CURLOPT_PINNEDPUBLICKEY(3) curl_easy_setopt options CURLOPT_PINNEDPUBLICKEY(3)NAMECURLOPT_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.
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
Added in 7.39.0 for OpenSSL, GnuTLS and GSKit. Added in 7.43.0 for NSS
and wolfSSL/CyaSSL. sha256 support added in 7.44.0 for OpenSSL, GnuTLS,
NSS and wolfSSL/CyaSSL. 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 ALSOCURLOPT_SSL_VERIFYPEER(3), CURLOPT_SSL_VERIFYHOST(3), CUR‐
LOPT_CAINFO(3), CURLOPT_CAPATH(3),
libcurl 7.38.0 27 Aug 2014 CURLOPT_PINNEDPUBLICKEY(3)
