curl: Backport SOCKS5 heap buffer overflow fix from curl 8.4.0

Backport upstream curl commit `fb4415d8ae` (socks: return error if
hostname too long for remote resolve, 2023-10-11, curl-8_4_0~2) to
address CVE-2023-38545.

Issue: #25329

Utilities/cmcurl/lib/socks.c

@@ -539,9 +539,9 @@ static CURLproxycode do_SOCKS5(struct Curl_cfilter *cf,
 
     /* RFC1928 chapter 5 specifies max 255 chars for domain name in packet */
     if(!socks5_resolve_local && hostname_len > 255) {
-      infof(data, "SOCKS5: server resolving disabled for hostnames of "
-            "length > 255 [actual len=%zu]", hostname_len);
-      socks5_resolve_local = TRUE;
+      failf(data, "SOCKS5: the destination hostname is too long to be "
+            "resolved remotely by the proxy.");
+      return CURLPX_LONG_HOSTNAME;
     }
 
     if(auth & ~(CURLAUTH_BASIC | CURLAUTH_GSSAPI))
@@ -882,7 +882,7 @@ static CURLproxycode do_SOCKS5(struct Curl_cfilter *cf,
       }
       else {
         socksreq[len++] = 3;
-        socksreq[len++] = (char) hostname_len; /* one byte address length */
+        socksreq[len++] = (unsigned char) hostname_len; /* one byte length */
         memcpy(&socksreq[len], sx->hostname, hostname_len); /* w/o NULL */
         len += hostname_len;
       }