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1 .\" $NetBSD: PKCS7_encrypt.3,v 1.14 2015/06/12 17:01:14 christos Exp $
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135 .\" ========================================================================
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137 .IX Title "PKCS7_encrypt 3"
138 .TH PKCS7_encrypt 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_encrypt \- create a PKCS#7 envelopedData 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_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, int flags);
153 .Ve
154 .SH "DESCRIPTION"
155 .IX Header "DESCRIPTION"
156 \&\fIPKCS7_encrypt()\fR creates and returns a PKCS#7 envelopedData structure. \fBcerts\fR
157 is a list of recipient certificates. \fBin\fR is the content to be encrypted.
158 \&\fBcipher\fR is the symmetric cipher to use. \fBflags\fR is an optional set of flags.
159 .SH "NOTES"
160 .IX Header "NOTES"
161 Only \s-1RSA\s0 keys are supported in PKCS#7 and envelopedData so the recipient
162 certificates supplied to this function must all contain \s-1RSA\s0 public keys, though
163 they do not have to be signed using the \s-1RSA\s0 algorithm.
164 .PP
165 \&\fIEVP_des_ede3_cbc()\fR (triple \s-1DES\s0) is the algorithm of choice for S/MIME use
166 because most clients will support it.
167 .PP
168 Some old \*(L"export grade\*(R" clients may only support weak encryption using 40 or 64
169 bit \s-1RC2.\s0 These can be used by passing \fIEVP_rc2_40_cbc()\fR and \fIEVP_rc2_64_cbc()\fR
170 respectively.
171 .PP
172 The algorithm passed in the \fBcipher\fR parameter must support \s-1ASN1\s0 encoding of
173 its parameters.
174 .PP
175 Many browsers implement a \*(L"sign and encrypt\*(R" option which is simply an S/MIME
176 envelopedData containing an S/MIME signed message. This can be readily produced
177 by storing the S/MIME signed message in a memory \s-1BIO\s0 and passing it to
178 \&\fIPKCS7_encrypt()\fR.
179 .PP
180 The following flags can be passed in the \fBflags\fR parameter.
181 .PP
182 If the \fB\s-1PKCS7_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are
183 prepended to the data.
184 .PP
185 Normally the supplied content is translated into \s-1MIME\s0 canonical format (as
186 required by the S/MIME specifications) if \fB\s-1PKCS7_BINARY\s0\fR is set no translation
187 occurs. This option should be used if the supplied data is in binary format
188 otherwise the translation will corrupt it. If \fB\s-1PKCS7_BINARY\s0\fR is set then
189 \&\fB\s-1PKCS7_TEXT\s0\fR is ignored.
190 .PP
191 If the \fB\s-1PKCS7_STREAM\s0\fR flag is set a partial \fB\s-1PKCS7\s0\fR structure is output
192 suitable for streaming I/O: no data is read from the \s-1BIO \s0\fBin\fR.
193 .SH "NOTES"
194 .IX Header "NOTES"
195 If the flag \fB\s-1PKCS7_STREAM\s0\fR is set the returned \fB\s-1PKCS7\s0\fR structure is \fBnot\fR
196 complete and outputting its contents via a function that does not
197 properly finalize the \fB\s-1PKCS7\s0\fR structure will give unpredictable
198 results.
199 .PP
200 Several functions including \fISMIME_write_PKCS7()\fR, \fIi2d_PKCS7_bio_stream()\fR,
201 \&\fIPEM_write_bio_PKCS7_stream()\fR finalize the structure. Alternatively finalization
202 can be performed by obtaining the streaming \s-1ASN1 \s0\fB\s-1BIO\s0\fR directly using
203 \&\fIBIO_new_PKCS7()\fR.
204 .SH "RETURN VALUES"
205 .IX Header "RETURN VALUES"
206 \&\fIPKCS7_encrypt()\fR returns either a \s-1PKCS7\s0 structure or \s-1NULL\s0 if an error occurred.
207 The error can be obtained from \fIERR_get_error\fR\|(3).
208 .SH "SEE ALSO"
209 .IX Header "SEE ALSO"
210 \&\fIERR_get_error\fR\|(3), \fIPKCS7_decrypt\fR\|(3)
211 .SH "HISTORY"
212 .IX Header "HISTORY"
213 \&\fIPKCS7_decrypt()\fR was added to OpenSSL 0.9.5
214 The \fB\s-1PKCS7_STREAM\s0\fR flag was first supported in OpenSSL 1.0.0.