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Deserialize invalid UTF-8 into byte bufs as WTF-8 #877

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Deserialize invalid UTF-8 into byte bufs as WTF-8 #877

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5 changes: 4 additions & 1 deletion src/de.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1570,7 +1570,10 @@ impl<'de, 'a, R: Read<'de>> de::Deserializer<'de> for &'a mut Deserializer<R> {
///
/// The behavior of serde_json is specified to fail on non-UTF-8 strings
/// when deserializing into Rust UTF-8 string types such as String, and
/// succeed with non-UTF-8 bytes when deserializing using this method.
/// succeed with the bytes representing the [WTF-8] encoding of code points
/// when deserializing using this method.
///
/// [WTF-8]: https://simonsapin.github.io/wtf-8
///
/// Escape sequences are processed as usual, and for `\uXXXX` escapes it is
/// still checked if the hex number represents a valid Unicode code point.
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41 changes: 30 additions & 11 deletions src/read.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -861,20 +861,33 @@ fn parse_escape<'de, R: Read<'de>>(
b'r' => scratch.push(b'\r'),
b't' => scratch.push(b'\t'),
b'u' => {
fn encode_surrogate(scratch: &mut Vec<u8>, n: u16) {
scratch.extend_from_slice(&[
(n >> 12 & 0b0000_1111) as u8 | 0b1110_0000,
(n >> 6 & 0b0011_1111) as u8 | 0b1000_0000,
(n & 0b0011_1111) as u8 | 0b1000_0000,
]);
fn encode_wtf8(scratch: &mut Vec<u8>, cp: u16) {
match cp {
0x0000..=0x007F => {
scratch.extend_from_slice(&[cp as u8]);
}
0x0080..=0x07FF => {
scratch
.extend_from_slice(&[0xC0 | (cp >> 6) as u8, 0x80 | (cp & 0x3F) as u8]);
}
0x0800..=0xFFFF => {
scratch.extend_from_slice(&[
0xE0 | (cp >> 12) as u8,
0x80 | ((cp >> 6) & 0x3F) as u8,
0x80 | (cp & 0x3F) as u8,
]);
}
}
}

let c = match tri!(read.decode_hex_escape()) {
n @ 0xDC00..=0xDFFF => {
return if validate {
// TODO: the error message is wrong, this is a lone
// _trailing_ surrogate
error(read, ErrorCode::LoneLeadingSurrogateInHexEscape)
Comment on lines +886 to 888
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Worth adding another error code? Would doing so even be semver compatible? (unrelated to this PR)

} else {
encode_surrogate(scratch, n);
encode_wtf8(scratch, n);
Ok(())
};
}
Expand All @@ -889,9 +902,9 @@ fn parse_escape<'de, R: Read<'de>>(
} else {
return if validate {
read.discard();
error(read, ErrorCode::UnexpectedEndOfHexEscape)
error(read, ErrorCode::LoneLeadingSurrogateInHexEscape)
} else {
encode_surrogate(scratch, n1);
encode_wtf8(scratch, n1);
Ok(())
};
}
Expand All @@ -903,7 +916,7 @@ fn parse_escape<'de, R: Read<'de>>(
read.discard();
error(read, ErrorCode::UnexpectedEndOfHexEscape)
} else {
encode_surrogate(scratch, n1);
encode_wtf8(scratch, n1);
// The \ prior to this byte started an escape sequence,
// so we need to parse that now. This recursive call
// does not blow the stack on malicious input because
Expand All @@ -916,7 +929,13 @@ fn parse_escape<'de, R: Read<'de>>(
let n2 = tri!(read.decode_hex_escape());

if n2 < 0xDC00 || n2 > 0xDFFF {
return error(read, ErrorCode::LoneLeadingSurrogateInHexEscape);
return if validate {
error(read, ErrorCode::LoneLeadingSurrogateInHexEscape)
} else {
encode_wtf8(scratch, n1);
encode_wtf8(scratch, n2);
Ok(())
};
}

let n = (((n1 - 0xD800) as u32) << 10 | (n2 - 0xDC00) as u32) + 0x1_0000;
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54 changes: 46 additions & 8 deletions tests/test.rs
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Expand Up @@ -1713,7 +1713,8 @@ fn test_byte_buf_de() {
}

#[test]
fn test_byte_buf_de_lone_surrogate() {
fn test_byte_buf_de_invalid_surrogates() {
// lone leading surrogate
let bytes = ByteBuf::from(vec![237, 160, 188]);
let v: ByteBuf = from_str(r#""\ud83c""#).unwrap();
assert_eq!(v, bytes);
Expand All @@ -1726,23 +1727,49 @@ fn test_byte_buf_de_lone_surrogate() {
let v: ByteBuf = from_str(r#""\ud83c ""#).unwrap();
assert_eq!(v, bytes);

let bytes = ByteBuf::from(vec![237, 176, 129]);
let v: ByteBuf = from_str(r#""\udc01""#).unwrap();
assert_eq!(v, bytes);

let res = from_str::<ByteBuf>(r#""\ud83c\!""#);
assert!(res.is_err());

let res = from_str::<ByteBuf>(r#""\ud83c\u""#);
assert!(res.is_err());

let res = from_str::<ByteBuf>(r#""\ud83c\ud83c""#);
assert!(res.is_err());
// lone trailing surrogate
let bytes = ByteBuf::from(vec![237, 176, 129]);
let v: ByteBuf = from_str(r#""\udc01""#).unwrap();
assert_eq!(v, bytes);

// leading surrogate followed by other leading surrogate
let bytes = ByteBuf::from(vec![237, 160, 188, 237, 160, 188]);
let v: ByteBuf = from_str(r#""\ud83c\ud83c""#).unwrap();
assert_eq!(v, bytes);

// leading surrogate followed by "a" (U+0061) in \u encoding
let bytes = ByteBuf::from(vec![237, 160, 188, 97]);
let v: ByteBuf = from_str(r#""\ud83c\u0061""#).unwrap();
assert_eq!(v, bytes);

// leading surrogate followed by U+0080
let bytes = ByteBuf::from(vec![237, 160, 188, 194, 128]);
let v: ByteBuf = from_str(r#""\ud83c\u0080""#).unwrap();
assert_eq!(v, bytes);

// leading surrogate followed by U+FFFF
let bytes = ByteBuf::from(vec![237, 160, 188, 239, 191, 191]);
let v: ByteBuf = from_str(r#""\ud83c\uffff""#).unwrap();
assert_eq!(v, bytes);
}

#[test]
fn test_byte_buf_de_surrogate_pair() {
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There was no test for parsing valid surrogate pairs into byte bufs that I could find, so I added one.

// leading surrogate followed by trailing surrogate
let bytes = ByteBuf::from(vec![240, 159, 128, 128]);
let v: ByteBuf = from_str(r#""\ud83c\udc00""#).unwrap();
assert_eq!(v, bytes);
}

#[cfg(feature = "raw_value")]
#[test]
fn test_raw_de_lone_surrogate() {
fn test_raw_de_invalid_surrogates() {
use serde_json::value::RawValue;

assert!(from_str::<Box<RawValue>>(r#""\ud83c""#).is_ok());
Expand All @@ -1752,6 +1779,17 @@ fn test_raw_de_lone_surrogate() {
assert!(from_str::<Box<RawValue>>(r#""\udc01\!""#).is_err());
assert!(from_str::<Box<RawValue>>(r#""\udc01\u""#).is_err());
assert!(from_str::<Box<RawValue>>(r#""\ud83c\ud83c""#).is_ok());
assert!(from_str::<Box<RawValue>>(r#""\ud83c\u0061""#).is_ok());
assert!(from_str::<Box<RawValue>>(r#""\ud83c\u0080""#).is_ok());
assert!(from_str::<Box<RawValue>>(r#""\ud83c\uffff""#).is_ok());
}

#[cfg(feature = "raw_value")]
#[test]
fn test_raw_de_surrogate_pair() {
use serde_json::value::RawValue;

assert!(from_str::<Box<RawValue>>(r#""\ud83c\udc00""#).is_ok());
}

#[test]
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