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Move restricted/pure-eval access control out of the evaluator and into the accessor

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This commit is contained in:
Eelco Dolstra 2023-11-30 16:16:17 +01:00
parent 3bebaefcd0
commit ea95327e72
8 changed files with 115 additions and 171 deletions
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119
src/libexpr/primops.cc
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@ -15,6 +15,7 @@
#include "value-to-json.hh"
#include "value-to-xml.hh"
#include "primops.hh"
#include "fs-input-accessor.hh"
#include <boost/container/small_vector.hpp>
#include <boost/regex.hpp>
@ -90,8 +91,8 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
for (auto & [outputName, outputPath] : outputs) {
/* Add the output of this derivations to the allowed
paths. */
if (allowedPaths) {
allowPath(outputPath);
if (rootFS->hasAccessControl()) {
allowPath(store->toRealPath(outputPath));
}
/* Get all the output paths corresponding to the placeholders we had */
if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations)) {
@ -110,27 +111,19 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
return res;
}
struct RealisePathFlags {
// Whether to check that the path is allowed in pure eval mode
bool checkForPureEval = true;
};
static SourcePath realisePath(EvalState & state, const PosIdx pos, Value & v, const RealisePathFlags flags = {})
static SourcePath realisePath(EvalState & state, const PosIdx pos, Value & v)
{
NixStringContext context;
auto path = state.coerceToPath(noPos, v, context, "while realising the context of a path");
try {
if (!context.empty()) {
if (!context.empty() && path.accessor == state.rootFS) {
auto rewrites = state.realiseContext(context);
auto realPath = state.toRealPath(rewriteStrings(path.path.abs(), rewrites), context);
return {path.accessor, CanonPath(realPath)};
}
return flags.checkForPureEval
? state.checkSourcePath(path)
: path;
} else
return path;
} catch (Error & e) {
e.addTrace(state.positions[pos], "while realising the context of path '%s'", path);
throw;
@ -1493,7 +1486,7 @@ static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args,
}));
NixStringContext context;
auto path = state.checkSourcePath(state.coerceToPath(pos, *args[0], context, "while evaluating the first argument passed to 'builtins.storePath'")).path;
auto path = state.coerceToPath(pos, *args[0], context, "while evaluating the first argument passed to 'builtins.storePath'").path;
/* Resolve symlinks in ‘path’, unless ‘path’ itself is a symlink
directly in the store. The latter condition is necessary so
e.g. nix-push does the right thing. */
@ -1535,12 +1528,7 @@ static void prim_pathExists(EvalState & state, const PosIdx pos, Value * * args,
{
auto & arg = *args[0];
/* We don’t check the path right now, because we don’t want to
throw if the path isn’t allowed, but just return false (and we
can’t just catch the exception here because we still want to
throw if something in the evaluation of `arg` tries to
access an unauthorized path). */
auto path = realisePath(state, pos, arg, { .checkForPureEval = false });
auto path = realisePath(state, pos, arg);
/* SourcePath doesn't know about trailing slash. */
auto mustBeDir = arg.type() == nString
@ -1548,14 +1536,9 @@ static void prim_pathExists(EvalState & state, const PosIdx pos, Value * * args,
|| arg.string_view().ends_with("/."));
try {
auto checked = state.checkSourcePath(path);
auto st = checked.maybeLstat();
auto st = path.maybeLstat();
auto exists = st && (!mustBeDir || st->type == SourceAccessor::tDirectory);
v.mkBool(exists);
} catch (SysError & e) {
/* Don't give away info from errors while canonicalising
‘path’ in restricted mode. */
v.mkBool(false);
} catch (RestrictedPathError & e) {
v.mkBool(false);
}
@ -1699,7 +1682,7 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
auto path = state.forceStringNoCtx(*args[1], pos, "while evaluating the second argument passed to builtins.findFile");
v.mkPath(state.checkSourcePath(state.findFile(searchPath, path, pos)));
v.mkPath(state.findFile(searchPath, path, pos));
}
static RegisterPrimOp primop_findFile(PrimOp {
@ -2178,11 +2161,35 @@ static RegisterPrimOp primop_toFile({
.fun = prim_toFile,
});
bool EvalState::callPathFilter(
Value * filterFun,
const SourcePath & path,
std::string_view pathArg,
PosIdx pos)
{
auto st = path.lstat();
/* Call the filter function. The first argument is the path, the
second is a string indicating the type of the file. */
Value arg1;
arg1.mkString(pathArg);
Value arg2;
// assert that type is not "unknown"
arg2.mkString(fileTypeToString(st.type));
Value * args []{&arg1, &arg2};
Value res;
callFunction(*filterFun, 2, args, res, pos);
return forceBool(res, pos, "while evaluating the return value of the path filter function");
}
static void addPath(
EvalState & state,
const PosIdx pos,
std::string_view name,
Path path,
SourcePath path,
Value * filterFun,
FileIngestionMethod method,
const std::optional<Hash> expectedHash,
@ -2190,48 +2197,29 @@ static void addPath(
const NixStringContext & context)
{
try {
// FIXME: handle CA derivation outputs (where path needs to
// be rewritten to the actual output).
auto rewrites = state.realiseContext(context);
path = state.toRealPath(rewriteStrings(path, rewrites), context);
StorePathSet refs;
if (state.store->isInStore(path)) {
if (path.accessor == state.rootFS && state.store->isInStore(path.path.abs())) {
// FIXME: handle CA derivation outputs (where path needs to
// be rewritten to the actual output).
auto rewrites = state.realiseContext(context);
path = {state.rootFS, CanonPath(state.toRealPath(rewriteStrings(path.path.abs(), rewrites), context))};
try {
auto [storePath, subPath] = state.store->toStorePath(path);
auto [storePath, subPath] = state.store->toStorePath(path.path.abs());
// FIXME: we should scanForReferences on the path before adding it
refs = state.store->queryPathInfo(storePath)->references;
path = state.store->toRealPath(storePath) + subPath;
path = {state.rootFS, CanonPath(state.store->toRealPath(storePath) + subPath)};
} catch (Error &) { // FIXME: should be InvalidPathError
}
}
path = evalSettings.pureEval && expectedHash
? path
: state.checkSourcePath(state.rootPath(CanonPath(path))).path.abs();
PathFilter filter = filterFun ? ([&](const Path & path) {
auto st = lstat(path);
/* Call the filter function. The first argument is the path,
the second is a string indicating the type of the file. */
Value arg1;
arg1.mkString(path);
Value arg2;
arg2.mkString(
S_ISREG(st.st_mode) ? "regular" :
S_ISDIR(st.st_mode) ? "directory" :
S_ISLNK(st.st_mode) ? "symlink" :
"unknown" /* not supported, will fail! */);
Value * args []{&arg1, &arg2};
Value res;
state.callFunction(*filterFun, 2, args, res, pos);
return state.forceBool(res, pos, "while evaluating the return value of the path filter function");
}) : defaultPathFilter;
std::unique_ptr<PathFilter> filter;
if (filterFun)
filter = std::make_unique<PathFilter>([&](const Path & p) {
auto p2 = CanonPath(p);
return state.callPathFilter(filterFun, {path.accessor, p2}, p2.abs(), pos);
});
std::optional<StorePath> expectedStorePath;
if (expectedHash)
@ -2242,7 +2230,7 @@ static void addPath(
});
if (!expectedHash || !state.store->isValidPath(*expectedStorePath)) {
auto dstPath = state.rootPath(CanonPath(path)).fetchToStore(state.store, name, method, &filter, state.repair);
auto dstPath = path.fetchToStore(state.store, name, method, filter.get(), state.repair);
if (expectedHash && expectedStorePath != dstPath)
state.debugThrowLastTrace(Error("store path mismatch in (possibly filtered) path added from '%s'", path));
state.allowAndSetStorePathString(dstPath, v);
@ -2261,7 +2249,8 @@ static void prim_filterSource(EvalState & state, const PosIdx pos, Value * * arg
auto path = state.coerceToPath(pos, *args[1], context,
"while evaluating the second argument (the path to filter) passed to 'builtins.filterSource'");
state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.filterSource");
addPath(state, pos, path.baseName(), path.path.abs(), args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
addPath(state, pos, path.baseName(), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
}
static RegisterPrimOp primop_filterSource({
@ -2356,7 +2345,7 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
if (name.empty())
name = path->baseName();
addPath(state, pos, name, path->path.abs(), filterFun, method, expectedHash, v, context);
addPath(state, pos, name, *path, filterFun, method, expectedHash, v, context);
}
static RegisterPrimOp primop_path({