tls: in AES-CBC code, do not set key for every record - do it once

function                                             old     new   delta
aes_setkey                                            16     212    +196
tls_handshake                                       1941    1977     +36
aes_encrypt_1                                        382     396     +14
xwrite_encrypted                                     605     604      -1
tls_xread_record                                     659     656      -3
aes_encrypt_one_block                                 65      59      -6
aes_cbc_encrypt                                      172     121     -51
aesgcm_setkey                                         58       -     -58
aes_cbc_decrypt                                      958     881     -77
KeyExpansion                                         188       -    -188
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 3/5 up/down: 246/-384)         Total: -138 bytes

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

5 files changed, 28 insertions, 32 deletions

diff --git a/networking/tls.c b/networking/tls.c
index 38a965ad6..23622d76e 100644
--- a/networking/tls.c
+++ b/networking/tls.c
@@ -758,7 +758,7 @@ static void xwrite_encrypted_and_hmac_signed(tls_state_t *tls, unsigned size, un
         /* Encrypt content+MAC+padding in place */
 //optimize key setup
         aes_cbc_encrypt(
-                tls->client_write_key, tls->key_size, /* selects 128/256 */
+                &tls->aes_decrypt, /* selects 128/256 */
                 buf - AES_BLOCK_SIZE, /* IV */
                 buf, size, /* plaintext */
                 buf /* ciphertext */
@@ -1061,7 +1061,7 @@ static int tls_xread_record(tls_state_t *tls, const char *expected)
                         /* Decrypt content+MAC+padding, moving it over IV in the process */
                         sz -= AES_BLOCK_SIZE; /* we will overwrite IV now */
                         aes_cbc_decrypt(
-                                tls->server_write_key, tls->key_size, /* selects 128/256 */
+                                &tls->aes_decrypt, /* selects 128/256 */
                                 p, /* IV */
                                 p + AES_BLOCK_SIZE, sz, /* ciphertext */
                                 p /* plaintext */
@@ -1934,8 +1934,14 @@ static void send_client_key_exchange(tls_state_t *tls)
                 dump_hex("client_write_IV:%s\n",
                         tls->client_write_IV, tls->IV_size
                 );
-                aesgcm_setkey(tls->H, &tls->aes_encrypt, tls->client_write_key, tls->key_size);
+
                 aes_setkey(&tls->aes_decrypt, tls->server_write_key, tls->key_size);
+                aes_setkey(&tls->aes_encrypt, tls->client_write_key, tls->key_size);
+                {
+                        uint8_t iv[AES_BLOCK_SIZE];
+                        memset(iv, 0, AES_BLOCK_SIZE);
+                        aes_encrypt_one_block(&tls->aes_encrypt, iv, tls->H);
+                }
         }
 }
 
diff --git a/networking/tls_aes.c b/networking/tls_aes.c
index 4d2b68975..cf6b5fe3d 100644
--- a/networking/tls_aes.c
+++ b/networking/tls_aes.c
@@ -326,8 +326,11 @@ static void InvMixColumns(unsigned astate[16])
         }
 }
 
-static void aes_encrypt_1(unsigned astate[16], unsigned rounds, const uint32_t *RoundKey)
+static void aes_encrypt_1(struct tls_aes *aes, unsigned astate[16])
 {
+        unsigned rounds = aes->rounds;
+        const uint32_t *RoundKey = aes->key;
+
         for (;;) {
                 AddRoundKey(astate, RoundKey);
                 RoundKey += 4;
@@ -355,22 +358,19 @@ void FAST_FUNC aes_encrypt_one_block(struct tls_aes *aes, const void *data, void
 
         for (i = 0; i < 16; i++)
                 astate[i] = pt[i];
-        aes_encrypt_1(astate, aes->rounds, aes->key);
+        aes_encrypt_1(aes, astate);
         for (i = 0; i < 16; i++)
                 ct[i] = astate[i];
 }
 
-void FAST_FUNC aes_cbc_encrypt(const void *key, int klen, void *iv, const void *data, size_t len, void *dst)
+void FAST_FUNC aes_cbc_encrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst)
 {
-        uint32_t RoundKey[60];
         uint8_t iv2[16];
-        unsigned rounds;
 
         const uint8_t *pt = data;
         uint8_t *ct = dst;
 
         memcpy(iv2, iv, 16);
-        rounds = KeyExpansion(RoundKey, key, klen);
         while (len > 0) {
                 {
                         /* almost aes_encrypt_one_block(rounds, RoundKey, pt, ct);
@@ -381,7 +381,7 @@ void FAST_FUNC aes_cbc_encrypt(const void *key, int klen, void *iv, const void *
                         unsigned astate[16];
                         for (i = 0; i < 16; i++)
                                 astate[i] = pt[i] ^ iv2[i];
-                        aes_encrypt_1(astate, rounds, RoundKey);
+                        aes_encrypt_1(aes, astate);
                         for (i = 0; i < 16; i++)
                                 iv2[i] = ct[i] = astate[i];
                 }
@@ -391,8 +391,11 @@ void FAST_FUNC aes_cbc_encrypt(const void *key, int klen, void *iv, const void *
         }
 }
 
-static void aes_decrypt_1(unsigned astate[16], unsigned rounds, const uint32_t *RoundKey)
+static void aes_decrypt_1(struct tls_aes *aes, unsigned astate[16])
 {
+        unsigned rounds = aes->rounds;
+        const uint32_t *RoundKey = aes->key;
+
         RoundKey += rounds * 4;
         AddRoundKey(astate, RoundKey);
         for (;;) {
@@ -407,8 +410,10 @@ static void aes_decrypt_1(unsigned astate[16], unsigned rounds, const uint32_t *
 }
 
 #if 0 //UNUSED
-static void aes_decrypt_one_block(unsigned rounds, const uint32_t *RoundKey, const void *data, void *dst)
+static void aes_decrypt_one_block(struct tls_aes *aes, const void *data, void *dst)
 {
+        unsigned rounds = aes->rounds;
+        const uint32_t *RoundKey = aes->key;
         unsigned astate[16];
         unsigned i;
 
@@ -417,25 +422,22 @@ static void aes_decrypt_one_block(unsigned rounds, const uint32_t *RoundKey, con
 
         for (i = 0; i < 16; i++)
                 astate[i] = ct[i];
-        aes_decrypt_1(astate, rounds, RoundKey);
+        aes_decrypt_1(aes, astate);
         for (i = 0; i < 16; i++)
                 pt[i] = astate[i];
 }
 #endif
 
-void FAST_FUNC aes_cbc_decrypt(const void *key, int klen, void *iv, const void *data, size_t len, void *dst)
+void FAST_FUNC aes_cbc_decrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst)
 {
-        uint32_t RoundKey[60];
         uint8_t iv2[16];
         uint8_t iv3[16];
-        unsigned rounds;
         uint8_t *ivbuf;
         uint8_t *ivnext;
 
         const uint8_t *ct = data;
         uint8_t *pt = dst;
 
-        rounds = KeyExpansion(RoundKey, key, klen);
         ivbuf = memcpy(iv2, iv, 16);
         while (len) {
                 ivnext = (ivbuf==iv2) ? iv3 : iv2;
@@ -447,7 +449,7 @@ void FAST_FUNC aes_cbc_decrypt(const void *key, int klen, void *iv, const void *
                         unsigned astate[16];
                         for (i = 0; i < 16; i++)
                                 ivnext[i] = astate[i] = ct[i];
-                        aes_decrypt_1(astate, rounds, RoundKey);
+                        aes_decrypt_1(aes, astate);
                         for (i = 0; i < 16; i++)
                                 pt[i] = astate[i] ^ ivbuf[i];
                 }
diff --git a/networking/tls_aes.h b/networking/tls_aes.h
index fc3881793..e9e3721f1 100644
--- a/networking/tls_aes.h
+++ b/networking/tls_aes.h
@@ -10,5 +10,5 @@ void aes_setkey(struct tls_aes *aes, const void *key, unsigned key_len) FAST_FUN
 
 void aes_encrypt_one_block(struct tls_aes *aes, const void *data, void *dst) FAST_FUNC;
 
-void aes_cbc_encrypt(const void *key, int klen, void *iv, const void *data, size_t len, void *dst) FAST_FUNC;
-void aes_cbc_decrypt(const void *key, int klen, void *iv, const void *data, size_t len, void *dst) FAST_FUNC;
+void aes_cbc_encrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst) FAST_FUNC;
+void aes_cbc_decrypt(struct tls_aes *aes, void *iv, const void *data, size_t len, void *dst) FAST_FUNC;
diff --git a/networking/tls_aesgcm.c b/networking/tls_aesgcm.c
index 584cee98e..eb32f4c05 100644
--- a/networking/tls_aesgcm.c
+++ b/networking/tls_aesgcm.c
@@ -136,13 +136,3 @@ void FAST_FUNC aesgcm_GHASH(byte* h, const byte* a, unsigned aSz, const byte* c,
     /* Copy the result into s. */
     XMEMCPY(s, x, sSz);
 }
-
-void FAST_FUNC aesgcm_setkey(uint8_t H[16], struct tls_aes *aes, const byte* key, unsigned len)
-{
-    byte iv[AES_BLOCK_SIZE];
-
-    aes_setkey(aes, key, len);
-
-    memset(iv, 0, AES_BLOCK_SIZE);
-    aes_encrypt_one_block(aes, iv, H);
-}
diff --git a/networking/tls_aesgcm.h b/networking/tls_aesgcm.h
index d4cde01f9..a71eced54 100644
--- a/networking/tls_aesgcm.h
+++ b/networking/tls_aesgcm.h
@@ -11,5 +11,3 @@ void aesgcm_GHASH(uint8_t* h,
         const uint8_t* c, unsigned cSz,
         uint8_t* s, unsigned sSz
 ) FAST_FUNC;
-
-void aesgcm_setkey(uint8_t H[16], struct tls_aes *aes, const uint8_t* key, unsigned len) FAST_FUNC;