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>

1 files changed, 4 insertions, 5 deletions

diff --git a/crypto/aead.c b/crypto/aead.c
index 4d04e12ffde8..547491e35c63 100644
--- a/crypto/aead.c
+++ b/crypto/aead.c
@@ -117,9 +117,8 @@ 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;
@@ -203,8 +202,8 @@ 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;