CURLOPT_PINNEDPUBLICKEY(3) curl_easy_setopt options CURLOPT_PINNEDPUBLICKEY(3)

NAME
       CURLOPT_PINNEDPUBLICKEY - set pinned public key

SYNOPSIS
       #include <curl/curl.h>

       CURLcode  curl_easy_setopt(CURL  *handle, CURLOPT_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 server sends a certifi-
       cate indicating its identity. A public key is extracted from this  cer-
       tificate  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_PINNEDPUBLICKEY, "/etc/publickey.der");
         /* OR
         curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, "sha256//YhKJKSzoTt2b5FP18fvpHo7fJYqQCjAa3HWY3tvRMwE=;sha256//t62CeU2tQiqkexU74Gxa2eg7fRbEgoChTociMee9wno=");
         */

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

PUBLIC KEY EXTRACTION
       If you do not have the server's public key file you can extract it from
       the 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:

         7.39.0: OpenSSL, GnuTLS and GSKit

         7.43.0: NSS and wolfSSL/CyaSSL

         7.47.0: mbedtls

         7.49.0: PolarSSL

       sha256 support:

         7.44.0: OpenSSL, GnuTLS, NSS and wolfSSL/CyaSSL

         7.47.0: mbedtls

         7.49.0: PolarSSL

       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_SSL_VERIFYPEER(3),        CURLOPT_SSL_VERIFYHOST(3),       CUR-
       LOPT_CAINFO(3), CURLOPT_CAPATH(3),

libcurl 7.54.0                 December 21, 2016    CURLOPT_PINNEDPUBLICKEY(3)