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Make the NAR parser much stricter wrt field order

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We really want to enforce a canonical representation since NAR
hashing/signing/deduplication depends on that.
This commit is contained in:
Eelco Dolstra 2024-09-12 15:57:46 +02:00
parent 27ec0def74
commit 7aa3e7e3a5
4 changed files with 85 additions and 100 deletions
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177
src/libutil/archive.cc
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@ -168,120 +168,97 @@ struct CaseInsensitiveCompare
static void parse(FileSystemObjectSink & sink, Source & source, const CanonPath & path)
{
std::string s;
s = readString(source);
if (s != "(") throw badArchive("expected open tag");
auto getString = [&]() {
checkInterrupt();
return readString(source);
};
// For first iteration
s = getString();
auto expectTag = [&](std::string_view expected) {
auto tag = getString();
if (tag != expected)
throw badArchive("expected tag '%s', got '%s'", expected, tag);
};
while (1) {
expectTag("(");
if (s == ")") {
break;
}
expectTag("type");
else if (s == "type") {
std::string t = getString();
auto type = getString();
if (t == "regular") {
sink.createRegularFile(path, [&](auto & crf) {
while (1) {
s = getString();
if (type == "regular") {
sink.createRegularFile(path, [&](auto & crf) {
auto tag = getString();
if (s == "contents") {
parseContents(crf, source);
}
else if (s == "executable") {
auto s2 = getString();
if (s2 != "") throw badArchive("executable marker has non-empty value");
crf.isExecutable();
}
else break;
}
});
if (tag == "executable") {
auto s2 = getString();
if (s2 != "") throw badArchive("executable marker has non-empty value");
crf.isExecutable();
tag = getString();
}
else if (t == "directory") {
sink.createDirectory(path);
if (tag == "contents")
parseContents(crf, source);
std::map<Path, int, CaseInsensitiveCompare> names;
std::string prevName;
while (1) {
s = getString();
if (s == "entry") {
std::string name;
s = getString();
if (s != "(") throw badArchive("expected open tag '%s'", s);
while (1) {
s = getString();
if (s == ")") {
break;
} else if (s == "name") {
name = getString();
if (name.empty() || name == "." || name == ".." || name.find('/') != std::string::npos || name.find((char) 0) != std::string::npos)
throw badArchive("NAR contains invalid file name '%1%'", name);
if (name <= prevName)
throw badArchive("NAR directory is not sorted");
prevName = name;
if (archiveSettings.useCaseHack) {
auto i = names.find(name);
if (i != names.end()) {
debug("case collision between '%1%' and '%2%'", i->first, name);
name += caseHackSuffix;
name += std::to_string(++i->second);
auto j = names.find(name);
if (j != names.end())
throw badArchive("NAR contains file name '%s' that collides with case-hacked file name '%s'", prevName, j->first);
} else
names[name] = 0;
}
} else if (s == "node") {
if (name.empty()) throw badArchive("entry name missing");
parse(sink, source, path / name);
} else
throw badArchive("unknown field '%s'", s);
}
}
else break;
}
}
else if (t == "symlink") {
s = getString();
if (s != "target")
throw badArchive("expected 'target', got '%s'", s);
std::string target = getString();
sink.createSymlink(path, target);
// for the next iteration
s = getString();
}
else throw badArchive("unknown file type '%s'", t);
}
else
throw badArchive("unknown field '%s'", s);
expectTag(")");
});
}
else if (type == "directory") {
sink.createDirectory(path);
std::map<Path, int, CaseInsensitiveCompare> names;
std::string prevName;
while (1) {
auto tag = getString();
if (tag == ")") break;
if (tag != "entry")
throw badArchive("expected tag 'entry' or ')', got '%s'", tag);
expectTag("(");
expectTag("name");
auto name = getString();
if (name.empty() || name == "." || name == ".." || name.find('/') != std::string::npos || name.find((char) 0) != std::string::npos)
throw badArchive("NAR contains invalid file name '%1%'", name);
if (name <= prevName)
throw badArchive("NAR directory is not sorted");
prevName = name;
if (archiveSettings.useCaseHack) {
auto i = names.find(name);
if (i != names.end()) {
debug("case collision between '%1%' and '%2%'", i->first, name);
name += caseHackSuffix;
name += std::to_string(++i->second);
auto j = names.find(name);
if (j != names.end())
throw badArchive("NAR contains file name '%s' that collides with case-hacked file name '%s'", prevName, j->first);
} else
names[name] = 0;
}
expectTag("node");
parse(sink, source, path / name);
expectTag(")");
}
}
else if (type == "symlink") {
expectTag("target");
auto target = getString();
sink.createSymlink(path, target);
expectTag(")");
}
else throw badArchive("unknown file type '%s'", type);
}

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tests/functional/executable-after-contents.nar Normal file
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tests/functional/name-after-node.nar Normal file
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8
tests/functional/nars.sh
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@ -112,3 +112,11 @@ expectStderr 1 nix-store --restore "$TEST_ROOT/out" < slash.nar | grepQuiet "NAR
# Likewise for an empty filename.
rm -rf "$TEST_ROOT/out"
expectStderr 1 nix-store --restore "$TEST_ROOT/out" < empty.nar | grepQuiet "NAR contains invalid file name ''"
# Test that the 'executable' field cannot come before the 'contents' field.
rm -rf "$TEST_ROOT/out"
expectStderr 1 nix-store --restore "$TEST_ROOT/out" < executable-after-contents.nar | grepQuiet "expected tag ')', got 'executable'"
# Test that the 'name' field cannot come before the 'node' field in a directory entry.
rm -rf "$TEST_ROOT/out"
expectStderr 1 nix-store --restore "$TEST_ROOT/out" < name-after-node.nar | grepQuiet "expected tag 'name'"