tls: simplify aesgcm_GHASH()

function                                             old     new   delta
xwrite_encrypted                                     604     599      -5
FlattenSzInBits                                       52       -     -52
aesgcm_GHASH                                         395     262    -133
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 0/2 up/down: 0/-190)           Total: -190 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 14 insertions, 16 deletions

diff --git a/networking/tls.c b/networking/tls.c
index 23622d76e..3b4f1b7e2 100644
--- a/networking/tls.c
+++ b/networking/tls.c
@@ -270,7 +270,7 @@ struct record_hdr {
 enum {
         NEED_EC_KEY            = 1 << 0,
         GOT_CERT_RSA_KEY_ALG   = 1 << 1,
-        GOT_CERT_ECDSA_KEY_ALG = 1 << 2,
+        GOT_CERT_ECDSA_KEY_ALG = 1 << 2,
         GOT_EC_KEY             = 1 << 3,
         ENCRYPTION_AESGCM      = 1 << 4,
 };
@@ -756,7 +756,6 @@ static void xwrite_encrypted_and_hmac_signed(tls_state_t *tls, unsigned size, un
         } while ((size & (AES_BLOCK_SIZE - 1)) != 0);
 
         /* Encrypt content+MAC+padding in place */
-//optimize key setup
         aes_cbc_encrypt(
                 &tls->aes_decrypt, /* selects 128/256 */
                 buf - AES_BLOCK_SIZE, /* IV */
@@ -787,8 +786,9 @@ static void xwrite_encrypted_and_hmac_signed(tls_state_t *tls, unsigned size, un
  */
 static void xwrite_encrypted_aesgcm(tls_state_t *tls, unsigned size, unsigned type)
 {
-//go for [16]
-        uint8_t aad[13];
+#define COUNTER(v) (*(uint32_t*)(v + 12))
+
+        uint8_t aad[13 + 3];   /* +3 creates [16] buffer, simplifying GHASH() */
         uint8_t nonce[12 + 4]; /* +4 creates space for AES block counter */
         uint8_t scratch[AES_BLOCK_SIZE]; //[16]
         uint8_t authtag[AES_BLOCK_SIZE]; //[16]
@@ -807,7 +807,8 @@ static void xwrite_encrypted_aesgcm(tls_state_t *tls, unsigned size, unsigned ty
         aad[9] = TLS_MAJ;
         aad[10] = TLS_MIN;
         aad[11] = size >> 8;
-        aad[12] = size & 0xff;
+        /* set aad[12], and clear aad[13..15] */
+        COUNTER(aad) = SWAP_LE32(size & 0xff);
 
         memcpy(nonce,     tls->client_write_IV, 4);
         memcpy(nonce + 4, &tls->write_seq64_be, 8);
@@ -817,8 +818,6 @@ static void xwrite_encrypted_aesgcm(tls_state_t *tls, unsigned size, unsigned ty
         /* seq64 is not used later in this func, can increment here */
         tls->write_seq64_be = SWAP_BE64(1 + SWAP_BE64(tls->write_seq64_be));
 
-#define COUNTER(v) (*(uint32_t*)(v + 12))
-
         cnt = 1;
         remaining = size;
         while (remaining != 0) {
@@ -833,8 +832,7 @@ static void xwrite_encrypted_aesgcm(tls_state_t *tls, unsigned size, unsigned ty
                 remaining -= n;
         }
 
-//optimize fixed sizes
-        aesgcm_GHASH(tls->H, aad, sizeof(aad), tls->outbuf + OUTBUF_PFX, size, authtag, sizeof(authtag));
+        aesgcm_GHASH(tls->H, aad, /*sizeof(aad),*/ tls->outbuf + OUTBUF_PFX, size, authtag /*, sizeof(authtag)*/);
         COUNTER(nonce) = htonl(1);
         aes_encrypt_one_block(&tls->aes_encrypt, nonce, scratch);
         xorbuf(authtag, scratch, sizeof(authtag));
@@ -923,8 +921,9 @@ static const char *alert_text(int code)
 
 static void tls_aesgcm_decrypt(tls_state_t *tls, uint8_t *buf, int size)
 {
-//go for [16]
-        //uint8_t aad[13];
+#define COUNTER(v) (*(uint32_t*)(v + 12))
+
+        //uint8_t aad[13 + 3]; /* +3 creates [16] buffer, simplifying GHASH() */
         uint8_t nonce[12 + 4]; /* +4 creates space for AES block counter */
         uint8_t scratch[AES_BLOCK_SIZE]; //[16]
         //uint8_t authtag[AES_BLOCK_SIZE]; //[16]
@@ -935,14 +934,14 @@ static void tls_aesgcm_decrypt(tls_state_t *tls, uint8_t *buf, int size)
         //aad[9] = TLS_MAJ;
         //aad[10] = TLS_MIN;
         //aad[11] = size >> 8;
-        //aad[12] = size & 0xff;
+        ///* set aad[12], and clear aad[13..15] */
+        //COUNTER(aad) = SWAP_LE32(size & 0xff);
 
+        //memcpy(aad,       &tls->write_seq64_be, 8);
         memcpy(nonce,     tls->server_write_IV, 4);
         memcpy(nonce + 4, buf, 8);
         buf += 8;
 
-#define COUNTER(v) (*(uint32_t*)(v + 12))
-
         cnt = 1;
         remaining = size;
         while (remaining != 0) {
@@ -957,8 +956,7 @@ static void tls_aesgcm_decrypt(tls_state_t *tls, uint8_t *buf, int size)
                 remaining -= n;
         }
 
-////optimize fixed sizes
-        //aesgcm_GHASH(tls->H, aad, sizeof(aad), tls->outbuf + OUTBUF_PFX, size, authtag, sizeof(authtag));
+        //aesgcm_GHASH(tls->H, aad, tls->outbuf + OUTBUF_PFX, size, authtag);
         //COUNTER(nonce) = htonl(1);
         //aes_encrypt_one_block(&tls->aes_encrypt, nonce, scratch);
         //xorbuf(authtag, scratch, sizeof(authtag));