SMIME_read_PKCS7_ex, SMIME_read_PKCS7 - parse S/MIME message

#include <openssl/pkcs7.h>
PKCS7 *SMIME_read_PKCS7_ex(BIO *bio, BIO **bcont, PKCS7 **p7);
PKCS7 *SMIME_read_PKCS7(BIO *in, BIO **bcont);

SMIME_read_PKCS7() 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 PKCS#7 structure is returned or NULL if an error occurred.

SMIME_read_PKCS7_ex() is similar to SMIME_read_PKCS7() but can optionally supply a previously created p7 PKCS#7 object. If p7 is NULL then it is identical to SMIME_read_PKCS7(). To create a p7 object use PKCS7_new_ex(3).

If *bcont is not NULL then the message is clear text signed. *bcont can then be passed to PKCS7_verify() with the PKCS7_DETACHED flag set.

Otherwise the type of the returned structure can be determined using PKCS7_type_is_enveloped(), etc.

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

BIO *cont = NULL;
PKCS7 *p7;
p7 = SMIME_read_PKCS7(in, &cont);

The MIME parser used by SMIME_read_PKCS7() is somewhat primitive. While it will handle most S/MIME messages more complex compound formats may not work.

The parser assumes that the PKCS7 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.

SMIME_read_PKCS7_ex() and SMIME_read_PKCS7() return a valid PKCS7 structure or NULL if an error occurred. The error can be obtained from ERR_get_error(3).

ERR_get_error(3), SMIME_read_PKCS7(3), PKCS7_sign(3), PKCS7_verify(3), PKCS7_encrypt(3) PKCS7_decrypt(3)

The function SMIME_read_PKCS7_ex() was added in OpenSSL 3.0.

Copyright 2002-2020 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

2024-06-04 3.3.1