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proxy: optimized env lookups

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Optimize proxy env var lookups for the commen case of 'https' and 'http'
urls. We do this for every transfer.

Closes #22168
This commit is contained in:
Stefan Eissing 2026-06-25 13:14:17 +02:00 • committed by Daniel Stenberg
parent a6af50c484
commit 00d5562650
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GPG key ID: 5CC908FDB71E12C2
1 changed files with 48 additions and 45 deletions
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93
lib/proxy.c
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@ -282,8 +282,6 @@ UNITTEST bool proxy_check_noproxy(const char *name, const char *no_proxy)
static char *proxy_detect_proxy(struct Curl_easy *data,
const struct Curl_scheme *scheme)
{
char *proxy = NULL;
/* If proxy was not specified, we check for default proxy environment
* variables, to enable i.e Lynx compliance:
*
@ -301,58 +299,63 @@ static char *proxy_detect_proxy(struct Curl_easy *data,
* For compatibility, the all-uppercase versions of these variables are
* checked if the lowercase versions do not exist.
*/
char proxy_env[20];
const char *envp;
VERBOSE(envp = proxy_env);
const char *env_name = NULL;
char *proxy = NULL;
char name_buf[20];
curl_msnprintf(proxy_env, sizeof(proxy_env), "%s_proxy", scheme->name);
/* Try scheme specific env var first, unless http(s).
* lowercase first, then uppercase. */
if((scheme != &Curl_scheme_https) && (scheme != &Curl_scheme_http)) {
curl_msnprintf(name_buf, sizeof(name_buf), "%s_proxy", scheme->name);
env_name = name_buf;
proxy = curl_getenv(env_name);
if(!proxy) {
Curl_strntoupper(name_buf, name_buf, sizeof(name_buf));
proxy = curl_getenv(env_name);
}
}
/* read the protocol proxy: */
proxy = curl_getenv(proxy_env);
/*
* We do not try the uppercase version of HTTP_PROXY because of
* security reasons:
*
* When curl is used in a webserver application
* environment (cgi or php), this environment variable can
* be controlled by the web server user by setting the
* http header 'Proxy:' to some value.
*
* This can cause 'internal' http/ftp requests to be
* arbitrarily redirected by any external attacker.
*/
if(!proxy && !curl_strequal("http_proxy", proxy_env)) {
/* There was no lowercase variable, try the uppercase version: */
Curl_strntoupper(proxy_env, proxy_env, sizeof(proxy_env));
proxy = curl_getenv(proxy_env);
if(!proxy &&
((scheme == &Curl_scheme_https) || (scheme == &Curl_scheme_wss))) {
/* Not found, check 'https' env vars, also for 'wss'.
* Again, first lowercase then uppercase. */
env_name = "https_proxy";
proxy = curl_getenv(env_name);
if(!proxy) {
env_name = "HTTPS_PROXY";
proxy = curl_getenv(env_name);
}
}
else if(!proxy &&
((scheme == &Curl_scheme_http) || (scheme == &Curl_scheme_ws))) {
/* Not found, check 'http' env vars, also for 'ws'.
* We do NOT try the uppercase version 'HTTP_PROXY' because of
* security reasons:
*
* When curl is used in a webserver application
* environment (cgi or php), this environment variable can
* be controlled by the web server user by setting the
* http header 'Proxy:' to some value.
*
* This can cause 'internal' http/ftp requests to be
* arbitrarily redirected by any external attacker.
*/
env_name = "http_proxy";
proxy = curl_getenv(env_name);
}
if(!proxy) {
#ifndef CURL_DISABLE_WEBSOCKETS
/* websocket proxy fallbacks */
if(curl_strequal("ws_proxy", proxy_env)) {
proxy = curl_getenv("http_proxy");
}
else if(curl_strequal("wss_proxy", proxy_env)) {
proxy = curl_getenv("https_proxy");
if(!proxy)
proxy = curl_getenv("HTTPS_PROXY");
}
/* still not found, last resort checks. */
env_name = "all_proxy";
proxy = curl_getenv(env_name);
if(!proxy) {
#endif
envp = "all_proxy";
proxy = curl_getenv(envp); /* default proxy to use */
if(!proxy) {
envp = "ALL_PROXY";
proxy = curl_getenv(envp);
}
#ifndef CURL_DISABLE_WEBSOCKETS
env_name = "ALL_PROXY";
proxy = curl_getenv(env_name);
}
#endif
}
if(proxy)
infof(data, "Uses proxy env variable %s == '%s'", envp, proxy);
infof(data, "Uses proxy env variable %s == '%s'", env_name, proxy);
return proxy;
}