Add negotiation for SHA2 HMAC algorithms

BUG: https://red.libssh.org/issues/91

Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

include/libssh/wrapper.h

@@ -45,6 +45,11 @@ enum ssh_des_e {
   SSH_DES
 };
 
+struct ssh_hmac_struct {
+  const char* name;
+  enum ssh_hmac_e hmac_type;
+};
+
 typedef struct ssh_mac_ctx_struct *ssh_mac_ctx;
 MD5CTX md5_init(void);
 void md5_update(MD5CTX c, const void *data, unsigned long len);
@@ -91,4 +96,6 @@ void crypto_free(struct ssh_crypto_struct *crypto);
 
 void ssh_reseed(void);
 
+struct ssh_hmac_struct *ssh_get_hmactab(void);
+
 #endif /* WRAPPER_H_ */

src/kex.c

@@ -88,8 +88,8 @@ static const char *default_methods[] = {
   HOSTKEYS,
   AES BLOWFISH DES,
   AES BLOWFISH DES,
-  "hmac-sha1",
+  "hmac-sha1,hmac-sha2-256,hmac-sha2-512",
-  "hmac-sha1",
+  "hmac-sha1,hmac-sha2-256,hmac-sha2-512",
   "none",
   "none",
   "",
@@ -103,8 +103,8 @@ static const char *supported_methods[] = {
   HOSTKEYS,
   AES BLOWFISH DES,
   AES BLOWFISH DES,
-  "hmac-sha1",
+  "hmac-sha1,hmac-sha2-256,hmac-sha2-512",
-  "hmac-sha1",
+  "hmac-sha1,hmac-sha2-256,hmac-sha2-512",
   ZLIB,
   ZLIB,
   "",

src/wrapper.c

@@ -48,6 +48,19 @@
 #include "libssh/wrapper.h"
 #include "libssh/pki.h"
 
+static struct ssh_hmac_struct ssh_hmac_tab[] = {
+  { "hmac-sha1",     SSH_HMAC_SHA1 },
+  { "hmac-sha2-256", SSH_HMAC_SHA256 },
+  { "hmac-sha2-384", SSH_HMAC_SHA384 },
+  { "hmac-sha2-512", SSH_HMAC_SHA512 },
+  { "hmac-md5",      SSH_HMAC_MD5 },
+  { NULL,            0}
+};
+
+struct ssh_hmac_struct *ssh_get_hmactab(void) {
+  return ssh_hmac_tab;
+}
+
 size_t hmac_digest_len(enum ssh_hmac_e type) {
   switch(type) {
     case SSH_HMAC_SHA1:
@@ -184,6 +197,7 @@ static int crypt_set_algorithms2(ssh_session session){
   const char *wanted;
   int i = 0;
   struct ssh_cipher_struct *ssh_ciphertab=ssh_get_ciphertab();
+  struct ssh_hmac_struct *ssh_hmactab=ssh_get_hmactab();
 
   /* we must scan the kex entries to find crypto algorithms and set their appropriate structure */
   /* out */
@@ -207,6 +221,24 @@ static int crypt_set_algorithms2(ssh_session session){
   }
   i = 0;
 
+  /* we must scan the kex entries to find hmac algorithms and set their appropriate structure */
+  /* out */
+  wanted = session->next_crypto->kex_methods[SSH_MAC_C_S];
+  while (ssh_hmactab[i].name && strcmp(wanted, ssh_hmactab[i].name)) {
+    i++;
+  }
+
+  if (ssh_hmactab[i].name == NULL) {
+    ssh_set_error(session, SSH_FATAL,
+        "crypt_set_algorithms2: no hmac algorithm function found for %s",
+        wanted);
+      return SSH_ERROR;
+  }
+  SSH_LOG(SSH_LOG_PACKET, "Set HMAC output algorithm to %s", wanted);
+
+  session->next_crypto->out_hmac = ssh_hmactab[i].hmac_type;
+  i = 0;
+
   /* in */
   wanted = session->next_crypto->kex_methods[SSH_CRYPT_S_C];
   while (ssh_ciphertab[i].name && strcmp(wanted, ssh_ciphertab[i].name)) {
@@ -226,6 +258,24 @@ static int crypt_set_algorithms2(ssh_session session){
       ssh_set_error_oom(session);
       return SSH_ERROR;
   }
+  i = 0;
+
+  /* we must scan the kex entries to find hmac algorithms and set their appropriate structure */
+  wanted = session->next_crypto->kex_methods[SSH_MAC_S_C];
+  while (ssh_hmactab[i].name && strcmp(wanted, ssh_hmactab[i].name)) {
+    i++;
+  }
+
+  if (ssh_hmactab[i].name == NULL) {
+    ssh_set_error(session, SSH_FATAL,
+        "crypt_set_algorithms2: no hmac algorithm function found for %s",
+        wanted);
+      return SSH_ERROR;
+  }
+  SSH_LOG(SSH_LOG_PACKET, "Set HMAC output algorithm to %s", wanted);
+
+  session->next_crypto->in_hmac = ssh_hmactab[i].hmac_type;
+  i = 0;
 
   /* compression */
   if (strcmp(session->next_crypto->kex_methods[SSH_COMP_C_S], "zlib") == 0) {
@@ -284,6 +334,7 @@ int crypt_set_algorithms_server(ssh_session session){
     char *method = NULL;
     int i = 0;
     struct ssh_cipher_struct *ssh_ciphertab=ssh_get_ciphertab();
+    struct ssh_hmac_struct   *ssh_hmactab=ssh_get_hmactab();
 
     if (session == NULL) {
         return SSH_ERROR;
@@ -326,6 +377,40 @@ int crypt_set_algorithms_server(ssh_session session){
         ssh_set_error_oom(session);
         return SSH_ERROR;
     }
+    i=0;
+
+    /* HMAC algorithm selection */
+    method = session->next_crypto->kex_methods[SSH_MAC_S_C];
+    while (ssh_hmactab[i].name && strcmp(method, ssh_hmactab[i].name)) {
+      i++;
+    }
+
+    if (ssh_hmactab[i].name == NULL) {
+      ssh_set_error(session, SSH_FATAL,
+          "crypt_set_algorithms_server: no hmac algorithm function found for %s",
+          method);
+        return SSH_ERROR;
+    }
+    SSH_LOG(SSH_LOG_PACKET, "Set HMAC output algorithm to %s", method);
+
+    session->next_crypto->out_hmac = ssh_hmactab[i].hmac_type;
+    i=0;
+
+    method = session->next_crypto->kex_methods[SSH_MAC_C_S];
+    while (ssh_hmactab[i].name && strcmp(method, ssh_hmactab[i].name)) {
+      i++;
+    }
+
+    if (ssh_hmactab[i].name == NULL) {
+      ssh_set_error(session, SSH_FATAL,
+          "crypt_set_algorithms_server: no hmac algorithm function found for %s",
+          method);
+        return SSH_ERROR;
+    }
+    SSH_LOG(SSH_LOG_PACKET, "Set HMAC input algorithm to %s", method);
+
+    session->next_crypto->in_hmac = ssh_hmactab[i].hmac_type;
+    i=0;
 
     /* compression */
     method = session->next_crypto->kex_methods[SSH_COMP_C_S];