Provided by: libcurl4-doc_8.9.1-2ubuntu2.1_all bug

NAME

       CURLOPT_PROXY_PINNEDPUBLICKEY - 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 null-terminated string as parameter. The string can be the filename 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, libcurl aborts 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

       This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

       This option works only with the following  TLS  backends:  GnuTLS,  OpenSSL,  mbedTLS  and
       wolfSSL

EXAMPLE

       int main(void)
       {
         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//YhKJKSzoTt2b5FP18fvpHo7fJYqQCjA"
                            "a3HWY3tvRMwE=;sha256//t62CeU2tQiqkexU74"
                            "Gxa2eg7fRbEgoChTociMee9wno=");

           /* 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 do not 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 do not 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-----

HISTORY

       PEM/DER support:

        7.52.0: GnuTLS, OpenSSL, mbedTLS, wolfSSL

       sha256 support:

        7.52.0: GnuTLS, OpenSSL, mbedTLS, wolfSSL

       Other SSL backends not supported.

AVAILABILITY

       Added in curl 7.52.0

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