Add support for HMAC-SHA-256 and HMAC-SHA-512.

Implement support for these algorithms and wire them up to the libgcrypt
and OpenSSL backends.  Increase the maximum MAC buffer size to 64 bytes
to prevent buffer overflows.  Prefer HMAC-SHA-256 over HMAC-SHA-512, and
that over HMAC-SHA-1, as OpenSSH does.

Closes #40

src/libgcrypt.h

@@ -42,6 +42,8 @@
 #define LIBSSH2_MD5 1
 
 #define LIBSSH2_HMAC_RIPEMD 1
+#define LIBSSH2_HMAC_SHA256 1
+#define LIBSSH2_HMAC_SHA512 1
 
 #define LIBSSH2_AES 1
 #define LIBSSH2_AES_CTR 1
@@ -95,6 +97,12 @@
 #define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
   gcry_md_open (ctx, GCRY_MD_RMD160, GCRY_MD_FLAG_HMAC), \
     gcry_md_setkey (*ctx, key, keylen)
+#define libssh2_hmac_sha256_init(ctx, key, keylen) \
+  gcry_md_open (ctx, GCRY_MD_SHA256, GCRY_MD_FLAG_HMAC), \
+    gcry_md_setkey (*ctx, key, keylen)
+#define libssh2_hmac_sha512_init(ctx, key, keylen) \
+  gcry_md_open (ctx, GCRY_MD_SHA512, GCRY_MD_FLAG_HMAC), \
+    gcry_md_setkey (*ctx, key, keylen)
 #define libssh2_hmac_update(ctx, data, datalen) \
   gcry_md_write (ctx, (unsigned char *) data, datalen)
 #define libssh2_hmac_final(ctx, data) \

src/mac.c

@@ -96,6 +96,97 @@ mac_method_common_dtor(LIBSSH2_SESSION * session, void **abstract)
 
 
 
+#if LIBSSH2_HMAC_SHA512
+/* mac_method_hmac_sha512_hash
+ * Calculate hash using full sha512 value
+ */
+static int
+mac_method_hmac_sha2_512_hash(LIBSSH2_SESSION * session,
+                          unsigned char *buf, uint32_t seqno,
+                          const unsigned char *packet,
+                          uint32_t packet_len,
+                          const unsigned char *addtl,
+                          uint32_t addtl_len, void **abstract)
+{
+    libssh2_hmac_ctx ctx;
+    unsigned char seqno_buf[4];
+    (void) session;
+
+    _libssh2_htonu32(seqno_buf, seqno);
+
+    libssh2_hmac_ctx_init(ctx);
+    libssh2_hmac_sha512_init(&ctx, *abstract, 64);
+    libssh2_hmac_update(ctx, seqno_buf, 4);
+    libssh2_hmac_update(ctx, packet, packet_len);
+    if (addtl && addtl_len) {
+        libssh2_hmac_update(ctx, addtl, addtl_len);
+    }
+    libssh2_hmac_final(ctx, buf);
+    libssh2_hmac_cleanup(&ctx);
+
+    return 0;
+}
+
+
+
+static const LIBSSH2_MAC_METHOD mac_method_hmac_sha2_512 = {
+    "hmac-sha2-512",
+    64,
+    64,
+    mac_method_common_init,
+    mac_method_hmac_sha2_512_hash,
+    mac_method_common_dtor,
+};
+#endif
+
+
+
+#if LIBSSH2_HMAC_SHA256
+/* mac_method_hmac_sha256_hash
+ * Calculate hash using full sha256 value
+ */
+static int
+mac_method_hmac_sha2_256_hash(LIBSSH2_SESSION * session,
+                          unsigned char *buf, uint32_t seqno,
+                          const unsigned char *packet,
+                          uint32_t packet_len,
+                          const unsigned char *addtl,
+                          uint32_t addtl_len, void **abstract)
+{
+    libssh2_hmac_ctx ctx;
+    unsigned char seqno_buf[4];
+    (void) session;
+
+    _libssh2_htonu32(seqno_buf, seqno);
+
+    libssh2_hmac_ctx_init(ctx);
+    libssh2_hmac_sha256_init(&ctx, *abstract, 32);
+    libssh2_hmac_update(ctx, seqno_buf, 4);
+    libssh2_hmac_update(ctx, packet, packet_len);
+    if (addtl && addtl_len) {
+        libssh2_hmac_update(ctx, addtl, addtl_len);
+    }
+    libssh2_hmac_final(ctx, buf);
+    libssh2_hmac_cleanup(&ctx);
+
+    return 0;
+}
+
+
+
+static const LIBSSH2_MAC_METHOD mac_method_hmac_sha2_256 = {
+    "hmac-sha2-256",
+    32,
+    32,
+    mac_method_common_init,
+    mac_method_hmac_sha2_256_hash,
+    mac_method_common_dtor,
+};
+#endif
+
+
+
+
 /* mac_method_hmac_sha1_hash
  * Calculate hash using full sha1 value
  */
@@ -294,6 +385,12 @@ static const LIBSSH2_MAC_METHOD mac_method_hmac_ripemd160_openssh_com = {
 #endif /* LIBSSH2_HMAC_RIPEMD */
 
 static const LIBSSH2_MAC_METHOD *mac_methods[] = {
+#if LIBSSH2_HMAC_SHA256
+    &mac_method_hmac_sha2_256,
+#endif
+#if LIBSSH2_HMAC_SHA512
+    &mac_method_hmac_sha2_512,
+#endif
     &mac_method_hmac_sha1,
     &mac_method_hmac_sha1_96,
 #if LIBSSH2_MD5

src/openssl.h

@@ -76,6 +76,9 @@
 # define LIBSSH2_HMAC_RIPEMD 1
 #endif
 
+#define LIBSSH2_HMAC_SHA256 1
+#define LIBSSH2_HMAC_SHA512 1
+
 #if OPENSSL_VERSION_NUMBER >= 0x00907000L && !defined(OPENSSL_NO_AES)
 # define LIBSSH2_AES_CTR 1
 # define LIBSSH2_AES 1
@@ -138,6 +141,10 @@ int _libssh2_md5_init(libssh2_md5_ctx *);
   HMAC_Init(ctx, key, keylen, EVP_md5())
 #define libssh2_hmac_ripemd160_init(ctx, key, keylen) \
   HMAC_Init(ctx, key, keylen, EVP_ripemd160())
+#define libssh2_hmac_sha256_init(ctx, key, keylen) \
+  HMAC_Init(ctx, key, keylen, EVP_sha256())
+#define libssh2_hmac_sha512_init(ctx, key, keylen) \
+  HMAC_Init(ctx, key, keylen, EVP_sha512())
 #define libssh2_hmac_update(ctx, data, datalen) \
   HMAC_Update(&(ctx), data, datalen)
 #define libssh2_hmac_final(ctx, data) HMAC_Final(&(ctx), data, NULL)

src/transport.c

@@ -52,7 +52,7 @@
 #include "mac.h"
 
 #define MAX_BLOCKSIZE 32    /* MUST fit biggest crypto block size we use/get */
-#define MAX_MACSIZE 20      /* MUST fit biggest MAC length we support */
+#define MAX_MACSIZE 64      /* MUST fit biggest MAC length we support */
 
 #ifdef LIBSSH2DEBUG
 #define UNPRINTABLE_CHAR '.'

src/wincng.h

@@ -51,6 +51,8 @@
 #define LIBSSH2_MD5 1
 
 #define LIBSSH2_HMAC_RIPEMD 0
+#define LIBSSH2_HMAC_SHA256 0
+#define LIBSSH2_HMAC_SHA512 0
 
 #define LIBSSH2_AES 1
 #define LIBSSH2_AES_CTR 0
@@ -158,6 +160,10 @@ typedef struct __libssh2_wincng_hash_ctx {
                             MD5_DIGEST_LENGTH, key, keylen)
 #define libssh2_hmac_ripemd160_init(ctx, key, keylen)
   /* not implemented */
+#define libssh2_hmac_sha256_init(ctx, key, keylen)
+  /* not implemented */
+#define libssh2_hmac_sha512_init(ctx, key, keylen)
+  /* not implemented */
 #define libssh2_hmac_update(ctx, data, datalen) \
   _libssh2_wincng_hash_update(&ctx, (unsigned char *) data, datalen)
 #define libssh2_hmac_final(ctx, hash) \