[ICAP] Stop reading the response after headers are read

[VicDeo]

Do not read the whole response as we need only ICAP headers and Encapsulated header.

So we read ICAP headers one by one until Encapsulated header is met.
Then we parse offsets provided by res-hdr and res-body of this header.

the content is considered to be infected if ANY of the following is true:

• ICAP headers contain the header specified in av_response_header
• HTTP header in res-hdr section has status code 403

the content is considered to be clean if the ICAP status code is 204

TL;DR

McAfee just hangs so if we want to read whole response we should wait until the network timeout happens
But the whole response is not needed for the virus detection as

• 204 ICAP status means 'clean'
• 200 ICAP status with encapsulated 403 HTTP status means 'infected'

Fixes #443 https://github.com/owncloud/enterprise/issues/4580
Obsoletes #444

[VicDeo]

@jnweiger if it possible to test this patch before merge?

[jnweiger]

@jnweiger if it possible to test this patch before merge?

OK. I'll give it a test first, then we merge.

[jnweiger]

With this patch, an infected file is reported immediately.
A clean file hangs for 60 seconds in 'processing file'.
Seen with McAfee via ICAP.

ClamAV and Kaspersky via ICAP work fine.

[VicDeo]

@jnweiger

With this patch, an infected file is reported immediately.
A clean file hangs for 60 seconds in 'processing file'.
Seen with McAfee via ICAP.

So is it acceptable or not?
If not I can't go further without access to McAfee.

[jnweiger]

@jnweiger
So is it acceptable or not?
If not I can't go further without access to McAfee.

A one minute delay per normal file is not acceptable. @VicDeo You now have access to my test system.

[CLAassistant]

All committers have signed the CLA.

[VicDeo]

@janackermann could you please sign the CLA for this repo?

[AlexAndBear]

Done

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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[AlexAndBear]

Codewise LGTM