This is a note to let you know that I've just added the patch titled

crypto: chacha20poly1305 - validate the digest size

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: crypto-chacha20poly1305-validate-the-digest-size.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From e57121d08c38dabec15cf3e1e2ad46721af30cae Mon Sep 17 00:00:00 2001

From: Eric Biggers ebiggers@google.com Date: Mon, 11 Dec 2017 12:15:17 -0800 Subject: crypto: chacha20poly1305 - validate the digest size

From: Eric Biggers ebiggers@google.com

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@googlegroups.com Fixes: 71ebc4d1b27d ("crypto: chacha20poly1305 - Add a ChaCha20-Poly1305 AEAD construction, RFC7539") Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- crypto/chacha20poly1305.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/crypto/chacha20poly1305.c +++ b/crypto/chacha20poly1305.c @@ -610,6 +610,11 @@ static int chachapoly_create(struct cryp algt->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); @@ -618,7 +623,6 @@ 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)

Patches currently in stable-queue which might be from ebiggers@google.com are

queue-4.9/crypto-chacha20poly1305-validate-the-digest-size.patch queue-4.9/crypto-pcrypt-fix-freeing-pcrypt-instances.patch