bionic (3) CURLOPT_PINNEDPUBLICKEY.3.gz

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 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_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

         7.54.1: SecureTransport/DarwinSSL on macOS 10.7+/iOS 10+

       sha256 support:

         7.44.0: OpenSSL, GnuTLS, NSS and wolfSSL/CyaSSL

         7.47.0: mbedtls

         7.49.0: PolarSSL

         7.54.1: SecureTransport/DarwinSSL on macOS 10.7+/iOS 10+

       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), CURLOPT_CAINFO(3), CURLOPT_CAPATH(3),