crypto: user - fix info leaks in report API

commit 9a5467bf7b6e9e02ec9c3da4e23747c05faeaac6 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
index f1ea0a064135..910497bd72be 100644
--- a/crypto/crypto_user.c
+++ b/crypto/crypto_user.c
@@ -75,7 +75,7 @@ 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;
@@ -94,8 +94,7 @@ 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));
 	NLA_PUT(skb, CRYPTOCFGA_REPORT_COMPRESS,
 		sizeof(struct crypto_report_comp), &rcomp);
 
@@ -108,12 +107,14 @@ nla_put_failure:
 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);
 
@@ -122,8 +123,7 @@ static int crypto_report_one(struct crypto_alg *alg,
 	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));
 		NLA_PUT(skb, CRYPTOCFGA_REPORT_LARVAL,
 			sizeof(struct crypto_report_larval), &rl);