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nix shell: Resolve symlinks in storeFS

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`storeFS` is the `MountedSourceAccessor` that wraps `store->getFSAccessor()`.
This commit is contained in:
Eelco Dolstra 2025-03-26 21:07:17 +01:00 committed by John Ericson
parent eb643d034f
commit 9d3595646d
4 changed files with 42 additions and 33 deletions
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47
src/libexpr/eval.cc
View File

@ -246,6 +246,30 @@ EvalState::EvalState(
}
, repair(NoRepair)
, emptyBindings(0)
, storeFS(
makeMountedSourceAccessor(
{
{CanonPath::root, makeEmptySourceAccessor()},
/* In the pure eval case, we can simply require
valid paths. However, in the *impure* eval
case this gets in the way of the union
mechanism, because an invalid access in the
upper layer will *not* be caught by the union
source accessor, but instead abort the entire
lookup.
This happens when the store dir in the
ambient file system has a path (e.g. because
another Nix store there), but the relocated
store does not.
TODO make the various source accessors doing
access control all throw the same type of
exception, and make union source accessor
catch it, so we don't need to do this hack.
*/
{CanonPath(store->storeDir), store->getFSAccessor(settings.pureEval)},
}))
, rootFS(
({
/* In pure eval mode, we provide a filesystem that only
@ -261,29 +285,6 @@ EvalState::EvalState(
auto realStoreDir = dirOf(store->toRealPath(StorePath::dummy));
if (settings.pureEval || store->storeDir != realStoreDir) {
auto storeFS = makeMountedSourceAccessor(
{
{CanonPath::root, makeEmptySourceAccessor()},
/* In the pure eval case, we can simply require
valid paths. However, in the *impure* eval
case this gets in the way of the union
mechanism, because an invalid access in the
upper layer will *not* be caught by the union
source accessor, but instead abort the entire
lookup.
This happens when the store dir in the
ambient file system has a path (e.g. because
another Nix store there), but the relocated
store does not.
TODO make the various source accessors doing
access control all throw the same type of
exception, and make union source accessor
catch it, so we don't need to do this hack.
*/
{CanonPath(store->storeDir), store->getFSAccessor(settings.pureEval)},
});
accessor = settings.pureEval
? storeFS
: makeUnionSourceAccessor({accessor, storeFS});

5
src/libexpr/include/nix/expr/eval.hh
View File

@ -265,6 +265,11 @@ public:
/** `"unknown"` */
Value vStringUnknown;
/**
* The accessor corresponding to `store`.
*/
const ref<SourceAccessor> storeFS;
/**
* The accessor for the root filesystem.
*/

21
src/nix/env.cc
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@ -65,11 +65,11 @@ struct CmdShell : InstallablesCommand, MixEnvironment
void run(ref<Store> store, Installables && installables) override
{
auto state = getEvalState();
auto outPaths =
Installable::toStorePaths(getEvalStore(), store, Realise::Outputs, OperateOn::Output, installables);
auto accessor = store->getFSAccessor();
std::unordered_set<StorePath> done;
std::queue<StorePath> todo;
for (auto & path : outPaths)
@ -85,13 +85,16 @@ struct CmdShell : InstallablesCommand, MixEnvironment
if (!done.insert(path).second)
continue;
if (true)
pathAdditions.push_back(store->printStorePath(path) + "/bin");
auto binDir = state->storeFS->resolveSymlinks(CanonPath(store->printStorePath(path)) / "bin");
if (!store->isInStore(binDir.abs()))
throw Error("path '%s' is not in the Nix store", binDir);
auto propPath =
accessor->resolveSymlinks(CanonPath(path.to_string()) / "nix-support" / "propagated-user-env-packages");
if (auto st = accessor->maybeLstat(propPath); st && st->type == SourceAccessor::tRegular) {
for (auto & p : tokenizeString<Paths>(accessor->readFile(propPath)))
pathAdditions.push_back(binDir.abs());
auto propPath = state->storeFS->resolveSymlinks(
CanonPath(store->printStorePath(path)) / "nix-support" / "propagated-user-env-packages");
if (auto st = state->storeFS->maybeLstat(propPath); st && st->type == SourceAccessor::tRegular) {
for (auto & p : tokenizeString<Paths>(state->storeFS->readFile(propPath)))
todo.push(store->parseStorePath(p));
}
}
@ -108,7 +111,7 @@ struct CmdShell : InstallablesCommand, MixEnvironment
// Release our references to eval caches to ensure they are persisted to disk, because
// we are about to exec out of this process without running C++ destructors.
getEvalState()->evalCaches.clear();
state->evalCaches.clear();
execProgramInStore(store, UseLookupPath::Use, *command.begin(), args);
}

2
tests/functional/shell.sh
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@ -21,7 +21,7 @@ nix shell -f shell-hello.nix 'hello^*' -c hello2 | grep 'Hello2'
nix shell -f shell-hello.nix hello-symlink -c hello | grep 'Hello World'
# Test that symlinks outside of the store don't work.
expect 1 nix shell -f shell-hello.nix forbidden-symlink -c hello 2>&1 | grepQuiet "points outside source tree"
expect 1 nix shell -f shell-hello.nix forbidden-symlink -c hello 2>&1 | grepQuiet "is not in the Nix store"
# Test that we're not setting any more environment variables than necessary.
# For instance, we might set an environment variable temporarily to affect some