X509_check_host(3) OpenSSL X509_check_host(3) NNAAMMEE X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 certificate matching SSYYNNOOPPSSIISS #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); DDEESSCCRRIIPPTTIIOONN The certificate matching functions are used to check whether a certifi- cate matches a given host name, email address, or IP address. The validity of the certificate and its trust level has to be checked by other means. _X_5_0_9___c_h_e_c_k___h_o_s_t_(_) checks if the certificate Subject Alternative Name (SAN) or Subject CommonName (CN) matches the specified host name, which must be encoded in the preferred name syntax described in section 3.5 of RFC 1034. 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 nnaammee "www.example.com" would match a certificate with a SAN or CN value of "*.example.com", "w*.example.com" or "*w.example.com". Per section 6.4.2 of RFC 6125, nnaammee values representing international domain names must be given in A-label form. The nnaammeelleenn argument must be the number of characters in the name string or zero in which case the length is calculated with strlen(nnaammee). When nnaammee starts with a dot (e.g ".example.com"), it will be matched by a certificate valid for any sub-domain of nnaammee, (see also XX550099__CCHHEECCKK__FFLLAAGG__SSIINNGGLLEE__LLAABBEELL__SSUUBBDDOO-- MMAAIINNSS below). When the certificate is matched, and ppeeeerrnnaammee is not NULL, a pointer to a copy of the matching SAN or CN from the peer certificate is stored at the address passed in ppeeeerrnnaammee. The application is responsible for freeing the peername via _O_P_E_N_S_S_L___f_r_e_e_(_) when it is no longer needed. _X_5_0_9___c_h_e_c_k___e_m_a_i_l_(_) checks if the certificate matches the specified email aaddddrreessss. Only the mailbox syntax of RFC 822 is supported, com- ments are not allowed, and no attempt is made to normalize quoted char- acters. The aaddddrreesssslleenn argument must be the number of characters in the address string or zero in which case the length is calculated with strlen(aaddddrreessss). _X_5_0_9___c_h_e_c_k___i_p_(_) checks if the certificate matches a specified IPv4 or IPv6 address. The aaddddrreessss 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; IP addresses stored in DNS names and Common Names are ignored. _X_5_0_9___c_h_e_c_k___i_p___a_s_c_(_) is similar, except that the NUL-terminated string aaddddrreessss is first converted to the internal representation. The ffllaaggss argument is usually 0. It can be the bitwise OR of the flags: XX550099__CCHHEECCKK__FFLLAAGG__AALLWWAAYYSS__CCHHEECCKK__SSUUBBJJEECCTT, XX550099__CCHHEECCKK__FFLLAAGG__NNOO__WWIILLDDCCAARRDDSS, XX550099__CCHHEECCKK__FFLLAAGG__NNOO__PPAARRTTIIAALL__WWIILLDDCCAARRDDSS, XX550099__CCHHEECCKK__FFLLAAGG__MMUULLTTII__LLAABBEELL__WWIILLDDCCAARRDDSS. XX550099__CCHHEECCKK__FFLLAAGG__SSIINNGGLLEE__LLAABBEELL__SSUUBBDDOOMMAAIINNSS. The XX550099__CCHHEECCKK__FFLLAAGG__AALLWWAAYYSS__CCHHEECCKK__SSUUBBJJEECCTT flag causes the function to consider the subject DN even if the certificate contains at least one subject alternative name of the right type (DNS name or email address as appropriate); the default is to ignore the subject DN when at least one corresponding subject alternative names is present. If set, XX550099__CCHHEECCKK__FFLLAAGG__NNOO__WWIILLDDCCAARRDDSS disables wildcard expansion; this only applies to XX550099__cchheecckk__hhoosstt. If set, XX550099__CCHHEECCKK__FFLLAAGG__NNOO__PPAARRTTIIAALL__WWIILLDDCCAARRDDSS suppresses support for "*" as wildcard pattern in labels that have a prefix or suffix, such as: "www*" or "*www"; this only aplies to XX550099__cchheecckk__hhoosstt. If set, XX550099__CCHHEECCKK__FFLLAAGG__MMUULLTTII__LLAABBEELL__WWIILLDDCCAARRDDSS allows a "*" that consti- tutes the complete label of a DNS name (e.g. "*.example.com") to match more than one label in nnaammee; this flag only applies to XX550099__cchheecckk__hhoosstt. If set, XX550099__CCHHEECCKK__FFLLAAGG__SSIINNGGLLEE__LLAABBEELL__SSUUBBDDOOMMAAIINNSS restricts nnaammee values which start with ".", 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 nnaammee of ".example.com" would match a peer certificate with a DNS name of "www.example.com", but would not match a peer certificate with a DNS name of "www.sub.example.com"; this flag only applies to XX550099__cchheecckk__hhoosstt. RREETTUURRNN VVAALLUUEESS 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 ASN.1 decoding error. All functions can also return -2 if the input is malformed. For exam- ple, _X_5_0_9___c_h_e_c_k___h_o_s_t_(_) returns -2 if the provided nnaammee contains embed- ded NULs. NNOOTTEESS Applications are encouraged to use _X_5_0_9___V_E_R_I_F_Y___P_A_R_A_M___s_e_t_1___h_o_s_t_(_) rather than explicitly calling _X_5_0_9___c_h_e_c_k___h_o_s_t(3). Host name checks are out of scope with the _D_A_N_E_-_E_E(3) certificate usage, and the internal checks will be suppressed as appropriate when DANE support is added to OpenSSL. SSEEEE AALLSSOO _S_S_L___g_e_t___v_e_r_i_f_y___r_e_s_u_l_t(3), _X_5_0_9___V_E_R_I_F_Y___P_A_R_A_M___s_e_t_1___h_o_s_t(3), _X_5_0_9___V_E_R_- _I_F_Y___P_A_R_A_M___a_d_d_1___h_o_s_t(3), _X_5_0_9___V_E_R_I_F_Y___P_A_R_A_M___s_e_t_1___e_m_a_i_l(3), _X_5_0_9___V_E_R_- _I_F_Y___P_A_R_A_M___s_e_t_1___i_p(3), _X_5_0_9___V_E_R_I_F_Y___P_A_R_A_M___s_e_t_1___i_p_a_s_c(3) HHIISSTTOORRYY These functions were added in OpenSSL 1.0.2. 1.0.2u 2019-12-20 X509_check_host(3)