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[dragonfly.git] / secure / lib / libcrypto / man / PKCS7_verify.3
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129.\" ========================================================================
130.\"
131.IX Title "PKCS7_verify 3"
aac4ff6f 132.TH PKCS7_verify 3 "2008-09-06" "0.9.8h" "OpenSSL"
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133.SH "NAME"
134PKCS7_verify \- verify a PKCS#7 signedData structure
135.SH "SYNOPSIS"
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136.IX Header "SYNOPSIS"
137int PKCS7_verify(\s-1PKCS7\s0 *p7, \s-1STACK_OF\s0(X509) *certs, X509_STORE *store, \s-1BIO\s0 *indata, \s-1BIO\s0 *out, int flags);
984263bc 138.PP
c6e28a8e 139\&\s-1STACK_OF\s0(X509) *PKCS7_get0_signers(\s-1PKCS7\s0 *p7, \s-1STACK_OF\s0(X509) *certs, int flags);
984263bc 140.SH "DESCRIPTION"
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141.IX Header "DESCRIPTION"
142\&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
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143structure to verify. \fBcerts\fR is a set of certificates in which to search for
144the signer's certificate. \fBstore\fR is a trusted certficate store (used for
145chain verification). \fBindata\fR is the signed data if the content is not
146present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
8b0cefbb 147if it is not \s-1NULL\s0.
984263bc 148.PP
8b0cefbb 149\&\fBflags\fR is an optional set of flags, which can be used to modify the verify
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150operation.
151.PP
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152\&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
153\&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
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154and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
155.SH "VERIFY PROCESS"
8b0cefbb 156.IX Header "VERIFY PROCESS"
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157Normally the verify process proceeds as follows.
158.PP
159Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
160be signedData. There must be at least one signature on the data and if
8b0cefbb 161the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
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162.PP
163An attempt is made to locate all the signer's certificates, first looking in
8b0cefbb 164the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
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165contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
166located the operation fails.
167.PP
168Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
169the supplied trusted certificate store. Any internal certificates in the message
170are used as untrusted CAs. If any chain verify fails an error code is returned.
171.PP
8b0cefbb 172Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
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173the signature's checked.
174.PP
175If all signature's verify correctly then the function is successful.
176.PP
177Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
8b0cefbb 178to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
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179meaningful to \fIPKCS7_get0_signers()\fR.
180.PP
8b0cefbb 181If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
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182searched when locating the signer's certificate. This means that all the signers
183certificates must be in the \fBcerts\fR parameter.
184.PP
8b0cefbb 185If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
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186from the content. If the content is not of type \fBtext/plain\fR then an error is
187returned.
188.PP
8b0cefbb 189If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
984263bc 190.PP
8b0cefbb 191If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
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192not used as untrusted CAs. This means that the whole verify chain (apart from
193the signer's certificate) must be contained in the trusted store.
194.PP
8b0cefbb 195If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
984263bc 196.SH "NOTES"
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197.IX Header "NOTES"
198One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
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199a small number of certificates. The acceptable certificates would be passed
200in the \fBcerts\fR parameter. In this case if the signer is not one of the
201certificates supplied in \fBcerts\fR then the verify will fail because the
202signer cannot be found.
203.PP
204Care should be taken when modifying the default verify behaviour, for example
205setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
206and any signed message will be considered valid. This combination is however
207useful if one merely wishes to write the content to \fBout\fR and its validity
208is not considered important.
209.PP
210Chain verification should arguably be performed using the signing time rather
211than the current time. However since the signing time is supplied by the
212signer it cannot be trusted without additional evidence (such as a trusted
213timestamp).
214.SH "RETURN VALUES"
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215.IX Header "RETURN VALUES"
216\&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
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217value if an error occurs.
218.PP
8b0cefbb 219\&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
984263bc 220.PP
8b0cefbb 221The error can be obtained from \fIERR_get_error\fR\|(3)
984263bc 222.SH "BUGS"
8b0cefbb 223.IX Header "BUGS"
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224The trusted certificate store is not searched for the signers certificate,
225this is primarily due to the inadequacies of the current \fBX509_STORE\fR
226functionality.
227.PP
228The lack of single pass processing and need to hold all data in memory as
229mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
230.SH "SEE ALSO"
74dab6c2 231.IX Header "SEE ALSO"
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232\&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
233.SH "HISTORY"
984263bc 234.IX Header "HISTORY"
8b0cefbb 235\&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5