CVE-2013-2546: Cryptographic Issues (CWE-310)
value: The report API in the crypto user configuration API in the Linux kernel through 3.8.2 uses an incorrect C library function for copying strings, which allows local users to obtain sensitive information from kernel stack memory by leveraging the CAP_NET_ADMIN capability.
CWE description: Weaknesses in this category are related to the design and implementation of data confidentiality and integrity. Frequently these deal with the use of encoding techniques, encryption libraries, and hashing algorithms. The weaknesses in this category could lead to a degradation of the quality data if they are not addressed.
Published: 2013-03-15T20:55Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: crypto/ablkcipher.c, crypto/aead.c, crypto/ahash.c, crypto/blkcipher.c, crypto/crypto_user.c, crypto/pcompress.c, crypto/rng.c, crypto/shash.c
Commit date: 2013-02-19 20:27:03 +0800
Commit message: crypto: user - fix info leaks in report API

Three errors resulting in kernel memory disclosure:

1/ The structures used for the netlink based crypto algorithm report API
are located on the stack. As snprintf() does not fill the remainder of
the buffer with null bytes, those stack bytes will be disclosed to users
of the API. Switch to strncpy() to fix this.

2/ crypto_report_one() does not initialize all field of struct
crypto_user_alg. Fix this to fix the heap info leak.

3/ For the module name we should copy only as many bytes as
module_name() returns -- not as much as the destination buffer could
hold. But the current code does not and therefore copies random data
from behind the end of the module name, as the module name is always
shorter than CRYPTO_MAX_ALG_NAME.

Also switch to use strncpy() to copy the algorithm's name and
driver_name. They are strings, after all.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Diff: diff --git a/crypto/ablkcipher.c b/crypto/ablkcipher.c
index 533de9550a8292..7d4a8d28277e18 100644
--- a/crypto/ablkcipher.c
+++ b/crypto/ablkcipher.c
@@ -386,13 +386,13 @@ static int crypto_init_ablkcipher_ops(struct crypto_tfm *tfm, u32 type,
 #ifdef CONFIG_NET
 static int crypto_ablkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_blkcipher rblkcipher;
 
-	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "ablkcipher");
-	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
-		 alg->cra_ablkcipher.geniv ?: "<default>");
+	strncpy(rblkcipher.type, "ablkcipher", sizeof(rblkcipher.type));
+	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
+		sizeof(rblkcipher.geniv));
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_ablkcipher.min_keysize;
 	rblkcipher.max_keysize = alg->cra_ablkcipher.max_keysize;
 	rblkcipher.ivsize = alg->cra_ablkcipher.ivsize;
@@ -467,13 +467,13 @@ static int crypto_init_givcipher_ops(struct crypto_tfm *tfm, u32 type,
 #ifdef CONFIG_NET
 static int crypto_givcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_blkcipher rblkcipher;
 
-	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "givcipher");
-	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
-		 alg->cra_ablkcipher.geniv ?: "<built-in>");
+	strncpy(rblkcipher.type, "givcipher", sizeof(rblkcipher.type));
+	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<built-in>",
+		sizeof(rblkcipher.geniv));
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_ablkcipher.min_keysize;
 	rblkcipher.max_keysize = alg->cra_ablkcipher.max_keysize;
 	rblkcipher.ivsize = alg->cra_ablkcipher.ivsize;
diff --git a/crypto/aead.c b/crypto/aead.c
index 4d04e12ffde837..547491e35c6373 100644
--- a/crypto/aead.c
+++ b/crypto/aead.c
@@ -115,13 +115,12 @@ static int crypto_init_aead_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
 static int crypto_aead_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_aead raead;
 	struct aead_alg *aead = &alg->cra_aead;
 
-	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "aead");
-	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s",
-		 aead->geniv ?: "<built-in>");
+	strncpy(raead.type, "aead", sizeof(raead.type));
+	strncpy(raead.geniv, aead->geniv ?: "<built-in>", sizeof(raead.geniv));
 
 	raead.blocksize = alg->cra_blocksize;
 	raead.maxauthsize = aead->maxauthsize;
 	raead.ivsize = aead->ivsize;
 
@@ -201,12 +200,12 @@ static int crypto_init_nivaead_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
 static int crypto_nivaead_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_aead raead;
 	struct aead_alg *aead = &alg->cra_aead;
 
-	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "nivaead");
-	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s", aead->geniv);
+	strncpy(raead.type, "nivaead", sizeof(raead.type));
+	strncpy(raead.geniv, aead->geniv, sizeof(raead.geniv));
 
 	raead.blocksize = alg->cra_blocksize;
 	raead.maxauthsize = aead->maxauthsize;
 	raead.ivsize = aead->ivsize;
 
diff --git a/crypto/ahash.c b/crypto/ahash.c
index 3887856c2dd684..793a27f2493e52 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -402,11 +402,11 @@ static unsigned int crypto_ahash_extsize(struct crypto_alg *alg)
 #ifdef CONFIG_NET
 static int crypto_ahash_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_hash rhash;
 
-	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "ahash");
+	strncpy(rhash.type, "ahash", sizeof(rhash.type));
 
 	rhash.blocksize = alg->cra_blocksize;
 	rhash.digestsize = __crypto_hash_alg_common(alg)->digestsize;
 
 	if (nla_put(skb, CRYPTOCFGA_REPORT_HASH,
diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c
index e9e7244d5ef5bc..a79e7e9ab86e89 100644
--- a/crypto/blkcipher.c
+++ b/crypto/blkcipher.c
@@ -497,13 +497,13 @@ static int crypto_init_blkcipher_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
 #ifdef CONFIG_NET
 static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_blkcipher rblkcipher;
 
-	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "blkcipher");
-	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
-		 alg->cra_blkcipher.geniv ?: "<default>");
+	strncpy(rblkcipher.type, "blkcipher", sizeof(rblkcipher.type));
+	strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
+		sizeof(rblkcipher.geniv));
 
 	rblkcipher.blocksize = alg->cra_blocksize;
 	rblkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
 	rblkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
 	rblkcipher.ivsize = alg->cra_blkcipher.ivsize;
diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
index 35d700a97d79bc..f6d9baf77f0a41 100644
--- a/crypto/crypto_user.c
+++ b/crypto/crypto_user.c
@@ -73,11 +73,11 @@ static struct crypto_alg *crypto_alg_match(struct crypto_user_alg *p, int exact)
 
 static int crypto_report_cipher(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_cipher rcipher;
 
-	snprintf(rcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "cipher");
+	strncpy(rcipher.type, "cipher", sizeof(rcipher.type));
 
 	rcipher.blocksize = alg->cra_blocksize;
 	rcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
 	rcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
 
@@ -92,12 +92,11 @@ static int crypto_report_cipher(struct sk_buff *skb, struct crypto_alg *alg)
 
 static int crypto_report_comp(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_comp rcomp;
 
-	snprintf(rcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "compression");
-
+	strncpy(rcomp.type, "compression", sizeof(rcomp.type));
 	if (nla_put(skb, CRYPTOCFGA_REPORT_COMPRESS,
 		    sizeof(struct crypto_report_comp), &rcomp))
 		goto nla_put_failure;
 	return 0;
 
@@ -106,26 +105,27 @@ static int crypto_report_comp(struct sk_buff *skb, struct crypto_alg *alg)
 }
 
 static int crypto_report_one(struct crypto_alg *alg,
 			     struct crypto_user_alg *ualg, struct sk_buff *skb)
 {
-	memcpy(&ualg->cru_name, &alg->cra_name, sizeof(ualg->cru_name));
-	memcpy(&ualg->cru_driver_name, &alg->cra_driver_name,
-	       sizeof(ualg->cru_driver_name));
-	memcpy(&ualg->cru_module_name, module_name(alg->cra_module),
-	       CRYPTO_MAX_ALG_NAME);
-
+	strncpy(ualg->cru_name, alg->cra_name, sizeof(ualg->cru_name));
+	strncpy(ualg->cru_driver_name, alg->cra_driver_name,
+		sizeof(ualg->cru_driver_name));
+	strncpy(ualg->cru_module_name, module_name(alg->cra_module),
+		sizeof(ualg->cru_module_name));
+
+	ualg->cru_type = 0;
+	ualg->cru_mask = 0;
 	ualg->cru_flags = alg->cra_flags;
 	ualg->cru_refcnt = atomic_read(&alg->cra_refcnt);
 
 	if (nla_put_u32(skb, CRYPTOCFGA_PRIORITY_VAL, alg->cra_priority))
 		goto nla_put_failure;
 	if (alg->cra_flags & CRYPTO_ALG_LARVAL) {
 		struct crypto_report_larval rl;
 
-		snprintf(rl.type, CRYPTO_MAX_ALG_NAME, "%s", "larval");
-
+		strncpy(rl.type, "larval", sizeof(rl.type));
 		if (nla_put(skb, CRYPTOCFGA_REPORT_LARVAL,
 			    sizeof(struct crypto_report_larval), &rl))
 			goto nla_put_failure;
 		goto out;
 	}
diff --git a/crypto/pcompress.c b/crypto/pcompress.c
index 04e083ff537352..7140fe70c7af04 100644
--- a/crypto/pcompress.c
+++ b/crypto/pcompress.c
@@ -51,12 +51,11 @@ static int crypto_pcomp_init_tfm(struct crypto_tfm *tfm)
 #ifdef CONFIG_NET
 static int crypto_pcomp_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_comp rpcomp;
 
-	snprintf(rpcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "pcomp");
-
+	strncpy(rpcomp.type, "pcomp", sizeof(rpcomp.type));
 	if (nla_put(skb, CRYPTOCFGA_REPORT_COMPRESS,
 		    sizeof(struct crypto_report_comp), &rpcomp))
 		goto nla_put_failure;
 	return 0;
 
diff --git a/crypto/rng.c b/crypto/rng.c
index f3b7894dec00ee..e0a25c2456de4f 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -63,11 +63,11 @@ static int crypto_init_rng_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
 #ifdef CONFIG_NET
 static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_rng rrng;
 
-	snprintf(rrng.type, CRYPTO_MAX_ALG_NAME, "%s", "rng");
+	strncpy(rrng.type, "rng", sizeof(rrng.type));
 
 	rrng.seedsize = alg->cra_rng.seedsize;
 
 	if (nla_put(skb, CRYPTOCFGA_REPORT_RNG,
 		    sizeof(struct crypto_report_rng), &rrng))
diff --git a/crypto/shash.c b/crypto/shash.c
index f426330f101755..929058a6856126 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -528,11 +528,12 @@ static unsigned int crypto_shash_extsize(struct crypto_alg *alg)
 static int crypto_shash_report(struct sk_buff *skb, struct crypto_alg *alg)
 {
 	struct crypto_report_hash rhash;
 	struct shash_alg *salg = __crypto_shash_alg(alg);
 
-	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "shash");
+	strncpy(rhash.type, "shash", sizeof(rhash.type));
+
 	rhash.blocksize = alg->cra_blocksize;
 	rhash.digestsize = salg->digestsize;
 
 	if (nla_put(skb, CRYPTOCFGA_REPORT_HASH,
 		    sizeof(struct crypto_report_hash), &rhash))

Vulnerable code: 	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "ablkcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_ablkcipher.geniv ?: "<default>");
	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "givcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_ablkcipher.geniv ?: "<built-in>");
	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "aead");
	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 aead->geniv ?: "<built-in>");
	snprintf(raead.type, CRYPTO_MAX_ALG_NAME, "%s", "nivaead");
	snprintf(raead.geniv, CRYPTO_MAX_ALG_NAME, "%s", aead->geniv);
	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "ahash");
	snprintf(rblkcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "blkcipher");
	snprintf(rblkcipher.geniv, CRYPTO_MAX_ALG_NAME, "%s",
		 alg->cra_blkcipher.geniv ?: "<default>");
	snprintf(rcipher.type, CRYPTO_MAX_ALG_NAME, "%s", "cipher");
	snprintf(rcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "compression");

	memcpy(&ualg->cru_name, &alg->cra_name, sizeof(ualg->cru_name));
	memcpy(&ualg->cru_driver_name, &alg->cra_driver_name,
	       sizeof(ualg->cru_driver_name));
	memcpy(&ualg->cru_module_name, module_name(alg->cra_module),
	       CRYPTO_MAX_ALG_NAME);

		snprintf(rl.type, CRYPTO_MAX_ALG_NAME, "%s", "larval");

	snprintf(rpcomp.type, CRYPTO_MAX_ALG_NAME, "%s", "pcomp");

	snprintf(rrng.type, CRYPTO_MAX_ALG_NAME, "%s", "rng");
	snprintf(rhash.type, CRYPTO_MAX_ALG_NAME, "%s", "shash");
Fixed code: 	strncpy(rblkcipher.type, "ablkcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<default>",
		sizeof(rblkcipher.geniv));
	strncpy(rblkcipher.type, "givcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_ablkcipher.geniv ?: "<built-in>",
		sizeof(rblkcipher.geniv));
	strncpy(raead.type, "aead", sizeof(raead.type));
	strncpy(raead.geniv, aead->geniv ?: "<built-in>", sizeof(raead.geniv));
	strncpy(raead.type, "nivaead", sizeof(raead.type));
	strncpy(raead.geniv, aead->geniv, sizeof(raead.geniv));
	strncpy(rhash.type, "ahash", sizeof(rhash.type));
	strncpy(rblkcipher.type, "blkcipher", sizeof(rblkcipher.type));
	strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
		sizeof(rblkcipher.geniv));
	strncpy(rcipher.type, "cipher", sizeof(rcipher.type));
	strncpy(rcomp.type, "compression", sizeof(rcomp.type));
	strncpy(ualg->cru_name, alg->cra_name, sizeof(ualg->cru_name));
	strncpy(ualg->cru_driver_name, alg->cra_driver_name,
		sizeof(ualg->cru_driver_name));
	strncpy(ualg->cru_module_name, module_name(alg->cra_module),
		sizeof(ualg->cru_module_name));

	ualg->cru_type = 0;
	ualg->cru_mask = 0;
		strncpy(rl.type, "larval", sizeof(rl.type));
	strncpy(rpcomp.type, "pcomp", sizeof(rpcomp.type));
	strncpy(rrng.type, "rng", sizeof(rrng.type));
	strncpy(rhash.type, "shash", sizeof(rhash.type));