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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc \- X.509 certificate matching .SH "LIBRARY" libcrypto, -lcrypto .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& int X509_check_host(X509 *, const char *name, size_t namelen, \& unsigned int flags, char **peername); \& int X509_check_email(X509 *, const char *address, size_t addresslen, \& unsigned int flags); \& int X509_check_ip(X509 *, const unsigned char *address, size_t addresslen, \& unsigned int flags); \& int X509_check_ip_asc(X509 *, const char *address, unsigned int flags); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" The certificate matching functions are used to check whether a certificate matches a given hostname, email address, or \s-1IP\s0 address. The validity of the certificate and its trust level has to be checked by other means. .PP \&\fBX509_check_host()\fR checks if the certificate Subject Alternative Name (\s-1SAN\s0) or Subject CommonName (\s-1CN\s0) matches the specified hostname, which must be encoded in the preferred name syntax described in section 3.5 of \s-1RFC 1034.\s0 By default, wildcards are supported and they match only in the left-most label; but they may match part of that label with an explicit prefix or suffix. For example, by default, the host \fBname\fR \*(L"www.example.com\*(R" would match a certificate with a \s-1SAN\s0 or \s-1CN\s0 value of \*(L"*.example.com\*(R", \*(L"w*.example.com\*(R" or \*(L"*w.example.com\*(R". .PP Per section 6.4.2 of \s-1RFC 6125,\s0 \fBname\fR values representing international domain names must be given in A\-label form. The \fBnamelen\fR argument must be the number of characters in the name string or zero in which case the length is calculated with strlen(\fBname\fR). When \fBname\fR starts with a dot (e.g. \*(L".example.com\*(R"), it will be matched by a certificate valid for any sub-domain of \fBname\fR, (see also \&\fBX509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS\fR below). .PP When the certificate is matched, and \fBpeername\fR is not \s-1NULL,\s0 a pointer to a copy of the matching \s-1SAN\s0 or \s-1CN\s0 from the peer certificate is stored at the address passed in \fBpeername\fR. The application is responsible for freeing the peername via \fBOPENSSL_free()\fR when it is no longer needed. .PP \&\fBX509_check_email()\fR checks if the certificate matches the specified email \fBaddress\fR. The mailbox syntax of \s-1RFC 822\s0 is supported, comments are not allowed, and no attempt is made to normalize quoted characters. The mailbox syntax of \s-1RFC 6531\s0 is supported for SmtpUTF8Mailbox address in subjectAltName according to \s-1RFC 8398,\s0 with similar limitations as for \s-1RFC 822\s0 syntax, and no attempt is made to convert from A\-label to U\-label before comparison. The \fBaddresslen\fR argument must be the number of characters in the address string or zero in which case the length is calculated with strlen(\fBaddress\fR). .PP \&\fBX509_check_ip()\fR checks if the certificate matches a specified IPv4 or IPv6 address. The \fBaddress\fR array is in binary format, in network byte order. The length is either 4 (IPv4) or 16 (IPv6). Only explicitly marked addresses in the certificates are considered; \s-1IP\s0 addresses stored in \s-1DNS\s0 names and Common Names are ignored. There are currently no \fBflags\fR that would affect the behavior of this call. .PP \&\fBX509_check_ip_asc()\fR is similar, except that the NUL-terminated string \fBaddress\fR is first converted to the internal representation. .PP The \fBflags\fR argument is usually 0. It can be the bitwise \s-1OR\s0 of the flags: .IP "\fBX509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT\fR," 4 .IX Item "X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT," .PD 0 .IP "\fBX509_CHECK_FLAG_NEVER_CHECK_SUBJECT\fR," 4 .IX Item "X509_CHECK_FLAG_NEVER_CHECK_SUBJECT," .IP "\fBX509_CHECK_FLAG_NO_WILDCARDS\fR," 4 .IX Item "X509_CHECK_FLAG_NO_WILDCARDS," .IP "\fBX509_CHECK_FLAG_NO_PARTIAL_WILDCARDS\fR," 4 .IX Item "X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS," .IP "\fBX509_CHECK_FLAG_MULTI_LABEL_WILDCARDS\fR." 4 .IX Item "X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS." .IP "\fBX509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS\fR." 4 .IX Item "X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS." .PD .PP The \fBX509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT\fR flag causes the function to consider the subject \s-1DN\s0 even if the certificate contains at least one subject alternative name of the right type (\s-1DNS\s0 name or email address as appropriate); the default is to ignore the subject \s-1DN\s0 when at least one corresponding subject alternative names is present. .PP The \fBX509_CHECK_FLAG_NEVER_CHECK_SUBJECT\fR flag causes the function to never consider the subject \s-1DN\s0 even if the certificate contains no subject alternative names of the right type (\s-1DNS\s0 name or email address as appropriate); the default is to use the subject \s-1DN\s0 when no corresponding subject alternative names are present. If both \fBX509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT\fR and \&\fBX509_CHECK_FLAG_NEVER_CHECK_SUBJECT\fR are specified, the latter takes precedence and the subject \s-1DN\s0 is not checked for matching names. .PP If set, \fBX509_CHECK_FLAG_NO_WILDCARDS\fR disables wildcard expansion; this only applies to \fBX509_check_host\fR. .PP If set, \fBX509_CHECK_FLAG_NO_PARTIAL_WILDCARDS\fR suppresses support for \*(L"*\*(R" as wildcard pattern in labels that have a prefix or suffix, such as: \*(L"www*\*(R" or \*(L"*www\*(R"; this only applies to \fBX509_check_host\fR. .PP If set, \fBX509_CHECK_FLAG_MULTI_LABEL_WILDCARDS\fR allows a \*(L"*\*(R" that constitutes the complete label of a \s-1DNS\s0 name (e.g. \*(L"*.example.com\*(R") to match more than one label in \fBname\fR; this flag only applies to \fBX509_check_host\fR. .PP If set, \fBX509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS\fR restricts \fBname\fR values which start with \*(L".\*(R", that would otherwise match any sub-domain in the peer certificate, to only match direct child sub-domains. Thus, for instance, with this flag set a \fBname\fR of \*(L".example.com\*(R" would match a peer certificate with a \s-1DNS\s0 name of \*(L"www.example.com\*(R", but would not match a peer certificate with a \s-1DNS\s0 name of \&\*(L"www.sub.example.com\*(R"; this flag only applies to \fBX509_check_host\fR. .SH "RETURN VALUES" .IX Header "RETURN VALUES" The functions return 1 for a successful match, 0 for a failed match and \-1 for an internal error: typically a memory allocation failure or an \s-1ASN.1\s0 decoding error. .PP All functions can also return \-2 if the input is malformed. For example, \&\fBX509_check_host()\fR returns \-2 if the provided \fBname\fR contains embedded NULs. .SH "NOTES" .IX Header "NOTES" Applications are encouraged to use \fBX509_VERIFY_PARAM_set1_host()\fR rather than explicitly calling \fBX509_check_host\fR\|(3). Hostname checks may be out of scope with the \s-1\fBDANE\-EE\s0\fR\|(3) certificate usage, and the internal checks will be suppressed as appropriate when \&\s-1DANE\s0 support is enabled. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBSSL_get_verify_result\fR\|(3), \&\fBX509_VERIFY_PARAM_set1_host\fR\|(3), \&\fBX509_VERIFY_PARAM_add1_host\fR\|(3), \&\fBX509_VERIFY_PARAM_set1_email\fR\|(3), \&\fBX509_VERIFY_PARAM_set1_ip\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" These functions were added in OpenSSL 1.0.2. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2012\-2022 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at .