[squid-dev] Drop cache_object protocol support

[Amos Jeffries]

On 25/01/2023 8:23 am, Alex Rousskov wrote:
> On 1/24/23 12:22, Eduard Bagdasaryan wrote:
>
>> Today we can query cache manager in two ways:
>>
>> 1. with cache_object:// URL scheme
>> 2. with an HTTP request having the 'squid-internal-mgr' path prefix.
>>
>> I guess that when (2) was initially added at e37bd29, its 
>> implementation was somewhat incomplete compared to the old 
>> cache_object scheme (e.g., it lacked authentication

No and intentionally. It is designed to share the proxy HTTP 
authentication and http_access policy instead of the obsolete userinfo@ 
standard that cache_object uses.

Blocker #1:  The cachemgr_passwd directly still needs to be cleanly 
removed, eg replaced by a manager_access ACL based mechanism.


>> ) and both methods existed. Since then, however, (2) has been 
>> improved and it should be equivalent to (1) by now.  If so, can we 
>> completely remove the non-standard cache_object scheme support from 
>> Squid? This would simplify request forwarding logic, including code 
>> paths where the existing code complexity may result in vulnerability 
>> issues.
>
>
> FWIW, I am not aware of any good reason to keep supporting the 
> "cache_object" URI scheme.
>

Blocker #2: The squidclient tool still sends cache_object: scheme when 
given "mgr:" on the CLI. We need to upgrade that first and allow admin 
some time to upgrade before removing the scheme support in squid itself.


> MgrFieldChars() already calls that scheme deprecated. That special 
> (and undocumented?) scheme did cause significant problems in the past. 
> I am sure it will continue to cause problems if not removed. Removing 
> it will simplify code in several tricky places. There will be some 
> upgrade pains for admins, but we will be better off without 
> cache_object long-term IMO.

Agreed.

> Needless to say, squidclient and cachemgr.cgi implementations would 
> need to be adjusted to use HTTP URLs instead, but I hope those 
> adjustments are straightforward.

cachemgr.cgi should already prefer http(s) and only use cache_object as 
a backup.

IMO the CGI tool should stay that way, supporting the scheme for older 
installations even after we drop it from the rest of Squid.

HTH
Amos