CURLOPT_PINNEDPUBLICKEY(3)

1CURLOPT_PINNEDPUBLICKEY(3) curl_easy_setopt options CURLOPT_PINNEDPUBLICKEY(3)
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NAME

6       CURLOPT_PINNEDPUBLICKEY - set pinned public key
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SYNOPSIS

9       #include <curl/curl.h>
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11       CURLcode  curl_easy_setopt(CURL  *handle, CURLOPT_PINNEDPUBLICKEY, char
12       *pinnedpubkey);
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DESCRIPTION

15       Pass a pointer to a zero terminated string as parameter. The string can
16       be the file name of your pinned public key. The file format expected is
17       "PEM" or "DER".  The string can also be any number  of  base64  encoded
18       sha256 hashes preceded by "sha256//" and separated by ";"
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20       When  negotiating  a TLS or SSL connection, the server sends a certifi‐
21       cate indicating its identity. A public key is extracted from this  cer‐
22       tificate  and  if  it does not exactly match the public key provided to
23       this option, curl will abort the connection before sending or receiving
24       any data.
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26       On mismatch, CURLE_SSL_PINNEDPUBKEYNOTMATCH is returned.
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28       The  application  does not have to keep the string around after setting
29       this option.
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DEFAULT

32       NULL
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PROTOCOLS

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

38       CURL *curl = curl_easy_init();
39       if(curl) {
40         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
41         curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, "/etc/publickey.der");
42         /* OR
43         curl_easy_setopt(curl, CURLOPT_PINNEDPUBLICKEY, "sha256//YhKJKSzoTt2b5FP18fvpHo7fJYqQCjAa3HWY3tvRMwE=;sha256//t62CeU2tQiqkexU74Gxa2eg7fRbEgoChTociMee9wno=");
44         */
45
46         /* Perform the request */
47         curl_easy_perform(curl);
48       }
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PUBLIC KEY EXTRACTION

51       If you do not have the server's public key file you can extract it from
52       the server's certificate.
53       # retrieve the server's certificate if you don't already have it
54       #
55       # be sure to examine the certificate to see if it is what you expected
56       #
57       # Windows-specific:
58       # - Use NUL instead of /dev/null.
59       # - OpenSSL may wait for input instead of disconnecting. Hit enter.
60       # - If you don't have sed, then just copy the certificate into a file:
61       #   Lines from -----BEGIN CERTIFICATE----- to -----END CERTIFICATE-----.
62       #
63       openssl s_client -servername www.example.com -connect www.example.com:443 < /dev/null | sed -n "/-----BEGIN/,/-----END/p" > www.example.com.pem
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65       # extract public key in pem format from certificate
66       openssl x509 -in www.example.com.pem -pubkey -noout > www.example.com.pubkey.pem
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68       # convert public key from pem to der
69       openssl asn1parse -noout -inform pem -in www.example.com.pubkey.pem -out www.example.com.pubkey.der
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71       # sha256 hash and base64 encode der to string for use
72       openssl dgst -sha256 -binary www.example.com.pubkey.der | openssl base64
73       The  public  key  in  PEM  format  contains a header, base64 data and a
74       footer:
75       -----BEGIN PUBLIC KEY-----
76       [BASE 64 DATA]
77       -----END PUBLIC KEY-----
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AVAILABILITY

80       PEM/DER support:
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82         7.39.0: OpenSSL, GnuTLS
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84         7.39.0-7.48.0,7.58.1+: GSKit
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86         7.43.0: NSS and wolfSSL
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88         7.47.0: mbedtls
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90         7.54.1: SecureTransport on macOS 10.7+/iOS 10+
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92         7.58.1: SChannel
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94       sha256 support:
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96         7.44.0: OpenSSL, GnuTLS, NSS and wolfSSL
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98         7.47.0: mbedtls
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100         7.54.1: SecureTransport on macOS 10.7+/iOS 10+
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102         7.58.1: SChannel Windows XP SP3+
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104       Other SSL backends not supported.
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RETURN VALUE

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