CURLOPT_TLSAUTH_TYPE man page
CURLOPT_TLSAUTH_TYPE — set TLS authentication methods
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TLSAUTH_TYPE, char *type);
Pass a pointer to a zero terminated string as parameter. The string should be the method of the TLS authentication. Supported method is "SRP".
TLS-SRP authentication. Secure Remote Password authentication for TLS is defined in RFC5054 and provides mutual authentication if both sides have a shared secret. To use TLS-SRP, you must also set the CURLOPT_TLSAUTH_USERNAME(3) and CURLOPT_TLSAUTH_PASSWORD(3) options.
The application does not have to keep the string around after setting this option.
All TLS-based protocols
You need to build libcurl with GnuTLS or OpenSSL with TLS-SRP support for this to work. Added in 7.21.4
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
curl_easy_setopt(3), CURLOPT_PROXY_TLSAUTH_PASSWORD(3), CURLOPT_PROXY_TLSAUTH_USERNAME(3), CURLOPT_TLSAUTH_PASSWORD(3), CURLOPT_TLSAUTH_USERNAME(3).