verify.pod revision 238405
1=pod 2 3=head1 NAME 4 5verify - Utility to verify certificates. 6 7=head1 SYNOPSIS 8 9B<openssl> B<verify> 10[B<-CApath directory>] 11[B<-CAfile file>] 12[B<-purpose purpose>] 13[B<-policy arg>] 14[B<-ignore_critical>] 15[B<-crl_check>] 16[B<-crl_check_all>] 17[B<-policy_check>] 18[B<-explicit_policy>] 19[B<-inhibit_any>] 20[B<-inhibit_map>] 21[B<-x509_strict>] 22[B<-extended_crl>] 23[B<-use_deltas>] 24[B<-policy_print>] 25[B<-untrusted file>] 26[B<-help>] 27[B<-issuer_checks>] 28[B<-verbose>] 29[B<->] 30[certificates] 31 32 33=head1 DESCRIPTION 34 35The B<verify> command verifies certificate chains. 36 37=head1 COMMAND OPTIONS 38 39=over 4 40 41=item B<-CApath directory> 42 43A directory of trusted certificates. The certificates should have names 44of the form: hash.0 or have symbolic links to them of this 45form ("hash" is the hashed certificate subject name: see the B<-hash> option 46of the B<x509> utility). Under Unix the B<c_rehash> script will automatically 47create symbolic links to a directory of certificates. 48 49=item B<-CAfile file> 50 51A file of trusted certificates. The file should contain multiple certificates 52in PEM format concatenated together. 53 54=item B<-untrusted file> 55 56A file of untrusted certificates. The file should contain multiple certificates 57 58=item B<-purpose purpose> 59 60the intended use for the certificate. Without this option no chain verification 61will be done. Currently accepted uses are B<sslclient>, B<sslserver>, 62B<nssslserver>, B<smimesign>, B<smimeencrypt>. See the B<VERIFY OPERATION> 63section for more information. 64 65=item B<-help> 66 67prints out a usage message. 68 69=item B<-verbose> 70 71print extra information about the operations being performed. 72 73=item B<-issuer_checks> 74 75print out diagnostics relating to searches for the issuer certificate 76of the current certificate. This shows why each candidate issuer 77certificate was rejected. However the presence of rejection messages 78does not itself imply that anything is wrong: during the normal 79verify process several rejections may take place. 80 81=item B<-policy arg> 82 83Enable policy processing and add B<arg> to the user-initial-policy-set 84(see RFC3280 et al). The policy B<arg> can be an object name an OID in numeric 85form. This argument can appear more than once. 86 87=item B<-policy_check> 88 89Enables certificate policy processing. 90 91=item B<-explicit_policy> 92 93Set policy variable require-explicit-policy (see RFC3280 et al). 94 95=item B<-inhibit_any> 96 97Set policy variable inhibit-any-policy (see RFC3280 et al). 98 99=item B<-inhibit_map> 100 101Set policy variable inhibit-policy-mapping (see RFC3280 et al). 102 103=item B<-policy_print> 104 105Print out diagnostics, related to policy checking 106 107=item B<-crl_check> 108 109Checks end entity certificate validity by attempting to lookup a valid CRL. 110If a valid CRL cannot be found an error occurs. 111 112=item B<-crl_check_all> 113 114Checks the validity of B<all> certificates in the chain by attempting 115to lookup valid CRLs. 116 117=item B<-ignore_critical> 118 119Normally if an unhandled critical extension is present which is not 120supported by OpenSSL the certificate is rejected (as required by 121RFC3280 et al). If this option is set critical extensions are 122ignored. 123 124=item B<-x509_strict> 125 126Disable workarounds for broken certificates which have to be disabled 127for strict X.509 compliance. 128 129=item B<-extended_crl> 130 131Enable extended CRL features such as indirect CRLs and alternate CRL 132signing keys. 133 134=item B<-use_deltas> 135 136Enable support for delta CRLs. 137 138=item B<-check_ss_sig> 139 140Verify the signature on the self-signed root CA. This is disabled by default 141because it doesn't add any security. 142 143=item B<-> 144 145marks the last option. All arguments following this are assumed to be 146certificate files. This is useful if the first certificate filename begins 147with a B<->. 148 149=item B<certificates> 150 151one or more certificates to verify. If no certificate filenames are included 152then an attempt is made to read a certificate from standard input. They should 153all be in PEM format. 154 155 156=back 157 158=head1 VERIFY OPERATION 159 160The B<verify> program uses the same functions as the internal SSL and S/MIME 161verification, therefore this description applies to these verify operations 162too. 163 164There is one crucial difference between the verify operations performed 165by the B<verify> program: wherever possible an attempt is made to continue 166after an error whereas normally the verify operation would halt on the 167first error. This allows all the problems with a certificate chain to be 168determined. 169 170The verify operation consists of a number of separate steps. 171 172Firstly a certificate chain is built up starting from the supplied certificate 173and ending in the root CA. It is an error if the whole chain cannot be built 174up. The chain is built up by looking up the issuers certificate of the current 175certificate. If a certificate is found which is its own issuer it is assumed 176to be the root CA. 177 178The process of 'looking up the issuers certificate' itself involves a number 179of steps. In versions of OpenSSL before 0.9.5a the first certificate whose 180subject name matched the issuer of the current certificate was assumed to be 181the issuers certificate. In OpenSSL 0.9.6 and later all certificates 182whose subject name matches the issuer name of the current certificate are 183subject to further tests. The relevant authority key identifier components 184of the current certificate (if present) must match the subject key identifier 185(if present) and issuer and serial number of the candidate issuer, in addition 186the keyUsage extension of the candidate issuer (if present) must permit 187certificate signing. 188 189The lookup first looks in the list of untrusted certificates and if no match 190is found the remaining lookups are from the trusted certificates. The root CA 191is always looked up in the trusted certificate list: if the certificate to 192verify is a root certificate then an exact match must be found in the trusted 193list. 194 195The second operation is to check every untrusted certificate's extensions for 196consistency with the supplied purpose. If the B<-purpose> option is not included 197then no checks are done. The supplied or "leaf" certificate must have extensions 198compatible with the supplied purpose and all other certificates must also be valid 199CA certificates. The precise extensions required are described in more detail in 200the B<CERTIFICATE EXTENSIONS> section of the B<x509> utility. 201 202The third operation is to check the trust settings on the root CA. The root 203CA should be trusted for the supplied purpose. For compatibility with previous 204versions of SSLeay and OpenSSL a certificate with no trust settings is considered 205to be valid for all purposes. 206 207The final operation is to check the validity of the certificate chain. The validity 208period is checked against the current system time and the notBefore and notAfter 209dates in the certificate. The certificate signatures are also checked at this 210point. 211 212If all operations complete successfully then certificate is considered valid. If 213any operation fails then the certificate is not valid. 214 215=head1 DIAGNOSTICS 216 217When a verify operation fails the output messages can be somewhat cryptic. The 218general form of the error message is: 219 220 server.pem: /C=AU/ST=Queensland/O=CryptSoft Pty Ltd/CN=Test CA (1024 bit) 221 error 24 at 1 depth lookup:invalid CA certificate 222 223The first line contains the name of the certificate being verified followed by 224the subject name of the certificate. The second line contains the error number 225and the depth. The depth is number of the certificate being verified when a 226problem was detected starting with zero for the certificate being verified itself 227then 1 for the CA that signed the certificate and so on. Finally a text version 228of the error number is presented. 229 230An exhaustive list of the error codes and messages is shown below, this also 231includes the name of the error code as defined in the header file x509_vfy.h 232Some of the error codes are defined but never returned: these are described 233as "unused". 234 235=over 4 236 237=item B<0 X509_V_OK: ok> 238 239the operation was successful. 240 241=item B<2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate> 242 243the issuer certificate of a looked up certificate could not be found. This 244normally means the list of trusted certificates is not complete. 245 246=item B<3 X509_V_ERR_UNABLE_TO_GET_CRL: unable to get certificate CRL> 247 248the CRL of a certificate could not be found. 249 250=item B<4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature> 251 252the certificate signature could not be decrypted. This means that the actual signature value 253could not be determined rather than it not matching the expected value, this is only 254meaningful for RSA keys. 255 256=item B<5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature> 257 258the CRL signature could not be decrypted: this means that the actual signature value 259could not be determined rather than it not matching the expected value. Unused. 260 261=item B<6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key> 262 263the public key in the certificate SubjectPublicKeyInfo could not be read. 264 265=item B<7 X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure> 266 267the signature of the certificate is invalid. 268 269=item B<8 X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure> 270 271the signature of the certificate is invalid. 272 273=item B<9 X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid> 274 275the certificate is not yet valid: the notBefore date is after the current time. 276 277=item B<10 X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired> 278 279the certificate has expired: that is the notAfter date is before the current time. 280 281=item B<11 X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid> 282 283the CRL is not yet valid. 284 285=item B<12 X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired> 286 287the CRL has expired. 288 289=item B<13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field> 290 291the certificate notBefore field contains an invalid time. 292 293=item B<14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field> 294 295the certificate notAfter field contains an invalid time. 296 297=item B<15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field> 298 299the CRL lastUpdate field contains an invalid time. 300 301=item B<16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field> 302 303the CRL nextUpdate field contains an invalid time. 304 305=item B<17 X509_V_ERR_OUT_OF_MEM: out of memory> 306 307an error occurred trying to allocate memory. This should never happen. 308 309=item B<18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate> 310 311the passed certificate is self signed and the same certificate cannot be found in the list of 312trusted certificates. 313 314=item B<19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain> 315 316the certificate chain could be built up using the untrusted certificates but the root could not 317be found locally. 318 319=item B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate> 320 321the issuer certificate could not be found: this occurs if the issuer 322certificate of an untrusted certificate cannot be found. 323 324=item B<21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate> 325 326no signatures could be verified because the chain contains only one certificate and it is not 327self signed. 328 329=item B<22 X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long> 330 331the certificate chain length is greater than the supplied maximum depth. Unused. 332 333=item B<23 X509_V_ERR_CERT_REVOKED: certificate revoked> 334 335the certificate has been revoked. 336 337=item B<24 X509_V_ERR_INVALID_CA: invalid CA certificate> 338 339a CA certificate is invalid. Either it is not a CA or its extensions are not consistent 340with the supplied purpose. 341 342=item B<25 X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded> 343 344the basicConstraints pathlength parameter has been exceeded. 345 346=item B<26 X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose> 347 348the supplied certificate cannot be used for the specified purpose. 349 350=item B<27 X509_V_ERR_CERT_UNTRUSTED: certificate not trusted> 351 352the root CA is not marked as trusted for the specified purpose. 353 354=item B<28 X509_V_ERR_CERT_REJECTED: certificate rejected> 355 356the root CA is marked to reject the specified purpose. 357 358=item B<29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch> 359 360the current candidate issuer certificate was rejected because its subject name 361did not match the issuer name of the current certificate. Only displayed when 362the B<-issuer_checks> option is set. 363 364=item B<30 X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch> 365 366the current candidate issuer certificate was rejected because its subject key 367identifier was present and did not match the authority key identifier current 368certificate. Only displayed when the B<-issuer_checks> option is set. 369 370=item B<31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch> 371 372the current candidate issuer certificate was rejected because its issuer name 373and serial number was present and did not match the authority key identifier 374of the current certificate. Only displayed when the B<-issuer_checks> option is set. 375 376=item B<32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing> 377 378the current candidate issuer certificate was rejected because its keyUsage extension 379does not permit certificate signing. 380 381=item B<50 X509_V_ERR_APPLICATION_VERIFICATION: application verification failure> 382 383an application specific error. Unused. 384 385=back 386 387=head1 BUGS 388 389Although the issuer checks are a considerably improvement over the old technique they still 390suffer from limitations in the underlying X509_LOOKUP API. One consequence of this is that 391trusted certificates with matching subject name must either appear in a file (as specified by the 392B<-CAfile> option) or a directory (as specified by B<-CApath>. If they occur in both then only 393the certificates in the file will be recognised. 394 395Previous versions of OpenSSL assume certificates with matching subject name are identical and 396mishandled them. 397 398Previous versions of this documentation swapped the meaning of the 399B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT> and 400B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY> error codes. 401 402=head1 SEE ALSO 403 404L<x509(1)|x509(1)> 405 406=cut 407