dh-gex: WIPgex_to_polish

1 files changed, 97 insertions, 10 deletions

diff --git a/src/dh-gex.c b/src/dh-gex.c
index 1bd1b49a..18e1b477 100644
--- a/src/dh-gex.c
+++ b/src/dh-gex.c
@@ -32,6 +32,8 @@
 #include "libssh/buffer.h"
 #include "libssh/session.h"
 
+#define PMIN 1534
+
 static SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_group);
 static SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_reply);
 
@@ -59,9 +61,15 @@ int ssh_client_dhgex_init(ssh_session session){
         goto error;
     }
 
+    session->next_crypto->dh_pmin = PMIN;
+    session->next_crypto->dh_pn = 2048;
+    session->next_crypto->dh_pmax = 8192;
     /* Minimum group size, preferred group size, maximum group size */
     rc = ssh_buffer_pack(session->out_buffer, "bddd",
-            SSH2_MSG_KEX_DH_GEX_REQUEST, 1534, 2048, 8192);
+            SSH2_MSG_KEX_DH_GEX_REQUEST,
+            session->next_crypto->dh_pmin,
+            session->next_crypto->dh_pn,
+            session->next_crypto->dh_pmax);
     if (rc != SSH_OK){
         goto error;
     }
@@ -75,7 +83,7 @@ int ssh_client_dhgex_init(ssh_session session){
     }
     return rc;
 error:
-    ssh_dh_cleanup(session);
+    ssh_dh_cleanup(session->next_crypto);
     return SSH_ERROR;
 }
 
@@ -89,6 +97,9 @@ SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_group){
     bignum pmin1=NULL, one=NULL;
     bignum_CTX ctx = bignum_ctx_new();
 
+    (void) type;
+    (void) user;
+
     SSH_LOG(SSH_LOG_PROTOCOL, "SSH_MSG_KEX_DH_GEX_GROUP received");
 
     if (bignum_ctx_invalid(ctx)) {
@@ -114,8 +125,8 @@ SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_group){
     /* basic checks */
     bignum_set_word(one, 1);
     blen = bignum_num_bits(session->next_crypto->p);
-    if (blen < 1534 || blen > 8192){
-        ssh_set_error(session, SSH_FATAL, "Invalid dh group parameter p: %d not in [1534:8192]", blen);
+    if (blen < PMIN || blen > 8192){
+        ssh_set_error(session, SSH_FATAL, "Invalid dh group parameter p: %d not in [%d:8192]", blen, PMIN);
         goto error;
     }
     if (bignum_cmp(session->next_crypto->p, one) <= 0){
@@ -139,6 +150,11 @@ SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_group){
     if (rc == SSH_ERROR){
         goto error;
     }
+    session->next_crypto->e = bignum_new();
+    if (session->next_crypto->e == NULL){
+        ssh_set_error_oom(session);
+        goto error;
+    }
     bignum_mod_exp(session->next_crypto->e, session->next_crypto->g, session->next_crypto->x,
         session->next_crypto->p, ctx);
 
@@ -159,7 +175,7 @@ SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_group){
 error:
     bignum_safe_free(one);
     bignum_safe_free(pmin1);
-    ssh_dh_cleanup(session);
+    ssh_dh_cleanup(session->next_crypto);
     session->session_state=SSH_SESSION_STATE_ERROR;
     return SSH_PACKET_USED;
 }
@@ -197,10 +213,9 @@ static SSH_PACKET_CALLBACK(ssh_packet_client_dhgex_reply) {
     }
     SSH_LOG(SSH_LOG_PROTOCOL, "SSH_MSG_NEWKEYS sent");
     session->dh_handshake_state = DH_STATE_NEWKEYS_SENT;
-
     return SSH_PACKET_USED;
   error:
-    ssh_dh_cleanup(session);
+    ssh_dh_cleanup(session->next_crypto);
     session->session_state=SSH_SESSION_STATE_ERROR;
     return SSH_PACKET_USED;
 }
@@ -358,6 +373,8 @@ static int ssh_retrieve_dhgroup(int pmin, int pn, int pmax, int *size, bignum *p
     if (*size == 0){
         return SSH_ERROR;
     }
+    *p=NULL;
+    *g=NULL;
     rc = bignum_hex2bn(generator, g);
     if (rc == 0){
         goto error;
@@ -379,13 +396,14 @@ error:
 }
 
 static SSH_PACKET_CALLBACK(ssh_packet_server_dhgex_request);
+static SSH_PACKET_CALLBACK(ssh_packet_server_dhgex_init);
 
 static ssh_packet_callback dhgex_server_callbacks[]= {
     NULL, /* SSH_MSG_KEX_DH_GEX_REQUEST_OLD */
     NULL, /* SSH_MSG_KEX_DH_GEX_GROUP */
-    NULL, /* SSH_MSG_KEX_DH_GEX_INIT */
-    NULL, /* SSH_MSG_KEX_DH_GEX_REPLY */
-    ssh_packet_server_dhgex_request
+    ssh_packet_server_dhgex_init,   /* SSH_MSG_KEX_DH_GEX_INIT */
+    NULL,                           /* SSH_MSG_KEX_DH_GEX_REPLY */
+    ssh_packet_server_dhgex_request /* SSH_MSG_GEX_DH_GEX_REQUEST */
 };
 
 static struct ssh_packet_callbacks_struct ssh_dhgex_server_callbacks = {
@@ -402,9 +420,78 @@ void ssh_server_dhgex_init(ssh_session session){
     /* register the packet callbacks */
     ssh_packet_set_callbacks(session, &ssh_dhgex_server_callbacks);
     ssh_dh_init_common(session);
+    session->dh_handshake_state = DH_STATE_INIT;
 }
 
 static SSH_PACKET_CALLBACK(ssh_packet_server_dhgex_request){
+    int pmin, pn, pmax;
+    int size = 0;
+    int rc;
+
+    (void) type;
+    (void) user;
+    if (session->dh_handshake_state != DH_STATE_INIT){
+        ssh_set_error(session, SSH_FATAL, "Received DH_GEX_REQUEST in invalid state");
+        goto error;
+    }
+
+    rc = ssh_dh_init_common(session);
+    if (rc != SSH_OK){
+        goto error;
+    }
+
+    /* Minimum group size, preferred group size, maximum group size */
+    rc = ssh_buffer_unpack(packet, "ddd", &pmin, &pn, &pmax);
+    if (rc != SSH_OK){
+        goto error;
+    }
+    SSH_LOG(SSH_LOG_INFO, "dh-gex: DHGEX_REQUEST[%d:%d:%d]", pmin, pn, pmax);
+    if (pmin > pn || pn > pmax || pn > pmax || pmax < PMIN){
+        ssh_set_error(session, SSH_FATAL, "Invalid dh-gex arguments [%d:%d:%d]", pmin, pn, pmax);
+        goto error;
+    }
+    session->next_crypto->dh_pmin = pmin;
+    session->next_crypto->dh_pn = pn;
+    session->next_crypto->dh_pmax = pmax;
+
+    /* ensure safe parameters */
+    if (pmin < PMIN){
+        pmin = PMIN;
+        if (pn < pmin){
+            pn = pmin;
+        }
+    }
+    rc = ssh_retrieve_dhgroup(pmin, pn, pmax, &size, &session->next_crypto->p, &session->next_crypto->g);
+    if (rc == SSH_ERROR){
+        ssh_set_error(session, SSH_FATAL, "Couldn't find DH group for [%d:%d:%d]", pmin, pn, pmax);
+        goto error;
+    }
+    session->next_crypto->dh_group_is_mutable = 1;
+    rc = ssh_buffer_pack(session->out_buffer, "bBB", SSH2_MSG_KEX_DH_GEX_GROUP,
+            session->next_crypto->p, session->next_crypto->g);
+    if (rc != SSH_OK) {
+        goto error;
+    }
+
+    session->dh_handshake_state = DH_STATE_GROUP_SENT;
+
+    rc = ssh_packet_send(session);
+error:
+
+    return SSH_PACKET_USED;
+}
+
+/** @internal
+ * @brief parse an incoming SSH_MSG_KEX_DH_GEX_INIT packet and complete
+ *        Diffie-Hellman key exchange
+ **/
+static SSH_PACKET_CALLBACK(ssh_packet_server_dhgex_init){
+
+    (void) type;
+    (void) user;
+    SSH_LOG(SSH_LOG_DEBUG, "Received SSH_MSG_KEX_DHGEX_INIT");
+    ssh_packet_remove_callbacks(session, &ssh_dhgex_server_callbacks);
+    ssh_server_dh_process_init(session, packet);
     return SSH_PACKET_USED;
 }