=pod

=head1 NAME

PKCS7_decrypt - decrypt content from a PKCS#7 envelopedData structure

=head1 SYNOPSIS

 #include <openssl/pkcs7.h>

 int PKCS7_decrypt(PKCS7 *p7, EVP_PKEY *pkey, X509 *cert, BIO *data, int flags);

=head1 DESCRIPTION

PKCS7_decrypt() extracts and decrypts the content from a PKCS#7 envelopedData
structure. B<pkey> is the private key of the recipient, B<cert> is the
recipients certificate, B<data> is a BIO to write the content to and
B<flags> is an optional set of flags.

=head1 NOTES

Although the recipients certificate is not needed to decrypt the data it is needed
to locate the appropriate (of possible several) recipients in the PKCS#7 structure.

When RSA PKCS#1 v1.5 Key Transport is in use, the invoked EVP_PKEY_decrypt()
will use implicit rejection mechanism. It always returns the result of RSA
decryption of the symmetric key to avoid Marvin attack. This result is
deterministic and can happen to match the symmetric cipher used for the content
encryption. In case when the certificate is not provided, the last
RecipientInfo producing the key looking valid will be used. It may cause
getting garbage content on decryption.

The following flags can be passed in the B<flags> parameter.

If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted
from the content. If the content is not of type B<text/plain> then an error is
returned.

=head1 RETURN VALUES

PKCS7_decrypt() returns either 1 for success or 0 for failure.
The error can be obtained from ERR_get_error(3)

=head1 BUGS

PKCS7_decrypt() must be passed the correct recipient key and certificate. It would
be better if it could look up the correct key and certificate from a database.

The lack of single pass processing and need to hold all data in memory as
mentioned in PKCS7_sign() also applies to PKCS7_verify().

=head1 SEE ALSO

L<ERR_get_error(3)>, L<PKCS7_encrypt(3)>, L<EVP_PKEY_decrypt(3)>

=head1 COPYRIGHT

Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

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