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restorecon context validation improvement

PATCH In review Yuli Khodorkovskiy 2 participants 5 messages Mar 30, 2018 – Apr 4, 2018 SELinux security module

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Yuli Khodorkovskiy

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#0 lore raw

v3 cover restorecon context validation improvement

In permissive, if a bad label is written to a file_context file, restorecon will not verify the label before succesfully applying the context. These patches fix validation of labels during restorecon while not breaking current behavior of lazy validation.

Changes since V1:
- Continue using lazy validation for restorecon that was broken in V1 of the patch.
- Add line number tracking for error messages in restorecon.

Changes since V2:
- Fix compiler error caused by unused variable in selabel_validate()

Yuli Khodorkovskiy (2):
libselinux: verify file_contexts when using restorecon
libselinux: echo line number of bad label in selabel_fini()

 libselinux/src/label.c                  | 7 +++----
 libselinux/src/label_backends_android.c | 2 +-
 libselinux/src/label_file.c             | 2 +-
 libselinux/src/label_file.h             | 3 ++-
 libselinux/src/label_internal.h         | 7 +++----
 libselinux/src/matchpathcon.c           | 5 ++---
 6 files changed, 12 insertions(+), 14 deletions(-)
Signature · 1 line
2.14.3
author
#1 lore raw

PATCH v3 1/2 libselinux: verify file_contexts when using restorecon

In permissive mode, calling restorecon with a bad label in file_contexts does not verify the label's existence in the loaded policy. This results in any label successfully applying to a file, as long as the file exists.

This issue has two assumptions:

1) file_contexts must be manually updated with the invalid label. Running semanage fcontext will error when attempting to add an invalid label to file_contexts.
2) the system must be in permissive. Although applying an invalid label in enforcing gives an error and fails, successfully labeling a file with a bad label could cause issues during policy development in permissive.

Instead, as each context is used, verify it is valid before blindly applying the label. If an error with validation occurs in restorecon, application of remaining valid labels will be uninterrupted as before.

Signed-off-by Yuli Khodorkovskiy <[email protected]>
---
 libselinux/src/label.c                  | 7 +++----
 libselinux/src/label_backends_android.c | 2 +-
 libselinux/src/label_file.c             | 2 +-
 libselinux/src/label_file.h             | 2 +-
 libselinux/src/label_internal.h         | 6 ++----
 libselinux/src/matchpathcon.c           | 5 ++---
 6 files changed, 10 insertions(+), 14 deletions(-)
libselinux/src/label.c +3 -4
index 48f4d2d6..c510edc1 100644
@@ -121,12 +121,11 @@ static inline int selabel_is_validate_set(const struct selinux_opt *opts,
 	return 0;
 }
 
-int selabel_validate(struct selabel_handle *rec,
-		     struct selabel_lookup_rec *contexts)
+int selabel_validate(struct selabel_lookup_rec *contexts)
 {
 	int rc = 0;
 
-	if (!rec->validating || contexts->validated)
+	if (contexts->validated)
 		goto out;
 
 	rc = selinux_validate(&contexts->ctx_raw);

@@ -143,7 +142,7 @@ static int selabel_fini(struct selabel_handle *rec,
 			    struct selabel_lookup_rec *lr,
 			    int translating)
 {
-	if (compat_validate(rec, lr, rec->spec_file, 0))
+	if (compat_validate(lr, rec->spec_file, 0))
 		return -1;
 
 	if (translating && !lr->ctx_trans &&
libselinux/src/label_backends_android.c +1 -1
index cb8aae26..49e39ec8 100644
@@ -122,7 +122,7 @@ static int process_line(struct selabel_handle *rec,
 		spec_arr[nspec].lr.ctx_raw = context;
 
 		if (rec->validating) {
-			if (selabel_validate(rec, &spec_arr[nspec].lr) < 0) {
+			if (selabel_validate(&spec_arr[nspec].lr) < 0) {
 				selinux_log(SELINUX_ERROR,
 					    "%s:  line %u has invalid context %s\n",
 					    path, lineno, spec_arr[nspec].lr.ctx_raw);
libselinux/src/label_file.c +1 -1
index 560d8c3d..169fed70 100644
@@ -328,7 +328,7 @@ end_arch_check:
 		spec->lr.ctx_raw = str_buf;
 
 		if (strcmp(spec->lr.ctx_raw, "<<none>>") && rec->validating) {
-			if (selabel_validate(rec, &spec->lr) < 0) {
+			if (selabel_validate(&spec->lr) < 0) {
 				selinux_log(SELINUX_ERROR,
 					    "%s: context %s is invalid\n",
 					    path, spec->lr.ctx_raw);
libselinux/src/label_file.h +1 -1
index aa576d8e..9e52a3c4 100644
@@ -506,7 +506,7 @@ static inline int process_line(struct selabel_handle *rec,
 	spec_hasMetaChars(&spec_arr[nspec]);
 
 	if (strcmp(context, "<<none>>") && rec->validating)
-		return compat_validate(rec, &spec_arr[nspec].lr, path, lineno);
+		return compat_validate(&spec_arr[nspec].lr, path, lineno);
 
 	return 0;
 }
libselinux/src/label_internal.h +2 -4
index c55efb75..75451858 100644
@@ -111,8 +111,7 @@ struct selabel_handle {
  * Validation function
  */
 extern int
-selabel_validate(struct selabel_handle *rec,
-		 struct selabel_lookup_rec *contexts) hidden;
+selabel_validate(struct selabel_lookup_rec *contexts) hidden;
 
 /*
  * Compatibility support

@@ -127,8 +126,7 @@ extern void __attribute__ ((format(printf, 1, 2)))
 		selinux_log(type, fmt);
 
 extern int
-compat_validate(struct selabel_handle *rec,
-		struct selabel_lookup_rec *contexts,
+compat_validate(struct selabel_lookup_rec *contexts,
 		const char *path, unsigned lineno) hidden;
 
 /*
libselinux/src/matchpathcon.c +2 -3
index 58b4144a..c66739af 100644
@@ -35,8 +35,7 @@ void set_matchpathcon_printf(void (*f) (const char *fmt, ...))
 	myprintf_compat = 1;
 }
 
-int compat_validate(struct selabel_handle *rec,
-		    struct selabel_lookup_rec *contexts,
+int compat_validate(struct selabel_lookup_rec *contexts,
 		    const char *path, unsigned lineno)
 {
 	int rc;

@@ -47,7 +46,7 @@ int compat_validate(struct selabel_handle *rec,
 	else if (mycanoncon)
 		rc = mycanoncon(path, lineno, ctx);
 	else {
-		rc = selabel_validate(rec, contexts);
+		rc = selabel_validate(contexts);
 		if (rc < 0) {
 			if (lineno) {
 				COMPAT_LOG(SELINUX_WARNING,
Signature · 1 line
2.14.3
author
#2 lore raw

PATCH v3 2/2 libselinux: echo line number of bad label in selabel_fini()

In reply to Yuli Khodorkovskiy

Keep track of line numbers for each file context in selabel_handle. If an error occurs in selabel_fini(), the line number of an invalid file context is echoed to the user.

Signed-off-by Yuli Khodorkovskiy <[email protected]>
---
 libselinux/src/label.c          | 2 +-
 libselinux/src/label_file.h     | 1 +
 libselinux/src/label_internal.h | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)
libselinux/src/label.c +1 -1
index c510edc1..591815a7 100644
@@ -142,7 +142,7 @@ static int selabel_fini(struct selabel_handle *rec,
 			    struct selabel_lookup_rec *lr,
 			    int translating)
 {
-	if (compat_validate(lr, rec->spec_file, 0))
+	if (compat_validate(lr, rec->spec_file, lr->lineno))
 		return -1;
 
 	if (translating && !lr->ctx_trans &&
libselinux/src/label_file.h +1 -0
index 9e52a3c4..3f9ce53b 100644
@@ -472,6 +472,7 @@ static inline int process_line(struct selabel_handle *rec,
 	spec_arr[nspec].mode = 0;
 
 	spec_arr[nspec].lr.ctx_raw = context;
+	spec_arr[nspec].lr.lineno = lineno;
 
 	/*
 	 * bump data->nspecs to cause closef() to cover it in its free
libselinux/src/label_internal.h +1 -0
index 75451858..b0d05882 100644
@@ -73,6 +73,7 @@ struct selabel_lookup_rec {
 	char * ctx_raw;
 	char * ctx_trans;
 	int validated;
+	unsigned lineno;
 };
 
 struct selabel_handle {
Signature · 1 line
2.14.3
#3 lore raw
In reply to Yuli Khodorkovskiy
Quoted 25 lines · Yuli Khodorkovskiy

In permissive, if a bad label is written to a file_context file, restorecon will not verify the label before succesfully applying the context. These patches fix validation of labels during restorecon while not breaking current behavior of lazy validation.

Changes since V1:
- Continue using lazy validation for restorecon that was broken in V1 of the patch.
- Add line number tracking for error messages in restorecon.

Changes since V2:
- Fix compiler error caused by unused variable in selabel_validate()

Yuli Khodorkovskiy (2):
libselinux: verify file_contexts when using restorecon
libselinux: echo line number of bad label in selabel_fini()

 libselinux/src/label.c                  | 7 +++----
 libselinux/src/label_backends_android.c | 2 +-
 libselinux/src/label_file.c             | 2 +-
 libselinux/src/label_file.h             | 3 ++-
 libselinux/src/label_internal.h         | 7 +++----
 libselinux/src/matchpathcon.c           | 5 ++---
 6 files changed, 12 insertions(+), 14 deletions(-)
Quoted 4 lines

--
2.14.3

These look good to me and pass all my testing. I have them on github passing CI as well:
https://github.com/SELinuxProject/selinux/pull/90

ack. Unless someone finds an issue, will merge
on 4/3.

#4 lore raw
Quoted 31 lines · William Roberts
Quoted 25 lines · Yuli Khodorkovskiy

In permissive, if a bad label is written to a file_context file, restorecon will not verify the label before succesfully applying the context. These patches fix validation of labels during restorecon while not breaking current behavior of lazy validation.

Changes since V1:
- Continue using lazy validation for restorecon that was broken in V1 of the patch.
- Add line number tracking for error messages in restorecon.

Changes since V2:
- Fix compiler error caused by unused variable in selabel_validate()

Yuli Khodorkovskiy (2):
libselinux: verify file_contexts when using restorecon
libselinux: echo line number of bad label in selabel_fini()

 libselinux/src/label.c                  | 7 +++----
 libselinux/src/label_backends_android.c | 2 +-
 libselinux/src/label_file.c             | 2 +-
 libselinux/src/label_file.h             | 3 ++-
 libselinux/src/label_internal.h         | 7 +++----
 libselinux/src/matchpathcon.c           | 5 ++---
 6 files changed, 12 insertions(+), 14 deletions(-)
Quoted 4 lines

--
2.14.3

Quoted 6 lines

These look good to me and pass all my testing. I have them on github passing CI as well:
https://github.com/SELinuxProject/selinux/pull/90

ack. Unless someone finds an issue, will merge
on 4/3.

merged. Thank you.