curl/packages
Johannes Schindelin 5450428491 schannel: add "best effort" revocation check option
- Implement new option CURLSSLOPT_REVOKE_BEST_EFFORT and
  --ssl-revoke-best-effort to allow a "best effort" revocation check.

A best effort revocation check ignores errors that the revocation check
was unable to take place. The reasoning is described in detail below and
discussed further in the PR.

---

When running e.g. with Fiddler, the schannel backend fails with an
unhelpful error message:

	Unknown error (0x80092012) - The revocation function was unable
	to check revocation for the certificate.

Sadly, many enterprise users who are stuck behind MITM proxies suffer
the very same problem.

This has been discussed in plenty of issues:
https://github.com/curl/curl/issues/3727,
https://github.com/curl/curl/issues/264, for example.

In the latter, a Microsoft Edge developer even made the case that the
common behavior is to ignore issues when a certificate has no recorded
distribution point for revocation lists, or when the server is offline.
This is also known as "best effort" strategy and addresses the Fiddler
issue.

Unfortunately, this strategy was not chosen as the default for schannel
(and is therefore a backend-specific behavior: OpenSSL seems to happily
ignore the offline servers and missing distribution points).

To maintain backward-compatibility, we therefore add a new flag
(`CURLSSLOPT_REVOKE_BEST_EFFORT`) and a new option
(`--ssl-revoke-best-effort`) to select the new behavior.

Due to the many related issues Git for Windows and GitHub Desktop, the
plan is to make this behavior the default in these software packages.

The test 2070 was added to verify this behavior, adapted from 310.

Based-on-work-by: georgeok <giorgos.n.oikonomou@gmail.com>
Co-authored-by: Markus Olsson <j.markus.olsson@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Closes https://github.com/curl/curl/pull/4981
2020-03-18 03:23:39 -04:00
..
Android whitespace fixes 2018-09-23 22:24:02 +00:00
DOS openssl: Remove SSLEAY leftovers 2018-11-17 21:36:10 +01:00
OS400 schannel: add "best effort" revocation check option 2020-03-18 03:23:39 -04:00
Symbian writeout: support to generate JSON output 2020-03-17 15:01:28 +01:00
TPF whitespace fixes 2018-09-23 22:24:02 +00:00
vms cleanup: fix some text/comment typos 2020-03-12 14:28:17 +01:00
Makefile.am packages: remove old leftover files and dirs 2018-12-05 15:29:24 +01:00
README removed trailing whitespace 2010-02-14 19:40:18 +00:00

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PACKAGES

 This directory and all its subdirectories are for special package
information, template, scripts and docs. The files herein should be of use for
those of you who want to package curl in a binary or source format using one
of those custom formats.

 The hierarchy for these directories is something like this:

   packages/[OS]/[FORMAT]/

 Currently, we have Win32 and Linux for [OS]. There might be different formats
for the same OS so for Linux we have RPM as format.

 We might need to add some differentiation for CPU as well, as there is
Linux-RPMs for several CPUs. However, it might not be necessary since the
packaging should be pretty much the same no matter what CPU that is used.

 For each unique OS-FORMAT pair, there's a directory to "fill"! I'd like to
see a single README with as much details as possible, and then I'd like some
template files for the package process.