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CURLOPT_PROXY_ISSUERCERT(3) Library Functions Manual CURLOPT_PROXY_ISSUERCERT(3) NAME CURLOPT_PROXY_ISSUERCERT - proxy issuer SSL certificate filename SYNOPSIS #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_ISSUERCERT, char *file); DESCRIPTION Pass a char pointer to a null-terminated string naming a file holding a CA certificate in PEM format. If the option is set, an additional check against the peer certificate is performed to verify the issuer of the HTTPS proxy is indeed the one associated with the certificate provided by the op- tion. This additional check is useful in multi-level PKI where one needs to enforce that the peer certificate is from a specific branch of the tree. This option makes sense only when used in combination with the CUR- LOPT_PROXY_SSL_VERIFYPEER(3) option. Otherwise, the result of the check is not considered as failure. A specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the option, which is returned if the setup of the SSL/TLS session has failed due to a mismatch with the issuer of peer certificate (CURLOPT_PROXY_SSL_VERI- FYPEER(3) has to be set too for the check to fail). 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. DEFAULT NULL PROTOCOLS This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. This option works only with the following TLS backends: GnuTLS and OpenSSL EXAMPLE int main(void) { CURL *curl = curl_easy_init(); if(curl) { CURLcode result; curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/"); /* using an HTTPS proxy */ curl_easy_setopt(curl, CURLOPT_PROXY, "https://proxy.example:443"); curl_easy_setopt(curl, CURLOPT_PROXY_ISSUERCERT, "/etc/certs/cacert.pem"); result = curl_easy_perform(curl); curl_easy_cleanup(curl); } } AVAILABILITY Added in curl 7.71.0 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_ISSUERCERT(3), CURLOPT_PROXY_SSL_VERIFYHOST(3), CUR- LOPT_PROXY_SSL_VERIFYPEER(3), CURLOPT_SSL_VERIFYHOST(3), CURLOPT_SSL_VERI- FYPEER(3) libcurl 2026-06-11 CURLOPT_PROXY_ISSUERCERT(3)
NAME | SYNOPSIS | DESCRIPTION | DEFAULT | PROTOCOLS | EXAMPLE | AVAILABILITY | RETURN VALUE | SEE ALSO
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