Merge from vendor branch OPENSSL:
[dragonfly.git] / secure / lib / libcrypto / man / PKCS7_verify.3
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124.\" ========================================================================
125.\"
126.IX Title "PKCS7_verify 3"
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127.TH PKCS7_verify 3 "2007-10-24" "0.9.8g" "OpenSSL"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
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132.SH "NAME"
133PKCS7_verify \- verify a PKCS#7 signedData structure
134.SH "SYNOPSIS"
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135.IX Header "SYNOPSIS"
136int 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 137.PP
c6e28a8e 138\&\s-1STACK_OF\s0(X509) *PKCS7_get0_signers(\s-1PKCS7\s0 *p7, \s-1STACK_OF\s0(X509) *certs, int flags);
984263bc 139.SH "DESCRIPTION"
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140.IX Header "DESCRIPTION"
141\&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
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142structure to verify. \fBcerts\fR is a set of certificates in which to search for
143the signer's certificate. \fBstore\fR is a trusted certficate store (used for
144chain verification). \fBindata\fR is the signed data if the content is not
145present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
8b0cefbb 146if it is not \s-1NULL\s0.
984263bc 147.PP
8b0cefbb 148\&\fBflags\fR is an optional set of flags, which can be used to modify the verify
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149operation.
150.PP
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151\&\fIPKCS7_get0_signers()\fR retrieves the signer's certificates from \fBp7\fR, it does
152\&\fBnot\fR check their validity or whether any signatures are valid. The \fBcerts\fR
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153and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
154.SH "VERIFY PROCESS"
8b0cefbb 155.IX Header "VERIFY PROCESS"
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156Normally the verify process proceeds as follows.
157.PP
158Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
159be signedData. There must be at least one signature on the data and if
8b0cefbb 160the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
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161.PP
162An attempt is made to locate all the signer's certificates, first looking in
8b0cefbb 163the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
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164contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
165located the operation fails.
166.PP
167Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
168the supplied trusted certificate store. Any internal certificates in the message
169are used as untrusted CAs. If any chain verify fails an error code is returned.
170.PP
8b0cefbb 171Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
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172the signature's checked.
173.PP
174If all signature's verify correctly then the function is successful.
175.PP
176Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
8b0cefbb 177to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
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178meaningful to \fIPKCS7_get0_signers()\fR.
179.PP
8b0cefbb 180If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
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181searched when locating the signer's certificate. This means that all the signers
182certificates must be in the \fBcerts\fR parameter.
183.PP
8b0cefbb 184If 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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185from the content. If the content is not of type \fBtext/plain\fR then an error is
186returned.
187.PP
8b0cefbb 188If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
984263bc 189.PP
8b0cefbb 190If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
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191not used as untrusted CAs. This means that the whole verify chain (apart from
192the signer's certificate) must be contained in the trusted store.
193.PP
8b0cefbb 194If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
984263bc 195.SH "NOTES"
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196.IX Header "NOTES"
197One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
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198a small number of certificates. The acceptable certificates would be passed
199in the \fBcerts\fR parameter. In this case if the signer is not one of the
200certificates supplied in \fBcerts\fR then the verify will fail because the
201signer cannot be found.
202.PP
203Care should be taken when modifying the default verify behaviour, for example
204setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
205and any signed message will be considered valid. This combination is however
206useful if one merely wishes to write the content to \fBout\fR and its validity
207is not considered important.
208.PP
209Chain verification should arguably be performed using the signing time rather
210than the current time. However since the signing time is supplied by the
211signer it cannot be trusted without additional evidence (such as a trusted
212timestamp).
213.SH "RETURN VALUES"
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214.IX Header "RETURN VALUES"
215\&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
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216value if an error occurs.
217.PP
8b0cefbb 218\&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
984263bc 219.PP
8b0cefbb 220The error can be obtained from \fIERR_get_error\fR\|(3)
984263bc 221.SH "BUGS"
8b0cefbb 222.IX Header "BUGS"
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223The trusted certificate store is not searched for the signers certificate,
224this is primarily due to the inadequacies of the current \fBX509_STORE\fR
225functionality.
226.PP
227The lack of single pass processing and need to hold all data in memory as
228mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
229.SH "SEE ALSO"
74dab6c2 230.IX Header "SEE ALSO"
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231\&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
232.SH "HISTORY"
984263bc 233.IX Header "HISTORY"
8b0cefbb 234\&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5