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.\" ========================================================================
.\"
.IX Title "CMS_decrypt 3"
.TH CMS_decrypt 3 "2011-02-08" "1.0.0d" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
.Vb 1
\& CMS_decrypt \- decrypt content from a CMS envelopedData structure
.Ve
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/cms.h>
\&
\& int CMS_decrypt(CMS_ContentInfo *cms, EVP_PKEY *pkey, X509 *cert, BIO *dcont, BIO *out, unsigned int flags);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fICMS_decrypt()\fR extracts and decrypts the content from a \s-1CMS\s0 EnvelopedData
structure. \fBpkey\fR is the private key of the recipient, \fBcert\fR is the
recipient's certificate, \fBout\fR is a \s-1BIO\s0 to write the content to and
\&\fBflags\fR is an optional set of flags.
.PP
The \fBdcont\fR parameter is used in the rare case where the encrypted content
is detached. It will normally be set to \s-1NULL\s0.
.SH "NOTES"
.IX Header "NOTES"
\&\fIOpenSSL_add_all_algorithms()\fR (or equivalent) should be called before using this
function or errors about unknown algorithms will occur.
.PP
Although the recipients certificate is not needed to decrypt the data it is
needed to locate the appropriate (of possible several) recipients in the \s-1CMS\s0
structure. If \fBcert\fR is set to \s-1NULL\s0 all possible recipients are tried.
.PP
It is possible to determine the correct recipient key by other means (for
example looking them up in a database) and setting them in the \s-1CMS\s0 structure
in advance using the \s-1CMS\s0 utility functions such as \fICMS_set1_pkey()\fR. In this
case both \fBcert\fR and \fBpkey\fR should be set to \s-1NULL\s0.
.PP
To process KEKRecipientInfo types \fICMS_set1_key()\fR or \fICMS_RecipientInfo_set0_key()\fR
and \fICMS_ReceipientInfo_decrypt()\fR should be called before \fICMS_decrypt()\fR and
\&\fBcert\fR and \fBpkey\fR set to \s-1NULL\s0.
.PP
The following flags can be passed in the \fBflags\fR parameter.
.PP
If the \fB\s-1CMS_TEXT\s0\fR flag is set \s-1MIME\s0 headers for type \fBtext/plain\fR are deleted
from the content. If the content is not of type \fBtext/plain\fR then an error is
returned.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fICMS_decrypt()\fR returns either 1 for success or 0 for failure.
The error can be obtained from \fIERR_get_error\fR\|(3)
.SH "BUGS"
.IX Header "BUGS"
The lack of single pass processing and the need to hold all data in memory as
mentioned in \fICMS_verify()\fR also applies to \fICMS_decrypt()\fR.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIERR_get_error\fR\|(3), \fICMS_encrypt\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fICMS_decrypt()\fR was added to OpenSSL 0.9.8