161 lines
6.3 KiB
Plaintext
161 lines
6.3 KiB
Plaintext
=pod
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=head1 NAME
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X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 certificate matching
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=head1 SYNOPSIS
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#include <openssl/x509v3.h>
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int X509_check_host(X509 *, const char *name, size_t namelen,
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unsigned int flags, char **peername);
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int X509_check_email(X509 *, const char *address, size_t addresslen,
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unsigned int flags);
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int X509_check_ip(X509 *, const unsigned char *address, size_t addresslen,
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unsigned int flags);
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int X509_check_ip_asc(X509 *, const char *address, unsigned int flags);
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=head1 DESCRIPTION
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The certificate matching functions are used to check whether a
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certificate matches a given hostname, email address, or IP address.
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The validity of the certificate and its trust level has to be checked by
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other means.
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X509_check_host() checks if the certificate Subject Alternative
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Name (SAN) or Subject CommonName (CN) matches the specified hostname,
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which must be encoded in the preferred name syntax described
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in section 3.5 of RFC 1034. By default, wildcards are supported
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and they match only in the left-most label; but they may match
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part of that label with an explicit prefix or suffix. For example,
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by default, the host B<name> "www.example.com" would match a
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certificate with a SAN or CN value of "*.example.com", "w*.example.com"
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or "*w.example.com".
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Per section 6.4.2 of RFC 6125, B<name> values representing international
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domain names must be given in A-label form. The B<namelen> argument
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must be the number of characters in the name string or zero in which
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case the length is calculated with strlen(B<name>). When B<name> starts
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with a dot (e.g. ".example.com"), it will be matched by a certificate
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valid for any sub-domain of B<name>, (see also
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B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below).
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When the certificate is matched, and B<peername> is not NULL, a
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pointer to a copy of the matching SAN or CN from the peer certificate
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is stored at the address passed in B<peername>. The application
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is responsible for freeing the peername via OPENSSL_free() when it
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is no longer needed.
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X509_check_email() checks if the certificate matches the specified
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email B<address>. Only the mailbox syntax of RFC 822 is supported,
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comments are not allowed, and no attempt is made to normalize quoted
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characters. The B<addresslen> argument must be the number of
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characters in the address string or zero in which case the length
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is calculated with strlen(B<address>).
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X509_check_ip() checks if the certificate matches a specified IPv4 or
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IPv6 address. The B<address> array is in binary format, in network
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byte order. The length is either 4 (IPv4) or 16 (IPv6). Only
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explicitly marked addresses in the certificates are considered; IP
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addresses stored in DNS names and Common Names are ignored.
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X509_check_ip_asc() is similar, except that the NUL-terminated
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string B<address> is first converted to the internal representation.
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The B<flags> argument is usually 0. It can be the bitwise OR of the
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flags:
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=over 4
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=item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>,
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=item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>,
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=item B<X509_CHECK_FLAG_NO_WILDCARDS>,
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=item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>,
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=item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>.
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=item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>.
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=back
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The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function
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to consider the subject DN even if the certificate contains at least
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one subject alternative name of the right type (DNS name or email
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address as appropriate); the default is to ignore the subject DN
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when at least one corresponding subject alternative names is present.
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The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never
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consider the subject DN even if the certificate contains no subject alternative
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names of the right type (DNS name or email address as appropriate); the default
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is to use the subject DN when no corresponding subject alternative names are
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present.
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If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and
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B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes
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precedence and the subject DN is not checked for matching names.
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If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard
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expansion; this only applies to B<X509_check_host>.
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If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support
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for "*" as wildcard pattern in labels that have a prefix or suffix,
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such as: "www*" or "*www"; this only applies to B<X509_check_host>.
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If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that
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constitutes the complete label of a DNS name (e.g. "*.example.com")
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to match more than one label in B<name>; this flag only applies
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to B<X509_check_host>.
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If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name>
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values which start with ".", that would otherwise match any sub-domain
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in the peer certificate, to only match direct child sub-domains.
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Thus, for instance, with this flag set a B<name> of ".example.com"
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would match a peer certificate with a DNS name of "www.example.com",
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but would not match a peer certificate with a DNS name of
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"www.sub.example.com"; this flag only applies to B<X509_check_host>.
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=head1 RETURN VALUES
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The functions return 1 for a successful match, 0 for a failed match
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and -1 for an internal error: typically a memory allocation failure
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or an ASN.1 decoding error.
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All functions can also return -2 if the input is malformed. For example,
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X509_check_host() returns -2 if the provided B<name> contains embedded
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NULs.
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=head1 NOTES
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Applications are encouraged to use X509_VERIFY_PARAM_set1_host()
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rather than explicitly calling L<X509_check_host(3)>. Host name
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checks may be out of scope with the DANE-EE(3) certificate usage,
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and the internal checks will be suppressed as appropriate when
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DANE support is enabled.
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=head1 SEE ALSO
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L<SSL_get_verify_result(3)>,
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L<X509_VERIFY_PARAM_set1_host(3)>,
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L<X509_VERIFY_PARAM_add1_host(3)>,
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L<X509_VERIFY_PARAM_set1_email(3)>,
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L<X509_VERIFY_PARAM_set1_ip(3)>,
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L<X509_VERIFY_PARAM_set1_ipasc(3)>
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=head1 HISTORY
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These functions were added in OpenSSL 1.0.2.
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=head1 COPYRIGHT
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Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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