pam_smtpauth is a pluggable authentication module that can be used with Linux-PAM and SMTP Authentication.
See INSTALL.
All parts of pam_smtpauth are GPL except MD5-related sources(md5.h,md5c.c,global.h).
MD5 Message Digest is used in various protocols and programs related to computer security. MD5 algorithm is defined in the RFC1321.
The most part of this source code is what I (Kondo) changed the "RSA Data Security, Inc. MD5 Message-Digest Algorithm" sample source code which is distributed within RFC1321 to work in the C++ code. The sample source code is allowed to copy and use provided that it is identified as above. For mor information, you should refer to the comment in the md5c.cpp file. Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All rights reserved.
The implementation of CRAM-MD5 is a straight port of the "sample implementation" presented in RFC2104, which is based on RFC1321.