On Wed, 14 Jan 2004 antonio.manfreda@realemutua.it wrote:

> 1. Who does create the challenge for the user? Squid or the helper?


> 2. In the case it is Squid, what does it pass to the helper on stdin?
> 3. And how does the helper reply? OK or ERR as usual?

2,3 is documented in the squid.conf comments

=== Parameters for the digest scheme follow ===

"program" cmdline
Specify the command for the external authenticator. Such
a program reads a line containing "username":"realm" and
replies with the appropriate H(A1) value base64 encoded.
See rfc 2616 for the definition of H(A1).

See also the operation of the operation of the digest_pw_auth helper as

> 4. What is intended for HHA1, since I can find no reference to it in
> RFC2617? Maybe a different notation?

Search for H(A1) and you will find the correct references.