OpenSSL

Cryptography and SSL/TLS Toolkit

SMIME_read_CMS

NAME

SMIME_read_CMS_ex, SMIME_read_CMS - parse S/MIME message

SYNOPSIS

 #include <openssl/cms.h>

 CMS_ContentInfo *SMIME_read_CMS_ex(BIO *bio, int flags, BIO **bcont,
                                    CMS_ContentInfo **cms);
 CMS_ContentInfo *SMIME_read_CMS(BIO *in, BIO **bcont);

DESCRIPTION

SMIME_read_CMS() parses a message in S/MIME format.

in is a BIO to read the message from.

If cleartext signing is used then the content is saved in a memory bio which is written to *bcont, otherwise *bcont is set to NULL.

The parsed CMS_ContentInfo structure is returned or NULL if an error occurred.

SMIME_read_CMS_ex() is similar to SMIME_read_CMS() but optionally a previously created cms CMS_ContentInfo object can be supplied as well as some flags. To create a cms object use CMS_ContentInfo_new_ex(3). If the flags argument contains CMS_BINARY then the input is assumed to be in binary format and is not translated to canonical form. If in addition SMIME_ASCIICRLF is set then the binary input is assumed to be followed by CR and LF characters, else only by an LF character. If flags is 0 and cms is NULL then it is identical to SMIME_read_CMS().

NOTES

If *bcont is not NULL then the message is clear text signed. *bcont can then be passed to CMS_verify() with the CMS_DETACHED flag set.

Otherwise the type of the returned structure can be determined using CMS_get0_type().

To support future functionality if bcont is not NULL *bcont should be initialized to NULL. For example:

 BIO *cont = NULL;
 CMS_ContentInfo *cms;

 cms = SMIME_read_CMS(in, &cont);

BUGS

The MIME parser used by SMIME_read_CMS() is somewhat primitive. While it will handle most S/MIME messages more complex compound formats may not work.

The parser assumes that the CMS_ContentInfo structure is always base64 encoded and will not handle the case where it is in binary format or uses quoted printable format.

The use of a memory BIO to hold the signed content limits the size of message which can be processed due to memory restraints: a streaming single pass option should be available.

RETURN VALUES

SMIME_read_CMS_ex() and SMIME_read_CMS() return a valid CMS_ContentInfo structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3).

SEE ALSO

ERR_get_error(3), CMS_sign(3), CMS_verify(3), CMS_encrypt(3), CMS_decrypt(3)

HISTORY

The function SMIME_read_CMS_ex() was added in OpenSSL 3.0.

Copyright 2008-2021 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 https://www.openssl.org/source/license.html.