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Add trust-tarballs-from-git-forges setting #10340

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Apr 2, 2024
Merged

Add trust-tarballs-from-git-forges setting #10340

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46d9e70
Add trust-tarballs-from-git-forges setting
edolstra Mar 27, 2024
00ce36f
Add test
edolstra Mar 27, 2024
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17 changes: 16 additions & 1 deletion src/libfetchers/fetch-settings.hh
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Expand Up @@ -78,7 +78,6 @@ struct FetchSettings : public Config
)",
{}, true, Xp::Flakes};


Setting<bool> useRegistries{this, true, "use-registries",
"Whether to use flake registries to resolve flake references.",
{}, true, Xp::Flakes};
Expand All @@ -94,6 +93,22 @@ struct FetchSettings : public Config
empty, the summary is generated based on the action performed.
)",
{}, true, Xp::Flakes};

Setting<bool> trustTarballsFromGitForges{
this, true, "trust-tarballs-from-git-forges",
R"(
If enabled (the default), Nix will consider tarballs from
GitHub and similar Git forges to be locked if a Git revision
is specified,
e.g. `github:NixOS/patchelf/7c2f768bf9601268a4e71c2ebe91e2011918a70f`.
This requires Nix to trust that the provider will return the
correct contents for the specified Git revision.
If disabled, such tarballs are only considered locked if a
`narHash` attribute is specified,
e.g. `github:NixOS/patchelf/7c2f768bf9601268a4e71c2ebe91e2011918a70f?narHash=sha256-PPXqKY2hJng4DBVE0I4xshv/vGLUskL7jl53roB8UdU%3D`.
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Suggested change
e.g. `github:NixOS/patchelf/7c2f768bf9601268a4e71c2ebe91e2011918a70f?narHash=sha256-PPXqKY2hJng4DBVE0I4xshv/vGLUskL7jl53roB8UdU%3D`.
e.g. `github:NixOS/patchelf/7c2f768bf9601268a4e71c2ebe91e2011918a70f?narHash=sha256-PPXqKY2hJng4DBVE0I4xshv/vGLUskL7jl53roB8UdU%3D`.
This `narHash` is not guaranteed to be required in future versions.

Not a promise, which we should be careful about, especially in reference docs, but some expectation management is in order.

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I don't think we have to document that requirements could be loosened in the future, since that wouldn't break anything.

)"};
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@Ericson2314 Ericson2314 Mar 27, 2024 •
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This should be marked experimental (under fetch-tree perhaps?); I don't want to need to have it long term.

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I don't think it should be experimental. It could be removed (made a no-op) in the future if it's no longer needed.

After all, what's the experimental behaviour? The "true" or "false" case?

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@Ericson2314 Ericson2314 Mar 27, 2024 •
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I wasn't there for the rest of the call Monday, but I consider this thing mostly a monkey patch because the other stuff for the fetchers hasn't been done yet.

In the end I think:

  1. When there are no submodules, everything should be trustlesss and ergonomic with a single hash. We record all the Merkle proofs we need.

  2. When there are submodules, the user should explicitly opt into fetching them or pruning them. And git vs github hardly matters because the real issue is not some service lying, but the fetched thing not corresponding to the hash used to fetch it with.

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Why wouldn't it be experimental? It only makes sense as part of fetchTree anyways, right?

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It's already implicitly behind fetch-tree. But we have a bunch of settings (access-tokens, allow-dirty, warn-dirty, ...) that are also fetcher-specific but not marked as experimental.


};

// FIXME: don't use a global variable.
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4 changes: 3 additions & 1 deletion src/libfetchers/github.cc
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Expand Up @@ -294,7 +294,9 @@ struct GitArchiveInputScheme : InputScheme
Git revision alone, we also require a NAR hash for
locking. FIXME: in the future, we may want to require a Git
tree hash instead of a NAR hash. */
return input.getRev().has_value() && input.getNarHash().has_value();
return input.getRev().has_value()
&& (fetchSettings.trustTarballsFromGitForges ||
input.getNarHash().has_value());
}

std::optional<ExperimentalFeature> experimentalFeature() const override
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7 changes: 6 additions & 1 deletion tests/nixos/github-flakes.nix
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Expand Up @@ -187,9 +187,14 @@ in
client.succeed("nix flake metadata nixpkgs --tarball-ttl 0 >&2")
# Test fetchTree on a github URL.
hash = client.succeed(f"nix eval --raw --expr '(fetchTree {info['url']}).narHash'")
hash = client.succeed(f"nix eval --no-trust-tarballs-from-git-forges --raw --expr '(fetchTree {info['url']}).narHash'")
assert hash == info['locked']['narHash']
# Fetching without a narHash should succeed if trust-github is set and fail otherwise.
client.succeed(f"nix eval --raw --expr 'builtins.fetchTree github:github:fancy-enterprise/private-flake/{info['revision']}'")
out = client.fail(f"nix eval --no-trust-tarballs-from-git-forges --raw --expr 'builtins.fetchTree github:github:fancy-enterprise/private-flake/{info['revision']}' 2>&1")
assert "will not fetch unlocked input" in out, "--no-trust-tarballs-from-git-forges did not fail with the expected error"
# Shut down the web server. The flake should be cached on the client.
github.succeed("systemctl stop httpd.service")
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