SMIME_read_CMS_ex, SMIME_read_CMS - parse S/MIME message
#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);
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().
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);
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.
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).
The function SMIME_read_CMS_ex() was added in OpenSSL 3.0.
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