Re: [PATCH v3 5/7] libsepol: fix overflow and 0 length allocations

James Carter <jwcart2@xxxxxxxxxxxxx> · Tue, 16 Aug 2016 09:10:12 -0400

On 08/15/2016 11:59 AM, william.c.roberts@xxxxxxxxx wrote:
From: William Roberts <william.c.roberts@xxxxxxxxx>

Throughout libsepol, values taken from sepolicy are used in
places where length == 0 or length == <saturated> matter,
find and fix these.

Also, correct any type mismatches noticed along the way.

Signed-off-by: William Roberts <william.c.roberts@xxxxxxxxx>
---
 libsepol/src/conditional.c    |  3 ++-
 libsepol/src/context.c        | 16 ++++++++-----
 libsepol/src/context_record.c | 52 ++++++++++++++++++++++++-------------------
 libsepol/src/module.c         | 13 +++++++++++
 libsepol/src/module_to_cil.c  |  4 +++-
 libsepol/src/policydb.c       | 52 ++++++++++++++++++++++++++++++++++++++++---
 libsepol/src/private.h        |  3 +++
 7 files changed, 110 insertions(+), 33 deletions(-)

diff --git a/libsepol/src/context_record.c b/libsepol/src/context_record.c
index ac2884a..fdf60a0 100644
--- a/libsepol/src/context_record.c
+++ b/libsepol/src/context_record.c
@@ -5,6 +5,7 @@

 #include "context_internal.h"
 #include "debug.h"
+#include "private.h"

 struct sepol_context {

@@ -284,39 +285,44 @@ int sepol_context_to_string(sepol_handle_t * handle,
 {

 	int rc;
-	const int user_sz = strlen(con->user);
-	const int role_sz = strlen(con->role);
-	const int type_sz = strlen(con->type);
-	const int mls_sz = (con->mls) ? strlen(con->mls) : 0;
-	const int total_sz = user_sz + role_sz + type_sz +
-	    mls_sz + ((con->mls) ? 3 : 2);
-
-	char *str = (char *)malloc(total_sz + 1);
-	if (!str)
-		goto omem;
+	char *str = NULL;
+	const size_t user_sz = strlen(con->user);
+	const size_t role_sz = strlen(con->role);
+	const size_t type_sz = strlen(con->type);
+	const size_t mls_sz = (con->mls) ? strlen(con->mls) : 0;
+	const size_t total_sz = user_sz + role_sz + type_sz +
+	    mls_sz + ((con->mls) ? 3 : 2) + 1;
+
+	if (zero_or_saturated(total_sz)) {
+		ERR(handle, "invalid size");
+		goto err;
+	}

+	str = (char *)malloc(total_sz);

Before, total_sz + 1 was malloc'd, so it made sense to check for saturation, but 
you add the 1 to total_sz before checking for saturation.

This case is also different in that multiple string lengths are being added, so 
overflow would be the real concern here, but I don't think that it is possible 
to overflow because of limits in checkpolicy (8K) and xattrs (64K).

Jim

+	if (!str) {
+		ERR(handle, "out of memory");
+		goto err;
+	}
 	if (con->mls) {
-		rc = snprintf(str, total_sz + 1, "%s:%s:%s:%s",
+		rc = snprintf(str, total_sz, "%s:%s:%s:%s",
 			      con->user, con->role, con->type, con->mls);
-		if (rc < 0 || (rc >= total_sz + 1)) {
-			ERR(handle, "print error");
-			goto err;
-		}
 	} else {
-		rc = snprintf(str, total_sz + 1, "%s:%s:%s",
+		rc = snprintf(str, total_sz, "%s:%s:%s",
 			      con->user, con->role, con->type);
-		if (rc < 0 || (rc >= total_sz + 1)) {
-			ERR(handle, "print error");
-			goto err;
-		}
+	}
+
+	/*
+	 * rc is >= 0 on the size_t cast and is safe to promote
+	 * to an unsigned value.
+	 */
+	if (rc < 0 || (size_t)rc >= total_sz) {
+		ERR(handle, "print error");
+		goto err;
 	}

 	*str_ptr = str;
 	return STATUS_SUCCESS;

-      omem:
-	ERR(handle, "out of memory");
-
       err:
 	ERR(handle, "could not convert context to string");
 	free(str);
diff --git a/libsepol/src/module.c b/libsepol/src/module.c
index 1665ede..f25df95 100644
--- a/libsepol/src/module.c
+++ b/libsepol/src/module.c
@@ -30,6 +30,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <limits.h>
+#include <inttypes.h>

 #define SEPOL_PACKAGE_SECTION_FC 0xf97cff90
 #define SEPOL_PACKAGE_SECTION_SEUSER 0x97cff91
@@ -793,6 +794,12 @@ int sepol_module_package_info(struct sepol_policy_file *spf, int *type,
 				goto cleanup;
 			}
 			len = le32_to_cpu(buf[0]);
+			if (zero_or_saturated(len)) {
+				ERR(file->handle,
+				    "invalid module name length: 0x%"PRIx32,
+				    len);
+				goto cleanup;
+			}
 			*name = malloc(len + 1);
 			if (!*name) {
 				ERR(file->handle, "out of memory");
@@ -814,6 +821,12 @@ int sepol_module_package_info(struct sepol_policy_file *spf, int *type,
 				goto cleanup;
 			}
 			len = le32_to_cpu(buf[0]);
+			if (zero_or_saturated(len)) {
+				ERR(file->handle,
+				    "invalid module version length: 0x%"PRIx32,
+				    len);
+				goto cleanup;
+			}
 			*version = malloc(len + 1);
 			if (!*version) {
 				ERR(file->handle, "out of memory");
diff --git a/libsepol/src/module_to_cil.c b/libsepol/src/module_to_cil.c
index 36f3b7d..fc65019 100644
--- a/libsepol/src/module_to_cil.c
+++ b/libsepol/src/module_to_cil.c
@@ -47,6 +47,8 @@
 #include <sepol/policydb/services.h>
 #include <sepol/policydb/util.h>

+#include "private.h"
+
 #ifdef __GNUC__
 #  define UNUSED(x) UNUSED_ ## x __attribute__((__unused__))
 #else
@@ -124,7 +126,7 @@ static int get_line(char **start, char *end, char **line)

 	for (len = 0; p < end && *p != '\n' && *p != '\0'; p++, len++);

-	if (len == 0) {
+	if (zero_or_saturated(len)) {
 		rc = 0;
 		goto exit;
 	}
diff --git a/libsepol/src/policydb.c b/libsepol/src/policydb.c
index 971793d..604e022 100644
--- a/libsepol/src/policydb.c
+++ b/libsepol/src/policydb.c
@@ -1911,6 +1911,9 @@ static int perm_read(policydb_t * p
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	perdatum->s.value = le32_to_cpu(buf[1]);

 	key = malloc(len + 1);
@@ -1949,6 +1952,9 @@ static int common_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	comdatum->s.value = le32_to_cpu(buf[1]);

 	if (symtab_init(&comdatum->permissions, PERM_SYMTAB_SIZE))
@@ -2092,7 +2098,11 @@ static int class_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
 	len2 = le32_to_cpu(buf[1]);
+	if (is_saturated(len2))
+		goto bad;
 	cladatum->s.value = le32_to_cpu(buf[2]);

 	if (symtab_init(&cladatum->permissions, PERM_SYMTAB_SIZE))
@@ -2199,6 +2209,9 @@ static int role_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	role->s.value = le32_to_cpu(buf[1]);
 	if (policydb_has_boundary_feature(p))
 		role->bounds = le32_to_cpu(buf[2]);
@@ -2287,6 +2300,9 @@ static int type_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
 		goto bad;

 	len = le32_to_cpu(buf[pos]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	typdatum->s.value = le32_to_cpu(buf[++pos]);
 	if (policydb_has_boundary_feature(p)) {
 		uint32_t properties;
@@ -2447,6 +2463,8 @@ int filename_trans_read(filename_trans_t **t, struct policy_file *fp)
 		if (rc < 0)
 			return -1;
 		len = le32_to_cpu(buf[0]);
+		if (zero_or_saturated(len))
+			return -1;

 		name = calloc(len + 1, sizeof(*name));
 		if (!name)
@@ -2556,6 +2574,9 @@ static int ocontext_read_xen(struct policydb_compat_info *info,
 				if (rc < 0)
 					return -1;
 				len = le32_to_cpu(buf[0]);
+				if (zero_or_saturated(len))
+					return -1;
+
 				c->u.name = malloc(len + 1);
 				if (!c->u.name)
 					return -1;
@@ -2618,6 +2639,8 @@ static int ocontext_read_selinux(struct policydb_compat_info *info,
 				if (rc < 0)
 					return -1;
 				len = le32_to_cpu(buf[0]);
+				if (zero_or_saturated(len))
+					return -1;
 				c->u.name = malloc(len + 1);
 				if (!c->u.name)
 					return -1;
@@ -2659,6 +2682,8 @@ static int ocontext_read_selinux(struct policydb_compat_info *info,
 					return -1;
 				c->v.behavior = le32_to_cpu(buf[0]);
 				len = le32_to_cpu(buf[1]);
+				if (zero_or_saturated(len))
+					return -1;
 				c->u.name = malloc(len + 1);
 				if (!c->u.name)
 					return -1;
@@ -2719,7 +2744,7 @@ static int genfs_read(policydb_t * p, struct policy_file *fp)
 	uint32_t buf[1];
 	size_t nel, nel2, len, len2;
 	genfs_t *genfs_p, *newgenfs, *genfs;
-	unsigned int i, j;
+	size_t i, j;
 	ocontext_t *l, *c, *newc = NULL;
 	int rc;

@@ -2733,6 +2758,8 @@ static int genfs_read(policydb_t * p, struct policy_file *fp)
 		if (rc < 0)
 			goto bad;
 		len = le32_to_cpu(buf[0]);
+		if (zero_or_saturated(len))
+			goto bad;
 		newgenfs = calloc(1, sizeof(genfs_t));
 		if (!newgenfs)
 			goto bad;
@@ -2778,6 +2805,8 @@ static int genfs_read(policydb_t * p, struct policy_file *fp)
 			if (rc < 0)
 				goto bad;
 			len = le32_to_cpu(buf[0]);
+			if (zero_or_saturated(len))
+				goto bad;
 			newc->u.name = malloc(len + 1);
 			if (!newc->u.name) {
 				goto bad;
@@ -2877,6 +2906,9 @@ static int user_read(policydb_t * p, hashtab_t h, struct policy_file *fp)
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	usrdatum->s.value = le32_to_cpu(buf[1]);
 	if (policydb_has_boundary_feature(p))
 		usrdatum->bounds = le32_to_cpu(buf[2]);
@@ -2960,6 +2992,9 @@ static int sens_read(policydb_t * p
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(len))
+		goto bad;
+
 	levdatum->isalias = le32_to_cpu(buf[1]);

 	key = malloc(len + 1);
@@ -3003,6 +3038,9 @@ static int cat_read(policydb_t * p
 		goto bad;

 	len = le32_to_cpu(buf[0]);
+	if(zero_or_saturated(len))
+		goto bad;
+
 	catdatum->s.value = le32_to_cpu(buf[1]);
 	catdatum->isalias = le32_to_cpu(buf[2]);

@@ -3339,6 +3377,8 @@ static int filename_trans_rule_read(filename_trans_rule_t ** r, struct policy_fi
 			return -1;

 		len = le32_to_cpu(buf[0]);
+		if (zero_or_saturated(len))
+			return -1;

 		ftr->name = malloc(len + 1);
 		if (!ftr->name)
@@ -3580,6 +3620,8 @@ static int scope_read(policydb_t * p, int symnum, struct policy_file *fp)
 	if (rc < 0)
 		goto cleanup;
 	key_len = le32_to_cpu(buf[0]);
+	if (zero_or_saturated(key_len))
+		goto cleanup;
 	key = malloc(key_len + 1);
 	if (!key)
 		goto cleanup;
@@ -3664,8 +3706,8 @@ int policydb_read(policydb_t * p, struct policy_file *fp, unsigned verbose)
 	}

 	len = buf[1];
-	if (len > POLICYDB_STRING_MAX_LENGTH) {
-		ERR(fp->handle, "policydb string length too long ");
+	if (len == 0 || len > POLICYDB_STRING_MAX_LENGTH) {
+		ERR(fp->handle, "policydb string length %s ", len ? "too long" : "zero");
 		return POLICYDB_ERROR;
 	}

@@ -3798,6 +3840,8 @@ int policydb_read(policydb_t * p, struct policy_file *fp, unsigned verbose)
 			goto bad;
 		}
 		len = le32_to_cpu(buf[0]);
+		if (zero_or_saturated(len))
+			goto bad;
 		if ((p->name = malloc(len + 1)) == NULL) {
 			goto bad;
 		}
@@ -3809,6 +3853,8 @@ int policydb_read(policydb_t * p, struct policy_file *fp, unsigned verbose)
 			goto bad;
 		}
 		len = le32_to_cpu(buf[0]);
+		if (zero_or_saturated(len))
+			goto bad;
 		if ((p->version = malloc(len + 1)) == NULL) {
 			goto bad;
 		}
diff --git a/libsepol/src/private.h b/libsepol/src/private.h
index 9c700c9..0beb4d4 100644
--- a/libsepol/src/private.h
+++ b/libsepol/src/private.h
@@ -45,6 +45,9 @@

 #define ARRAY_SIZE(x) (sizeof(x)/sizeof((x)[0]))

+#define is_saturated(x) (x == (typeof(x))-1)
+#define zero_or_saturated(x) ((x == 0) || is_saturated(x))
+
 /* Policy compatibility information. */
 struct policydb_compat_info {
 	unsigned int type;



--
James Carter <jwcart2@xxxxxxxxxxxxx>
National Security Agency
_______________________________________________
Selinux mailing list
Selinux@xxxxxxxxxxxxx
To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx.
To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.






