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134 .\" ========================================================================
135 .\"
136 .IX Title "PKCS7_verify 3"
137 .TH PKCS7_verify 3 "2006-05-14" "1.1.0-dev" "OpenSSL"
138 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
139 .\" way too many mistakes in technical documents.
140 .if n .ad l
141 .nh
142 .SH "NAME"
143 PKCS7_verify \- verify a PKCS#7 signedData structure
144 .SH "LIBRARY"
145 libcrypto, -lcrypto
146 .SH "SYNOPSIS"
147 .IX Header "SYNOPSIS"
148 .Vb 1
149 \& #include <openssl/pkcs7.h>
150 \&
151 \& int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags);
152 \&
153 \& STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
154 .Ve
155 .SH "DESCRIPTION"
156 .IX Header "DESCRIPTION"
157 \&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
158 structure to verify. \fBcerts\fR is a set of certificates in which to search for
159 the signer's certificate. \fBstore\fR is a trusted certficate store (used for
160 chain verification). \fBindata\fR is the signed data if the content is not
161 present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
162 if it is not \s-1NULL\s0.
163 .PP
164 \&\fBflags\fR is an optional set of flags, which can be used to modify the verify
165 operation.
166 .PP
167 \&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
168 \&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
169 and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
170 .SH "VERIFY PROCESS"
171 .IX Header "VERIFY PROCESS"
172 Normally the verify process proceeds as follows.
173 .PP
174 Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
175 be signedData. There must be at least one signature on the data and if
176 the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
177 .PP
178 An attempt is made to locate all the signer's certificates, first looking in
179 the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
180 contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
181 located the operation fails.
182 .PP
183 Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
184 the supplied trusted certificate store. Any internal certificates in the message
185 are used as untrusted CAs. If any chain verify fails an error code is returned.
186 .PP
187 Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
188 the signature's checked.
189 .PP
190 If all signature's verify correctly then the function is successful.
191 .PP
192 Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
193 to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
194 meaningful to \fIPKCS7_get0_signers()\fR.
195 .PP
196 If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
197 searched when locating the signer's certificate. This means that all the signers
198 certificates must be in the \fBcerts\fR parameter.
199 .PP
200 If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
201 from the content. If the content is not of type \fBtext/plain\fR then an error is
202 returned.
203 .PP
204 If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
205 .PP
206 If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
207 not used as untrusted CAs. This means that the whole verify chain (apart from
208 the signer's certificate) must be contained in the trusted store.
209 .PP
210 If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
211 .SH "NOTES"
212 .IX Header "NOTES"
213 One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
214 a small number of certificates. The acceptable certificates would be passed
215 in the \fBcerts\fR parameter. In this case if the signer is not one of the
216 certificates supplied in \fBcerts\fR then the verify will fail because the
217 signer cannot be found.
218 .PP
219 Care should be taken when modifying the default verify behaviour, for example
220 setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
221 and any signed message will be considered valid. This combination is however
222 useful if one merely wishes to write the content to \fBout\fR and its validity
223 is not considered important.
224 .PP
225 Chain verification should arguably be performed using the signing time rather
226 than the current time. However since the signing time is supplied by the
227 signer it cannot be trusted without additional evidence (such as a trusted
228 timestamp).
229 .SH "RETURN VALUES"
230 .IX Header "RETURN VALUES"
231 \&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
232 value if an error occurs.
233 .PP
234 \&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
235 .PP
236 The error can be obtained from \fIERR_get_error\fR\|(3)
237 .SH "BUGS"
238 .IX Header "BUGS"
239 The trusted certificate store is not searched for the signers certificate,
240 this is primarily due to the inadequacies of the current \fBX509_STORE\fR
241 functionality.
242 .PP
243 The lack of single pass processing and need to hold all data in memory as
244 mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
245 .SH "SEE ALSO"
246 .IX Header "SEE ALSO"
247 \&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
248 .SH "HISTORY"
249 .IX Header "HISTORY"
250 \&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5