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CURLOPT_PROXY_ISSUERCERT(3) curl_easy_setopt options
CURLOPT_PROXY_ISSUERCERT - proxy issuer SSL certificate filename
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY_ISSUERCERT, char *file);
Pass a char * 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
the HTTPS proxy is indeed the one associated with the certificate
provided by the option. 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
CURLOPT_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_VERIFYPEER(3) has to be set too for the check to
The application does not have to keep the string around after setting
All TLS-based protocols
CURL *curl = curl_easy_init();
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_ISSUERCERT, "/etc/certs/cacert.pem");
ret = curl_easy_perform(curl);
Added in 7.71.0. This option is supported by the OpenSSL backends.
Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if
not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.
libcurl 7.86.0 May 17, 2022 CURLOPT_PROXY_ISSUERCERT(3)