CURLOPT_PROXY_CAINFO(3) Library Functions Manual CURLOPT_PROXY_CAINFO(3)
NAME
CURLOPT_PROXY_CAINFO - path to proxy Certificate Authority (CA) bundle
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_CAINFO, char *path);
DESCRIPTION
This option is for connecting to an HTTPS proxy, not an HTTPS server.
Pass a char pointer to a null-terminated string naming a file holding
one or more certificates to verify the HTTPS proxy with.
If CURLOPT_PROXY_SSL_VERIFYPEER(3) is zero and you avoid verifying the
server's certificate, CURLOPT_PROXY_CAINFO(3) need not even indicate an
accessible file.
This option is by default set to the system path where libcurl's CA cer-
tificate bundle is assumed to be stored, as established at build time.
(iOS and macOS only) If curl is built against Secure Transport, then
this option is supported for backward compatibility with other SSL en-
gines, but it should not be set. If the option is not set, then curl
uses the certificates in the system and user Keychain to verify the
peer, which is the preferred method of verifying the peer's certificate
chain.
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again and switches back
to internal default.
The default value for this can be figured out with CURLINFO_CAINFO(3).
DEFAULT
Built-in system specific
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
All TLS backends support this option.
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode res;
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
/* using an HTTPS proxy */
curl_easy_setopt(curl, CURLOPT_PROXY, "https://localhost:443");
curl_easy_setopt(curl, CURLOPT_PROXY_CAINFO, "/etc/certs/cabundle.pem");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
NOTES
For TLS backends that do not support certificate files, the CUR-
LOPT_PROXY_CAINFO(3) option is ignored. Refer to
https://curl.se/docs/ssl-compared.html
AVAILABILITY
Added in curl 7.52.0
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_CAINFO(3), CURLOPT_CAINFO_BLOB(3), CURLOPT_CAPATH(3), CUR-
LOPT_PROXY_CAINFO_BLOB(3), CURLOPT_PROXY_CAPATH(3), CUR-
LOPT_PROXY_SSL_VERIFYHOST(3), CURLOPT_PROXY_SSL_VERIFYPEER(3), CUR-
LOPT_SSL_VERIFYHOST(3), CURLOPT_SSL_VERIFYPEER(3)
libcurl 2026-07-12 CURLOPT_PROXY_CAINFO(3)
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