first pass

[PuTTY.git] / sshsh256.c

diff --git a/sshsh256.c b/sshsh256.c
index 70c2d7d3dec76f25c318d7a8fe82be8414f1b7f3..4186f3e8180fc54b54fdefa19851200fd17157fe 100644 (file)
--- a/sshsh256.c
+++ b/sshsh256.c
@@ -184,6 +184,7 @@ void SHA256_Simple(const void *p, int len, unsigned char *output) {
     SHA256_Init(&s);
     SHA256_Bytes(&s, p, len);
     SHA256_Final(&s, output);
+    smemclr(&s, sizeof(s));
 }
 
 /*
@@ -199,7 +200,25 @@ static void *sha256_init(void)
     return s;
 }
 
-static void sha256_bytes(void *handle, void *p, int len)
+static void *sha256_copy(const void *vold)
+{
+    const SHA256_State *old = (const SHA256_State *)vold;
+    SHA256_State *s;
+
+    s = snew(SHA256_State);
+    *s = *old;
+    return s;
+}
+
+static void sha256_free(void *handle)
+{
+    SHA256_State *s = handle;
+
+    smemclr(s, sizeof(*s));
+    sfree(s);
+}
+
+static void sha256_bytes(void *handle, const void *p, int len)
 {
     SHA256_State *s = handle;
 
@@ -211,11 +230,123 @@ static void sha256_final(void *handle, unsigned char *output)
     SHA256_State *s = handle;
 
     SHA256_Final(s, output);
-    sfree(s);
+    sha256_free(s);
 }
 
 const struct ssh_hash ssh_sha256 = {
-    sha256_init, sha256_bytes, sha256_final, 32
+    sha256_init, sha256_copy, sha256_bytes, sha256_final, sha256_free,
+    32, "SHA-256"
+};
+
+/* ----------------------------------------------------------------------
+ * The above is the SHA-256 algorithm itself. Now we implement the
+ * HMAC wrapper on it.
+ */
+
+static void *sha256_make_context(void *cipher_ctx)
+{
+    return snewn(3, SHA256_State);
+}
+
+static void sha256_free_context(void *handle)
+{
+    smemclr(handle, 3 * sizeof(SHA256_State));
+    sfree(handle);
+}
+
+static void sha256_key_internal(void *handle, unsigned char *key, int len)
+{
+    SHA256_State *keys = (SHA256_State *)handle;
+    unsigned char foo[64];
+    int i;
+
+    memset(foo, 0x36, 64);
+    for (i = 0; i < len && i < 64; i++)
+       foo[i] ^= key[i];
+    SHA256_Init(&keys[0]);
+    SHA256_Bytes(&keys[0], foo, 64);
+
+    memset(foo, 0x5C, 64);
+    for (i = 0; i < len && i < 64; i++)
+       foo[i] ^= key[i];
+    SHA256_Init(&keys[1]);
+    SHA256_Bytes(&keys[1], foo, 64);
+
+    smemclr(foo, 64);                 /* burn the evidence */
+}
+
+static void sha256_key(void *handle, unsigned char *key)
+{
+    sha256_key_internal(handle, key, 32);
+}
+
+static void hmacsha256_start(void *handle)
+{
+    SHA256_State *keys = (SHA256_State *)handle;
+
+    keys[2] = keys[0];               /* structure copy */
+}
+
+static void hmacsha256_bytes(void *handle, unsigned char const *blk, int len)
+{
+    SHA256_State *keys = (SHA256_State *)handle;
+    SHA256_Bytes(&keys[2], (void *)blk, len);
+}
+
+static void hmacsha256_genresult(void *handle, unsigned char *hmac)
+{
+    SHA256_State *keys = (SHA256_State *)handle;
+    SHA256_State s;
+    unsigned char intermediate[32];
+
+    s = keys[2];                      /* structure copy */
+    SHA256_Final(&s, intermediate);
+    s = keys[1];                      /* structure copy */
+    SHA256_Bytes(&s, intermediate, 32);
+    SHA256_Final(&s, hmac);
+}
+
+static void sha256_do_hmac(void *handle, unsigned char *blk, int len,
+                        unsigned long seq, unsigned char *hmac)
+{
+    unsigned char seqbuf[4];
+
+    PUT_32BIT_MSB_FIRST(seqbuf, seq);
+    hmacsha256_start(handle);
+    hmacsha256_bytes(handle, seqbuf, 4);
+    hmacsha256_bytes(handle, blk, len);
+    hmacsha256_genresult(handle, hmac);
+}
+
+static void sha256_generate(void *handle, unsigned char *blk, int len,
+                         unsigned long seq)
+{
+    sha256_do_hmac(handle, blk, len, seq, blk + len);
+}
+
+static int hmacsha256_verresult(void *handle, unsigned char const *hmac)
+{
+    unsigned char correct[32];
+    hmacsha256_genresult(handle, correct);
+    return smemeq(correct, hmac, 32);
+}
+
+static int sha256_verify(void *handle, unsigned char *blk, int len,
+                      unsigned long seq)
+{
+    unsigned char correct[32];
+    sha256_do_hmac(handle, blk, len, seq, correct);
+    return smemeq(correct, blk + len, 32);
+}
+
+const struct ssh_mac ssh_hmac_sha256 = {
+    sha256_make_context, sha256_free_context, sha256_key,
+    sha256_generate, sha256_verify,
+    hmacsha256_start, hmacsha256_bytes,
+    hmacsha256_genresult, hmacsha256_verresult,
+    "hmac-sha2-256", "hmac-sha2-256-etm@openssh.com",
+    32, 32,
+    "HMAC-SHA-256"
 };
 
 #ifdef TEST