[glib-networking/mcatanzaro/proxy-validation] genvironmentproxyresolver: validate environment variable values

[Michael Catanzaro <mcatanzaro src gnome org>]

commit da3397dd2b2c8979875d3a7e4e306846c26c13f0
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Thu Jun 9 16:28:32 2022 -0500

    genvironmentproxyresolver: validate environment variable values
    
    Instead of blindly trusting the environment, let's make sure we have
    actually received proper URLs. An empty string will be assumed to mean
    "no proxy, please." Any empty environment variable will still cause all
    GNOME proxy settings to be ignored, because you might want to use an
    empty environment variable to temporarily suppress use of GNOME proxy
    settings without messing with XDG_CURRENT_DESKTOP.
    
    Helps with glib#2597
    
    Fixes #189

 proxy/environment/genvironmentproxyresolver.c | 50 +++++++++++++++++++--------
 1 file changed, 36 insertions(+), 14 deletions(-)
---
diff --git a/proxy/environment/genvironmentproxyresolver.c b/proxy/environment/genvironmentproxyresolver.c
index d15e4590..cfbdbb8e 100644
--- a/proxy/environment/genvironmentproxyresolver.c
+++ b/proxy/environment/genvironmentproxyresolver.c
@@ -118,11 +118,34 @@ g_environment_proxy_resolver_finalize (GObject *object)
   G_OBJECT_CLASS (g_environment_proxy_resolver_parent_class)->finalize (object);
 }
 
+static const char *
+validate_proxy_envvar (const char *var)
+{
+  const char *url;
+  GError *error = NULL;
+
+  if ((url = g_getenv (var)))
+    {
+      /* Empty strings mean no proxy. */
+      if (*url == '\0')
+        return NULL;
+
+      if (g_uri_is_valid (url, G_URI_FLAGS_NONE, &error))
+        return url;
+
+      g_warning ("Environment variable %s specifies invalid proxy URL %s: %s", var, url, error->message);
+      g_error_free (error);
+    }
+
+  return NULL;
+}
+
 static void
 g_environment_proxy_resolver_init (GEnvironmentProxyResolver *resolver)
 {
   char **ignore_hosts = NULL;
   const char *default_proxy = NULL;
+  const char *url;
 
   if (g_getenv ("no_proxy"))
     ignore_hosts = g_strsplit (g_getenv ("no_proxy"), ",", -1);
@@ -134,24 +157,23 @@ g_environment_proxy_resolver_init (GEnvironmentProxyResolver *resolver)
    * This matches the behavior of libproxy's environment variable module, or
    * GNOME's use-same-proxy setting.
    */
-  if (g_getenv ("http_proxy"))
-    default_proxy = g_getenv ("http_proxy");
-  else if (g_getenv ("HTTP_PROXY"))
-    default_proxy = g_getenv ("HTTP_PROXY");
+  if ((url = validate_proxy_envvar ("http_proxy")))
+    default_proxy = url;
+  else if ((url = validate_proxy_envvar ("HTTP_PROXY")))
+    default_proxy = url;
 
   resolver->base_resolver = g_simple_proxy_resolver_new (default_proxy, ignore_hosts);
+  g_strfreev (ignore_hosts);
 
-  if (g_getenv ("ftp_proxy"))
-    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "ftp", 
g_getenv ("ftp_proxy"));
-  else if (g_getenv ("FTP_PROXY"))
-    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "ftp", 
g_getenv ("FTP_PROXY"));
-
-  if (g_getenv ("https_proxy"))
-    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "https", 
g_getenv ("https_proxy"));
-  else if (g_getenv ("HTTPS_PROXY"))
-    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "https", 
g_getenv ("HTTPS_PROXY"));
+  if ((url = validate_proxy_envvar ("ftp_proxy")))
+    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "ftp", url);
+  else if ((url = validate_proxy_envvar ("FTP_PROXY")))
+    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "ftp", url);
 
-  g_strfreev (ignore_hosts);
+  if ((url = validate_proxy_envvar ("https_proxy")))
+    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "https", url);
+  else if ((url = validate_proxy_envvar ("HTTPS_PROXY")))
+    g_simple_proxy_resolver_set_uri_proxy (G_SIMPLE_PROXY_RESOLVER (resolver->base_resolver), "https", url);
 }
 
 static void