From 02685906d3afa4f7c72d86cf99242e3b08078865 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 17 Nov 2020 14:32:11 +0100 Subject: [PATCH] crypto: aegis128 - wipe plaintext and tag if decryption fails The AEGIS spec mentions explicitly that the security guarantees hold only if the resulting plaintext and tag of a failed decryption are withheld. So ensure that we abide by this. While at it, drop the unused struct aead_request *req parameter from crypto_aegis128_process_crypt(). Reviewed-by: Ondrej Mosnacek Signed-off-by: Ard Biesheuvel Signed-off-by: Herbert Xu --- crypto/aegis128-core.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/crypto/aegis128-core.c b/crypto/aegis128-core.c index 44fb4956f0dd..3a71235892f5 100644 --- a/crypto/aegis128-core.c +++ b/crypto/aegis128-core.c @@ -154,6 +154,12 @@ static void crypto_aegis128_ad(struct aegis_state *state, } } +static void crypto_aegis128_wipe_chunk(struct aegis_state *state, u8 *dst, + const u8 *src, unsigned int size) +{ + memzero_explicit(dst, size); +} + static void crypto_aegis128_encrypt_chunk(struct aegis_state *state, u8 *dst, const u8 *src, unsigned int size) { @@ -324,7 +330,6 @@ static void crypto_aegis128_process_ad(struct aegis_state *state, static __always_inline int crypto_aegis128_process_crypt(struct aegis_state *state, - struct aead_request *req, struct skcipher_walk *walk, void (*crypt)(struct aegis_state *state, u8 *dst, const u8 *src, @@ -403,14 +408,14 @@ static int crypto_aegis128_encrypt(struct aead_request *req) if (aegis128_do_simd()) { crypto_aegis128_init_simd(&state, &ctx->key, req->iv); crypto_aegis128_process_ad(&state, req->src, req->assoclen); - crypto_aegis128_process_crypt(&state, req, &walk, + crypto_aegis128_process_crypt(&state, &walk, crypto_aegis128_encrypt_chunk_simd); crypto_aegis128_final_simd(&state, &tag, req->assoclen, cryptlen); } else { crypto_aegis128_init(&state, &ctx->key, req->iv); crypto_aegis128_process_ad(&state, req->src, req->assoclen); - crypto_aegis128_process_crypt(&state, req, &walk, + crypto_aegis128_process_crypt(&state, &walk, crypto_aegis128_encrypt_chunk); crypto_aegis128_final(&state, &tag, req->assoclen, cryptlen); } @@ -438,19 +443,34 @@ static int crypto_aegis128_decrypt(struct aead_request *req) if (aegis128_do_simd()) { crypto_aegis128_init_simd(&state, &ctx->key, req->iv); crypto_aegis128_process_ad(&state, req->src, req->assoclen); - crypto_aegis128_process_crypt(&state, req, &walk, + crypto_aegis128_process_crypt(&state, &walk, crypto_aegis128_decrypt_chunk_simd); crypto_aegis128_final_simd(&state, &tag, req->assoclen, cryptlen); } else { crypto_aegis128_init(&state, &ctx->key, req->iv); crypto_aegis128_process_ad(&state, req->src, req->assoclen); - crypto_aegis128_process_crypt(&state, req, &walk, + crypto_aegis128_process_crypt(&state, &walk, crypto_aegis128_decrypt_chunk); crypto_aegis128_final(&state, &tag, req->assoclen, cryptlen); } - return crypto_memneq(tag.bytes, zeros, authsize) ? -EBADMSG : 0; + if (unlikely(crypto_memneq(tag.bytes, zeros, authsize))) { + /* + * From Chapter 4. 'Security Analysis' of the AEGIS spec [0] + * + * "3. If verification fails, the decrypted plaintext and the + * wrong authentication tag should not be given as output." + * + * [0] https://competitions.cr.yp.to/round3/aegisv11.pdf + */ + skcipher_walk_aead_decrypt(&walk, req, false); + crypto_aegis128_process_crypt(NULL, &walk, + crypto_aegis128_wipe_chunk); + memzero_explicit(&tag, sizeof(tag)); + return -EBADMSG; + } + return 0; } static struct aead_alg crypto_aegis128_alg = {