Commit e57121d0 authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu

crypto: chacha20poly1305 - validate the digest size

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

Fix it by, when instantiating the template, requiring that the
underlying hash algorithm has the digest size expected for Poly1305.


    #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: default avatarsyzbot <>
Fixes: 71ebc4d1 ("crypto: chacha20poly1305 - Add a ChaCha20-Poly1305 AEAD construction, RFC7539")
Cc: <> # v4.2+
Signed-off-by: default avatarEric Biggers <>
Signed-off-by: default avatarHerbert Xu <>
parent d042566d
......@@ -610,6 +610,11 @@ static int chachapoly_create(struct crypto_template *tmpl, struct rtattr **tb,
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 crypto_template *tmpl, struct rtattr **tb,
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,
if (err)
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