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[v10.x] buffer: fix crash for invalid index types #23795

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[v10.x] buffer: fix crash for invalid index types #23795

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62 changes: 36 additions & 26 deletions src/node_buffer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -40,16 +40,18 @@

#define THROW_AND_RETURN_IF_OOB(r) \
do { \
if (!(r)) return node::THROW_ERR_INDEX_OUT_OF_RANGE(env); \
} while (0)
if ((r).IsNothing()) return; \
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Nit: If my understanding is correct, this return; would make the Copy return with undefined. Would it be better to include a test which checks that?

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It would not return any value – this is the case where coercing to integer throws an exception (i.e. the last part of the test)

if (!(r).FromJust()) \
return node::THROW_ERR_INDEX_OUT_OF_RANGE(env); \
} while (0) \

#define SLICE_START_END(start_arg, end_arg, end_max) \
#define SLICE_START_END(env, start_arg, end_arg, end_max) \
size_t start; \
size_t end; \
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(start_arg, 0, &start)); \
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(end_arg, end_max, &end)); \
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, start_arg, 0, &start)); \
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, end_arg, end_max, &end)); \
if (end < start) end = start; \
THROW_AND_RETURN_IF_OOB(end <= end_max); \
THROW_AND_RETURN_IF_OOB(Just(end <= end_max)); \
size_t length = end - start;

namespace node {
Expand All @@ -76,9 +78,11 @@ using v8::EscapableHandleScope;
using v8::FunctionCallbackInfo;
using v8::Integer;
using v8::Isolate;
using v8::Just;
using v8::Local;
using v8::Maybe;
using v8::MaybeLocal;
using v8::Nothing;
using v8::Object;
using v8::String;
using v8::Uint32;
Expand Down Expand Up @@ -161,29 +165,32 @@ void CallbackInfo::WeakCallback(Isolate* isolate) {
}


// Parse index for external array data.
inline MUST_USE_RESULT bool ParseArrayIndex(Local<Value> arg,
size_t def,
size_t* ret) {
// Parse index for external array data. An empty Maybe indicates
// a pending exception. `false` indicates that the index is out-of-bounds.
inline MUST_USE_RESULT Maybe<bool> ParseArrayIndex(Environment* env,
Local<Value> arg,
size_t def,
size_t* ret) {
if (arg->IsUndefined()) {
*ret = def;
return true;
return Just(true);
}

CHECK(arg->IsNumber());
int64_t tmp_i = arg.As<Integer>()->Value();
int64_t tmp_i;
if (!arg->IntegerValue(env->context()).To(&tmp_i))
return Nothing<bool>();

if (tmp_i < 0)
return false;
return Just(false);

// Check that the result fits in a size_t.
const uint64_t kSizeMax = static_cast<uint64_t>(static_cast<size_t>(-1));
// coverity[pointless_expression]
if (static_cast<uint64_t>(tmp_i) > kSizeMax)
return false;
return Just(false);

*ret = static_cast<size_t>(tmp_i);
return true;
return Just(true);
}

} // anonymous namespace
Expand Down Expand Up @@ -452,7 +459,7 @@ void StringSlice(const FunctionCallbackInfo<Value>& args) {
if (ts_obj_length == 0)
return args.GetReturnValue().SetEmptyString();

SLICE_START_END(args[0], args[1], ts_obj_length)
SLICE_START_END(env, args[0], args[1], ts_obj_length)

Local<Value> error;
MaybeLocal<Value> ret =
Expand Down Expand Up @@ -485,9 +492,10 @@ void Copy(const FunctionCallbackInfo<Value> &args) {
size_t source_start;
size_t source_end;

THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[2], 0, &target_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[3], 0, &source_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[4], ts_obj_length, &source_end));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], 0, &target_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[3], 0, &source_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[4], ts_obj_length,
&source_end));

// Copy 0 bytes; we're done
if (target_start >= target_length || source_start >= source_end)
Expand Down Expand Up @@ -617,13 +625,13 @@ void StringWrite(const FunctionCallbackInfo<Value>& args) {
size_t offset;
size_t max_length;

THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[1], 0, &offset));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[1], 0, &offset));
if (offset > ts_obj_length) {
return node::THROW_ERR_BUFFER_OUT_OF_BOUNDS(
env, "\"offset\" is outside of buffer bounds");
}

THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[2], ts_obj_length - offset,
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], ts_obj_length - offset,
&max_length));

max_length = MIN(ts_obj_length - offset, max_length);
Expand Down Expand Up @@ -678,10 +686,12 @@ void CompareOffset(const FunctionCallbackInfo<Value> &args) {
size_t source_end;
size_t target_end;

THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[2], 0, &target_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[3], 0, &source_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[4], target_length, &target_end));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(args[5], ts_obj_length, &source_end));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], 0, &target_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[3], 0, &source_start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[4], target_length,
&target_end));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[5], ts_obj_length,
&source_end));

if (source_start > ts_obj_length)
return node::THROW_ERR_INDEX_OUT_OF_RANGE(env);
Expand Down
26 changes: 26 additions & 0 deletions test/parallel/test-buffer-copy.js
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Expand Up @@ -18,6 +18,17 @@ let cntr = 0;
}
}

{
// Current behavior is to coerce values to integers.
b.fill(++cntr);
c.fill(++cntr);
const copied = b.copy(c, '0', '0', '512');
assert.strictEqual(copied, 512);
for (let i = 0; i < c.length; i++) {
assert.strictEqual(c[i], b[i]);
}
}

{
// copy c into b, without specifying sourceEnd
b.fill(++cntr);
Expand Down Expand Up @@ -144,3 +155,18 @@ assert.strictEqual(b.copy(c, 512, 0, 10), 0);
assert.strictEqual(c[i], e[i]);
}
}

// https://github.com/nodejs/node/issues/23668: Do not crash for invalid input.
c.fill('c');
b.copy(c, 'not a valid offset');
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Nit: An assertion after an invalid copy which ensures that nothing actually copied would be good. If the behaviour changes later on, this assertion would be able to catch that.

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@addaleax addaleax Oct 24, 2018 •
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@thefourtheye I’ve documented the behaviour – it is not not copying anything, it is coercing, values to integer, i.e. 'not a valid offset' becomes 0 (as in, ('foo' | 0) === 0)

// Make sure this acted like a regular copy with `0` offset.
assert.deepStrictEqual(c, b.slice(0, c.length));

{
c.fill('C');
assert.throws(() => {
b.copy(c, { [Symbol.toPrimitive]() { throw new Error('foo'); } });
}, /foo/);
// No copying took place:
assert.deepStrictEqual(c.toString(), 'C'.repeat(c.length));
}