verify.pod revision 279265
1=pod 2 3=head1 NAME 4 5verify - Utility to verify certificates. 6 7=head1 SYNOPSIS 8 9B<openssl> B<verify> 10[B<-CAfile file>] 11[B<-CApath directory>] 12[B<-attime timestamp>] 13[B<-check_ss_sig>] 14[B<-crl_check>] 15[B<-crl_check_all>] 16[B<-explicit_policy>] 17[B<-help>] 18[B<-ignore_critical>] 19[B<-inhibit_any>] 20[B<-inhibit_map>] 21[B<-issuer_checks>] 22[B<-policy arg>] 23[B<-policy_check>] 24[B<-policy_print>] 25[B<-purpose purpose>] 26[B<-untrusted file>] 27[B<-use_deltas>] 28[B<-verbose>] 29[B<-verify_depth num>] 30[B<-x509_strict>] 31[B<->] 32[certificates] 33 34 35=head1 DESCRIPTION 36 37The B<verify> command verifies certificate chains. 38 39=head1 COMMAND OPTIONS 40 41=over 4 42 43=item B<-CAfile file> 44 45A file of trusted certificates. The file should contain multiple certificates 46in PEM format concatenated together. 47 48=item B<-CApath directory> 49 50A directory of trusted certificates. The certificates should have names 51of the form: hash.0 or have symbolic links to them of this 52form ("hash" is the hashed certificate subject name: see the B<-hash> option 53of the B<x509> utility). Under Unix the B<c_rehash> script will automatically 54create symbolic links to a directory of certificates. 55 56=item B<-attime timestamp> 57 58Perform validation checks using time specified by B<timestamp> and not 59current system time. B<timestamp> is the number of seconds since 6001.01.1970 (UNIX time). 61 62=item B<-check_ss_sig> 63 64Verify the signature on the self-signed root CA. This is disabled by default 65because it doesn't add any security. 66 67=item B<-crl_check> 68 69Checks end entity certificate validity by attempting to look up a valid CRL. 70If a valid CRL cannot be found an error occurs. 71 72=item B<-crl_check_all> 73 74Checks the validity of B<all> certificates in the chain by attempting 75to look up valid CRLs. 76 77=item B<-explicit_policy> 78 79Set policy variable require-explicit-policy (see RFC5280). 80 81=item B<-help> 82 83Print out a usage message. 84 85=item B<-ignore_critical> 86 87Normally if an unhandled critical extension is present which is not 88supported by OpenSSL the certificate is rejected (as required by RFC5280). 89If this option is set critical extensions are ignored. 90 91=item B<-inhibit_any> 92 93Set policy variable inhibit-any-policy (see RFC5280). 94 95=item B<-inhibit_map> 96 97Set policy variable inhibit-policy-mapping (see RFC5280). 98 99=item B<-issuer_checks> 100 101Print out diagnostics relating to searches for the issuer certificate of the 102current certificate. This shows why each candidate issuer certificate was 103rejected. The presence of rejection messages does not itself imply that 104anything is wrong; during the normal verification process, several 105rejections may take place. 106 107=item B<-policy arg> 108 109Enable policy processing and add B<arg> to the user-initial-policy-set (see 110RFC5280). The policy B<arg> can be an object name an OID in numeric form. 111This argument can appear more than once. 112 113=item B<-policy_check> 114 115Enables certificate policy processing. 116 117=item B<-policy_print> 118 119Print out diagnostics related to policy processing. 120 121=item B<-purpose purpose> 122 123The intended use for the certificate. If this option is not specified, 124B<verify> will not consider certificate purpose during chain verification. 125Currently accepted uses are B<sslclient>, B<sslserver>, B<nssslserver>, 126B<smimesign>, B<smimeencrypt>. See the B<VERIFY OPERATION> section for more 127information. 128 129=item B<-untrusted file> 130 131A file of untrusted certificates. The file should contain multiple certificates 132in PEM format concatenated together. 133 134=item B<-use_deltas> 135 136Enable support for delta CRLs. 137 138=item B<-verbose> 139 140Print extra information about the operations being performed. 141 142=item B<-verify_depth num> 143 144Limit the maximum depth of the certificate chain to B<num> certificates. 145 146=item B<-x509_strict> 147 148For strict X.509 compliance, disable non-compliant workarounds for broken 149certificates. 150 151=item B<-> 152 153Indicates the last option. All arguments following this are assumed to be 154certificate files. This is useful if the first certificate filename begins 155with a B<->. 156 157=item B<certificates> 158 159One or more certificates to verify. If no certificates are given, B<verify> 160will attempt to read a certificate from standard input. Certificates must be 161in PEM format. 162 163=back 164 165=head1 VERIFY OPERATION 166 167The B<verify> program uses the same functions as the internal SSL and S/MIME 168verification, therefore this description applies to these verify operations 169too. 170 171There is one crucial difference between the verify operations performed 172by the B<verify> program: wherever possible an attempt is made to continue 173after an error whereas normally the verify operation would halt on the 174first error. This allows all the problems with a certificate chain to be 175determined. 176 177The verify operation consists of a number of separate steps. 178 179Firstly a certificate chain is built up starting from the supplied certificate 180and ending in the root CA. It is an error if the whole chain cannot be built 181up. The chain is built up by looking up the issuers certificate of the current 182certificate. If a certificate is found which is its own issuer it is assumed 183to be the root CA. 184 185The process of 'looking up the issuers certificate' itself involves a number 186of steps. In versions of OpenSSL before 0.9.5a the first certificate whose 187subject name matched the issuer of the current certificate was assumed to be 188the issuers certificate. In OpenSSL 0.9.6 and later all certificates 189whose subject name matches the issuer name of the current certificate are 190subject to further tests. The relevant authority key identifier components 191of the current certificate (if present) must match the subject key identifier 192(if present) and issuer and serial number of the candidate issuer, in addition 193the keyUsage extension of the candidate issuer (if present) must permit 194certificate signing. 195 196The lookup first looks in the list of untrusted certificates and if no match 197is found the remaining lookups are from the trusted certificates. The root CA 198is always looked up in the trusted certificate list: if the certificate to 199verify is a root certificate then an exact match must be found in the trusted 200list. 201 202The second operation is to check every untrusted certificate's extensions for 203consistency with the supplied purpose. If the B<-purpose> option is not included 204then no checks are done. The supplied or "leaf" certificate must have extensions 205compatible with the supplied purpose and all other certificates must also be valid 206CA certificates. The precise extensions required are described in more detail in 207the B<CERTIFICATE EXTENSIONS> section of the B<x509> utility. 208 209The third operation is to check the trust settings on the root CA. The root 210CA should be trusted for the supplied purpose. For compatibility with previous 211versions of SSLeay and OpenSSL a certificate with no trust settings is considered 212to be valid for all purposes. 213 214The final operation is to check the validity of the certificate chain. The validity 215period is checked against the current system time and the notBefore and notAfter 216dates in the certificate. The certificate signatures are also checked at this 217point. 218 219If all operations complete successfully then certificate is considered valid. If 220any operation fails then the certificate is not valid. 221 222=head1 DIAGNOSTICS 223 224When a verify operation fails the output messages can be somewhat cryptic. The 225general form of the error message is: 226 227 server.pem: /C=AU/ST=Queensland/O=CryptSoft Pty Ltd/CN=Test CA (1024 bit) 228 error 24 at 1 depth lookup:invalid CA certificate 229 230The first line contains the name of the certificate being verified followed by 231the subject name of the certificate. The second line contains the error number 232and the depth. The depth is number of the certificate being verified when a 233problem was detected starting with zero for the certificate being verified itself 234then 1 for the CA that signed the certificate and so on. Finally a text version 235of the error number is presented. 236 237An exhaustive list of the error codes and messages is shown below, this also 238includes the name of the error code as defined in the header file x509_vfy.h 239Some of the error codes are defined but never returned: these are described 240as "unused". 241 242=over 4 243 244=item B<0 X509_V_OK: ok> 245 246the operation was successful. 247 248=item B<2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate> 249 250the issuer certificate of a looked up certificate could not be found. This 251normally means the list of trusted certificates is not complete. 252 253=item B<3 X509_V_ERR_UNABLE_TO_GET_CRL: unable to get certificate CRL> 254 255the CRL of a certificate could not be found. 256 257=item B<4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature> 258 259the certificate signature could not be decrypted. This means that the actual signature value 260could not be determined rather than it not matching the expected value, this is only 261meaningful for RSA keys. 262 263=item B<5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature> 264 265the CRL signature could not be decrypted: this means that the actual signature value 266could not be determined rather than it not matching the expected value. Unused. 267 268=item B<6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key> 269 270the public key in the certificate SubjectPublicKeyInfo could not be read. 271 272=item B<7 X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure> 273 274the signature of the certificate is invalid. 275 276=item B<8 X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure> 277 278the signature of the certificate is invalid. 279 280=item B<9 X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid> 281 282the certificate is not yet valid: the notBefore date is after the current time. 283 284=item B<10 X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired> 285 286the certificate has expired: that is the notAfter date is before the current time. 287 288=item B<11 X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid> 289 290the CRL is not yet valid. 291 292=item B<12 X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired> 293 294the CRL has expired. 295 296=item B<13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field> 297 298the certificate notBefore field contains an invalid time. 299 300=item B<14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field> 301 302the certificate notAfter field contains an invalid time. 303 304=item B<15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field> 305 306the CRL lastUpdate field contains an invalid time. 307 308=item B<16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field> 309 310the CRL nextUpdate field contains an invalid time. 311 312=item B<17 X509_V_ERR_OUT_OF_MEM: out of memory> 313 314an error occurred trying to allocate memory. This should never happen. 315 316=item B<18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate> 317 318the passed certificate is self signed and the same certificate cannot be found in the list of 319trusted certificates. 320 321=item B<19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain> 322 323the certificate chain could be built up using the untrusted certificates but the root could not 324be found locally. 325 326=item B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate> 327 328the issuer certificate could not be found: this occurs if the issuer 329certificate of an untrusted certificate cannot be found. 330 331=item B<21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate> 332 333no signatures could be verified because the chain contains only one certificate and it is not 334self signed. 335 336=item B<22 X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long> 337 338the certificate chain length is greater than the supplied maximum depth. Unused. 339 340=item B<23 X509_V_ERR_CERT_REVOKED: certificate revoked> 341 342the certificate has been revoked. 343 344=item B<24 X509_V_ERR_INVALID_CA: invalid CA certificate> 345 346a CA certificate is invalid. Either it is not a CA or its extensions are not consistent 347with the supplied purpose. 348 349=item B<25 X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded> 350 351the basicConstraints pathlength parameter has been exceeded. 352 353=item B<26 X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose> 354 355the supplied certificate cannot be used for the specified purpose. 356 357=item B<27 X509_V_ERR_CERT_UNTRUSTED: certificate not trusted> 358 359the root CA is not marked as trusted for the specified purpose. 360 361=item B<28 X509_V_ERR_CERT_REJECTED: certificate rejected> 362 363the root CA is marked to reject the specified purpose. 364 365=item B<29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch> 366 367the current candidate issuer certificate was rejected because its subject name 368did not match the issuer name of the current certificate. Only displayed when 369the B<-issuer_checks> option is set. 370 371=item B<30 X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch> 372 373the current candidate issuer certificate was rejected because its subject key 374identifier was present and did not match the authority key identifier current 375certificate. Only displayed when the B<-issuer_checks> option is set. 376 377=item B<31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch> 378 379the current candidate issuer certificate was rejected because its issuer name 380and serial number was present and did not match the authority key identifier 381of the current certificate. Only displayed when the B<-issuer_checks> option is set. 382 383=item B<32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing> 384 385the current candidate issuer certificate was rejected because its keyUsage extension 386does not permit certificate signing. 387 388=item B<50 X509_V_ERR_APPLICATION_VERIFICATION: application verification failure> 389 390an application specific error. Unused. 391 392=back 393 394=head1 BUGS 395 396Although the issuer checks are a considerable improvement over the old technique they still 397suffer from limitations in the underlying X509_LOOKUP API. One consequence of this is that 398trusted certificates with matching subject name must either appear in a file (as specified by the 399B<-CAfile> option) or a directory (as specified by B<-CApath>). If they occur in both then only 400the certificates in the file will be recognised. 401 402Previous versions of OpenSSL assume certificates with matching subject name are identical and 403mishandled them. 404 405Previous versions of this documentation swapped the meaning of the 406B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT> and 407B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY> error codes. 408 409=head1 SEE ALSO 410 411L<x509(1)|x509(1)> 412 413=cut 414