This topic branch addresses the following vulnerability:
- **CVE-2025-66413**:
When a user clones a repository from an attacker-controlled server,
Git may attempt NTLM authentication and disclose the user's NTLMv2 hash
to the remote server. Since NTLM hashing is weak, the captured hash can
potentially be brute-forced to recover the user's credentials. This is
addressed by disabling NTLM authentication by default.
(https://github.com/git-for-windows/git/security/advisories/GHSA-hv9c-4jm9-jh3x)
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The previous commits disabled NTLM authentication by default due to its
cryptographic weaknesses. Users can re-enable it via the config setting
http.<url>.allowNTLMAuth, but this requires manual intervention.
Credential helpers may have knowledge about which servers are trusted
for NTLM authentication (e.g., known on-prem Azure DevOps instances).
To allow them to signal this trust, introduce a simple negotiation:
when NTLM is suppressed and the server offered it, Git advertises
ntlm=suppressed to the credential helper. The helper can respond with
ntlm=allow to re-enable NTLM for this request.
This happens precisely at the point where we would otherwise warn the
user about NTLM being suppressed, ensuring the capability is only
advertised when relevant.
Helped-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The new default of Git is to disable NTLM authentication by default.
To help users find the escape hatch of that config setting, should they
need it, suggest it when the authentication failed and the server had
offered NTLM, i.e. if re-enabling it would fix the problem.
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
NTLM authentication is relatively weak. This is the case even with the
default setting of modern Windows versions, where NTLMv1 and LanManager
are disabled and only NTLMv2 is enabled: NTLMv2 hashes of even
reasonably complex 8-character passwords can be broken in a matter of
days, given enough compute resources.
Even worse: On Windows, NTLM authentication uses Security Support
Provider Interface ("SSPI"), which provides the credentials without
requiring the user to type them in.
Which means that an attacker could talk an unsuspecting user into
cloning from a server that is under the attacker's control and extracts
the user's NTLMv2 hash without their knowledge.
For that reason, let's disallow NTLM authentication by default.
NTLM authentication is quite simple to set up, though, and therefore
there are still some on-prem Azure DevOps setups out there whose users
and/or automation rely on this type of authentication. To give them an
escape hatch, introduce the `http.<url>.allowNTLMAuth` config setting
that can be set to `true` to opt back into using NTLM for a specific
remote repository.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This adds support for a new http.sslAutoClientCert config value.
In cURL 7.77 or later the schannel backend does not automatically send
client certificates from the Windows Certificate Store anymore.
This config value is only used if http.sslBackend is set to "schannel",
and can be used to opt in to the old behavior and force cURL to send
client certificates.
This fixes https://github.com/git-for-windows/git/issues/3292
Signed-off-by: Pascal Muller <pascalmuller@gmail.com>
The native Windows HTTPS backend is based on Secure Channel which lets
the caller decide how to handle revocation checking problems caused by
missing information in the certificate or offline CRL distribution
points.
Unfortunately, cURL chose to handle these problems differently than
OpenSSL by default: while OpenSSL happily ignores those problems
(essentially saying "¯\_(ツ)_/¯"), the Secure Channel backend will error
out instead.
As a remedy, the "no revoke" mode was introduced, which turns off
revocation checking altogether. This is a bit heavy-handed. We support
this via the `http.schannelCheckRevoke` setting.
In https://github.com/curl/curl/pull/4981, we contributed an opt-in
"best effort" strategy that emulates what OpenSSL seems to do.
In Git for Windows, we actually want this to be the default. This patch
makes it so, introducing it as a new value for the
`http.schannelCheckRevoke" setting, which now becmes a tristate: it
accepts the values "false", "true" or "best-effort" (defaulting to the
last one).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
The source files for libgit.a have been moved into a new "lib/"
directory to clean up the top-level directory and clearly separate
library code.
* ps/libgit-in-subdir:
Move libgit.a sources into separate "lib/" directory
t/helper: prepare "test-example-tap.c" for introduction of "lib/"
The Git project is not exactly the easiest project to get started in:
it's written in C and POSIX shell, with bits of Perl, Rust and other
languages sprinkled into it. On top of that, the project has grown
somewhat organically over time, making the codebase hard to navigate.
These are problems that we're aware of, and there have been and still
are efforts to clean up some of the technical debt that is natural to
exist an a project that is more than 20 years old. Furthermore, we
provide resources to newcomers that help them out like our coding
guidelines, code of conduct or "MyFirstContribution.adoc".
But there is a rather practical problem: finding your way around in our
project's tree is not easy. Doing a directory listing in the top-level
directory will present you with more than 550 files, which makes it
extremely hard for a newcomer to figure out what files they are even
supposed to look at. This makes the onboarding experience somewhat
harder than it really needs to be. This isn't only a problem for
newcomers though, as I myself struggle to find the files I am looking
for because of the sheer number of files.
Besides the problem of discoverability it also creates a problem of
structure. It is not obvious at all which files are part of "libgit.a"
and which files are only linked into our final executables. So while we
have this split in our build systems, that split is not evident at all
in our tree.
Introduce a new "lib/" directory and move all of our sources for
"libgit.a" into it to fix these issues. It makes the split we have
evident and reduces the number of files in our top-level tree from 550
files to ~80 files.
This is still a lot of files, but it's significantly easier to navigate
already. Furthermore, we can further iterate after this step and think
about introducing a better structure for remaining files, as well.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
