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124 .\" ========================================================================
126 .IX Title "PKCS7_verify 3"
127 .TH PKCS7_verify 3 "2012-05-10" "1.0.1c" "OpenSSL"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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133 PKCS7_verify \- verify a PKCS#7 signedData structure
135 .IX Header "SYNOPSIS"
137 \& #include <openssl/pkcs7.h>
139 \& int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags);
141 \& STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
144 .IX Header "DESCRIPTION"
145 \&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
146 structure to verify. \fBcerts\fR is a set of certificates in which to search for
147 the signer's certificate. \fBstore\fR is a trusted certficate store (used for
148 chain verification). \fBindata\fR is the signed data if the content is not
149 present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
150 if it is not \s-1NULL\s0.
152 \&\fBflags\fR is an optional set of flags, which can be used to modify the verify
155 \&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
156 \&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
157 and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
159 .IX Header "VERIFY PROCESS"
160 Normally the verify process proceeds as follows.
162 Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
163 be signedData. There must be at least one signature on the data and if
164 the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
166 An attempt is made to locate all the signer's certificates, first looking in
167 the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
168 contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
169 located the operation fails.
171 Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
172 the supplied trusted certificate store. Any internal certificates in the message
173 are used as untrusted CAs. If any chain verify fails an error code is returned.
175 Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
176 the signature's checked.
178 If all signature's verify correctly then the function is successful.
180 Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
181 to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
182 meaningful to \fIPKCS7_get0_signers()\fR.
184 If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
185 searched when locating the signer's certificate. This means that all the signers
186 certificates must be in the \fBcerts\fR parameter.
188 If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
189 from the content. If the content is not of type \fBtext/plain\fR then an error is
192 If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
194 If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
195 not used as untrusted CAs. This means that the whole verify chain (apart from
196 the signer's certificate) must be contained in the trusted store.
198 If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
201 One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
202 a small number of certificates. The acceptable certificates would be passed
203 in the \fBcerts\fR parameter. In this case if the signer is not one of the
204 certificates supplied in \fBcerts\fR then the verify will fail because the
205 signer cannot be found.
207 Care should be taken when modifying the default verify behaviour, for example
208 setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
209 and any signed message will be considered valid. This combination is however
210 useful if one merely wishes to write the content to \fBout\fR and its validity
211 is not considered important.
213 Chain verification should arguably be performed using the signing time rather
214 than the current time. However since the signing time is supplied by the
215 signer it cannot be trusted without additional evidence (such as a trusted
218 .IX Header "RETURN VALUES"
219 \&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
220 value if an error occurs.
222 \&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
224 The error can be obtained from \fIERR_get_error\fR\|(3)
227 The trusted certificate store is not searched for the signers certificate,
228 this is primarily due to the inadequacies of the current \fBX509_STORE\fR
231 The lack of single pass processing and need to hold all data in memory as
232 mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
234 .IX Header "SEE ALSO"
235 \&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
238 \&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5