Curl_inet_ntop: always check the return code

Reported-by: Siva Sivaraman
Fixes #5412
Closes #5597

lib/ftp.c

@@ -1043,6 +1043,7 @@ static CURLcode ftp_state_use_port(struct connectdata *conn,
   } /* data->set.ftpport */
 
   if(!host) {
+    const char *r;
     /* not an interface and not a host name, get default by extracting
        the IP from the control connection */
     sslen = sizeof(ss);
@@ -1055,13 +1056,15 @@ static CURLcode ftp_state_use_port(struct connectdata *conn,
     switch(sa->sa_family) {
 #ifdef ENABLE_IPV6
     case AF_INET6:
-      Curl_inet_ntop(sa->sa_family, &sa6->sin6_addr, hbuf, sizeof(hbuf));
+      r = Curl_inet_ntop(sa->sa_family, &sa6->sin6_addr, hbuf, sizeof(hbuf));
       break;
 #endif
     default:
-      Curl_inet_ntop(sa->sa_family, &sa4->sin_addr, hbuf, sizeof(hbuf));
+      r = Curl_inet_ntop(sa->sa_family, &sa4->sin_addr, hbuf, sizeof(hbuf));
       break;
     }
+    if(!r)
+      return CURLE_FTP_PORT_FAILED;
     host = hbuf; /* use this host name */
     possibly_non_local = FALSE; /* we know it is local now */
   }

lib/if2ip.c

@@ -118,7 +118,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
         if(iface->ifa_addr->sa_family == af) {
           if(strcasecompare(iface->ifa_name, interf)) {
             void *addr;
-            char *ip;
+            const char *ip;
             char scope[12] = "";
             char ipstr[64];
 #ifdef ENABLE_IPV6
@@ -153,15 +153,15 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
               }
 
               if(scopeid)
-                  msnprintf(scope, sizeof(scope), "%%%u", scopeid);
+                msnprintf(scope, sizeof(scope), "%%%u", scopeid);
 #endif
             }
             else
 #endif
               addr =
-                  &((struct sockaddr_in *)(void *)iface->ifa_addr)->sin_addr;
+                &((struct sockaddr_in *)(void *)iface->ifa_addr)->sin_addr;
             res = IF2IP_FOUND;
-            ip = (char *) Curl_inet_ntop(af, addr, ipstr, sizeof(ipstr));
+            ip = Curl_inet_ntop(af, addr, ipstr, sizeof(ipstr));
             msnprintf(buf, buf_size, "%s%s", ip, scope);
             break;
           }
@@ -190,6 +190,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
   struct sockaddr_in *s;
   curl_socket_t dummy;
   size_t len;
+  const char *r;
 
   (void)remote_scope;
   (void)local_scope_id;
@@ -219,9 +220,11 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
 
   s = (struct sockaddr_in *)(void *)&req.ifr_addr;
   memcpy(&in, &s->sin_addr, sizeof(in));
-  Curl_inet_ntop(s->sin_family, &in, buf, buf_size);
+  r = Curl_inet_ntop(s->sin_family, &in, buf, buf_size);
 
   sclose(dummy);
+  if(!r)
+    return IF2IP_NOT_FOUND;
   return IF2IP_FOUND;
 }