verify.pod revision 306196
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<-no_alt_chains>]
26[B<-allow_proxy_certs>]
27[B<-untrusted file>]
28[B<-help>]
29[B<-issuer_checks>]
30[B<-attime timestamp>]
31[B<-verbose>]
32[B<->]
33[certificates]
34
35
36=head1 DESCRIPTION
37
38The B<verify> command verifies certificate chains.
39
40=head1 COMMAND OPTIONS
41
42=over 4
43
44=item B<-CApath directory>
45
46A directory of trusted certificates. The certificates should have names
47of the form: hash.0 or have symbolic links to them of this
48form ("hash" is the hashed certificate subject name: see the B<-hash> option
49of the B<x509> utility). Under Unix the B<c_rehash> script will automatically
50create symbolic links to a directory of certificates.
51
52=item B<-CAfile file>
53A file of trusted certificates. The file should contain multiple certificates
54in PEM format concatenated together.
55
56=item B<-untrusted file>
57
58A file of untrusted certificates. The file should contain multiple certificates
59in PEM format concatenated together.
60
61=item B<-purpose purpose>
62
63The intended use for the certificate. If this option is not specified,
64B<verify> will not consider certificate purpose during chain verification.
65Currently accepted uses are B<sslclient>, B<sslserver>, B<nssslserver>,
66B<smimesign>, B<smimeencrypt>. See the B<VERIFY OPERATION> section for more
67information.
68
69=item B<-help>
70
71Print out a usage message.
72
73=item B<-verbose>
74
75Print extra information about the operations being performed.
76
77=item B<-issuer_checks>
78
79Print out diagnostics relating to searches for the issuer certificate of the
80current certificate. This shows why each candidate issuer certificate was
81rejected. The presence of rejection messages does not itself imply that
82anything is wrong; during the normal verification process, several
83rejections may take place.
84
85=item B<-attime timestamp>
86
87Perform validation checks using time specified by B<timestamp> and not
88current system time. B<timestamp> is the number of seconds since
8901.01.1970 (UNIX time).
90
91=item B<-policy arg>
92
93Enable policy processing and add B<arg> to the user-initial-policy-set (see
94RFC5280). The policy B<arg> can be an object name an OID in numeric form.
95This argument can appear more than once.
96
97=item B<-policy_check>
98
99Enables certificate policy processing.
100
101=item B<-explicit_policy>
102
103Set policy variable require-explicit-policy (see RFC5280).
104
105=item B<-inhibit_any>
106
107Set policy variable inhibit-any-policy (see RFC5280).
108
109=item B<-inhibit_map>
110
111Set policy variable inhibit-policy-mapping (see RFC5280).
112
113=item B<-no_alt_chains>
114
115When building a certificate chain, if the first certificate chain found is not
116trusted, then OpenSSL will continue to check to see if an alternative chain can
117be found that is trusted. With this option that behaviour is suppressed so that
118only the first chain found is ever used. Using this option will force the
119behaviour to match that of previous OpenSSL versions.
120
121=item B<-allow_proxy_certs>
122
123Allow the verification of proxy certificates.
124
125=item B<-policy_print>
126
127Print out diagnostics related to policy processing.
128
129=item B<-crl_check>
130
131Checks end entity certificate validity by attempting to look up a valid CRL.
132If a valid CRL cannot be found an error occurs. 
133
134=item B<-crl_check_all>
135
136Checks the validity of B<all> certificates in the chain by attempting
137to look up valid CRLs.
138
139=item B<-ignore_critical>
140
141Normally if an unhandled critical extension is present which is not
142supported by OpenSSL the certificate is rejected (as required by RFC5280).
143If this option is set critical extensions are ignored.
144
145=item B<-x509_strict>
146
147For strict X.509 compliance, disable non-compliant workarounds for broken
148certificates.
149
150=item B<-extended_crl>
151
152Enable extended CRL features such as indirect CRLs and alternate CRL
153signing keys.
154
155=item B<-use_deltas>
156
157Enable support for delta CRLs.
158
159=item B<-check_ss_sig>
160
161Verify the signature on the self-signed root CA. This is disabled by default
162because it doesn't add any security.
163
164=item B<->
165
166Indicates the last option. All arguments following this are assumed to be
167certificate files. This is useful if the first certificate filename begins
168with a B<->.
169
170=item B<certificates>
171
172One or more certificates to verify. If no certificates are given, B<verify>
173will attempt to read a certificate from standard input. Certificates must be
174in PEM format.
175
176=back
177
178=head1 VERIFY OPERATION
179
180The B<verify> program uses the same functions as the internal SSL and S/MIME
181verification, therefore this description applies to these verify operations
182too.
183
184There is one crucial difference between the verify operations performed
185by the B<verify> program: wherever possible an attempt is made to continue
186after an error whereas normally the verify operation would halt on the
187first error. This allows all the problems with a certificate chain to be
188determined.
189
190The verify operation consists of a number of separate steps.
191
192Firstly a certificate chain is built up starting from the supplied certificate
193and ending in the root CA. It is an error if the whole chain cannot be built
194up. The chain is built up by looking up the issuers certificate of the current
195certificate. If a certificate is found which is its own issuer it is assumed 
196to be the root CA.
197
198The process of 'looking up the issuers certificate' itself involves a number
199of steps. In versions of OpenSSL before 0.9.5a the first certificate whose
200subject name matched the issuer of the current certificate was assumed to be
201the issuers certificate. In OpenSSL 0.9.6 and later all certificates
202whose subject name matches the issuer name of the current certificate are 
203subject to further tests. The relevant authority key identifier components
204of the current certificate (if present) must match the subject key identifier
205(if present) and issuer and serial number of the candidate issuer, in addition
206the keyUsage extension of the candidate issuer (if present) must permit
207certificate signing.
208
209The lookup first looks in the list of untrusted certificates and if no match
210is found the remaining lookups are from the trusted certificates. The root CA
211is always looked up in the trusted certificate list: if the certificate to
212verify is a root certificate then an exact match must be found in the trusted
213list.
214
215The second operation is to check every untrusted certificate's extensions for
216consistency with the supplied purpose. If the B<-purpose> option is not included
217then no checks are done. The supplied or "leaf" certificate must have extensions
218compatible with the supplied purpose and all other certificates must also be valid
219CA certificates. The precise extensions required are described in more detail in
220the B<CERTIFICATE EXTENSIONS> section of the B<x509> utility.
221
222The third operation is to check the trust settings on the root CA. The root
223CA should be trusted for the supplied purpose. For compatibility with previous
224versions of SSLeay and OpenSSL a certificate with no trust settings is considered
225to be valid for all purposes. 
226
227The final operation is to check the validity of the certificate chain. The validity
228period is checked against the current system time and the notBefore and notAfter
229dates in the certificate. The certificate signatures are also checked at this
230point.
231
232If all operations complete successfully then certificate is considered valid. If
233any operation fails then the certificate is not valid.
234
235=head1 DIAGNOSTICS
236
237When a verify operation fails the output messages can be somewhat cryptic. The
238general form of the error message is:
239
240 server.pem: /C=AU/ST=Queensland/O=CryptSoft Pty Ltd/CN=Test CA (1024 bit)
241 error 24 at 1 depth lookup:invalid CA certificate
242
243The first line contains the name of the certificate being verified followed by
244the subject name of the certificate. The second line contains the error number
245and the depth. The depth is number of the certificate being verified when a
246problem was detected starting with zero for the certificate being verified itself
247then 1 for the CA that signed the certificate and so on. Finally a text version
248of the error number is presented.
249
250An exhaustive list of the error codes and messages is shown below, this also
251includes the name of the error code as defined in the header file x509_vfy.h
252Some of the error codes are defined but never returned: these are described
253as "unused".
254
255=over 4
256
257=item B<0 X509_V_OK: ok>
258
259the operation was successful.
260
261=item B<2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate>
262
263the issuer certificate of a looked up certificate could not be found. This
264normally means the list of trusted certificates is not complete.
265
266=item B<3 X509_V_ERR_UNABLE_TO_GET_CRL: unable to get certificate CRL>
267
268the CRL of a certificate could not be found.
269
270=item B<4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature>
271
272the certificate signature could not be decrypted. This means that the actual signature value
273could not be determined rather than it not matching the expected value, this is only
274meaningful for RSA keys.
275
276=item B<5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature>
277
278the CRL signature could not be decrypted: this means that the actual signature value
279could not be determined rather than it not matching the expected value. Unused.
280
281=item B<6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key>
282
283the public key in the certificate SubjectPublicKeyInfo could not be read.
284
285=item B<7 X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure>
286
287the signature of the certificate is invalid.
288
289=item B<8 X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure>
290
291the signature of the certificate is invalid.
292
293=item B<9 X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid>
294
295the certificate is not yet valid: the notBefore date is after the current time.
296
297=item B<10 X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired>
298
299the certificate has expired: that is the notAfter date is before the current time.
300
301=item B<11 X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid>
302
303the CRL is not yet valid.
304
305=item B<12 X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired>
306
307the CRL has expired.
308
309=item B<13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field>
310
311the certificate notBefore field contains an invalid time.
312
313=item B<14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field>
314
315the certificate notAfter field contains an invalid time.
316
317=item B<15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field>
318
319the CRL lastUpdate field contains an invalid time.
320
321=item B<16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field>
322
323the CRL nextUpdate field contains an invalid time.
324
325=item B<17 X509_V_ERR_OUT_OF_MEM: out of memory>
326
327an error occurred trying to allocate memory. This should never happen.
328
329=item B<18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate>
330
331the passed certificate is self signed and the same certificate cannot be found in the list of
332trusted certificates.
333
334=item B<19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain>
335
336the certificate chain could be built up using the untrusted certificates but the root could not
337be found locally.
338
339=item B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate>
340
341the issuer certificate could not be found: this occurs if the issuer
342certificate of an untrusted certificate cannot be found.
343
344=item B<21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate>
345
346no signatures could be verified because the chain contains only one certificate and it is not
347self signed.
348
349=item B<22 X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long>
350
351the certificate chain length is greater than the supplied maximum depth. Unused.
352
353=item B<23 X509_V_ERR_CERT_REVOKED: certificate revoked>
354
355the certificate has been revoked.
356
357=item B<24 X509_V_ERR_INVALID_CA: invalid CA certificate>
358
359a CA certificate is invalid. Either it is not a CA or its extensions are not consistent
360with the supplied purpose.
361
362=item B<25 X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded>
363
364the basicConstraints pathlength parameter has been exceeded.
365
366=item B<26 X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose>
367
368the supplied certificate cannot be used for the specified purpose.
369
370=item B<27 X509_V_ERR_CERT_UNTRUSTED: certificate not trusted>
371
372the root CA is not marked as trusted for the specified purpose.
373
374=item B<28 X509_V_ERR_CERT_REJECTED: certificate rejected>
375
376the root CA is marked to reject the specified purpose.
377
378=item B<29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch>
379
380the current candidate issuer certificate was rejected because its subject name
381did not match the issuer name of the current certificate. Only displayed when
382the B<-issuer_checks> option is set.
383
384=item B<30 X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch>
385
386the current candidate issuer certificate was rejected because its subject key
387identifier was present and did not match the authority key identifier current
388certificate. Only displayed when the B<-issuer_checks> option is set.
389
390=item B<31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch>
391
392the current candidate issuer certificate was rejected because its issuer name
393and serial number was present and did not match the authority key identifier
394of the current certificate. Only displayed when the B<-issuer_checks> option is set.
395
396=item B<32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing>
397
398the current candidate issuer certificate was rejected because its keyUsage extension
399does not permit certificate signing.
400
401=item B<50 X509_V_ERR_APPLICATION_VERIFICATION: application verification failure>
402
403an application specific error. Unused.
404
405=back
406
407=head1 BUGS
408
409Although the issuer checks are a considerable improvement over the old technique they still
410suffer from limitations in the underlying X509_LOOKUP API. One consequence of this is that
411trusted certificates with matching subject name must either appear in a file (as specified by the
412B<-CAfile> option) or a directory (as specified by B<-CApath>. If they occur in both then only
413the certificates in the file will be recognised.
414
415Previous versions of OpenSSL assume certificates with matching subject name are identical and
416mishandled them.
417
418Previous versions of this documentation swapped the meaning of the
419B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT> and
420B<20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY> error codes.
421
422=head1 SEE ALSO
423
424L<x509(1)|x509(1)>
425
426=head1 HISTORY
427
428The -no_alt_chains options was first added to OpenSSL 1.0.1n and 1.0.2b.
429
430=cut
431