Cryptography and SSL/TLS Toolkit



SMIME_read_PKCS7 - parse S/MIME message.


 #include <openssl/pkcs7.h>

 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.


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().

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


ERR_get_error(3), PKCS7_type(3) SMIME_read_PKCS7(3), PKCS7_sign(3), PKCS7_verify(3), PKCS7_encrypt(3) PKCS7_decrypt(3)


SMIME_read_PKCS7() was added to OpenSSL 0.9.5