Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / CMS_verify.3
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124.\" ========================================================================
125.\"
126.IX Title "CMS_verify 3"
e3261593 127.TH CMS_verify 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
132.SH "NAME"
133.Vb 1
134\& CMS_verify \- verify a CMS SignedData structure
135.Ve
136.SH "SYNOPSIS"
137.IX Header "SYNOPSIS"
138.Vb 1
139\& #include <openssl/cms.h>
140\&
141\& int CMS_verify(CMS_ContentInfo *cms, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, unsigned int flags);
142\&
143\& STACK_OF(X509) *CMS_get0_signers(CMS_ContentInfo *cms);
144.Ve
145.SH "DESCRIPTION"
146.IX Header "DESCRIPTION"
147\&\fICMS_verify()\fR verifies a \s-1CMS\s0 SignedData structure. \fBcms\fR is the CMS_ContentInfo
148structure to verify. \fBcerts\fR is a set of certificates in which to search for
149the signing certificate(s). \fBstore\fR is a trusted certificate store used for
150chain verification. \fBindata\fR is the detached content if the content is not
151present in \fBcms\fR. The content is written to \fBout\fR if it is not \s-1NULL\s0.
152.PP
153\&\fBflags\fR is an optional set of flags, which can be used to modify the verify
154operation.
155.PP
156\&\fICMS_get0_signers()\fR retrieves the signing certificate(s) from \fBcms\fR, it must
157be called after a successful \fICMS_verify()\fR operation.
158.SH "VERIFY PROCESS"
159.IX Header "VERIFY PROCESS"
160Normally the verify process proceeds as follows.
161.PP
162Initially some sanity checks are performed on \fBcms\fR. The type of \fBcms\fR must
163be SignedData. There must be at least one signature on the data and if
164the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
165.PP
166An attempt is made to locate all the signing certificate(s), first looking in
167the \fBcerts\fR parameter (if it is not \s-1NULL\s0) and then looking in any
168certificates contained in the \fBcms\fR structure itself. If any signing
169certificate cannot be located the operation fails.
170.PP
171Each signing certificate is chain verified using the \fBsmimesign\fR purpose and
172the supplied trusted certificate store. Any internal certificates in the message
173are used as untrusted CAs. If \s-1CRL\s0 checking is enabled in \fBstore\fR any internal
174CRLs are used in addition to attempting to look them up in \fBstore\fR. If any
175chain verify fails an error code is returned.
176.PP
177Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0)
178and the signature's checked.
179.PP
180If all signature's verify correctly then the function is successful.
181.PP
182Any of the following flags (ored together) can be passed in the \fBflags\fR
183parameter to change the default verify behaviour.
184.PP
185If \fB\s-1CMS_NOINTERN\s0\fR is set the certificates in the message itself are not
186searched when locating the signing certificate(s). This means that all the
187signing certificates must be in the \fBcerts\fR parameter.
188.PP
189If \fB\s-1CMS_NOCRL\s0\fR is set and \s-1CRL\s0 checking is enabled in \fBstore\fR then any
190CRLs in the message itself are ignored.
191.PP
192If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
193from the content. If the content is not of type \fBtext/plain\fR then an error is
194returned.
195.PP
196If \fB\s-1CMS_NO_SIGNER_CERT_VERIFY\s0\fR is set the signing certificates are not
197verified.
198.PP
199If \fB\s-1CMS_NO_ATTR_VERIFY\s0\fR is set the signed attributes signature is not
200verified.
201.PP
202If \fB\s-1CMS_NO_CONTENT_VERIFY\s0\fR is set then the content digest is not checked.
203.SH "NOTES"
204.IX Header "NOTES"
205One application of \fB\s-1CMS_NOINTERN\s0\fR is to only accept messages signed by
206a small number of certificates. The acceptable certificates would be passed
207in the \fBcerts\fR parameter. In this case if the signer is not one of the
208certificates supplied in \fBcerts\fR then the verify will fail because the
209signer cannot be found.
210.PP
211In some cases the standard techniques for looking up and validating
212certificates are not appropriate: for example an application may wish to
213lookup certificates in a database or perform customised verification. This
214can be achieved by setting and verifying the signers certificates manually
215using the signed data utility functions.
216.PP
217Care should be taken when modifying the default verify behaviour, for example
218setting \fB\s-1CMS_NO_CONTENT_VERIFY\s0\fR will totally disable all content verification
219and any modified content will be considered valid. This combination is however
220useful if one merely wishes to write the content to \fBout\fR and its validity
221is not considered important.
222.PP
223Chain verification should arguably be performed using the signing time rather
224than the current time. However since the signing time is supplied by the
225signer it cannot be trusted without additional evidence (such as a trusted
226timestamp).
227.SH "RETURN VALUES"
228.IX Header "RETURN VALUES"
229\&\fICMS_verify()\fR returns 1 for a successful verification and zero if an error
230occurred.
231.PP
232\&\fICMS_get0_signers()\fR returns all signers or \s-1NULL\s0 if an error occurred.
233.PP
234The error can be obtained from \fIERR_get_error\fR\|(3)
235.SH "BUGS"
236.IX Header "BUGS"
237The trusted certificate store is not searched for the signing certificate,
238this is primarily due to the inadequacies of the current \fBX509_STORE\fR
239functionality.
240.PP
241The lack of single pass processing means that the signed content must all
242be held in memory if it is not detached.
243.SH "SEE ALSO"
244.IX Header "SEE ALSO"
245\&\fIERR_get_error\fR\|(3), \fICMS_sign\fR\|(3)
246.SH "HISTORY"
247.IX Header "HISTORY"
248\&\fICMS_verify()\fR was added to OpenSSL 0.9.8