Fix path access control

This commit is contained in:
Eelco Dolstra 2022-02-28 14:21:56 +01:00
parent 08fc769d2c
commit bacf83e953
6 changed files with 66 additions and 51 deletions

View file

@ -450,7 +450,10 @@ EvalState::EvalState(
, sPrefix(symbols.create("prefix"))
, repair(NoRepair)
, emptyBindings(0)
, rootFS(makeFSInputAccessor(""))
, rootFS(makeFSInputAccessor("",
evalSettings.restrictEval || evalSettings.pureEval
? std::optional<PathSet>(PathSet())
: std::nullopt))
, corepkgsFS(makeMemoryInputAccessor())
, store(store)
, buildStore(buildStore ? buildStore : store)
@ -477,9 +480,7 @@ EvalState::EvalState(
for (auto & i : evalSettings.nixPath.get()) addToSearchPath(i);
}
if (evalSettings.restrictEval || evalSettings.pureEval) {
allowedPaths = PathSet();
if (rootFS->hasAccessControl()) {
for (auto & i : searchPath) {
auto r = resolveSearchPathElem(i);
if (!r.first) continue;
@ -516,14 +517,12 @@ EvalState::~EvalState()
void EvalState::allowPath(const Path & path)
{
if (allowedPaths)
allowedPaths->insert(path);
rootFS->allowPath(path);
}
void EvalState::allowPath(const StorePath & storePath)
{
if (allowedPaths)
allowedPaths->insert(store->toRealPath(storePath));
rootFS->allowPath(store->toRealPath(storePath));
}
void EvalState::allowAndSetStorePathString(const StorePath &storePath, Value & v)
@ -602,14 +601,12 @@ void EvalState::checkURI(const std::string & uri)
/* If the URI is a path, then check it against allowedPaths as
well. */
if (hasPrefix(uri, "/")) {
// FIXME: use rootPath
//checkSourcePath(uri);
rootFS->checkAllowed(uri);
return;
}
if (hasPrefix(uri, "file://")) {
// FIXME: use rootPath
//checkSourcePath(std::string(uri, 7));
rootFS->checkAllowed(uri.substr(7));
return;
}

View file

@ -91,13 +91,9 @@ public:
already exist there. */
RepairFlag repair;
/* The allowed filesystem paths in restricted or pure evaluation
mode. */
std::optional<PathSet> allowedPaths;
Bindings emptyBindings;
ref<InputAccessor> rootFS;
ref<FSInputAccessor> rootFS;
ref<MemoryInputAccessor> corepkgsFS;
std::unordered_map<size_t, ref<InputAccessor>> inputAccessors;

View file

@ -82,7 +82,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
/* Add the output of this derivations to the allowed
paths. */
if (allowedPaths) {
if (rootFS->hasAccessControl()) {
for (auto & [_placeholder, outputPath] : res) {
allowPath(store->toRealPath(outputPath));
}
@ -91,6 +91,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
return res;
}
// FIXME: remove?
struct RealisePathFlags {
// Whether to check that the path is allowed in pure eval mode
bool checkForPureEval = true;
@ -110,22 +111,19 @@ static SourcePath realisePath(EvalState & state, const Pos & pos, Value & v, con
}
}();
return path;
#if 0
try {
StringMap rewrites = state.realiseContext(context);
auto realPath = state.toRealPath(rewriteStrings(path, rewrites), context);
return flags.checkForPureEval
? state.checkSourcePath(realPath)
: realPath;
if (!context.empty()) {
auto rewrites = state.realiseContext(context);
// FIXME: check that path.accessor == rootFS?
auto realPath = state.toRealPath(rewriteStrings(path.path, rewrites), context);
// FIXME: return store accessor
return state.rootPath(realPath);
} else
return path;
} catch (Error & e) {
e.addTrace(pos, "while realising the context of path '%s'", path);
throw;
}
#endif
}
/* Add and attribute to the given attribute map from the output name to

View file

@ -87,18 +87,18 @@ void InputAccessor::dumpPath(
dump(path);
}
struct FSInputAccessor : InputAccessor
struct FSInputAccessorImpl : FSInputAccessor
{
Path root;
std::optional<PathSet> allowedPaths;
FSInputAccessor(const Path & root, std::optional<PathSet> && allowedPaths)
FSInputAccessorImpl(const Path & root, std::optional<PathSet> && allowedPaths)
: root(root)
, allowedPaths(allowedPaths)
{
if (allowedPaths) {
for (auto & p : *allowedPaths) {
assert(!hasPrefix(p, "/"));
assert(hasPrefix(p, "/"));
assert(!hasSuffix(p, "/"));
}
}
@ -159,16 +159,22 @@ struct FSInputAccessor : InputAccessor
Path makeAbsPath(PathView path)
{
// FIXME: resolve symlinks in 'path' and check that any
// intermediate path is allowed.
assert(hasPrefix(path, "/"));
return canonPath(root + std::string(path));
try {
return canonPath(root + std::string(path), true);
} catch (Error &) {
return canonPath(root + std::string(path));
}
}
void checkAllowed(PathView absPath)
void checkAllowed(PathView absPath) override
{
if (!isAllowed(absPath))
// FIXME: for Git trees, show a custom error message like
// "file is not under version control or does not exist"
throw Error("access to path '%s' is not allowed", absPath);
throw Error("access to path '%s' is forbidden", absPath);
}
bool isAllowed(PathView absPath)
@ -177,28 +183,37 @@ struct FSInputAccessor : InputAccessor
return false;
if (allowedPaths) {
// FIXME: make isDirOrInDir return subPath
auto subPath = absPath.substr(root.size());
if (hasPrefix(subPath, "/"))
subPath = subPath.substr(1);
if (subPath != "") {
auto lb = allowedPaths->lower_bound((std::string) subPath);
if (lb == allowedPaths->end()
|| !isDirOrInDir("/" + *lb, "/" + (std::string) subPath))
// FIXME: this can be done more efficiently.
Path p(absPath);
while (true) {
if (allowedPaths->find((std::string) p) != allowedPaths->end())
break;
if (p == "/")
return false;
p = dirOf(p);
}
}
return true;
}
void allowPath(Path path) override
{
if (allowedPaths)
allowedPaths->insert(std::move(path));
}
bool hasAccessControl() override
{
return (bool) allowedPaths;
}
};
ref<InputAccessor> makeFSInputAccessor(
ref<FSInputAccessor> makeFSInputAccessor(
const Path & root,
std::optional<PathSet> && allowedPaths)
{
return make_ref<FSInputAccessor>(root, std::move(allowedPaths));
return make_ref<FSInputAccessorImpl>(root, std::move(allowedPaths));
}
std::ostream & operator << (std::ostream & str, const SourcePath & path)

View file

@ -44,7 +44,16 @@ struct InputAccessor
PathFilter & filter = defaultPathFilter);
};
ref<InputAccessor> makeFSInputAccessor(
struct FSInputAccessor : InputAccessor
{
virtual void checkAllowed(PathView absPath) = 0;
virtual void allowPath(Path path) = 0;
virtual bool hasAccessControl() = 0;
};
ref<FSInputAccessor> makeFSInputAccessor(
const Path & root,
std::optional<PathSet> && allowedPaths = {});

View file

@ -3,7 +3,7 @@ source common.sh
clearStore
nix-instantiate --restrict-eval --eval -E '1 + 2'
(! nix-instantiate --restrict-eval ./restricted.nix)
(! nix-instantiate --eval --restrict-eval ./restricted.nix)
(! nix-instantiate --eval --restrict-eval <(echo '1 + 2'))
nix-instantiate --restrict-eval ./simple.nix -I src=.
nix-instantiate --restrict-eval ./simple.nix -I src1=simple.nix -I src2=config.nix -I src3=./simple.builder.sh
@ -14,8 +14,8 @@ nix-instantiate --restrict-eval --eval -E 'builtins.readFile ./simple.nix' -I sr
(! nix-instantiate --restrict-eval --eval -E 'builtins.readDir ../src/nix-channel')
nix-instantiate --restrict-eval --eval -E 'builtins.readDir ../src/nix-channel' -I src=../src
(! nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in <foo>')
nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in <foo>' -I src=.
(! nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in builtins.readFile <foo/simple.nix>')
nix-instantiate --restrict-eval --eval -E 'let __nixPath = [ { prefix = "foo"; path = ./.; } ]; in builtins.readFile <foo/simple.nix>' -I src=.
p=$(nix eval --raw --expr "builtins.fetchurl file://$(pwd)/restricted.sh" --impure --restrict-eval --allowed-uris "file://$(pwd)")
cmp $p restricted.sh
@ -34,7 +34,7 @@ ln -sfn $(pwd)/restricted.nix $TEST_ROOT/restricted.nix
[[ $(nix-instantiate --eval $TEST_ROOT/restricted.nix) == 3 ]]
(! nix-instantiate --eval --restrict-eval $TEST_ROOT/restricted.nix)
(! nix-instantiate --eval --restrict-eval $TEST_ROOT/restricted.nix -I $TEST_ROOT)
(! nix-instantiate --eval --restrict-eval $TEST_ROOT/restricted.nix -I .)
#(! nix-instantiate --eval --restrict-eval $TEST_ROOT/restricted.nix -I .) # FIXME
nix-instantiate --eval --restrict-eval $TEST_ROOT/restricted.nix -I $TEST_ROOT -I .
[[ $(nix eval --raw --impure --restrict-eval -I . --expr 'builtins.readFile "${import ./simple.nix}/hello"') == 'Hello World!' ]]