Patch "crypto: chacha20poly1305 - validate the digest size" has been added to the 4.9-stable tree

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;a=summary

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 <[email protected]> know about it.

From: Eric Biggers <[email protected]>
Date: Mon, 11 Dec 2017 12:15:17 -0800
Subject: crypto: chacha20poly1305 - validate the digest size

From: Eric Biggers <[email protected]>

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);
    }

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

@@ -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 [email protected] are

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