audit_context, GFP_KERNEL,
                             AUDIT_ANOM_LINK);
        if (!ab)
-               goto out;
+               return;
        audit_log_format(ab, "op=%s", operation);
        audit_log_task_info(ab, current);
        audit_log_format(ab, " res=0");
        audit_log_end(ab);
-
-       /* Generate AUDIT_PATH record with object. */
-       name->type = AUDIT_TYPE_NORMAL;
-       audit_copy_inode(name, link->dentry, d_backing_inode(link->dentry));
-       audit_log_name(current->audit_context, name, link, 0, NULL);
-out:
-       kfree(name);
 }
 
 /**
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
author
#9 lore raw

Re: [RFC PATCH ghak21 2/4] audit: link denied should not directly generate PATH record

Quoted 5 lines · Paul Moore
Quoted 4 lines · Richard Guy Briggs

Audit link denied events generate duplicate PATH records which disagree in different ways from symlink and hardlink denials. audit_log_link_denied() should not directly generate PATH records.

Quoted 7 lines
Quoted 5 lines

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 kernel/audit.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

Merged, thanks.

Self-NACK. Please un-merge this RFC v1 version and merge instead the v2 patch since it removes the now-unnecessary struct path * parameter from audit_log_link_denied().

Quoted 36 lines
Quoted 36 lines
kernel/audit.c +1 -13
index 4c3fd24..683b249 100644
@@ -2259,31 +2259,19 @@ void audit_log_task_info(struct audit_buffer *ab, struct task_struct *tsk)
 void audit_log_link_denied(const char *operation, const struct path *link)
 {
        struct audit_buffer *ab;
-       struct audit_names *name;
 
        if (!audit_enabled || audit_dummy_context())
                return;
 
-       name = kzalloc(sizeof(*name), GFP_NOFS);
-       if (!name)
-               return;
-
        /* Generate AUDIT_ANOM_LINK with subject, operation, outcome. */
        ab = audit_log_start(current->audit_context, GFP_KERNEL,
                             AUDIT_ANOM_LINK);
        if (!ab)
-               goto out;
+               return;
        audit_log_format(ab, "op=%s", operation);
        audit_log_task_info(ab, current);
        audit_log_format(ab, " res=0");
        audit_log_end(ab);
-
-       /* Generate AUDIT_PATH record with object. */
-       name->type = AUDIT_TYPE_NORMAL;
-       audit_copy_inode(name, link->dentry, d_backing_inode(link->dentry));
-       audit_log_name(current->audit_context, name, link, 0, NULL);
-out:
-       kfree(name);
 }
Quoted 10 lines
Quoted 4 lines
kernel/audit.c +0 -1
 /**
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

author
#10 lore raw

RFC PATCH 3/4 audit: add refused symlink to audit_names

In reply to Richard Guy Briggs

Audit link denied events for symlinks had duplicate PATH records rather than just updating the existing PATH record. Update the symlink's PATH record with the current dentry and inode information.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 1 +
 1 file changed, 1 insertion(+)
fs/namei.c +1 -0
index 9cc91fb..0edf133 100644
@@ -945,6 +945,7 @@ static inline int may_follow_link(struct nameidata *nd)
 	if (nd->flags & LOOKUP_RCU)
 		return -ECHILD;
 
+	audit_inode(nd->name, nd->stack[0].link.dentry, 0);
 	audit_log_link_denied("follow_link", &nd->stack[0].link);
 	return -EACCES;
 }
Signature · 1 line
1.8.3.1
maintainer
#11 lore raw

Re: [RFC PATCH ghak21 3/4] audit: add refused symlink to audit_names

Quoted 9 lines · Richard Guy Briggs

Audit link denied events for symlinks had duplicate PATH records rather than just updating the existing PATH record. Update the symlink's PATH record with the current dentry and inode information.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 1 +
 1 file changed, 1 insertion(+)

Merged.

Quoted 15 lines
fs/namei.c +1 -1
index 9cc91fb..0edf133 100644
@@ -945,6 +945,7 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
 
+       audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
        return -EACCES;
 }
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
maintainer
#12 lore raw

Re: [RFC PATCH ghak21 3/4] audit: add refused symlink to audit_names

Quoted 5 lines · Paul Moore
Quoted 4 lines · Richard Guy Briggs

Audit link denied events for symlinks had duplicate PATH records rather than just updating the existing PATH record. Update the symlink's PATH record with the current dentry and inode information.

Quoted 7 lines
Quoted 5 lines

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 1 +
 1 file changed, 1 insertion(+)

Merged.

Scratch that, not merged, although only because I think we need to refactor patch 4/4 and the refactoring can/should encompass this patch.

See my comments on 4/4.

Quoted 14 lines
Quoted 14 lines
fs/namei.c +1 -1
index 9cc91fb..0edf133 100644
@@ -945,6 +945,7 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
 
+       audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
        return -EACCES;
 }
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
author
#13 lore raw

RFC PATCH 4/4 audit: add parent of refused symlink to audit_names

In reply to Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +9 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
 	const struct inode *inode;
 	const struct inode *parent;
 	kuid_t puid;
+	char *pathname;
 
 	if (!sysctl_protected_symlinks)
 		return 0;

@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
 	if (nd->flags & LOOKUP_RCU)
 		return -ECHILD;
 
+	pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+	if (!pathname)
+		return -ENOMEM;
+	audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+						   PATH_MAX + 1)),
+		    nd->stack[0].link.dentry, 0);
+	audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
 	audit_inode(nd->name, nd->stack[0].link.dentry, 0);
 	audit_log_link_denied("follow_link", &nd->stack[0].link);
 	return -EACCES;
Signature · 1 line
1.8.3.1
maintainer
#14 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

Quoted 23 lines · Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +1 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
        const struct inode *inode;
        const struct inode *parent;
        kuid_t puid;
+       char *pathname;
 
        if (!sysctl_protected_symlinks)
                return 0;

fs/namei.c static inline int may_follow_link(struct nameidata *nd) · line 954

Quoted 9 lines
fs/namei.c +6 -0
@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
 
+       pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+       if (!pathname)
+               return -ENOMEM;
+       audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+                                                  PATH_MAX + 1)),
+                   nd->stack[0].link.dentry, 0);

Hmm, it's been a while since I've looked at the audit vfs/inode code, but isn't the audit_inode() call directly above effectively a duplicate of the audit_inode(nd->name, nd->stack[0].link.dentry, 0) call you added in patch 3/4?

Quoted 7 lines
fs/namei.c +2 -1
+       audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
        audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
        return -EACCES;
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
author
#15 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

Quoted 27 lines · Paul Moore
Quoted 26 lines · Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +1 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
        const struct inode *inode;
        const struct inode *parent;
        kuid_t puid;
+       char *pathname;
 
        if (!sysctl_protected_symlinks)
                return 0;

@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
Quoted 11 lines

fs/namei.c static inline int may_follow_link(struct nameidata *nd) · line 954

Quoted 6 lines
fs/namei.c +6 -0
+       pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+       if (!pathname)
+               return -ENOMEM;
+       audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+                                                  PATH_MAX + 1)),
+                   nd->stack[0].link.dentry, 0);

Hmm, it's been a while since I've looked at the audit vfs/inode code, but isn't the audit_inode() call directly above effectively a duplicate of the audit_inode(nd->name, nd->stack[0].link.dentry, 0) call you added in patch 3/4?

It gets the full pathname string of the link, then converts it to a struct filename*, and then below, we feed it that struct filename* with the parent's dentry and the LOOKUP_PARENT flag to drop the last part of the pathname and set the filetype to PARENT.

I didn't try, it, but I expect if I feed it parent's dentry above, I'd get only the parent pathname and when I feed it to audit_inode() below it would again drop the last part of the pathname when the LOOKUP_PARENT flag is included, or not label it as a filetype PARENT if we don't include the flag to get the full parent pathname.

Quoted 16 lines
Quoted 7 lines
fs/namei.c +2 -1
+       audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
        audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
        return -EACCES;
--

1.8.3.1

Signature · 7 lines
paul moore
www.paul-moore.com

--
Linux-audit mailing list
[email protected]
https://www.redhat.com/mailman/listinfo/linux-audit

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

maintainer
#16 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

Quoted 40 lines · Richard Guy Briggs
Quoted 27 lines · Paul Moore
Quoted 26 lines · Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +1 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
        const struct inode *inode;
        const struct inode *parent;
        kuid_t puid;
+       char *pathname;
 
        if (!sysctl_protected_symlinks)
                return 0;

@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
Quoted 11 lines

fs/namei.c static inline int may_follow_link(struct nameidata *nd) · line 954

Quoted 6 lines
fs/namei.c +6 -0
+       pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+       if (!pathname)
+               return -ENOMEM;
+       audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+                                                  PATH_MAX + 1)),
+                   nd->stack[0].link.dentry, 0);

Hmm, it's been a while since I've looked at the audit vfs/inode code, but isn't the audit_inode() call directly above effectively a duplicate of the audit_inode(nd->name, nd->stack[0].link.dentry, 0) call you added in patch 3/4?

Quoted 4 lines

It gets the full pathname string of the link, then converts it to a struct filename*, and then below, we feed it that struct filename* with the parent's dentry and the LOOKUP_PARENT flag to drop the last part of the pathname and set the filetype to PARENT.

I think that last bit is what I was forgetting, thanks.

Quoted 13 lines

I didn't try, it, but I expect if I feed it parent's dentry above, I'd get only the parent pathname and when I feed it to audit_inode() below it would again drop the last part of the pathname when the LOOKUP_PARENT flag is included, or not label it as a filetype PARENT if we don't include the flag to get the full parent pathname.

Quoted 7 lines
Quoted 7 lines
fs/namei.c +2 -1
+       audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
        audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
        return -EACCES;
--

1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
maintainer
#17 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

In reply to Richard Guy Briggs
Quoted 23 lines · Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +1 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
        const struct inode *inode;
        const struct inode *parent;
        kuid_t puid;
+       char *pathname;
 
        if (!sysctl_protected_symlinks)
                return 0;

fs/namei.c static inline int may_follow_link(struct nameidata *nd) · line 951

Quoted 6 lines
fs/namei.c +3 -0
@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
 
+       pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+       if (!pathname)
+               return -ENOMEM;

Two things here:

1. We need to allocate a buffer to feed to d_absolute_path(), and getname_kernel() is just going to make another copy so we need to make sure we clean up after ourselves. Perhaps I missing it, but I'm not seeing where we free the kmalloc'd buffer or call putname(). Feel free to correct me if I'm missing something obvious.

2. While the audit_* calls are going to bail early in the cases where audit is disabled, or not configured, we are going to pay the penalty for the kmalloc() call above, as well as the getname_kernel() and d_absolute_path() calls below. I think it might be beneficial to create a new function (audit_log_symlink_denied() perhaps?) which encapsulates all the audit bits in may_follow_link() and exits early when needed. What do you think?

(Point #2 is why I didn't merge patch 3/4, just include it in this revised patch)

Quoted 11 lines
fs/namei.c +5 -0
+       audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+                                                  PATH_MAX + 1)),
+                   nd->stack[0].link.dentry, 0);
+       audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
        audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
 

        return -EACCES;

--
1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com
author
#18 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

Quoted 33 lines · Paul Moore
Quoted 23 lines · Richard Guy Briggs

Audit link denied events for symlinks were missing the parent PATH record. Add it. Since the full pathname may not be available, reconstruct it from the path in the nameidata supplied.

See: https://github.com/linux-audit/audit-kernel/issues/21

Signed-off-by Richard Guy Briggs <[email protected]>
---
 fs/namei.c | 9 +++++++++
 1 file changed, 9 insertions(+)
fs/namei.c +1 -0
index 0edf133..bf1c046b 100644
@@ -923,6 +923,7 @@ static inline int may_follow_link(struct nameidata *nd)
        const struct inode *inode;
        const struct inode *parent;
        kuid_t puid;
+       char *pathname;
 
        if (!sysctl_protected_symlinks)
                return 0;

fs/namei.c static inline int may_follow_link(struct nameidata *nd) · line 951

Quoted 6 lines
fs/namei.c +3 -0
@@ -945,6 +946,14 @@ static inline int may_follow_link(struct nameidata *nd)
        if (nd->flags & LOOKUP_RCU)
                return -ECHILD;
 
+       pathname = kmalloc(PATH_MAX + 1, GFP_KERNEL);
+       if (!pathname)
+               return -ENOMEM;

Two things here:

Quoted 5 lines

1. We need to allocate a buffer to feed to d_absolute_path(), and getname_kernel() is just going to make another copy so we need to make sure we clean up after ourselves. Perhaps I missing it, but I'm not seeing where we free the kmalloc'd buffer or call putname(). Feel free to correct me if I'm missing something obvious.

That is put very diplomatically! Both fixed, with audit_panic() as needed.

Quoted 7 lines

2. While the audit_* calls are going to bail early in the cases where audit is disabled, or not configured, we are going to pay the penalty for the kmalloc() call above, as well as the getname_kernel() and d_absolute_path() calls below. I think it might be beneficial to create a new function (audit_log_symlink_denied() perhaps?) which encapsulates all the audit bits in may_follow_link() and exits early when needed. What do you think?

I agree a seperate function is appropriate. There was some back and forth between namei.c and audit.c due to struct nameidata and audit_panic() not able to co-exist due to them both being local to their respective sub-systems.

Quoted 2 lines

(Point #2 is why I didn't merge patch 3/4, just include it in this revised patch)

On reviewing this, I'm not totally convinced the parent record is necessary to fully understand what happenned since there is a CWD record. I left 3 and 4 as seperate patches in case it is found that only 3 is necessary.

Quoted 8 lines
Quoted 8 lines
fs/namei.c +5 -0
+       audit_inode(getname_kernel(d_absolute_path(&nd->stack[0].link, pathname,
+                                                  PATH_MAX + 1)),
+                   nd->stack[0].link.dentry, 0);
+       audit_inode(nd->name, nd->stack[0].link.dentry->d_parent, LOOKUP_PARENT);
+
        audit_inode(nd->name, nd->stack[0].link.dentry, 0);
        audit_log_link_denied("follow_link", &nd->stack[0].link);
Quoted 7 lines
Quoted 3 lines
        return -EACCES;

--
1.8.3.1

Signature · 2 lines
paul moore
www.paul-moore.com

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

maintainer
#19 lore raw

Re: [RFC PATCH ghak21 4/4] audit: add parent of refused symlink to audit_names

Quoted 1 line · Richard Guy Briggs

On 2018-03-08 19:50, Paul Moore wrote:

...

Quoted 7 lines
Quoted 2 lines

(Point #2 is why I didn't merge patch 3/4, just include it in this revised patch)

On reviewing this, I'm not totally convinced the parent record is necessary to fully understand what happenned since there is a CWD record. I left 3 and 4 as seperate patches in case it is found that only 3 is necessary.

You need to figure this out and decide what is necessary.

Signature · 2 lines
paul moore
www.paul-moore.com
#20 lore raw
In reply to Richard Guy Briggs
Quoted 5 lines · EST Richard Guy Briggs

Audit link denied events were being unexpectedly produced in a disjoint way when audit was disabled, and when they were expected, there were duplicate PATH records. This patchset addresses both issues for symlinks and hardlinks.

Quoted 7 lines

This was introduced with

	commit b24a30a7305418ff138ff51776fc555ec57c011a
	("audit: fix event coverage of AUDIT_ANOM_LINK")
	commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
	("fs: add link restriction audit reporting")

Here are the resulting events:

Have these been tested with ausearch-test?

Quoted 14 lines

symlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:21.635:238) : proctitle=cat my-passwd type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=1 name=/tmp/my-passwd inode=17618 dev=00:27 mode=link,777 ouid=rgb ogid=rgb rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=0 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:21.635:238) :
cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:21.635:238) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c a1=0x7ffc6c1acdda a2=O_RDONLY a3=0x0 items=2 ppid=549 pid=606 auid=root

Quoted 8 lines

uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm= cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:21.635:238) : op=follow_link ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=roo t sgid=root fsgid=root tty=ttyS0 ses=1 comm=cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

This record duplicates the SYSCALL event except for the op field. I would suggest that is the only field needed.

Quoted 22 lines

----
hardlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:25.373:239) : proctitle=ln test test-ln type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=1 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=0 name=test inode=17619 dev=00:27 mode=file,700 ouid=root ogid=root rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:25.373:239) : cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:25.373:239) : arch=x86_64 syscall=linkat success=no exit=EPERM(Operation not permitted) a0=0xffffff9c a1=0x7fffe6c3f628 a2=0xffffff9c a3=0x7fffe6c3f62d items=2 ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:25.373:239) : op=linkat ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

Quoted 5 lines

The remaining problem is how to address this when syscall logging is disabled since it needs a parent path record and/or a CWD record to complete it. It could also use a proctitle record too. In fact, it looks like we need a way to have multiple auxiliary records to support an arbitrary record. Comments please.

Perhaps this can only be emitted correctly with SYSCALL auditing enabled. Otherwise, the event should stand completely on its own without syscall and path records. The information from them can be added, but it risks hitting the record size limit.

-Steve

Quoted 12 lines

See: https://github.com/linux-audit/audit-kernel/issues/21
See also: https://github.com/linux-audit/audit-kernel/issues/51

Richard Guy Briggs (4):
audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
audit: link denied should not directly generate PATH record
audit: add refused symlink to audit_names
audit: add parent of refused symlink to audit_names

 fs/namei.c     | 10 ++++++++++
 kernel/audit.c | 13 ++-----------
 2 files changed, 12 insertions(+), 11 deletions(-)
author
#21 lore raw
Quoted 12 lines · Steve Grubb
Quoted 11 lines · EST Richard Guy Briggs

Audit link denied events were being unexpectedly produced in a disjoint way when audit was disabled, and when they were expected, there were duplicate PATH records. This patchset addresses both issues for symlinks and hardlinks.

This was introduced with

	commit b24a30a7305418ff138ff51776fc555ec57c011a
	("audit: fix event coverage of AUDIT_ANOM_LINK")
	commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
	("fs: add link restriction audit reporting")
Quoted 3 lines
Quoted 1 line

Here are the resulting events:

Have these been tested with ausearch-test?

Not yet.

Quoted 23 lines
Quoted 14 lines

symlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:21.635:238) : proctitle=cat my-passwd type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=1 name=/tmp/my-passwd inode=17618 dev=00:27 mode=link,777 ouid=rgb ogid=rgb rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=0 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:21.635:238) :
cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:21.635:238) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c a1=0x7ffc6c1acdda a2=O_RDONLY a3=0x0 items=2 ppid=549 pid=606 auid=root

Quoted 8 lines

uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm= cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:21.635:238) : op=follow_link ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=roo t sgid=root fsgid=root tty=ttyS0 ses=1 comm=cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

Quoted 2 lines

This record duplicates the SYSCALL event except for the op field. I would suggest that is the only field needed.

Agreed, but at the moment, removal of fields isn't possible unless there is a conflict, and even then the value should simply be corrected if possible.

Quoted 28 lines
Quoted 22 lines

----
hardlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:25.373:239) : proctitle=ln test test-ln type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=1 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=0 name=test inode=17619 dev=00:27 mode=file,700 ouid=root ogid=root rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:25.373:239) : cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:25.373:239) : arch=x86_64 syscall=linkat success=no exit=EPERM(Operation not permitted) a0=0xffffff9c a1=0x7fffe6c3f628 a2=0xffffff9c a3=0x7fffe6c3f62d items=2 ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:25.373:239) : op=linkat ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

Quoted 5 lines

The remaining problem is how to address this when syscall logging is disabled since it needs a parent path record and/or a CWD record to complete it. It could also use a proctitle record too. In fact, it looks like we need a way to have multiple auxiliary records to support an arbitrary record. Comments please.

Quoted 4 lines

Perhaps this can only be emitted correctly with SYSCALL auditing enabled. Otherwise, the event should stand completely on its own without syscall and path records. The information from them can be added, but it risks hitting the record size limit.

As Paul just pointed out (which rang a bell...) in:

	https://github.com/linux-audit/audit-kernel/issues/51#issuecomment-365759325

CONFIG_AUDITSYSCALL is now forced on and if you sabbotage your audit.rules with -a task,never, your warranty is void.

So now, the lurking questions in the back of my head about the availability of syscall records has been alleviated and we should always see a syscall record available unless an audit rule says we are not interested.

Quoted 18 lines

-Steve

Quoted 12 lines

See: https://github.com/linux-audit/audit-kernel/issues/21
See also: https://github.com/linux-audit/audit-kernel/issues/51

Richard Guy Briggs (4):
audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
audit: link denied should not directly generate PATH record
audit: add refused symlink to audit_names
audit: add parent of refused symlink to audit_names

 fs/namei.c     | 10 ++++++++++
 kernel/audit.c | 13 ++-----------
 2 files changed, 12 insertions(+), 11 deletions(-)

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

author
#22 lore raw
Quoted 13 lines · Richard Guy Briggs
Quoted 12 lines · Steve Grubb
Quoted 11 lines · EST Richard Guy Briggs

Audit link denied events were being unexpectedly produced in a disjoint way when audit was disabled, and when they were expected, there were duplicate PATH records. This patchset addresses both issues for symlinks and hardlinks.

This was introduced with

	commit b24a30a7305418ff138ff51776fc555ec57c011a
	("audit: fix event coverage of AUDIT_ANOM_LINK")
	commit a51d9eaa41866ab6b4b6ecad7b621f8b66ece0dc
	("fs: add link restriction audit reporting")
Quoted 5 lines
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Here are the resulting events:

Have these been tested with ausearch-test?

Not yet.

I should have reported that a day or two later I ran the ausearch-test which passed.

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symlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:21.635:238) : proctitle=cat my-passwd type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=1 name=/tmp/my-passwd inode=17618 dev=00:27 mode=link,777 ouid=rgb ogid=rgb rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:21.635:238) : item=0 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:21.635:238) :
cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:21.635:238) : arch=x86_64 syscall=openat success=no exit=EACCES(Permission denied) a0=0xffffff9c a1=0x7ffc6c1acdda a2=O_RDONLY a3=0x0 items=2 ppid=549 pid=606 auid=root

Quoted 8 lines

uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm= cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:21.635:238) : op=follow_link ppid=549 pid=606 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=roo t sgid=root fsgid=root tty=ttyS0 ses=1 comm=cat exe=/usr/bin/cat subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

Quoted 2 lines

This record duplicates the SYSCALL event except for the op field. I would suggest that is the only field needed.

Agreed, but at the moment, removal of fields isn't possible unless there is a conflict, and even then the value should simply be corrected if possible.

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----
hardlink:
type=PROCTITLE msg=audit(02/14/2018 04:40:25.373:239) : proctitle=ln test test-ln type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=1 name=/tmp inode=13446 dev=00:27 mode=dir,sticky,777 ouid=root ogid=root rdev=00:00 obj=system_u:object_r:tmp_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=PATH msg=audit(02/14/2018 04:40:25.373:239) : item=0 name=test inode=17619 dev=00:27 mode=file,700 ouid=root ogid=root rdev=00:00 obj=unconfined_u:object_r:user_tmp_t:s0 nametype=NORMAL cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 type=CWD msg=audit(02/14/2018 04:40:25.373:239) : cwd=/tmp
type=SYSCALL msg=audit(02/14/2018 04:40:25.373:239) : arch=x86_64 syscall=linkat success=no exit=EPERM(Operation not permitted) a0=0xffffff9c a1=0x7fffe6c3f628 a2=0xffffff9c a3=0x7fffe6c3f62d items=2 ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null) type=ANOM_LINK msg=audit(02/14/2018 04:40:25.373:239) : op=linkat ppid=578 pid=607 auid=rgb uid=rgb gid=rgb euid=rgb suid=rgb fsuid=rgb egid=rgb sgid=rgb fsgid=rgb tty=pts0 ses=3 comm=ln exe=/usr/bin/ln subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 res=no

Quoted 5 lines

The remaining problem is how to address this when syscall logging is disabled since it needs a parent path record and/or a CWD record to complete it. It could also use a proctitle record too. In fact, it looks like we need a way to have multiple auxiliary records to support an arbitrary record. Comments please.

Quoted 4 lines

Perhaps this can only be emitted correctly with SYSCALL auditing enabled. Otherwise, the event should stand completely on its own without syscall and path records. The information from them can be added, but it risks hitting the record size limit.

As Paul just pointed out (which rang a bell...) in:

	https://github.com/linux-audit/audit-kernel/issues/51#issuecomment-365759325

CONFIG_AUDITSYSCALL is now forced on and if you sabbotage your audit.rules with -a task,never, your warranty is void.

So now, the lurking questions in the back of my head about the availability of syscall records has been alleviated and we should always see a syscall record available unless an audit rule says we are not interested.

Quoted 11 lines

-Steve

Quoted 9 lines

See: https://github.com/linux-audit/audit-kernel/issues/21
See also: https://github.com/linux-audit/audit-kernel/issues/51

Richard Guy Briggs (4):
audit: make ANOM_LINK obey audit_enabled and audit_dummy_context
audit: link denied should not directly generate PATH record
audit: add refused symlink to audit_names
audit: add parent of refused symlink to audit_names

Quoted 5 lines
Quoted 3 lines
Quoted 3 lines
 fs/namei.c     | 10 ++++++++++
 kernel/audit.c | 13 ++-----------
 2 files changed, 12 insertions(+), 11 deletions(-)

- RGB

- RGB

--
Richard Guy Briggs <[email protected]>
Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635