verify.pod revision 325337
1=pod 2 3=head1 NAME 4 5openssl-verify, 6verify - Utility to verify certificates. 7 8=head1 SYNOPSIS 9 10B<openssl> B<verify> 11[B<-CApath directory>] 12[B<-CAfile file>] 13[B<-purpose purpose>] 14[B<-policy arg>] 15[B<-ignore_critical>] 16[B<-attime timestamp>] 17[B<-check_ss_sig>] 18[B<-crlfile file>] 19[B<-crl_download>] 20[B<-crl_check>] 21[B<-crl_check_all>] 22[B<-policy_check>] 23[B<-explicit_policy>] 24[B<-inhibit_any>] 25[B<-inhibit_map>] 26[B<-x509_strict>] 27[B<-extended_crl>] 28[B<-use_deltas>] 29[B<-policy_print>] 30[B<-no_alt_chains>] 31[B<-allow_proxy_certs>] 32[B<-untrusted file>] 33[B<-help>] 34[B<-issuer_checks>] 35[B<-trusted file>] 36[B<-verbose>] 37[B<->] 38[certificates] 39 40 41=head1 DESCRIPTION 42 43The B<verify> command verifies certificate chains. 44 45=head1 COMMAND OPTIONS 46 47=over 4 48 49=item B<-CApath directory> 50 51A directory of trusted certificates. The certificates should have names 52of the form: hash.0 or have symbolic links to them of this 53form ("hash" is the hashed certificate subject name: see the B<-hash> option 54of the B<x509> utility). Under Unix the B<c_rehash> script will automatically 55create symbolic links to a directory of certificates. 56 57=item B<-CAfile file> 58A file of trusted certificates. The file should contain multiple certificates 59in PEM format concatenated together. 60 61=item B<-attime timestamp> 62 63Perform validation checks using time specified by B<timestamp> and not 64current system time. B<timestamp> is the number of seconds since 6501.01.1970 (UNIX time). 66 67=item B<-check_ss_sig> 68 69Verify the signature on the self-signed root CA. This is disabled by default 70because it doesn't add any security. 71 72=item B<-crlfile file> 73 74File containing one or more CRL's (in PEM format) to load. 75 76=item B<-crl_download> 77 78Attempt to download CRL information for this certificate. 79 80=item B<-crl_check> 81 82Checks end entity certificate validity by attempting to look up a valid CRL. 83If a valid CRL cannot be found an error occurs. 84 85=item B<-untrusted file> 86 87A file of untrusted certificates. The file should contain multiple certificates 88in PEM format concatenated together. 89 90=item B<-purpose purpose> 91 92The intended use for the certificate. If this option is not specified, 93B<verify> will not consider certificate purpose during chain verification. 94Currently accepted uses are B<sslclient>, B<sslserver>, B<nssslserver>, 95B<smimesign>, B<smimeencrypt>. See the B<VERIFY OPERATION> section for more 96information. 97 98=item B<-help> 99 100Print out a usage message. 101 102=item B<-verbose> 103 104Print extra information about the operations being performed. 105 106=item B<-issuer_checks> 107 108Print out diagnostics relating to searches for the issuer certificate of the 109current certificate. This shows why each candidate issuer certificate was 110rejected. The presence of rejection messages does not itself imply that 111anything is wrong; during the normal verification process, several 112rejections may take place. 113 114=item B<-policy arg> 115 116Enable policy processing and add B<arg> to the user-initial-policy-set (see 117RFC5280). The policy B<arg> can be an object name an OID in numeric form. 118This argument can appear more than once. 119 120=item B<-policy_check> 121 122Enables certificate policy processing. 123 124=item B<-explicit_policy> 125 126Set policy variable require-explicit-policy (see RFC5280). 127 128=item B<-inhibit_any> 129 130Set policy variable inhibit-any-policy (see RFC5280). 131 132=item B<-inhibit_map> 133 134Set policy variable inhibit-policy-mapping (see RFC5280). 135 136=item B<-no_alt_chains> 137 138When building a certificate chain, if the first certificate chain found is not 139trusted, then OpenSSL will continue to check to see if an alternative chain can 140be found that is trusted. With this option that behaviour is suppressed so that 141only the first chain found is ever used. Using this option will force the 142behaviour to match that of previous OpenSSL versions. 143 144=item B<-allow_proxy_certs> 145 146Allow the verification of proxy certificates. 147 148=item B<-trusted file> 149 150A file of additional trusted certificates. The file should contain multiple 151certificates in PEM format concatenated together. 152 153=item B<-policy_print> 154 155Print out diagnostics related to policy processing. 156 157=item B<-crl_check> 158 159Checks end entity certificate validity by attempting to look up a valid CRL. 160If a valid CRL cannot be found an error occurs. 161 162=item B<-crl_check_all> 163 164Checks the validity of B<all> certificates in the chain by attempting 165to look up valid CRLs. 166 167=item B<-ignore_critical> 168 169Normally if an unhandled critical extension is present which is not 170supported by OpenSSL the certificate is rejected (as required by RFC5280). 171If this option is set critical extensions are ignored. 172 173=item B<-x509_strict> 174 175For strict X.509 compliance, disable non-compliant workarounds for broken 176certificates. 177 178=item B<-extended_crl> 179 180Enable extended CRL features such as indirect CRLs and alternate CRL 181signing keys. 182 183=item B<-use_deltas> 184 185Enable support for delta CRLs. 186 187=item B<-check_ss_sig> 188 189Verify the signature on the self-signed root CA. This is disabled by default 190because it doesn't add any security. 191 192=item B<-> 193 194Indicates the last option. All arguments following this are assumed to be 195certificate files. This is useful if the first certificate filename begins 196with a B<->. 197 198=item B<certificates> 199 200One or more certificates to verify. If no certificates are given, B<verify> 201will attempt to read a certificate from standard input. Certificates must be 202in PEM format. 203 204=back 205 206=head1 VERIFY OPERATION 207 208The B<verify> program uses the same functions as the internal SSL and S/MIME 209verification, therefore this description applies to these verify operations 210too. 211 212There is one crucial difference between the verify operations performed 213by the B<verify> program: wherever possible an attempt is made to continue 214after an error whereas normally the verify operation would halt on the 215first error. This allows all the problems with a certificate chain to be 216determined. 217 218The verify operation consists of a number of separate steps. 219 220Firstly a certificate chain is built up starting from the supplied certificate 221and ending in the root CA. It is an error if the whole chain cannot be built 222up. The chain is built up by looking up the issuers certificate of the current 223certificate. If a certificate is found which is its own issuer it is assumed 224to be the root CA. 225 226The process of 'looking up the issuers certificate' itself involves a number 227of steps. In versions of OpenSSL before 0.9.5a the first certificate whose 228subject name matched the issuer of the current certificate was assumed to be 229the issuers certificate. In OpenSSL 0.9.6 and later all certificates 230whose subject name matches the issuer name of the current certificate are 231subject to further tests. The relevant authority key identifier components 232of the current certificate (if present) must match the subject key identifier 233(if present) and issuer and serial number of the candidate issuer, in addition 234the keyUsage extension of the candidate issuer (if present) must permit 235certificate signing. 236 237The lookup first looks in the list of untrusted certificates and if no match 238is found the remaining lookups are from the trusted certificates. The root CA 239is always looked up in the trusted certificate list: if the certificate to 240verify is a root certificate then an exact match must be found in the trusted 241list. 242 243The second operation is to check every untrusted certificate's extensions for 244consistency with the supplied purpose. If the B<-purpose> option is not included 245then no checks are done. The supplied or "leaf" certificate must have extensions 246compatible with the supplied purpose and all other certificates must also be valid 247CA certificates. The precise extensions required are described in more detail in 248the B<CERTIFICATE EXTENSIONS> section of the B<x509> utility. 249 250The third operation is to check the trust settings on the root CA. The root 251CA should be trusted for the supplied purpose. For compatibility with previous 252versions of SSLeay and OpenSSL a certificate with no trust settings is considered 253to be valid for all purposes. 254 255The final operation is to check the validity of the certificate chain. The validity 256period is checked against the current system time and the notBefore and notAfter 257dates in the certificate. The certificate signatures are also checked at this 258point. 259 260If all operations complete successfully then certificate is considered valid. If 261any operation fails then the certificate is not valid. 262 263=head1 DIAGNOSTICS 264 265When a verify operation fails the output messages can be somewhat cryptic. The 266general form of the error message is: 267 268 server.pem: /C=AU/ST=Queensland/O=CryptSoft Pty Ltd/CN=Test CA (1024 bit) 269 error 24 at 1 depth lookup:invalid CA certificate 270 271The first line contains the name of the certificate being verified followed by 272the subject name of the certificate. The second line contains the error number 273and the depth. The depth is number of the certificate being verified when a 274problem was detected starting with zero for the certificate being verified itself 275then 1 for the CA that signed the certificate and so on. Finally a text version 276of the error number is presented. 277 278An exhaustive list of the error codes and messages is shown below, this also 279includes the name of the error code as defined in the header file x509_vfy.h 280Some of the error codes are defined but never returned: these are described 281as "unused". 282 283=over 4 284 285=item B<0 X509_V_OK: ok> 286 287the operation was successful. 288 289=item B<2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate> 290 291the issuer certificate of a looked up certificate could not be found. This 292normally means the list of trusted certificates is not complete. 293 294=item B<3 X509_V_ERR_UNABLE_TO_GET_CRL: unable to get certificate CRL> 295 296the CRL of a certificate could not be found. 297 298=item B<4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature> 299 300the certificate signature could not be decrypted. This means that the actual signature value 301could not be determined rather than it not matching the expected value, this is only 302meaningful for RSA keys. 303 304=item B<5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature> 305 306the CRL signature could not be decrypted: this means that the actual signature value 307could not be determined rather than it not matching the expected value. Unused. 308 309=item B<6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key> 310 311the public key in the certificate SubjectPublicKeyInfo could not be read. 312 313=item B<7 X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure> 314 315the signature of the certificate is invalid. 316 317=item B<8 X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure> 318 319the signature of the certificate is invalid. 320 321=item B<9 X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid> 322 323the certificate is not yet valid: the notBefore date is after the current time. 324 325=item B<10 X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired> 326 327the certificate has expired: that is the notAfter date is before the current time. 328 329=item B<11 X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid> 330 331the CRL is not yet valid. 332 333=item B<12 X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired> 334 335the CRL has expired. 336 337=item B<13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field> 338 339the certificate notBefore field contains an invalid time. 340 341=item B<14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field> 342 343the certificate notAfter field contains an invalid time. 344 345=item B<15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field> 346 347the CRL lastUpdate field contains an invalid time. 348 349=item B<16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field> 350 351the CRL nextUpdate field contains an invalid time. 352 353=item B<17 X509_V_ERR_OUT_OF_MEM: out of memory> 354 355an error occurred trying to allocate memory. This should never happen. 356 357=item B<18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate> 358 359the passed certificate is self signed and the same certificate cannot be found in the list of 360trusted certificates. 361 362=item B<19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain> 363 364the certificate chain could be built up using the untrusted certificates but the root could not 365be found locally. 366 367=item B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate> 368 369the issuer certificate could not be found: this occurs if the issuer 370certificate of an untrusted certificate cannot be found. 371 372=item B<21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate> 373 374no signatures could be verified because the chain contains only one certificate and it is not 375self signed. 376 377=item B<22 X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long> 378 379the certificate chain length is greater than the supplied maximum depth. Unused. 380 381=item B<23 X509_V_ERR_CERT_REVOKED: certificate revoked> 382 383the certificate has been revoked. 384 385=item B<24 X509_V_ERR_INVALID_CA: invalid CA certificate> 386 387a CA certificate is invalid. Either it is not a CA or its extensions are not consistent 388with the supplied purpose. 389 390=item B<25 X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded> 391 392the basicConstraints pathlength parameter has been exceeded. 393 394=item B<26 X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose> 395 396the supplied certificate cannot be used for the specified purpose. 397 398=item B<27 X509_V_ERR_CERT_UNTRUSTED: certificate not trusted> 399 400the root CA is not marked as trusted for the specified purpose. 401 402=item B<28 X509_V_ERR_CERT_REJECTED: certificate rejected> 403 404the root CA is marked to reject the specified purpose. 405 406=item B<29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch> 407 408the current candidate issuer certificate was rejected because its subject name 409did not match the issuer name of the current certificate. Only displayed when 410the B<-issuer_checks> option is set. 411 412=item B<30 X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch> 413 414the current candidate issuer certificate was rejected because its subject key 415identifier was present and did not match the authority key identifier current 416certificate. Only displayed when the B<-issuer_checks> option is set. 417 418=item B<31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch> 419 420the current candidate issuer certificate was rejected because its issuer name 421and serial number was present and did not match the authority key identifier 422of the current certificate. Only displayed when the B<-issuer_checks> option is set. 423 424=item B<32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing> 425 426the current candidate issuer certificate was rejected because its keyUsage extension 427does not permit certificate signing. 428 429=item B<50 X509_V_ERR_APPLICATION_VERIFICATION: application verification failure> 430 431an application specific error. Unused. 432 433=back 434 435=head1 BUGS 436 437Although the issuer checks are a considerable improvement over the old technique they still 438suffer from limitations in the underlying X509_LOOKUP API. One consequence of this is that 439trusted certificates with matching subject name must either appear in a file (as specified by the 440B<-CAfile> option) or a directory (as specified by B<-CApath>. If they occur in both then only 441the certificates in the file will be recognised. 442 443Previous versions of OpenSSL assume certificates with matching subject name are identical and 444mishandled them. 445 446Previous versions of this documentation swapped the meaning of the 447B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT> and 448B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY> error codes. 449 450=head1 SEE ALSO 451 452L<x509(1)|x509(1)> 453 454=head1 HISTORY 455 456The -no_alt_chains options was first added to OpenSSL 1.0.2b. 457 458=cut 459