Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / PKCS7_verify.3
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124.\" ========================================================================
125.\"
126.IX Title "PKCS7_verify 3"
e3261593 127.TH PKCS7_verify 3 "2012-01-04" "1.0.0f" "OpenSSL"
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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"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/pkcs7.h>
138\&
139\& int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags);
140\&
141\& STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
142.Ve
984263bc 143.SH "DESCRIPTION"
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144.IX Header "DESCRIPTION"
145\&\fIPKCS7_verify()\fR verifies a PKCS#7 signedData structure. \fBp7\fR is the \s-1PKCS7\s0
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146structure to verify. \fBcerts\fR is a set of certificates in which to search for
147the signer's certificate. \fBstore\fR is a trusted certficate store (used for
148chain verification). \fBindata\fR is the signed data if the content is not
149present in \fBp7\fR (that is it is detached). The content is written to \fBout\fR
8b0cefbb 150if it is not \s-1NULL\s0.
984263bc 151.PP
8b0cefbb 152\&\fBflags\fR is an optional set of flags, which can be used to modify the verify
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153operation.
154.PP
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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
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157and \fBflags\fR parameters have the same meanings as in \fIPKCS7_verify()\fR.
158.SH "VERIFY PROCESS"
8b0cefbb 159.IX Header "VERIFY PROCESS"
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160Normally the verify process proceeds as follows.
161.PP
162Initially some sanity checks are performed on \fBp7\fR. The type of \fBp7\fR must
163be signedData. There must be at least one signature on the data and if
8b0cefbb 164the content is detached \fBindata\fR cannot be \fB\s-1NULL\s0\fR.
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165.PP
166An attempt is made to locate all the signer's certificates, first looking in
8b0cefbb 167the \fBcerts\fR parameter (if it is not \fB\s-1NULL\s0\fR) and then looking in any certificates
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168contained in the \fBp7\fR structure itself. If any signer's certificates cannot be
169located the operation fails.
170.PP
171Each signer's certificate is chain verified using the \fBsmimesign\fR purpose and
172the supplied trusted certificate store. Any internal certificates in the message
173are used as untrusted CAs. If any chain verify fails an error code is returned.
174.PP
8b0cefbb 175Finally the signed content is read (and written to \fBout\fR is it is not \s-1NULL\s0) and
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176the signature's checked.
177.PP
178If all signature's verify correctly then the function is successful.
179.PP
180Any of the following flags (ored together) can be passed in the \fBflags\fR parameter
8b0cefbb 181to change the default verify behaviour. Only the flag \fB\s-1PKCS7_NOINTERN\s0\fR is
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182meaningful to \fIPKCS7_get0_signers()\fR.
183.PP
8b0cefbb 184If \fB\s-1PKCS7_NOINTERN\s0\fR is set the certificates in the message itself are not
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185searched when locating the signer's certificate. This means that all the signers
186certificates must be in the \fBcerts\fR parameter.
187.PP
8b0cefbb 188If 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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189from the content. If the content is not of type \fBtext/plain\fR then an error is
190returned.
191.PP
8b0cefbb 192If \fB\s-1PKCS7_NOVERIFY\s0\fR is set the signer's certificates are not chain verified.
984263bc 193.PP
8b0cefbb 194If \fB\s-1PKCS7_NOCHAIN\s0\fR is set then the certificates contained in the message are
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195not used as untrusted CAs. This means that the whole verify chain (apart from
196the signer's certificate) must be contained in the trusted store.
197.PP
8b0cefbb 198If \fB\s-1PKCS7_NOSIGS\s0\fR is set then the signatures on the data are not checked.
984263bc 199.SH "NOTES"
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200.IX Header "NOTES"
201One application of \fB\s-1PKCS7_NOINTERN\s0\fR is to only accept messages signed by
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202a small number of certificates. The acceptable certificates would be passed
203in the \fBcerts\fR parameter. In this case if the signer is not one of the
204certificates supplied in \fBcerts\fR then the verify will fail because the
205signer cannot be found.
206.PP
207Care should be taken when modifying the default verify behaviour, for example
208setting \fBPKCS7_NOVERIFY|PKCS7_NOSIGS\fR will totally disable all verification
209and any signed message will be considered valid. This combination is however
210useful if one merely wishes to write the content to \fBout\fR and its validity
211is not considered important.
212.PP
213Chain verification should arguably be performed using the signing time rather
214than the current time. However since the signing time is supplied by the
215signer it cannot be trusted without additional evidence (such as a trusted
216timestamp).
217.SH "RETURN VALUES"
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218.IX Header "RETURN VALUES"
219\&\fIPKCS7_verify()\fR returns 1 for a successful verification and zero or a negative
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220value if an error occurs.
221.PP
8b0cefbb 222\&\fIPKCS7_get0_signers()\fR returns all signers or \fB\s-1NULL\s0\fR if an error occurred.
984263bc 223.PP
8b0cefbb 224The error can be obtained from \fIERR_get_error\fR\|(3)
984263bc 225.SH "BUGS"
8b0cefbb 226.IX Header "BUGS"
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227The trusted certificate store is not searched for the signers certificate,
228this is primarily due to the inadequacies of the current \fBX509_STORE\fR
229functionality.
230.PP
231The lack of single pass processing and need to hold all data in memory as
232mentioned in \fIPKCS7_sign()\fR also applies to \fIPKCS7_verify()\fR.
233.SH "SEE ALSO"
74dab6c2 234.IX Header "SEE ALSO"
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235\&\fIERR_get_error\fR\|(3), \fIPKCS7_sign\fR\|(3)
236.SH "HISTORY"
984263bc 237.IX Header "HISTORY"
8b0cefbb 238\&\fIPKCS7_verify()\fR was added to OpenSSL 0.9.5