Toshiba e-STUDIO190F, Руководство по обслуживанию

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9.16. SMTP Service Extension for Authentication (SMTP Auth)
- Extended Feature
SMTP is widely deployed and high-quality implementations have proven to be very robust. However, the
Internet community now considers some services to be important that SMTP AUTH is an SMTP service
extension (ESMTP) whereby an SMTP client may indicate an authentication mechanism to the server,
perform an authentication protocol exchange, and optionally negotiate a security layer for subsequent
protocol interactions. This extension is a profile of the Simple Authentication and Security Layer (SASL). To
use SASL, a protocol includes a command for identifying and authenticating a user to a server and for
optionally negotiating protection of subsequent protocol interactions.
The AUTH command indicates an authentication mechanism to the server. If the server supports the
requested authentication mechanism, it performs an authentication protocol exchange to authenticate and
identify the user. Optionally, it also negotiates a security layer for subsequent protocol interactions. If the
requested authentication mechanism is not supported, the server rejects the AUTH command with a 504
reply.
The authentication protocol exchange consists of a series of server challenges and client answers that are
specific to the authentication mechanism. A server challenge, otherwise known as a ready response, is a
334 reply with the text part containing a BASE64 encoded string. The client answer consists of a line
Client Server
250-smtp.example.com
250 AUTH LOGIN DIGEST-MD5 CRAM-MD5
AUTH CRAM-MD5
ZnJlZCA5ZTk1YWVlMDljNDBhZjJiODRhMGMyYjNiYmFlNzg2ZQ==
Establish TCP connection (TCP port No. 25)
220 smtp.example.com ESMTP server ready
EHLO jgm.example.com
Continue to follow the SMTP procedure
334
PENCeUxFREJoU0NnbmhNWitOMjNGNndA
ZWx3b29kLmlubm9zb2Z0LmNvbT4=
235 Authentication successful
SMTP AUTH overview
Genrates Digest parameter
Cha PASSWD with HMAC (keyed-Hashing for Message
Authentication Code), produces a 16 octet digest value of:
USER
Produces a Challenge
334 PENCeUxFREJoU0NnbmhNWitOMjNGNndAZWx3b29kLmlubm9zb2Z0LmNvbT4=
Challenge Response
BASE64 decoded string
BASE64 encoded string
Fred
ZnJlZCA5ZTk1YWVlMDljNDBhZjJiODRhMGMyYjNiYmFlNzg2ZQ==
<CByLEDBhN23F6w@elwood.innosoft>
9e95aee09c40af2b84a0c2b3bbae786e