[PATCH 0/2] Fix AppArmor issues found through static analysis

[PATCH 0/2] Fix AppArmor issues found through static analysis

[Tyler Hicks]

This set fixes three issues, discovered by CoverityScan, that I don't
believe are serious in practice but are worth fixing to make the
AppArmor code more robust and prevent them from becoming more serious
issues in the future. The first patch fixes possible out of bounds
access issues when mapping a permissions mask to a string. The second
fixes an uninitialized struct that could have some of its contents
leaked to userspace during a permissions query.

I've tested the patches with the AppArmor regression test suite. The
test results are the same with and without these patches applied. There
are identical failures, in both situations, from the aa_policy_cache
test but that's likely due to some unrelated, recent changes in the
AppArmor userspace code.

Tyler

[PATCH 1/2] apparmor: Check buffer bounds when mapping permissions mask

[Tyler Hicks]

Don't read past the end of the buffer containing permissions
characters or write past the end of the destination string.

Detected by CoverityScan CID#1415361, 1415376 ("Out-of-bounds access")

Fixes: e53cfe6c7caa ("apparmor: rework perm mapping to a slightly broader set")
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
 security/apparmor/file.c          |  3 ++-
 security/apparmor/include/perms.h |  3 ++-
 security/apparmor/lib.c           | 17 +++++++++++++----
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index 224b2fef93ca..4285943f7260 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -47,7 +47,8 @@ static void audit_file_mask(struct audit_buffer *ab, u32 mask)
 {
 	char str[10];
 
-	aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
+	aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
+			    map_mask_to_chr_mask(mask));
 	audit_log_string(ab, str);
 }
 
diff --git a/security/apparmor/include/perms.h b/security/apparmor/include/perms.h
index 38aa6247d00f..b94ec114d1a4 100644
--- a/security/apparmor/include/perms.h
+++ b/security/apparmor/include/perms.h
@@ -137,7 +137,8 @@ extern struct aa_perms allperms;
 	xcheck(fn_for_each((L1), (P), (FN1)), fn_for_each((L2), (P), (FN2)))
 
 
-void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask);
+void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs,
+			 u32 mask);
 void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
 			 u32 mask);
 void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
diff --git a/security/apparmor/lib.c b/security/apparmor/lib.c
index a7b3f681b80e..7ab368c3789b 100644
--- a/security/apparmor/lib.c
+++ b/security/apparmor/lib.c
@@ -198,15 +198,24 @@ const char *aa_file_perm_names[] = {
 /**
  * aa_perm_mask_to_str - convert a perm mask to its short string
  * @str: character buffer to store string in (at least 10 characters)
+ * @str_size: size of the @str buffer
+ * @chrs: NUL-terminated character buffer of permission characters
  * @mask: permission mask to convert
  */
-void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask)
+void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs, u32 mask)
 {
 	unsigned int i, perm = 1;
+	size_t num_chrs = strlen(chrs);
+
+	for (i = 0; i < num_chrs; perm <<= 1, i++) {
+		if (mask & perm) {
+			/* Ensure that one byte is left for NUL-termination */
+			if (WARN_ON_ONCE(str_size <= 1))
+				continue;
 
-	for (i = 0; i < 32; perm <<= 1, i++) {
-		if (mask & perm)
 			*str++ = chrs[i];
+			str_size--;
+		}
 	}
 	*str = '\0';
 }
@@ -236,7 +245,7 @@ void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
 
 	audit_log_format(ab, "\"");
 	if ((mask & chrsmask) && chrs) {
-		aa_perm_mask_to_str(str, chrs, mask & chrsmask);
+		aa_perm_mask_to_str(str, sizeof(str), chrs, mask & chrsmask);
 		mask &= ~chrsmask;
 		audit_log_format(ab, "%s", str);
 		if (mask & namesmask)
-- 
2.7.4

[PATCH 2/2] apparmor: Fully initialize aa_perms struct when answering userspace query

[Tyler Hicks]

Fully initialize the aa_perms struct in profile_query_cb() to avoid the
potential of using an uninitialized struct member's value in a response
to a query from userspace.

Detected by CoverityScan CID#1415126 ("Uninitialized scalar variable")

Fixes: 4f3b3f2d79a4 ("apparmor: add profile permission query ability")
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
 security/apparmor/apparmorfs.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 949dd8a48164..e09fe4d7307c 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -603,7 +603,7 @@ static const struct file_operations aa_fs_ns_revision_fops = {
 static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
 			     const char *match_str, size_t match_len)
 {
-	struct aa_perms tmp;
+	struct aa_perms tmp = { };
 	struct aa_dfa *dfa;
 	unsigned int state = 0;
 
@@ -613,7 +613,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
 		dfa = profile->file.dfa;
 		state = aa_dfa_match_len(dfa, profile->file.start,
 					 match_str + 1, match_len - 1);
-		tmp = nullperms;
 		if (state) {
 			struct path_cond cond = { };
 
@@ -627,8 +626,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
 					 match_str, match_len);
 		if (state)
 			aa_compute_perms(dfa, state, &tmp);
-		else
-			tmp = nullperms;
 	}
 	aa_apply_modes_to_perms(profile, &tmp);
 	aa_perms_accum_raw(perms, &tmp);
-- 
2.7.4

Re: [PATCH 1/2] apparmor: Check buffer bounds when mapping permissions mask

[Serge E. Hallyn]

Quoting Tyler Hicks (tyhicks@canonical.com):
> Don't read past the end of the buffer containing permissions
> characters or write past the end of the destination string.
> 
> Detected by CoverityScan CID#1415361, 1415376 ("Out-of-bounds access")
> 
> Fixes: e53cfe6c7caa ("apparmor: rework perm mapping to a slightly broader set")
> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

Acked-by: Serge Hallyn <serge@hallyn.com>

> ---
>  security/apparmor/file.c          |  3 ++-
>  security/apparmor/include/perms.h |  3 ++-
>  security/apparmor/lib.c           | 17 +++++++++++++----
>  3 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/security/apparmor/file.c b/security/apparmor/file.c
> index 224b2fef93ca..4285943f7260 100644
> --- a/security/apparmor/file.c
> +++ b/security/apparmor/file.c
> @@ -47,7 +47,8 @@ static void audit_file_mask(struct audit_buffer *ab, u32 mask)
>  {
>  	char str[10];
>  
> -	aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
> +	aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
> +			    map_mask_to_chr_mask(mask));
>  	audit_log_string(ab, str);
>  }
>  
> diff --git a/security/apparmor/include/perms.h b/security/apparmor/include/perms.h
> index 38aa6247d00f..b94ec114d1a4 100644
> --- a/security/apparmor/include/perms.h
> +++ b/security/apparmor/include/perms.h
> @@ -137,7 +137,8 @@ extern struct aa_perms allperms;
>  	xcheck(fn_for_each((L1), (P), (FN1)), fn_for_each((L2), (P), (FN2)))
>  
>  
> -void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask);
> +void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs,
> +			 u32 mask);
>  void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
>  			 u32 mask);
>  void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
> diff --git a/security/apparmor/lib.c b/security/apparmor/lib.c
> index a7b3f681b80e..7ab368c3789b 100644
> --- a/security/apparmor/lib.c
> +++ b/security/apparmor/lib.c
> @@ -198,15 +198,24 @@ const char *aa_file_perm_names[] = {
>  /**
>   * aa_perm_mask_to_str - convert a perm mask to its short string
>   * @str: character buffer to store string in (at least 10 characters)
> + * @str_size: size of the @str buffer
> + * @chrs: NUL-terminated character buffer of permission characters
>   * @mask: permission mask to convert
>   */
> -void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask)
> +void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs, u32 mask)
>  {
>  	unsigned int i, perm = 1;
> +	size_t num_chrs = strlen(chrs);
> +
> +	for (i = 0; i < num_chrs; perm <<= 1, i++) {
> +		if (mask & perm) {
> +			/* Ensure that one byte is left for NUL-termination */
> +			if (WARN_ON_ONCE(str_size <= 1))
> +				continue;
>  
> -	for (i = 0; i < 32; perm <<= 1, i++) {
> -		if (mask & perm)
>  			*str++ = chrs[i];
> +			str_size--;
> +		}
>  	}
>  	*str = '\0';
>  }
> @@ -236,7 +245,7 @@ void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
>  
>  	audit_log_format(ab, "\"");
>  	if ((mask & chrsmask) && chrs) {
> -		aa_perm_mask_to_str(str, chrs, mask & chrsmask);
> +		aa_perm_mask_to_str(str, sizeof(str), chrs, mask & chrsmask);
>  		mask &= ~chrsmask;
>  		audit_log_format(ab, "%s", str);
>  		if (mask & namesmask)
> -- 
> 2.7.4

Re: [PATCH 2/2] apparmor: Fully initialize aa_perms struct when answering userspace query

[Serge E. Hallyn]

Quoting Tyler Hicks (tyhicks@canonical.com):
> Fully initialize the aa_perms struct in profile_query_cb() to avoid the
> potential of using an uninitialized struct member's value in a response
> to a query from userspace.
> 
> Detected by CoverityScan CID#1415126 ("Uninitialized scalar variable")
> 
> Fixes: 4f3b3f2d79a4 ("apparmor: add profile permission query ability")
> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

Acked-by: Serge Hallyn <serge@hallyn.com>

> ---
>  security/apparmor/apparmorfs.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
> index 949dd8a48164..e09fe4d7307c 100644
> --- a/security/apparmor/apparmorfs.c
> +++ b/security/apparmor/apparmorfs.c
> @@ -603,7 +603,7 @@ static const struct file_operations aa_fs_ns_revision_fops = {
>  static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  			     const char *match_str, size_t match_len)
>  {
> -	struct aa_perms tmp;
> +	struct aa_perms tmp = { };
>  	struct aa_dfa *dfa;
>  	unsigned int state = 0;
>  
> @@ -613,7 +613,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  		dfa = profile->file.dfa;
>  		state = aa_dfa_match_len(dfa, profile->file.start,
>  					 match_str + 1, match_len - 1);
> -		tmp = nullperms;
>  		if (state) {
>  			struct path_cond cond = { };
>  
> @@ -627,8 +626,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  					 match_str, match_len);
>  		if (state)
>  			aa_compute_perms(dfa, state, &tmp);
> -		else
> -			tmp = nullperms;
>  	}
>  	aa_apply_modes_to_perms(profile, &tmp);
>  	aa_perms_accum_raw(perms, &tmp);
> -- 
> 2.7.4

Re: [PATCH 1/2] apparmor: Check buffer bounds when mapping permissions mask

[John Johansen]

On 07/05/2018 10:25 PM, Tyler Hicks wrote:
> Don't read past the end of the buffer containing permissions
> characters or write past the end of the destination string.
> 
> Detected by CoverityScan CID#1415361, 1415376 ("Out-of-bounds access")
> 
> Fixes: e53cfe6c7caa ("apparmor: rework perm mapping to a slightly broader set")
> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

I've pulled this into apparmor-next with a minor modification noted below

>  security/apparmor/file.c          |  3 ++-
>  security/apparmor/include/perms.h |  3 ++-
>  security/apparmor/lib.c           | 17 +++++++++++++----
>  3 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/security/apparmor/file.c b/security/apparmor/file.c
> index 224b2fef93ca..4285943f7260 100644
> --- a/security/apparmor/file.c
> +++ b/security/apparmor/file.c
> @@ -47,7 +47,8 @@ static void audit_file_mask(struct audit_buffer *ab, u32 mask)
>  {
>  	char str[10];
>  
> -	aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
> +	aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
> +			    map_mask_to_chr_mask(mask));
>  	audit_log_string(ab, str);
>  }
>  
> diff --git a/security/apparmor/include/perms.h b/security/apparmor/include/perms.h
> index 38aa6247d00f..b94ec114d1a4 100644
> --- a/security/apparmor/include/perms.h
> +++ b/security/apparmor/include/perms.h
> @@ -137,7 +137,8 @@ extern struct aa_perms allperms;
>  	xcheck(fn_for_each((L1), (P), (FN1)), fn_for_each((L2), (P), (FN2)))
>  
>  
> -void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask);
> +void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs,
> +			 u32 mask);
>  void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
>  			 u32 mask);
>  void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
> diff --git a/security/apparmor/lib.c b/security/apparmor/lib.c
> index a7b3f681b80e..7ab368c3789b 100644
> --- a/security/apparmor/lib.c
> +++ b/security/apparmor/lib.c
> @@ -198,15 +198,24 @@ const char *aa_file_perm_names[] = {
>  /**
>   * aa_perm_mask_to_str - convert a perm mask to its short string
>   * @str: character buffer to store string in (at least 10 characters)
> + * @str_size: size of the @str buffer
> + * @chrs: NUL-terminated character buffer of permission characters
>   * @mask: permission mask to convert
>   */
> -void aa_perm_mask_to_str(char *str, const char *chrs, u32 mask)
> +void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs, u32 mask)
>  {
>  	unsigned int i, perm = 1;
> +	size_t num_chrs = strlen(chrs);
> +
> +	for (i = 0; i < num_chrs; perm <<= 1, i++> +		if (mask & perm) {
> +			/* Ensure that one byte is left for NUL-termination */
> +			if (WARN_ON_ONCE(str_size <= 1))
> +				continue;
might as well break here

>  
> -	for (i = 0; i < 32; perm <<= 1, i++) {
> -		if (mask & perm)
>  			*str++ = chrs[i];
> +			str_size--;
> +		}
>  	}
>  	*str = '\0';
>  }
> @@ -236,7 +245,7 @@ void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
>  
>  	audit_log_format(ab, "\"");
>  	if ((mask & chrsmask) && chrs) {
> -		aa_perm_mask_to_str(str, chrs, mask & chrsmask);
> +		aa_perm_mask_to_str(str, sizeof(str), chrs, mask & chrsmask);
>  		mask &= ~chrsmask;
>  		audit_log_format(ab, "%s", str);
>  		if (mask & namesmask)
> 

Re: [PATCH 2/2] apparmor: Fully initialize aa_perms struct when answering userspace query

[John Johansen]

On 07/05/2018 10:25 PM, Tyler Hicks wrote:
> Fully initialize the aa_perms struct in profile_query_cb() to avoid the
> potential of using an uninitialized struct member's value in a response
> to a query from userspace.
> 
> Detected by CoverityScan CID#1415126 ("Uninitialized scalar variable")
> 
> Fixes: 4f3b3f2d79a4 ("apparmor: add profile permission query ability"> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>

I've pulled this into apparmor-next

> ---
>  security/apparmor/apparmorfs.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
> index 949dd8a48164..e09fe4d7307c 100644
> --- a/security/apparmor/apparmorfs.c
> +++ b/security/apparmor/apparmorfs.c
> @@ -603,7 +603,7 @@ static const struct file_operations aa_fs_ns_revision_fops = {
>  static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  			     const char *match_str, size_t match_len)
>  {
> -	struct aa_perms tmp;
> +	struct aa_perms tmp = { };
>  	struct aa_dfa *dfa;
>  	unsigned int state = 0;
>  
> @@ -613,7 +613,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  		dfa = profile->file.dfa;
>  		state = aa_dfa_match_len(dfa, profile->file.start,
>  					 match_str + 1, match_len - 1);
> -		tmp = nullperms;
>  		if (state) {
>  			struct path_cond cond = { };
>  
> @@ -627,8 +626,6 @@ static void profile_query_cb(struct aa_profile *profile, struct aa_perms *perms,
>  					 match_str, match_len);
>  		if (state)
>  			aa_compute_perms(dfa, state, &tmp);
> -		else
> -			tmp = nullperms;
>  	}
>  	aa_apply_modes_to_perms(profile, &tmp);
>  	aa_perms_accum_raw(perms, &tmp);
>