NAME

       CURLOPT_PROXY_PINNEDPUBLICKEY - set pinned public key for https proxy

SYNOPSIS

       #include <curl/curl.h>

       CURLcode     curl_easy_setopt(CURL     *handle,     CURLOPT_PROXY_PINNEDPUBLICKEY,    char
       *pinnedpubkey);

DESCRIPTION

       Pass a pointer to a zero terminated string as parameter. The string can be the  file  name
       of  your  pinned  public  key. The file format expected is "PEM" or "DER".  The string can
       also be any number of base64 encoded sha256 hashes preceded by "sha256//" and separated by
       ";"

       When  negotiating  a TLS or SSL connection, the https proxy sends a certificate indicating
       its identity. A public key is extracted from this certificate and if it does  not  exactly
       match  the  public  key  provided  to  this  option, curl will abort the connection before
       sending or receiving any data.

       On mismatch, CURLE_SSL_PINNEDPUBKEYNOTMATCH is returned.

       The application does not have to keep the string around after setting this option.

DEFAULT

       NULL

PROTOCOLS

       All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
         curl_easy_setopt(curl, CURLOPT_PROXY, "https://proxy:443");
         curl_easy_setopt(curl, CURLOPT_PROXY_PINNEDPUBLICKEY,
         "sha256//YhKJKSzoTt2b5FP18fvpHo7fJYqQCjAa3HWY3tvRMwE=;sha256//t62CeU2tQiqkexU74Gxa2eg7fRbEgoChTociMee9wno=");

         /* Perform the request */
         curl_easy_perform(curl);
       }

PUBLIC KEY EXTRACTION

       If you do not have the https proxy server's public key file you can extract  it  from  the
       https proxy server's certificate.
       # retrieve the server's certificate if you don't already have it
       #
       # be sure to examine the certificate to see if it is what you expected
       #
       # Windows-specific:
       # - Use NUL instead of /dev/null.
       # - OpenSSL may wait for input instead of disconnecting. Hit enter.
       # - If you don't have sed, then just copy the certificate into a file:
       #   Lines from -----BEGIN CERTIFICATE----- to -----END CERTIFICATE-----.
       #
       openssl s_client -servername www.example.com -connect www.example.com:443 < /dev/null | sed -n "/-----BEGIN/,/-----END/p" > www.example.com.pem

       # extract public key in pem format from certificate
       openssl x509 -in www.example.com.pem -pubkey -noout > www.example.com.pubkey.pem

       # convert public key from pem to der
       openssl asn1parse -noout -inform pem -in www.example.com.pubkey.pem -out www.example.com.pubkey.der

       # sha256 hash and base64 encode der to string for use
       openssl dgst -sha256 -binary www.example.com.pubkey.der | openssl base64
       The public key in PEM format contains a header, base64 data and a footer:
       -----BEGIN PUBLIC KEY-----
       [BASE 64 DATA]

       -----END PUBLIC KEY-----

AVAILABILITY

       PEM/DER support:

         7.52.0: GSKit, GnuTLS, NSS, OpenSSL, mbedtls, wolfSSL

       sha256 support:

         7.52.0: GnuTLS, NSS, OpenSSL, mbedtls, wolfSSL

       Other SSL backends not supported.

RETURN VALUE

       Returns  CURLE_OK  if  TLS enabled, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if
       there was insufficient heap space.

SEE ALSO

       CURLOPT_PROXY_SSL_VERIFYPEER(3), CURLOPT_PROXY_SSL_VERIFYHOST(3), CURLOPT_PROXY_CAINFO(3),
       CURLOPT_PROXY_CAPATH(3),