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[dragonfly.git] / secure / lib / libcrypto / man / PKCS7_verify.3
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138.\" ======================================================================
139.\"
140.IX Title "PKCS7_verify 3"
141.TH PKCS7_verify 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144PKCS7_verify \- verify a PKCS#7 signedData structure
145.SH "SYNOPSIS"
146.IX Header "SYNOPSIS"
147int PKCS7_verify(\s-1PKCS7\s0 *p7, STACK_OF(X509) *certs, X509_STORE *store, \s-1BIO\s0 *indata, \s-1BIO\s0 *out, int flags);
148.PP
149int PKCS7_get0_signers(\s-1PKCS7\s0 *p7, STACK_OF(X509) *certs, int flags);
150.SH "DESCRIPTION"
151.IX Header "DESCRIPTION"
152\&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
153structure to verify. \fBcerts\fR is a set of certificates in which to search for
154the signer's certificate. \fBstore\fR is a trusted certficate store (used for
155chain verification). \fBindata\fR is the signed data if the content is not
156present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
157if it is not \s-1NULL\s0.
158.PP
159\&\fBflags\fR is an optional set of flags, which can be used to modify the verify
160operation.
161.PP
162\&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
163\&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
164and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
165.SH "VERIFY PROCESS"
166.IX Header "VERIFY PROCESS"
167Normally the verify process proceeds as follows.
168.PP
169Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
170be signedData. There must be at least one signature on the data and if
171the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
172.PP
173An attempt is made to locate all the signer's certificates, first looking in
174the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
175contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
176located the operation fails.
177.PP
178Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
179the supplied trusted certificate store. Any internal certificates in the message
180are used as untrusted CAs. If any chain verify fails an error code is returned.
181.PP
182Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
183the signature's checked.
184.PP
185If all signature's verify correctly then the function is successful.
186.PP
187Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
188to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
189meaningful to \fIPKCS7_get0_signers()\fR.
190.PP
191If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
192searched when locating the signer's certificate. This means that all the signers
193certificates must be in the \fBcerts\fR parameter.
194.PP
195If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
196from the content. If the content is not of type \fBtext/plain\fR then an error is
197returned.
198.PP
199If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
200.PP
201If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
202not used as untrusted CAs. This means that the whole verify chain (apart from
203the signer's certificate) must be contained in the trusted store.
204.PP
205If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
206.SH "NOTES"
207.IX Header "NOTES"
208One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
209a small number of certificates. The acceptable certificates would be passed
210in the \fBcerts\fR parameter. In this case if the signer is not one of the
211certificates supplied in \fBcerts\fR then the verify will fail because the
212signer cannot be found.
213.PP
214Care should be taken when modifying the default verify behaviour, for example
215setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
216and any signed message will be considered valid. This combination is however
217useful if one merely wishes to write the content to \fBout\fR and its validity
218is not considered important.
219.PP
220Chain verification should arguably be performed using the signing time rather
221than the current time. However since the signing time is supplied by the
222signer it cannot be trusted without additional evidence (such as a trusted
223timestamp).
224.SH "RETURN VALUES"
225.IX Header "RETURN VALUES"
226\&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
227value if an error occurs.
228.PP
229\&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
230.PP
231The error can be obtained from ERR_get_error(3)
232.SH "BUGS"
233.IX Header "BUGS"
234The trusted certificate store is not searched for the signers certificate,
235this is primarily due to the inadequacies of the current \fBX509_STORE\fR
236functionality.
237.PP
238The lack of single pass processing and need to hold all data in memory as
239mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
240.SH "SEE ALSO"
241.IX Header "SEE ALSO"
242ERR_get_error(3), PKCS7_sign(3)
243.SH "HISTORY"
244.IX Header "HISTORY"
245\&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5