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135 .\" ========================================================================
136 .\"
137 .IX Title "PKCS7_sign 3"
138 .TH PKCS7_sign 3 "2009-12-26" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
141 .if n .ad l
142 .nh
143 .SH "NAME"
144 PKCS7_sign \- create a PKCS#7 signedData structure
145 .SH "LIBRARY"
146 libcrypto, -lcrypto
147 .SH "SYNOPSIS"
148 .IX Header "SYNOPSIS"
149 .Vb 1
150 \& #include <openssl/pkcs7.h>
151 \&
152 \& PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, BIO *data, int flags);
153 .Ve
154 .SH "DESCRIPTION"
155 .IX Header "DESCRIPTION"
156 \&\fIPKCS7_sign()\fR creates and returns a PKCS#7 signedData structure. \fBsigncert\fR is
157 the certificate to sign with, \fBpkey\fR is the corresponsding private key.
158 \&\fBcerts\fR is an optional additional set of certificates to include in the PKCS#7
159 structure (for example any intermediate CAs in the chain).
160 .PP
161 The data to be signed is read from \s-1BIO \s0\fBdata\fR.
162 .PP
163 \&\fBflags\fR is an optional set of flags.
164 .SH "NOTES"
165 .IX Header "NOTES"
166 Any of the following flags (ored together) can be passed in the \fBflags\fR
167 parameter.
168 .PP
169 Many S/MIME clients expect the signed content to include valid \s-1MIME\s0 headers. If
170 the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are prepended
171 to the data.
172 .PP
173 If \fB\s-1PKCS7_NOCERTS\s0\fR is set the signer's certificate will not be included in the
174 \&\s-1PKCS7\s0 structure, the signer's certificate must still be supplied in the
175 \&\fBsigncert\fR parameter though. This can reduce the size of the signature if the
176 signers certificate can be obtained by other means: for example a previously
177 signed message.
178 .PP
179 The data being signed is included in the \s-1PKCS7\s0 structure, unless
180 \&\fB\s-1PKCS7_DETACHED\s0\fR is set in which case it is omitted. This is used for \s-1PKCS7\s0
181 detached signatures which are used in S/MIME plaintext signed messages for
182 example.
183 .PP
184 Normally the supplied content is translated into \s-1MIME\s0 canonical format (as
185 required by the S/MIME specifications) if \fB\s-1PKCS7_BINARY\s0\fR is set no translation
186 occurs. This option should be used if the supplied data is in binary format
187 otherwise the translation will corrupt it.
188 .PP
189 The signedData structure includes several PKCS#7 autenticatedAttributes
190 including the signing time, the PKCS#7 content type and the supported list of
191 ciphers in an SMIMECapabilities attribute. If \fB\s-1PKCS7_NOATTR\s0\fR is set then no
192 authenticatedAttributes will be used. If \fB\s-1PKCS7_NOSMIMECAP\s0\fR is set then just
193 the SMIMECapabilities are omitted.
194 .PP
195 If present the SMIMECapabilities attribute indicates support for the following
196 algorithms: triple \s-1DES, 128\s0 bit \s-1RC2, 64\s0 bit \s-1RC2, DES\s0 and 40 bit \s-1RC2.\s0 If any of
197 these algorithms is disabled then it will not be included.
198 .PP
199 If the flags \fB\s-1PKCS7_STREAM\s0\fR is set then the returned \fB\s-1PKCS7\s0\fR structure is
200 just initialized ready to perform the signing operation. The signing is however
201 \&\fBnot\fR performed and the data to be signed is not read from the \fBdata\fR
202 parameter. Signing is deferred until after the data has been written. In this
203 way data can be signed in a single pass.
204 .PP
205 If the \fB\s-1PKCS7_PARTIAL\s0\fR flag is set a partial \fB\s-1PKCS7\s0\fR structure is output to
206 which additional signers and capabilities can be added before finalization.
207 .SH "NOTES"
208 .IX Header "NOTES"
209 If the flag \fB\s-1PKCS7_STREAM\s0\fR is set the returned \fB\s-1PKCS7\s0\fR structure is \fBnot\fR
210 complete and outputting its contents via a function that does not properly
211 finalize the \fB\s-1PKCS7\s0\fR structure will give unpredictable results.
212 .PP
213 Several functions including \fISMIME_write_PKCS7()\fR, \fIi2d_PKCS7_bio_stream()\fR,
214 \&\fIPEM_write_bio_PKCS7_stream()\fR finalize the structure. Alternatively finalization
215 can be performed by obtaining the streaming \s-1ASN1 \s0\fB\s-1BIO\s0\fR directly using
216 \&\fIBIO_new_PKCS7()\fR.
217 .PP
218 If a signer is specified it will use the default digest for the signing
219 algorithm. This is \fB\s-1SHA1\s0\fR for both \s-1RSA\s0 and \s-1DSA\s0 keys.
220 .PP
221 In OpenSSL 1.0.0 the \fBcerts\fR, \fBsigncert\fR and \fBpkey\fR parameters can all be
222 \&\fB\s-1NULL\s0\fR if the \fB\s-1PKCS7_PARTIAL\s0\fR flag is set. One or more signers can be added
223 using the function \fB\f(BIPKCS7_sign_add_signer()\fB\fR. \fB\f(BIPKCS7_final()\fB\fR must also be
224 called to finalize the structure if streaming is not enabled. Alternative
225 signing digests can also be specified using this method.
226 .PP
227 In OpenSSL 1.0.0 if \fBsigncert\fR and \fBpkey\fR are \s-1NULL\s0 then a certificates only
228 PKCS#7 structure is output.
229 .PP
230 In versions of OpenSSL before 1.0.0 the \fBsigncert\fR and \fBpkey\fR parameters must
231 \&\fB\s-1NOT\s0\fR be \s-1NULL.\s0
232 .SH "BUGS"
233 .IX Header "BUGS"
234 Some advanced attributes such as counter signatures are not supported.
235 .SH "RETURN VALUES"
236 .IX Header "RETURN VALUES"
237 \&\fIPKCS7_sign()\fR returns either a valid \s-1PKCS7\s0 structure or \s-1NULL\s0 if an error
238 occurred. The error can be obtained from \fIERR_get_error\fR\|(3).
239 .SH "SEE ALSO"
240 .IX Header "SEE ALSO"
241 \&\fIERR_get_error\fR\|(3), \fIPKCS7_verify\fR\|(3)
242 .SH "HISTORY"
243 .IX Header "HISTORY"
244 \&\fIPKCS7_sign()\fR was added to OpenSSL 0.9.5
245 .PP
246 The \fB\s-1PKCS7_PARTIAL\s0\fR flag was added in OpenSSL 1.0.0
247 .PP
248 The \fB\s-1PKCS7_STREAM\s0\fR flag was added in OpenSSL 1.0.0