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131 .IX Title "PKCS7_verify 3"
132 .TH PKCS7_verify 3 "2018-03-27" "1.0.2o" "OpenSSL"
133 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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138 PKCS7_verify, PKCS7_get0_signers \- verify a PKCS#7 signedData structure
140 .IX Header "SYNOPSIS"
142 \& #include <openssl/pkcs7.h>
144 \& int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags);
146 \& STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
149 .IX Header "DESCRIPTION"
150 \&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
151 structure to verify. \fBcerts\fR is a set of certificates in which to search for
152 the signer's certificate. \fBstore\fR is a trusted certficate store (used for
153 chain verification). \fBindata\fR is the signed data if the content is not
154 present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
155 if it is not \s-1NULL.\s0
157 \&\fBflags\fR is an optional set of flags, which can be used to modify the verify
160 \&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
161 \&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
162 and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
164 .IX Header "VERIFY PROCESS"
165 Normally the verify process proceeds as follows.
167 Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
168 be signedData. There must be at least one signature on the data and if
169 the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
171 An attempt is made to locate all the signer's certificates, first looking in
172 the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
173 contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
174 located the operation fails.
176 Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
177 the supplied trusted certificate store. Any internal certificates in the message
178 are used as untrusted CAs. If any chain verify fails an error code is returned.
180 Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
181 the signature's checked.
183 If all signature's verify correctly then the function is successful.
185 Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
186 to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
187 meaningful to \fIPKCS7_get0_signers()\fR.
189 If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
190 searched when locating the signer's certificate. This means that all the signers
191 certificates must be in the \fBcerts\fR parameter.
193 If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
194 from the content. If the content is not of type \fBtext/plain\fR then an error is
197 If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
199 If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
200 not used as untrusted CAs. This means that the whole verify chain (apart from
201 the signer's certificate) must be contained in the trusted store.
203 If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
206 One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
207 a small number of certificates. The acceptable certificates would be passed
208 in the \fBcerts\fR parameter. In this case if the signer is not one of the
209 certificates supplied in \fBcerts\fR then the verify will fail because the
210 signer cannot be found.
212 Care should be taken when modifying the default verify behaviour, for example
213 setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
214 and any signed message will be considered valid. This combination is however
215 useful if one merely wishes to write the content to \fBout\fR and its validity
216 is not considered important.
218 Chain verification should arguably be performed using the signing time rather
219 than the current time. However since the signing time is supplied by the
220 signer it cannot be trusted without additional evidence (such as a trusted
223 .IX Header "RETURN VALUES"
224 \&\fIPKCS7_verify()\fR returns one for a successful verification and zero
227 \&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
229 The error can be obtained from \fIERR_get_error\fR\|(3)
232 The trusted certificate store is not searched for the signers certificate,
233 this is primarily due to the inadequacies of the current \fBX509_STORE\fR
236 The lack of single pass processing and need to hold all data in memory as
237 mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
239 .IX Header "SEE ALSO"
240 \&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
243 \&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5