Prevent oracle attacks in the legacy protocol (CVE-2018-16737, CVE-2018-16738)

[tinc] / src / protocol_auth.c

diff --git a/src/protocol_auth.c b/src/protocol_auth.c
index 1e00f09..9d61ab8 100644 (file)
--- a/src/protocol_auth.c
+++ b/src/protocol_auth.c
@@ -300,7 +300,7 @@ static bool receive_invitation_sptps(void *handle, uint8_t type, const void *dat
 
        buf[len] = 0;
 
-       if(!*buf || !*name || strcasecmp(buf, "Name") || !check_id(name)) {
+       if(!*buf || !*name || strcasecmp(buf, "Name") || !check_id(name) || !strcmp(name, myself->name)) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Invalid invitation file %s\n", cookie);
                fclose(f);
                return false;
@@ -346,6 +346,10 @@ bool id_h(connection_t *c, const char *request) {
                free(c->name);
                c->name = xstrdup("<control>");
 
+               if(!c->outgoing) {
+                       send_id(c);
+               }
+
                return send_request(c, "%d %d %d", ACK, TINC_CTL_VERSION_CURRENT, getpid());
        }
 
@@ -369,6 +373,10 @@ bool id_h(connection_t *c, const char *request) {
                        return false;
                }
 
+               if(!c->outgoing) {
+                       send_id(c);
+               }
+
                if(!send_request(c, "%d %s", ACK, mykey)) {
                        return false;
                }
@@ -382,7 +390,7 @@ bool id_h(connection_t *c, const char *request) {
 
        /* Check if identity is a valid name */
 
-       if(!check_id(name)) {
+       if(!check_id(name) || !strcmp(name, myself->name)) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s): %s", "ID", c->name,
                       c->hostname, "invalid name");
                return false;
@@ -418,6 +426,11 @@ bool id_h(connection_t *c, const char *request) {
                }
 
                c->allow_request = ACK;
+
+               if(!c->outgoing) {
+                       send_id(c);
+               }
+
                return send_ack(c);
        }
 
@@ -454,6 +467,10 @@ bool id_h(connection_t *c, const char *request) {
 
        c->allow_request = METAKEY;
 
+       if(!c->outgoing) {
+               send_id(c);
+       }
+
        if(c->protocol_minor >= 2) {
                c->allow_request = ACK;
                char label[25 + strlen(myself->name) + strlen(c->name)];
@@ -618,7 +635,8 @@ bool metakey_h(connection_t *c, const char *request) {
                        return false;
                }
        } else {
-               c->incipher = NULL;
+               logger(DEBUG_ALWAYS, LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "null cipher");
+               return false;
        }
 
        c->inbudget = cipher_budget(c->incipher);
@@ -629,7 +647,8 @@ bool metakey_h(connection_t *c, const char *request) {
                        return false;
                }
        } else {
-               c->indigest = NULL;
+               logger(DEBUG_ALWAYS, LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "null digest");
+               return false;
        }
 
        c->status.decryptin = true;
@@ -647,9 +666,7 @@ bool send_challenge(connection_t *c) {
        const size_t len = rsa_size(c->rsa);
        char buffer[len * 2 + 1];
 
-       if(!c->hischallenge) {
-               c->hischallenge = xrealloc(c->hischallenge, len);
-       }
+       c->hischallenge = xrealloc(c->hischallenge, len);
 
        /* Copy random data to the buffer */
 
@@ -676,41 +693,59 @@ bool challenge_h(connection_t *c, const char *request) {
 
        char buffer[MAX_STRING_SIZE];
        const size_t len = rsa_size(myself->connection->rsa);
-       size_t digestlen = digest_length(c->indigest);
-       char digest[digestlen];
 
        if(sscanf(request, "%*d " MAX_STRING, buffer) != 1) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Got bad %s from %s (%s)", "CHALLENGE", c->name, c->hostname);
                return false;
        }
 
-       /* Convert the challenge from hexadecimal back to binary */
-
-       int inlen = hex2bin(buffer, buffer, sizeof(buffer));
-
        /* Check if the length of the challenge is all right */
 
-       if(inlen != len) {
+       if(strlen(buffer) != (size_t)len * 2) {
                logger(DEBUG_ALWAYS, LOG_ERR, "Possible intruder %s (%s): %s", c->name, c->hostname, "wrong challenge length");
                return false;
        }
 
+       c->mychallenge = xrealloc(c->mychallenge, len);
+
+       /* Convert the challenge from hexadecimal back to binary */
+
+       hex2bin(buffer, c->mychallenge, len);
+
+       /* The rest is done by send_chal_reply() */
+
+       c->allow_request = CHAL_REPLY;
+
+       if(c->outgoing) {
+               return send_chal_reply(c);
+       } else {
+               return true;
+       }
+
+#endif
+}
+
+bool send_chal_reply(connection_t *c) {
+       const size_t len = rsa_size(myself->connection->rsa);
+       size_t digestlen = digest_length(c->indigest);
+       char digest[digestlen * 2 + 1];
+
        /* Calculate the hash from the challenge we received */
 
-       if(!digest_create(c->indigest, buffer, len, digest)) {
+       if(!digest_create(c->indigest, c->mychallenge, len, digest)) {
                return false;
        }
 
+       free(c->mychallenge);
+       c->mychallenge = NULL;
+
        /* Convert the hash to a hexadecimal formatted string */
 
-       bin2hex(digest, buffer, digestlen);
+       bin2hex(digest, digest, digestlen);
 
        /* Send the reply */
 
-       c->allow_request = CHAL_REPLY;
-
-       return send_request(c, "%d %s", CHAL_REPLY, buffer);
-#endif
+       return send_request(c, "%d %s", CHAL_REPLY, digest);
 }
 
 bool chal_reply_h(connection_t *c, const char *request) {
@@ -752,6 +787,10 @@ bool chal_reply_h(connection_t *c, const char *request) {
        c->hischallenge = NULL;
        c->allow_request = ACK;
 
+       if(!c->outgoing) {
+               send_chal_reply(c);
+       }
+
        return send_ack(c);
 #endif
 }