1=pod 2 3=head1 NAME 4 5PKCS7_sign_ex, PKCS7_sign 6- create a PKCS#7 signedData structure 7 8=head1 SYNOPSIS 9 10 #include <openssl/pkcs7.h> 11 12 PKCS7 *PKCS7_sign_ex(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, 13 BIO *data, int flags, OSSL_LIB_CTX *libctx, 14 const char *propq); 15 PKCS7 *PKCS7_sign(X509 *signcert, EVP_PKEY *pkey, STACK_OF(X509) *certs, 16 BIO *data, int flags); 17 18=head1 DESCRIPTION 19 20PKCS7_sign_ex() creates and returns a PKCS#7 signedData structure. 21I<signcert> is the certificate to sign with, I<pkey> is the corresponding 22private key. I<certs> is an optional set of extra certificates to include 23in the PKCS#7 structure (for example any intermediate CAs in the chain). 24The library context I<libctx> and property query I<propq> are used when 25retrieving algorithms from providers. 26 27The data to be signed is read from BIO I<data>. 28 29I<flags> is an optional set of flags. 30 31Any of the following flags (ored together) can be passed in the I<flags> 32parameter. 33 34Many S/MIME clients expect the signed content to include valid MIME headers. If 35the B<PKCS7_TEXT> flag is set MIME headers for type C<text/plain> are prepended 36to the data. 37 38If B<PKCS7_NOCERTS> is set the signer's certificate and the extra I<certs> 39will not be included in the PKCS7 structure. 40The signer's certificate must still be supplied in the I<signcert> parameter 41though. This can reduce the size of the signatures if the signer's certificates 42can be obtained by other means: for example a previously signed message. 43 44The data being signed is included in the PKCS7 structure, unless 45B<PKCS7_DETACHED> is set in which case it is omitted. This is used for PKCS7 46detached signatures which are used in S/MIME plaintext signed messages for 47example. 48 49Normally the supplied content is translated into MIME canonical format (as 50required by the S/MIME specifications) if B<PKCS7_BINARY> is set no translation 51occurs. This option should be used if the supplied data is in binary format 52otherwise the translation will corrupt it. 53 54The signedData structure includes several PKCS#7 authenticatedAttributes 55including the signing time, the PKCS#7 content type and the supported list of 56ciphers in an SMIMECapabilities attribute. If B<PKCS7_NOATTR> is set then no 57authenticatedAttributes will be used. If B<PKCS7_NOSMIMECAP> is set then just 58the SMIMECapabilities are omitted. 59 60If present the SMIMECapabilities attribute indicates support for the following 61algorithms: triple DES, 128 bit RC2, 64 bit RC2, DES and 40 bit RC2. If any of 62these algorithms is disabled then it will not be included. 63 64If the flags B<PKCS7_STREAM> is set then the returned B<PKCS7> structure is 65just initialized ready to perform the signing operation. The signing is however 66B<not> performed and the data to be signed is not read from the I<data> 67parameter. Signing is deferred until after the data has been written. In this 68way data can be signed in a single pass. 69 70If the B<PKCS7_PARTIAL> flag is set a partial B<PKCS7> structure is output to 71which additional signers and capabilities can be added before finalization. 72 73If the flag B<PKCS7_STREAM> is set the returned B<PKCS7> structure is B<not> 74complete and outputting its contents via a function that does not properly 75finalize the B<PKCS7> structure will give unpredictable results. 76 77Several functions including SMIME_write_PKCS7(), i2d_PKCS7_bio_stream(), 78PEM_write_bio_PKCS7_stream() finalize the structure. Alternatively finalization 79can be performed by obtaining the streaming ASN1 B<BIO> directly using 80BIO_new_PKCS7(). 81 82If a signer is specified it will use the default digest for the signing 83algorithm. This is B<SHA1> for both RSA and DSA keys. 84 85The I<certs>, I<signcert> and I<pkey> parameters can all be 86NULL if the B<PKCS7_PARTIAL> flag is set. One or more signers can be added 87using the function PKCS7_sign_add_signer(). PKCS7_final() must also be 88called to finalize the structure if streaming is not enabled. Alternative 89signing digests can also be specified using this method. 90 91If I<signcert> and I<pkey> are NULL then a certificates only 92PKCS#7 structure is output. 93 94In versions of OpenSSL before 1.0.0 the I<signcert> and I<pkey> parameters must 95not be NULL. 96 97PKCS7_sign() is like PKCS7_sign_ex() except that it uses default values of 98NULL for the library context I<libctx> and the property query I<propq>. 99This is retained for API backward compatibility. 100 101=head1 BUGS 102 103Some advanced attributes such as counter signatures are not supported. 104 105=head1 RETURN VALUES 106 107PKCS7_sign_ex() and PKCS7_sign() return either a valid PKCS7 structure 108or NULL if an error occurred. The error can be obtained from ERR_get_error(3). 109 110=head1 SEE ALSO 111 112L<ERR_get_error(3)>, L<PKCS7_verify(3)> 113 114=head1 HISTORY 115 116The function PKCS7_sign_ex() was added in OpenSSL 3.0. 117 118The B<PKCS7_PARTIAL> flag, and the ability for I<certs>, I<signcert>, 119and I<pkey> parameters to be NULL were added in OpenSSL 1.0.0. 120 121The B<PKCS7_STREAM> flag was added in OpenSSL 1.0.0. 122 123=head1 COPYRIGHT 124 125Copyright 2002-2023 The OpenSSL Project Authors. All Rights Reserved. 126 127Licensed under the Apache License 2.0 (the "License"). You may not use 128this file except in compliance with the License. You can obtain a copy 129in the file LICENSE in the source distribution or at 130L<https://www.openssl.org/source/license.html>. 131 132=cut 133