4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Biggers <ebiggers@xxxxxxxxxx>
commit e57121d08c38dabec15cf3e1e2ad46721af30cae upstream.
If the rfc7539 template was instantiated with a hash algorithm with
digest size larger than 16 bytes (POLY1305_DIGEST_SIZE), then the digest
overran the 'tag' buffer in 'struct chachapoly_req_ctx', corrupting the
subsequent memory, including 'cryptlen'. This caused a crash during
crypto_skcipher_decrypt().
Fix it by, when instantiating the template, requiring that the
underlying hash algorithm has the digest size expected for Poly1305.
Reproducer:
#include <linux/if_alg.h>
#include <sys/socket.h>
#include <unistd.h>
int main()
{
int algfd, reqfd;
struct sockaddr_alg addr = {
.salg_type = "aead",
.salg_name = "rfc7539(chacha20,sha256)",
};
unsigned char buf[32] = { 0 };
algfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
bind(algfd, (void *)&addr, sizeof(addr));
setsockopt(algfd, SOL_ALG, ALG_SET_KEY, buf, sizeof(buf));
reqfd = accept(algfd, 0, 0);
write(reqfd, buf, 16);
read(reqfd, buf, 16);
}
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Fixes: 71ebc4d1b27d ("crypto: chacha20poly1305 - Add a ChaCha20-Poly1305 AEAD construction, RFC7539")
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
crypto/chacha20poly1305.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/crypto/chacha20poly1305.c
+++ b/crypto/chacha20poly1305.c
@@ -600,6 +600,11 @@ static int chachapoly_create(struct cryp
CRYPTO_ALG_TYPE_AHASH_MASK);
if (IS_ERR(poly))
return PTR_ERR(poly);
+ poly_hash = __crypto_hash_alg_common(poly);
+
+ err = -EINVAL;
+ if (poly_hash->digestsize != POLY1305_DIGEST_SIZE)
+ goto out_put_poly;
err = -ENOMEM;
inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
@@ -608,7 +613,6 @@ static int chachapoly_create(struct cryp
ctx = aead_instance_ctx(inst);
ctx->saltlen = CHACHAPOLY_IV_SIZE - ivsize;
- poly_hash = __crypto_hash_alg_common(poly);
err = crypto_init_ahash_spawn(&ctx->poly, poly_hash,
aead_crypto_instance(inst));
if (err)