1=pod 2 3=head1 NAME 4 5PKCS7_sign - create a PKCS#7 signedData structure 6 7=head1 SYNOPSIS 8 9 #include <openssl/pkcs7.h> 10 11 PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, 12 BIO *data, int flags); 13 14=head1 DESCRIPTION 15 16PKCS7_sign() creates and returns a PKCS#7 signedData structure. B<signcert> is 17the certificate to sign with, B<pkey> is the corresponding private key. 18B<certs> is an optional additional set of certificates to include in the PKCS#7 19structure (for example any intermediate CAs in the chain). 20 21The data to be signed is read from BIO B<data>. 22 23B<flags> is an optional set of flags. 24 25=head1 NOTES 26 27Any of the following flags (ored together) can be passed in the B<flags> 28parameter. 29 30Many S/MIME clients expect the signed content to include valid MIME headers. If 31the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are prepended 32to the data. 33 34If B<PKCS7_NOCERTS> is set the signer's certificate will not be included in the 35PKCS7 structure, the signer's certificate must still be supplied in the 36B<signcert> parameter though. This can reduce the size of the signature if the 37signers certificate can be obtained by other means: for example a previously 38signed message. 39 40The data being signed is included in the PKCS7 structure, unless 41B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7 42detached signatures which are used in S/MIME plaintext signed messages for 43example. 44 45Normally the supplied content is translated into MIME canonical format (as 46required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation 47occurs. This option should be used if the supplied data is in binary format 48otherwise the translation will corrupt it. 49 50The signedData structure includes several PKCS#7 authenticatedAttributes 51including the signing time, the PKCS#7 content type and the supported list of 52ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no 53authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just 54the SMIMECapabilities are omitted. 55 56If present the SMIMECapabilities attribute indicates support for the following 57algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of 58these algorithms is disabled then it will not be included. 59 60If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is 61just initialized ready to perform the signing operation. The signing is however 62B<not> performed and the data to be signed is not read from the B<data> 63parameter. Signing is deferred until after the data has been written. In this 64way data can be signed in a single pass. 65 66If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to 67which additional signers and capabilities can be added before finalization. 68 69=head1 NOTES 70 71If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not> 72complete and outputting its contents via a function that does not properly 73finalize the B<PKCS7> structure will give unpredictable results. 74 75Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), 76PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization 77can be performed by obtaining the streaming ASN1 B<BIO> directly using 78BIO_new_PKCS7(). 79 80If a signer is specified it will use the default digest for the signing 81algorithm. This is B<SHA1> for both RSA and DSA keys. 82 83The B<certs>, B<signcert> and B<pkey> parameters can all be 84B<NULL> if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added 85using the function PKCS7_sign_add_signer(). PKCS7_final() must also be 86called to finalize the structure if streaming is not enabled. Alternative 87signing digests can also be specified using this method. 88 89If B<signcert> and B<pkey> are NULL then a certificates only 90PKCS#7 structure is output. 91 92In versions of OpenSSL before 1.0.0 the B<signcert> and B<pkey> parameters must 93B<NOT> be NULL. 94 95=head1 BUGS 96 97Some advanced attributes such as counter signatures are not supported. 98 99=head1 RETURN VALUES 100 101PKCS7_sign() returns either a valid PKCS7 structure or NULL if an error 102occurred. The error can be obtained from ERR_get_error(3). 103 104=head1 SEE ALSO 105 106L<ERR_get_error(3)>, L<PKCS7_verify(3)> 107 108=head1 HISTORY 109 110The B<PKCS7_PARTIAL> flag, and the ability for B<certs>, B<signcert>, 111and B<pkey> parameters to be B<NULL> were added in OpenSSL 1.0.0. 112 113The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0. 114 115=head1 COPYRIGHT 116 117Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved. 118 119Licensed under the OpenSSL license (the "License"). You may not use 120this file except in compliance with the License. You can obtain a copy 121in the file LICENSE in the source distribution or at 122L<https://www.openssl.org/source/license.html>. 123 124=cut 125