Consolidate check_http_status from gpst.c and ppp.c

This function checks a buffer for an unexpected HTTP status line ("HTTP/xxx
nnn ...") and returns the numeric status value (nnn) if found.

Also fixes a crash when GP config request ("/ssl-vpn/getconfig.esp") returns
no body at all.

Signed-off-by: Daniel Lenski <dlenski@gmail.com>

gpst.c

@@ -650,7 +650,7 @@ static int gpst_get_config(struct openconnect_info *vpninfo)
 		/* XX: if our "cookie" is bogus (doesn't include at least 'user', 'authcookie',
 		 * and 'portal' fields) the server will respond like this.
 		 */
-		if (result == -EINVAL && !strcmp(xml_buf, "errors getting SSL/VPN config"))
+		if (result == -EINVAL && xml_buf && !strcmp(xml_buf, "errors getting SSL/VPN config"))
 			result = -EPERM;
 		goto out;
 	}
@@ -741,10 +741,15 @@ static int gpst_connect(struct openconnect_info *vpninfo)
 			ret = vpninfo->ssl_gets(vpninfo, buf+sizeof(start_tunnel), sizeof(buf)-sizeof(start_tunnel));
 			ret = (ret>0 ? ret : 0) + sizeof(start_tunnel);
 		}
-		vpn_progress(vpninfo, PRG_ERR,
-		             _("Got inappropriate HTTP GET-tunnel response: %.*s\n"), ret, buf);
-		/* XX: this is what GP servers return when they don't like the cookie */
-		ret = !strncmp(buf, "HTTP/1.1 502 ", 13) ? -EPERM : -EINVAL;
+		int status = check_http_status(buf, ret);
+		/* XX: GP servers return 502 when they don't like the cookie */
+		if (status == 502)
+			ret = -EPERM;
+		else {
+			vpn_progress(vpninfo, PRG_ERR, _("Got unexpected HTTP response: %.*s\n"),
+				     ret, buf);
+			ret = -EINVAL;
+		}
 	}
 
 	if (ret < 0)

openconnect-internal.h

@@ -1062,6 +1062,7 @@ int ppp_tcp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readabl
 int ppp_udp_mainloop(struct openconnect_info *vpninfo, int *timeout, int readable);
 int openconnect_ppp_new(struct openconnect_info *vpninfo, int encap, int want_ipv4, int want_ipv6);
 int ppp_reset(struct openconnect_info *vpninfo);
+int check_http_status(const char *buf, int len);
 
 /* auth-globalprotect.c */
 int gpst_obtain_cookie(struct openconnect_info *vpninfo);

ppp.c

@@ -1047,6 +1047,17 @@ static inline void add_ppp_header(struct pkt *p, struct oc_ppp *ppp, int proto)
 	p->ppp.hlen = p->data - ph;
 }
 
+int check_http_status(const char *buf, int len)
+{
+	if (len >= 5 && !memcmp(buf, "HTTP/", 5)) {
+		const char *eol = memchr(buf, '\r', len) ?: memchr(buf, '\n', len);
+		const char *sp1 = memchr(buf, ' ', len);
+		const char *sp2 = sp1 ? memchr(sp1+1, ' ', len - (sp1-buf) + 1) : NULL;
+		return (sp1 && sp2 && (!eol || sp2<eol)) ? atoi(sp1+1) : 500;
+	}
+	return -EINVAL;
+}
+
 static int ppp_mainloop(struct openconnect_info *vpninfo, int dtls,
 			struct keepalive_info *kai, int *timeout, int readable)
 {
@@ -1101,17 +1112,11 @@ static int ppp_mainloop(struct openconnect_info *vpninfo, int dtls,
 		 * of the first packet
 		 */
 		if (ppp->check_http_response) {
+			int status = check_http_status((const char *)eh, len);
 			ppp->check_http_response = 0;
-			if (!memcmp(eh, "HTTP/", 5)) {
-				const char *sol = (const char *)eh;
-				const char *eol = memchr(sol, '\r', len) ?: memchr(sol, '\n', len);
-				const char *sp1 = memchr(sol, ' ', len);
-				const char *sp2 = memchr(sp1+1, ' ', len - (sp1-sol) + 1);
-				int status = sp1 && sp2 ? atoi(sp1+1) : -1;
-				if (eol)
-					len = eol - sol;
-				vpn_progress(vpninfo, PRG_ERR,
-					     _("Got unexpected HTTP response: %.*s\n"), len, sol);
+		        if (status >= 0) {
+				vpn_progress(vpninfo, PRG_ERR,_("Got unexpected HTTP response: %.*s\n"),
+					     len, (const char *)eh);
 				vpninfo->quit_reason = "Received HTTP response (not a PPP packet)";
 				return (status >= 400 && status <= 499) ? -EPERM : -EINVAL;
 			}