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json: disallow overlong and out-of-range UTF-8 #4097

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Merged
merged 1 commit into from
Jan 7, 2020
Merged

json: disallow overlong and out-of-range UTF-8 #4097

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76 changes: 57 additions & 19 deletions lib/std/json.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,8 @@ pub const StreamingParser = struct {
string_last_was_high_surrogate: bool,
// Used inside of StringEscapeHexUnicode* states
string_unicode_codepoint: u21,
// The first byte needs to be stored to validate 3- and 4-byte sequences.
sequence_first_byte: u8 = undefined,
// When in .Number states, is the number a (still) valid integer?
number_is_integer: bool,

Expand Down Expand Up @@ -132,9 +134,12 @@ pub const StreamingParser = struct {
ValueBeginNoClosing,

String,
StringUtf8Byte3,
StringUtf8Byte2,
StringUtf8Byte1,
StringUtf8Byte2Of2,
StringUtf8Byte2Of3,
StringUtf8Byte3Of3,
StringUtf8Byte2Of4,
StringUtf8Byte3Of4,
StringUtf8Byte4Of4,
StringEscapeCharacter,
StringEscapeHexUnicode4,
StringEscapeHexUnicode3,
Expand Down Expand Up @@ -581,35 +586,68 @@ pub const StreamingParser = struct {
// non-control ascii
p.string_last_was_high_surrogate = false;
},
0xC0...0xDF => {
p.state = .StringUtf8Byte1;
0xC2...0xDF => {
p.state = .StringUtf8Byte2Of2;
},
0xE0...0xEF => {
p.state = .StringUtf8Byte2;
p.state = .StringUtf8Byte2Of3;
p.sequence_first_byte = c;
},
0xF0...0xFF => {
p.state = .StringUtf8Byte3;
0xF0...0xF4 => {
p.state = .StringUtf8Byte2Of4;
p.sequence_first_byte = c;
},
else => {
return error.InvalidUtf8Byte;
},
},

.StringUtf8Byte3 => switch (c >> 6) {
0b10 => p.state = .StringUtf8Byte2,
.StringUtf8Byte2Of2 => switch (c >> 6) {
0b10 => p.state = .String,
else => return error.InvalidUtf8Byte,
},

.StringUtf8Byte2 => switch (c >> 6) {
0b10 => p.state = .StringUtf8Byte1,
.StringUtf8Byte2Of3 => {
switch (p.sequence_first_byte) {
0xE0 => switch (c) {
0xA0...0xBF => {},
else => return error.InvalidUtf8Byte,
},
0xE1...0xEF => switch (c) {
0x80...0xBF => {},
else => return error.InvalidUtf8Byte,
},
else => return error.InvalidUtf8Byte,
}
p.state = .StringUtf8Byte3Of3;
},
.StringUtf8Byte3Of3 => switch (c) {
0x80...0xBF => p.state = .String,
else => return error.InvalidUtf8Byte,
},

.StringUtf8Byte1 => switch (c >> 6) {
0b10 => {
p.state = .String;
p.string_last_was_high_surrogate = false;
},
.StringUtf8Byte2Of4 => {
switch (p.sequence_first_byte) {
0xF0 => switch (c) {
0x90...0xBF => {},
else => return error.InvalidUtf8Byte,
},
0xF1...0xF3 => switch (c) {
0x80...0xBF => {},
else => return error.InvalidUtf8Byte,
},
0xF4 => switch (c) {
0x80...0x8F => {},
else => return error.InvalidUtf8Byte,
},
else => return error.InvalidUtf8Byte,
}
p.state = .StringUtf8Byte3Of4;
},
.StringUtf8Byte3Of4 => switch (c) {
0x80...0xBF => p.state = .StringUtf8Byte4Of4,
else => return error.InvalidUtf8Byte,
},
.StringUtf8Byte4Of4 => switch (c) {
0x80...0xBF => p.state = .String,
else => return error.InvalidUtf8Byte,
},

Expand Down
66 changes: 66 additions & 0 deletions lib/std/json/test.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,20 @@ fn err(comptime s: []const u8) void {
} else |_| {}
}

fn utf8Error(comptime s: []const u8) void {
std.testing.expect(!std.json.validate(s));

var mem_buffer: [1024 * 20]u8 = undefined;
const allocator = &std.heap.FixedBufferAllocator.init(&mem_buffer).allocator;
var p = std.json.Parser.init(allocator, false);

if (p.parse(s)) |_| {
unreachable;
} else |e| {
std.testing.expect(e == error.InvalidUtf8Byte);
}
}

fn any(comptime s: []const u8) void {
_ = std.json.validate(s);

Expand Down Expand Up @@ -1936,3 +1950,55 @@ test "i_structure_UTF-8_BOM_empty_object" {
\\{}
);
}

test "truncated UTF-8 sequence" {
utf8Error("\"\xc2\"");
utf8Error("\"\xdf\"");
utf8Error("\"\xed\xa0\"");
utf8Error("\"\xf0\x80\"");
utf8Error("\"\xf0\x80\x80\"");
}

test "invalid continuation byte" {
utf8Error("\"\xc2\x00\"");
utf8Error("\"\xc2\x7f\"");
utf8Error("\"\xc2\xc0\"");
utf8Error("\"\xc3\xc1\"");
utf8Error("\"\xc4\xf5\"");
utf8Error("\"\xc5\xff\"");
utf8Error("\"\xe4\x80\x00\"");
utf8Error("\"\xe5\x80\x10\"");
utf8Error("\"\xe6\x80\xc0\"");
utf8Error("\"\xe7\x80\xf5\"");
utf8Error("\"\xe8\x00\x80\"");
utf8Error("\"\xf2\x00\x80\x80\"");
utf8Error("\"\xf0\x80\x00\x80\"");
utf8Error("\"\xf1\x80\xc0\x80\"");
utf8Error("\"\xf2\x80\x80\x00\"");
utf8Error("\"\xf3\x80\x80\xc0\"");
utf8Error("\"\xf4\x80\x80\xf5\"");
}

test "disallowed overlong form" {
utf8Error("\"\xc0\x80\"");
utf8Error("\"\xc0\x90\"");
utf8Error("\"\xc1\x80\"");
utf8Error("\"\xc1\x90\"");
utf8Error("\"\xe0\x80\x80\"");
utf8Error("\"\xf0\x80\x80\x80\"");
}

test "out of UTF-16 range" {
utf8Error("\"\xf4\x90\x80\x80\"");
utf8Error("\"\xf5\x80\x80\x80\"");
utf8Error("\"\xf6\x80\x80\x80\"");
utf8Error("\"\xf7\x80\x80\x80\"");
utf8Error("\"\xf8\x80\x80\x80\"");
utf8Error("\"\xf9\x80\x80\x80\"");
utf8Error("\"\xfa\x80\x80\x80\"");
utf8Error("\"\xfb\x80\x80\x80\"");
utf8Error("\"\xfc\x80\x80\x80\"");
utf8Error("\"\xfd\x80\x80\x80\"");
utf8Error("\"\xfe\x80\x80\x80\"");
utf8Error("\"\xff\x80\x80\x80\"");
}