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Fix various overflows and UB in src/ #7494

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Fix various overflows and UB in src/ #7494

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f5ca5a0
buffer: fix unintended unsigned overflow
indutny Jun 30, 2016
05d0321
crypto: fix undefined behavior in ParseExtension
indutny Jun 30, 2016
27bfdc5
string_search: fix various overflows
indutny Jun 30, 2016
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6 changes: 3 additions & 3 deletions src/node_buffer.cc
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Expand Up @@ -693,16 +693,16 @@ void StringWrite(const FunctionCallbackInfo<Value>& args) {
size_t max_length;

CHECK_NOT_OOB(ParseArrayIndex(args[1], 0, &offset));
if (offset >= ts_obj_length)
return env->ThrowRangeError("Offset is out of bounds");

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

max_length = MIN(ts_obj_length - offset, max_length);

if (max_length == 0)
return args.GetReturnValue().Set(0);

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@trevnorris trevnorris Jun 30, 2016 •
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just curious, are we missing test coverage that would have caught this?

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There is one edge case with max_length equal to 0, but otherwise nothing bad happens here. Btw, should we consider this as a breaking change?

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IMO you're simply making this defined behavior, which falls under a bug fix and a semver-minor.

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@trevnorris @indutny Tracked issue I got after upgrade to this point. Apparently this broke some of my code e.g. using protocol-buffers (and I'm sure some other binary encoders too) which, for certain data, are writing empty strings in the end of the buffer, which is safe operation (no-op) on its own and worked up until this PR without any extra checks.

I was going to prepare PR to fix this but sounds like it falls under

There is one edge case with max_length equal to 0

and I'm wondering whether we consider this an expected behavior?

Minimal sample: Buffer.alloc(0).write('') - works in pre-6.4.0, throws now.

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Yikes, sorry to break your code!

I don't have any strong opinion on how it should work, but to me it will be fine to not throw in this case.

cc @trevnorris

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@RReverser @indutny See #8127/#8154, it should already been fixed on master.

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@addaleax By master you mean v6.x? (because that's where issue is present, at least it was when I checked yesterday)

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@RReverser I’m a bit confused – the commit from #8154 is only in master, not yet on the v6.x branch, yes. I’d anticipate that it lands cleanly, so there should be no need for manual backporting?

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@addaleax Ah I thought you meant it should already work on v6.x branch (as in already landed). Sorry for misunderstanding.

if (offset >= ts_obj_length)
return env->ThrowRangeError("Offset is out of bounds");

uint32_t written = StringBytes::Write(env->isolate(),
ts_obj_data + offset,
max_length,
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4 changes: 2 additions & 2 deletions src/node_crypto_clienthello.cc
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Expand Up @@ -103,7 +103,7 @@ void ClientHelloParser::ParseHeader(const uint8_t* data, size_t avail) {
}


void ClientHelloParser::ParseExtension(ClientHelloParser::ExtensionType type,
void ClientHelloParser::ParseExtension(const uint16_t type,
const uint8_t* data,
size_t len) {
// NOTE: In case of anything we're just returning back, ignoring the problem.
Expand Down Expand Up @@ -210,7 +210,7 @@ bool ClientHelloParser::ParseTLSClientHello(const uint8_t* data, size_t avail) {
if (ext_off + ext_len > avail)
return false;

ParseExtension(static_cast<ExtensionType>(ext_type),
ParseExtension(ext_type,
data + ext_off,
ext_len);

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2 changes: 1 addition & 1 deletion src/node_crypto_clienthello.h
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Expand Up @@ -91,7 +91,7 @@ class ClientHelloParser {

bool ParseRecordHeader(const uint8_t* data, size_t avail);
void ParseHeader(const uint8_t* data, size_t avail);
void ParseExtension(ExtensionType type,
void ParseExtension(const uint16_t type,
const uint8_t* data,
size_t len);
bool ParseTLSClientHello(const uint8_t* data, size_t avail);
Expand Down
12 changes: 6 additions & 6 deletions src/string_search.h
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Expand Up @@ -404,7 +404,7 @@ size_t StringSearch<Char>::BoyerMooreSearch(
} else {
int gs_shift = good_suffix_shift[j + 1];
int bc_occ = CharOccurrence(bad_char_occurence, c);
int shift = j - bc_occ;
int shift = static_cast<int>(j) - bc_occ;
if (gs_shift > shift) {
shift = gs_shift;
}
Expand Down Expand Up @@ -494,12 +494,12 @@ size_t StringSearch<Char>::BoyerMooreHorspoolSearch(
const size_t subject_length = subject.length();
const size_t pattern_length = pattern.length();
int* char_occurrences = search->bad_char_table();
int64_t badness = -pattern_length;
int64_t badness = -static_cast<int64_t>(pattern_length);

// How bad we are doing without a good-suffix table.
Char last_char = pattern[pattern_length - 1];
int last_char_shift =
pattern_length - 1 -
static_cast<int>(pattern_length) - 1 -
CharOccurrence(char_occurrences, static_cast<Char>(last_char));

// Perform search
Expand All @@ -509,7 +509,7 @@ size_t StringSearch<Char>::BoyerMooreHorspoolSearch(
int subject_char;
while (last_char != (subject_char = subject[index + j])) {
int bc_occ = CharOccurrence(char_occurrences, subject_char);
int shift = j - bc_occ;
int shift = static_cast<int>(j) - bc_occ;
index += shift;
badness += 1 - shift; // at most zero, so badness cannot increase.
if (index > subject_length - pattern_length) {
Expand All @@ -528,7 +528,7 @@ size_t StringSearch<Char>::BoyerMooreHorspoolSearch(
// checked, and decreases by the number of characters we
// can skip by shifting. It's a measure of how we are doing
// compared to reading each character exactly once.
badness += (pattern_length - j) - last_char_shift;
badness += static_cast<int64_t>(pattern_length - j) - last_char_shift;
if (badness > 0) {
search->PopulateBoyerMooreTable();
search->strategy_ = &BoyerMooreSearch;
Expand Down Expand Up @@ -602,7 +602,7 @@ size_t StringSearch<Char>::InitialSearch(
if (j == pattern_length) {
return i;
}
badness += j;
badness += static_cast<int64_t>(j);
} else {
search->PopulateBoyerMooreHorspoolTable();
search->strategy_ = &BoyerMooreHorspoolSearch;
Expand Down