[PATCH v2 2/3] libselinux: bail out on path truncations

[Christian Göttsche <cgzones@xxxxxxxxxxxxxx>]

Bail out if computed paths based on user input are being truncated, to
avoid wrong files to be opened.

Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
v2:
  - drop now obsolete assert(3) statements
  - use size_t as type for length variables
---
 libselinux/src/booleans.c            |  9 +++------
 libselinux/src/get_initial_context.c |  8 ++++++--
 libselinux/src/stringrep.c           | 15 ++++++++++++---
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/libselinux/src/booleans.c b/libselinux/src/booleans.c
index ef1f64a0..dbcccd70 100644
--- a/libselinux/src/booleans.c
+++ b/libselinux/src/booleans.c
@@ -7,7 +7,6 @@
 
 #ifndef DISABLE_BOOL
 
-#include <assert.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -147,7 +146,7 @@ out:
 static int bool_open(const char *name, int flag) {
 	char *fname = NULL;
 	char *alt_name = NULL;
-	int len;
+	size_t len;
 	int fd = -1;
 	int ret;
 	char *ptr;
@@ -164,9 +163,8 @@ static int bool_open(const char *name, int flag) {
 		return -1;
 
 	ret = snprintf(fname, len, "%s%s%s", selinux_mnt, SELINUX_BOOL_DIR, name);
-	if (ret < 0)
+	if (ret < 0 || (size_t)ret >= len)
 		goto out;
-	assert(ret < len);
 
 	fd = open(fname, flag);
 	if (fd >= 0 || errno != ENOENT)
@@ -184,9 +182,8 @@ static int bool_open(const char *name, int flag) {
 	fname = ptr;
 
 	ret = snprintf(fname, len, "%s%s%s", selinux_mnt, SELINUX_BOOL_DIR, alt_name);
-	if (ret < 0)
+	if (ret < 0 || (size_t)ret >= len)
 		goto out;
-	assert(ret < len);
 
 	fd = open(fname, flag);
 out:
diff --git a/libselinux/src/get_initial_context.c b/libselinux/src/get_initial_context.c
index 97ae3dcf..87c8adfa 100644
--- a/libselinux/src/get_initial_context.c
+++ b/libselinux/src/get_initial_context.c
@@ -23,8 +23,12 @@ int security_get_initial_context_raw(const char * name, char ** con)
 		return -1;
 	}
 
-	snprintf(path, sizeof path, "%s%s%s", 
-		 selinux_mnt, SELINUX_INITCON_DIR, name);
+	ret = snprintf(path, sizeof path, "%s%s%s", selinux_mnt, SELINUX_INITCON_DIR, name);
+	if (ret < 0 || (size_t)ret >= sizeof path) {
+		errno = EOVERFLOW;
+		return -1;
+	}
+
 	fd = open(path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0)
 		return -1;
diff --git a/libselinux/src/stringrep.c b/libselinux/src/stringrep.c
index 592410e5..d2237d1c 100644
--- a/libselinux/src/stringrep.c
+++ b/libselinux/src/stringrep.c
@@ -82,7 +82,10 @@ static struct discover_class_node * discover_class(const char *s)
 		goto err2;
 
 	/* load up class index */
-	snprintf(path, sizeof path, "%s/class/%s/index", selinux_mnt,s);
+	ret = snprintf(path, sizeof path, "%s/class/%s/index", selinux_mnt,s);
+	if (ret < 0 || (size_t)ret >= sizeof path)
+		goto err3;
+
 	fd = open(path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0)
 		goto err3;
@@ -97,7 +100,10 @@ static struct discover_class_node * discover_class(const char *s)
 		goto err3;
 
 	/* load up permission indices */
-	snprintf(path, sizeof path, "%s/class/%s/perms",selinux_mnt,s);
+	ret = snprintf(path, sizeof path, "%s/class/%s/perms",selinux_mnt,s);
+	if (ret < 0 || (size_t)ret >= sizeof path)
+		goto err3;
+
 	dir = opendir(path);
 	if (dir == NULL)
 		goto err3;
@@ -107,7 +113,10 @@ static struct discover_class_node * discover_class(const char *s)
 		unsigned int value;
 		struct stat m;
 
-		snprintf(path, sizeof path, "%s/class/%s/perms/%s", selinux_mnt,s,dentry->d_name);
+		ret = snprintf(path, sizeof path, "%s/class/%s/perms/%s", selinux_mnt,s,dentry->d_name);
+		if (ret < 0 || (size_t)ret >= sizeof path)
+			goto err4;
+
 		fd = open(path, O_RDONLY | O_CLOEXEC);
 		if (fd < 0)
 			goto err4;
-- 
2.38.1