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