rcon server: add an explicit check against empty password, instead of assuming the...

This logic had a bug in the past that had been introduced by r8886 and
accidentally fixed when introducing multi-account support in r9420. The bug was
that rcon_password being empty led to the empty password being accepted in some
cases, as there was never any explicit logic to handle that in rcon - it was
more "accidentally" rejected by a packet formatting check which does not apply
to srcon as the empty password wouldn't be empty over the wire.

In other words: DP builds from [r8886, r9419] had a serious vulnerability and
the only workaround is to always have rcon_password set.

The check added here will complain and reject in case the calling code for some
reason no longer prevents empty passwords from being accepted.

Also adding comments to the new logic explaining how it prevents the empty
password from being accepted.

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@12334 d7cf8633-e32d-0410-b094-e92efae38249

diff --git a/netconn.c b/netconn.c
index 97f07bac167179115afd2ab3f8c45a3bf6f6d1ad..342d78b253cdb623d36ad5c1c9fee34b025bf970 100755 (executable)
--- a/netconn.c
+++ b/netconn.c
@@ -2739,6 +2739,11 @@ static qboolean hmac_mdfour_time_matching(lhnetaddress_t *peeraddress, const cha
        char mdfourbuf[16];
        long t1, t2;
 
+       if (!password[0]) {
+               Con_Print("^4LOGIC ERROR: RCon_Authenticate should never call the comparator with an empty password. Please report.\n");
+               return false;
+       }
+
        t1 = (long) time(NULL);
        t2 = strtol(s, NULL, 0);
        if(abs(t1 - t2) > rcon_secure_maxdiff.integer)
@@ -2755,6 +2760,11 @@ static qboolean hmac_mdfour_challenge_matching(lhnetaddress_t *peeraddress, cons
        char mdfourbuf[16];
        int i;
 
+       if (!password[0]) {
+               Con_Print("^4LOGIC ERROR: RCon_Authenticate should never call the comparator with an empty password. Please report.\n");
+               return false;
+       }
+
        if(slen < (int)(sizeof(challenges[0].string)) - 1)
                return false;
 
@@ -2781,6 +2791,11 @@ static qboolean hmac_mdfour_challenge_matching(lhnetaddress_t *peeraddress, cons
 
 static qboolean plaintext_matching(lhnetaddress_t *peeraddress, const char *password, const char *hash, const char *s, int slen)
 {
+       if (!password[0]) {
+               Con_Print("^4LOGIC ERROR: RCon_Authenticate should never call the comparator with an empty password. Please report.\n");
+               return false;
+       }
+
        return !strcmp(password, hash);
 }
 
@@ -2799,12 +2814,12 @@ static const char *RCon_Authenticate(lhnetaddress_t *peeraddress, const char *pa
        {
                have_usernames = true;
                strlcpy(buf, userpass_start, ((size_t)(userpass_end-userpass_start) >= sizeof(buf)) ? (int)(sizeof(buf)) : (int)(userpass_end-userpass_start+1));
-               if(buf[0])
+               if(buf[0])  // Ignore empty entries due to leading/duplicate space.
                        if(comparator(peeraddress, buf, password, cs, cslen))
                                goto allow;
                userpass_start = userpass_end + 1;
        }
-       if(userpass_start[0])
+       if(userpass_start[0])  // Ignore empty trailing entry due to trailing space or password not set.
        {
                userpass_end = userpass_start + strlen(userpass_start);
                if(comparator(peeraddress, userpass_start, password, cs, cslen))
@@ -2818,12 +2833,12 @@ static const char *RCon_Authenticate(lhnetaddress_t *peeraddress, const char *pa
        {
                have_usernames = true;
                strlcpy(buf, userpass_start, ((size_t)(userpass_end-userpass_start) >= sizeof(buf)) ? (int)(sizeof(buf)) : (int)(userpass_end-userpass_start+1));
-               if(buf[0])
+               if(buf[0])  // Ignore empty entries due to leading/duplicate space.
                        if(comparator(peeraddress, buf, password, cs, cslen))
                                goto check;
                userpass_start = userpass_end + 1;
        }
-       if(userpass_start[0])
+       if(userpass_start[0])  // Ignore empty trailing entry due to trailing space or password not set.
        {
                userpass_end = userpass_start + strlen(userpass_start);
                if(comparator(peeraddress, userpass_start, password, cs, cslen))