Merge pull request #8848 from BootRhetoric/flake-authentication

This commit is contained in:
Valentin Gagarin 2023-11-04 00:23:28 +01:00 committed by GitHub
commit 8e222fbb12
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
11 changed files with 268 additions and 9 deletions

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@ -16,7 +16,6 @@
- `builtins.fetchTree` is now marked as stable.
- The interface for creating and updating lock files has been overhauled:
- [`nix flake lock`](@docroot@/command-ref/new-cli/nix3-flake-lock.md) only creates lock files and adds missing inputs now.
@ -29,3 +28,5 @@
- The flake-specific flags `--recreate-lock-file` and `--update-input` have been removed from all commands operating on installables.
They are superceded by `nix flake update`.
- Commit signature verification for the [`builtins.fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) is added as the new [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).

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@ -185,6 +185,7 @@
buildPackages.git
buildPackages.mercurial # FIXME: remove? only needed for tests
buildPackages.jq # Also for custom mdBook preprocessor.
buildPackages.openssh # only needed for tests (ssh-keygen)
]
++ lib.optionals stdenv.hostPlatform.isLinux [(buildPackages.util-linuxMinimal or buildPackages.utillinuxMinimal)];

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@ -8,6 +8,7 @@
#include "fetchers.hh"
#include "finally.hh"
#include "fetch-settings.hh"
#include "value-to-json.hh"
namespace nix {
@ -140,8 +141,13 @@ static FlakeInput parseFlakeInput(EvalState & state,
attrs.emplace(state.symbols[attr.name], (long unsigned int)attr.value->integer);
break;
default:
throw TypeError("flake input attribute '%s' is %s while a string, Boolean, or integer is expected",
state.symbols[attr.name], showType(*attr.value));
if (attr.name == state.symbols.create("publicKeys")) {
experimentalFeatureSettings.require(Xp::VerifiedFetches);
NixStringContext emptyContext = {};
attrs.emplace(state.symbols[attr.name], printValueAsJSON(state, true, *attr.value, pos, emptyContext).dump());
} else
throw TypeError("flake input attribute '%s' is %s while a string, Boolean, or integer is expected",
state.symbols[attr.name], showType(*attr.value));
}
#pragma GCC diagnostic pop
}

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@ -7,6 +7,7 @@
#include "registry.hh"
#include "tarball.hh"
#include "url.hh"
#include "value-to-json.hh"
#include <ctime>
#include <iomanip>
@ -125,6 +126,10 @@ static void fetchTree(
attrs.emplace(state.symbols[attr.name], Explicit<bool>{attr.value->boolean});
else if (attr.value->type() == nInt)
attrs.emplace(state.symbols[attr.name], uint64_t(attr.value->integer));
else if (state.symbols[attr.name] == "publicKeys") {
experimentalFeatureSettings.require(Xp::VerifiedFetches);
attrs.emplace(state.symbols[attr.name], printValueAsJSON(state, true, *attr.value, pos, context).dump());
}
else
state.debugThrowLastTrace(TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
state.symbols[attr.name], showType(*attr.value)));
@ -427,6 +432,42 @@ static RegisterPrimOp primop_fetchGit({
With this argument being true, it's possible to load a `rev` from *any* `ref`
(by default only `rev`s from the specified `ref` are supported).
- `verifyCommit` (default: `true` if `publicKey` or `publicKeys` are provided, otherwise `false`)
Whether to check `rev` for a signature matching `publicKey` or `publicKeys`.
If `verifyCommit` is enabled, then `fetchGit` cannot use a local repository with uncommitted changes.
Requires the [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
- `publicKey`
The public key against which `rev` is verified if `verifyCommit` is enabled.
Requires the [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
- `keytype` (default: `"ssh-ed25519"`)
The key type of `publicKey`.
Possible values:
- `"ssh-dsa"`
- `"ssh-ecdsa"`
- `"ssh-ecdsa-sk"`
- `"ssh-ed25519"`
- `"ssh-ed25519-sk"`
- `"ssh-rsa"`
Requires the [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
- `publicKeys`
The public keys against which `rev` is verified if `verifyCommit` is enabled.
Must be given as a list of attribute sets with the following form:
```nix
{
key = "<public key>";
type = "<key type>"; # optional, default: "ssh-ed25519"
}
```
Requires the [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
Here are some examples of how to use `fetchGit`.
- To fetch a private repository over SSH:
@ -501,6 +542,21 @@ static RegisterPrimOp primop_fetchGit({
}
```
- To verify the commit signature:
```nix
builtins.fetchGit {
url = "ssh://git@github.com/nixos/nix.git";
verifyCommit = true;
publicKeys = [
{
type = "ssh-ed25519";
key = "AAAAC3NzaC1lZDI1NTE5AAAAIArPKULJOid8eS6XETwUjO48/HKBWl7FTCK0Z//fplDi";
}
];
}
```
Nix will refetch the branch according to the [`tarball-ttl`](@docroot@/command-ref/conf-file.md#conf-tarball-ttl) setting.
This behavior is disabled in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).

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@ -360,4 +360,9 @@ std::optional<ExperimentalFeature> InputScheme::experimentalFeature() const
return {};
}
std::string publicKeys_to_string(const std::vector<PublicKey>& publicKeys)
{
return ((nlohmann::json) publicKeys).dump();
}
}

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@ -182,4 +182,13 @@ void registerInputScheme(std::shared_ptr<InputScheme> && fetcher);
nlohmann::json dumpRegisterInputSchemeInfo();
struct PublicKey
{
std::string type = "ssh-ed25519";
std::string key;
};
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT(PublicKey, type, key)
std::string publicKeys_to_string(const std::vector<PublicKey>&);
}

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@ -143,6 +143,69 @@ struct WorkdirInfo
bool hasHead = false;
};
std::vector<PublicKey> getPublicKeys(const Attrs & attrs) {
std::vector<PublicKey> publicKeys;
if (attrs.contains("publicKeys")) {
nlohmann::json publicKeysJson = nlohmann::json::parse(getStrAttr(attrs, "publicKeys"));
ensureType(publicKeysJson, nlohmann::json::value_t::array);
publicKeys = publicKeysJson.get<std::vector<PublicKey>>();
}
else {
publicKeys = {};
}
if (attrs.contains("publicKey"))
publicKeys.push_back(PublicKey{maybeGetStrAttr(attrs, "keytype").value_or("ssh-ed25519"),getStrAttr(attrs, "publicKey")});
return publicKeys;
}
void doCommitVerification(const Path repoDir, const Path gitDir, const std::string rev, const std::vector<PublicKey>& publicKeys) {
// Create ad-hoc allowedSignersFile and populate it with publicKeys
auto allowedSignersFile = createTempFile().second;
std::string allowedSigners;
for (const PublicKey& k : publicKeys) {
if (k.type != "ssh-dsa"
&& k.type != "ssh-ecdsa"
&& k.type != "ssh-ecdsa-sk"
&& k.type != "ssh-ed25519"
&& k.type != "ssh-ed25519-sk"
&& k.type != "ssh-rsa")
warn("Unknown keytype: %s\n"
"Please use one of\n"
"- ssh-dsa\n"
" ssh-ecdsa\n"
" ssh-ecdsa-sk\n"
" ssh-ed25519\n"
" ssh-ed25519-sk\n"
" ssh-rsa", k.type);
allowedSigners += "* " + k.type + " " + k.key + "\n";
}
writeFile(allowedSignersFile, allowedSigners);
// Run verification command
auto [status, output] = runProgram(RunOptions {
.program = "git",
.args = {"-c", "gpg.ssh.allowedSignersFile=" + allowedSignersFile, "-C", repoDir,
"--git-dir", gitDir, "verify-commit", rev},
.mergeStderrToStdout = true,
});
/* Evaluate result through status code and checking if public key fingerprints appear on stderr
* This is neccessary because the git command might also succeed due to the commit being signed by gpg keys
* that are present in the users key agent. */
std::string re = R"(Good "git" signature for \* with .* key SHA256:[)";
for (const PublicKey& k : publicKeys){
// Calculate sha256 fingerprint from public key and escape the regex symbol '+' to match the key literally
auto fingerprint = trim(hashString(htSHA256, base64Decode(k.key)).to_string(nix::HashFormat::Base64, false), "=");
auto escaped_fingerprint = std::regex_replace(fingerprint, std::regex("\\+"), "\\+" );
re += "(" + escaped_fingerprint + ")";
}
re += "]";
if (status == 0 && std::regex_search(output, std::regex(re)))
printTalkative("Signature verification on commit %s succeeded", rev);
else
throw Error("Commit signature verification on commit %s failed: \n%s", rev, output);
}
// Returns whether a git workdir is clean and has commits.
WorkdirInfo getWorkdirInfo(const Input & input, const Path & workdir)
{
@ -272,9 +335,9 @@ struct GitInputScheme : InputScheme
attrs.emplace("type", "git");
for (auto & [name, value] : url.query) {
if (name == "rev" || name == "ref")
if (name == "rev" || name == "ref" || name == "keytype" || name == "publicKey" || name == "publicKeys")
attrs.emplace(name, value);
else if (name == "shallow" || name == "submodules" || name == "allRefs")
else if (name == "shallow" || name == "submodules" || name == "allRefs" || name == "verifyCommit")
attrs.emplace(name, Explicit<bool> { value == "1" });
else
url2.query.emplace(name, value);
@ -306,14 +369,26 @@ struct GitInputScheme : InputScheme
"name",
"dirtyRev",
"dirtyShortRev",
"verifyCommit",
"keytype",
"publicKey",
"publicKeys",
};
}
std::optional<Input> inputFromAttrs(const Attrs & attrs) const override
{
for (auto & [name, _] : attrs)
if (name == "verifyCommit"
|| name == "keytype"
|| name == "publicKey"
|| name == "publicKeys")
experimentalFeatureSettings.require(Xp::VerifiedFetches);
maybeGetBoolAttr(attrs, "shallow");
maybeGetBoolAttr(attrs, "submodules");
maybeGetBoolAttr(attrs, "allRefs");
maybeGetBoolAttr(attrs, "verifyCommit");
if (auto ref = maybeGetStrAttr(attrs, "ref")) {
if (std::regex_search(*ref, badGitRefRegex))
@ -336,6 +411,15 @@ struct GitInputScheme : InputScheme
if (auto ref = input.getRef()) url.query.insert_or_assign("ref", *ref);
if (maybeGetBoolAttr(input.attrs, "shallow").value_or(false))
url.query.insert_or_assign("shallow", "1");
if (maybeGetBoolAttr(input.attrs, "verifyCommit").value_or(false))
url.query.insert_or_assign("verifyCommit", "1");
auto publicKeys = getPublicKeys(input.attrs);
if (publicKeys.size() == 1) {
url.query.insert_or_assign("keytype", publicKeys.at(0).type);
url.query.insert_or_assign("publicKey", publicKeys.at(0).key);
}
else if (publicKeys.size() > 1)
url.query.insert_or_assign("publicKeys", publicKeys_to_string(publicKeys));
return url;
}
@ -425,6 +509,8 @@ struct GitInputScheme : InputScheme
bool shallow = maybeGetBoolAttr(input.attrs, "shallow").value_or(false);
bool submodules = maybeGetBoolAttr(input.attrs, "submodules").value_or(false);
bool allRefs = maybeGetBoolAttr(input.attrs, "allRefs").value_or(false);
std::vector<PublicKey> publicKeys = getPublicKeys(input.attrs);
bool verifyCommit = maybeGetBoolAttr(input.attrs, "verifyCommit").value_or(!publicKeys.empty());
std::string cacheType = "git";
if (shallow) cacheType += "-shallow";
@ -445,6 +531,8 @@ struct GitInputScheme : InputScheme
{"type", cacheType},
{"name", name},
{"rev", input.getRev()->gitRev()},
{"verifyCommit", verifyCommit},
{"publicKeys", publicKeys_to_string(publicKeys)},
});
};
@ -467,12 +555,15 @@ struct GitInputScheme : InputScheme
auto [isLocal, actualUrl_] = getActualUrl(input);
auto actualUrl = actualUrl_; // work around clang bug
/* If this is a local directory and no ref or revision is given,
/* If this is a local directory, no ref or revision is given and no signature verification is needed,
allow fetching directly from a dirty workdir. */
if (!input.getRef() && !input.getRev() && isLocal) {
auto workdirInfo = getWorkdirInfo(input, actualUrl);
if (!workdirInfo.clean) {
return fetchFromWorkdir(store, input, actualUrl, workdirInfo);
if (verifyCommit)
throw Error("Can't fetch from a dirty workdir with commit signature verification enabled.");
else
return fetchFromWorkdir(store, input, actualUrl, workdirInfo);
}
}
@ -480,6 +571,8 @@ struct GitInputScheme : InputScheme
{"type", cacheType},
{"name", name},
{"url", actualUrl},
{"verifyCommit", verifyCommit},
{"publicKeys", publicKeys_to_string(publicKeys)},
});
Path repoDir;
@ -637,6 +730,9 @@ struct GitInputScheme : InputScheme
);
}
if (verifyCommit)
doCommitVerification(repoDir, gitDir, input.getRev()->gitRev(), publicKeys);
if (submodules) {
Path tmpGitDir = createTempDir();
AutoDelete delTmpGitDir(tmpGitDir, true);

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@ -12,7 +12,7 @@ struct ExperimentalFeatureDetails
std::string_view description;
};
constexpr std::array<ExperimentalFeatureDetails, 15> xpFeatureDetails = {{
constexpr std::array<ExperimentalFeatureDetails, 16> xpFeatureDetails = {{
{
.tag = Xp::CaDerivations,
.name = "ca-derivations",
@ -227,7 +227,14 @@ constexpr std::array<ExperimentalFeatureDetails, 15> xpFeatureDetails = {{
.description = R"(
Allow the use of the [impure-env](@docroot@/command-ref/conf-file.md#conf-impure-env) setting.
)",
}
},
{
.tag = Xp::VerifiedFetches,
.name = "verified-fetches",
.description = R"(
Enables verification of git commit signatures through the [`fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) built-in.
)",
},
}};
static_assert(

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@ -32,6 +32,7 @@ enum struct ExperimentalFeature
ParseTomlTimestamps,
ReadOnlyLocalStore,
ConfigurableImpureEnv,
VerifiedFetches,
};
/**

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@ -0,0 +1,76 @@
source common.sh
requireGit
[[ $(type -p ssh-keygen) ]] || skipTest "ssh-keygen not installed" # require ssh-keygen
enableFeatures "verified-fetches"
clearStore
repo="$TEST_ROOT/git"
# generate signing keys
keysDir=$TEST_ROOT/.ssh
mkdir -p "$keysDir"
ssh-keygen -f "$keysDir/testkey1" -t ed25519 -P "" -C "test key 1"
key1File="$keysDir/testkey1.pub"
publicKey1=$(awk '{print $2}' "$key1File")
ssh-keygen -f "$keysDir/testkey2" -t rsa -P "" -C "test key 2"
key2File="$keysDir/testkey2.pub"
publicKey2=$(awk '{print $2}' "$key2File")
git init $repo
git -C $repo config user.email "foobar@example.com"
git -C $repo config user.name "Foobar"
git -C $repo config gpg.format ssh
echo 'hello' > $repo/text
git -C $repo add text
git -C $repo -c "user.signingkey=$key1File" commit -S -m 'initial commit'
out=$(nix eval --impure --raw --expr "builtins.fetchGit { url = \"file://$repo\"; keytype = \"ssh-rsa\"; publicKey = \"$publicKey2\"; }" 2>&1) || status=$?
[[ $status == 1 ]]
[[ $out =~ 'No principal matched.' ]]
[[ $(nix eval --impure --raw --expr "builtins.readFile (builtins.fetchGit { url = \"file://$repo\"; publicKey = \"$publicKey1\"; } + \"/text\")") = 'hello' ]]
echo 'hello world' > $repo/text
git -C $repo add text
git -C $repo -c "user.signingkey=$key2File" commit -S -m 'second commit'
[[ $(nix eval --impure --raw --expr "builtins.readFile (builtins.fetchGit { url = \"file://$repo\"; publicKeys = [{key = \"$publicKey1\";} {type = \"ssh-rsa\"; key = \"$publicKey2\";}]; } + \"/text\")") = 'hello world' ]]
# Flake input test
flakeDir="$TEST_ROOT/flake"
mkdir -p "$flakeDir"
cat > "$flakeDir/flake.nix" <<EOF
{
inputs.test = {
type = "git";
url = "file://$repo";
flake = false;
publicKeys = [
{ type = "ssh-rsa"; key = "$publicKey2"; }
];
};
outputs = { test, ... }: { test = test.outPath; };
}
EOF
nix build --out-link "$flakeDir/result" "$flakeDir#test"
[[ $(cat "$flakeDir/result/text") = 'hello world' ]]
cat > "$flakeDir/flake.nix" <<EOF
{
inputs.test = {
type = "git";
url = "file://$repo";
flake = false;
publicKey= "$publicKey1";
};
outputs = { test, ... }: { test = test.outPath; };
}
EOF
out=$(nix build "$flakeDir#test" 2>&1) || status=$?
[[ $status == 1 ]]
[[ $out =~ 'No principal matched.' ]]

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@ -55,6 +55,7 @@ nix_tests = \
secure-drv-outputs.sh \
restricted.sh \
fetchGitSubmodules.sh \
fetchGitVerification.sh \
flakes/search-root.sh \
readfile-context.sh \
nix-channel.sh \