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 <omosnacek@xxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
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 = {
--
2.17.1
