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std::str: Deny surrogates in is_utf8 #8982

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std::str: Deny surrogates in is_utf8 #8982

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15 changes: 12 additions & 3 deletions src/libstd/str.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -798,6 +798,8 @@ pub fn is_utf8(v: &[u8]) -> bool {
// first C2 80 last DF BF
// 3-byte encoding is for codepoints \u0800 to \uffff
// first E0 A0 80 last EF BF BF
// excluding surrogates codepoints \ud800 to \udfff
// ED A0 80 to ED BF BF
// 4-byte encoding is for codepoints \u10000 to \u10ffff
// first F0 90 80 80 last F4 8F BF BF
//
Expand All @@ -811,8 +813,6 @@ pub fn is_utf8(v: &[u8]) -> bool {
// UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) /
// %xF4 %x80-8F 2( UTF8-tail )
// UTF8-tail = %x80-BF
// --
// This code allows surrogate pairs: \uD800 to \uDFFF -> ED A0 80 to ED BF BF
match w {
2 => if unsafe_get(v, i + 1) & 192u8 != TAG_CONT_U8 {
return false
Expand All @@ -821,7 +821,9 @@ pub fn is_utf8(v: &[u8]) -> bool {
unsafe_get(v, i + 1),
unsafe_get(v, i + 2) & 192u8) {
(0xE0 , 0xA0 .. 0xBF, TAG_CONT_U8) => (),
(0xE1 .. 0xEF, 0x80 .. 0xBF, TAG_CONT_U8) => (),
(0xE1 .. 0xEC, 0x80 .. 0xBF, TAG_CONT_U8) => (),
(0xED , 0x80 .. 0x9F, TAG_CONT_U8) => (),
(0xEE .. 0xEF, 0x80 .. 0xBF, TAG_CONT_U8) => (),
_ => return false,
},
_ => match (v_i,
Expand Down Expand Up @@ -3015,6 +3017,7 @@ mod tests {

#[test]
fn test_is_utf8() {
// deny overlong encodings
assert!(!is_utf8([0xc0, 0x80]));
assert!(!is_utf8([0xc0, 0xae]));
assert!(!is_utf8([0xe0, 0x80, 0x80]));
Expand All @@ -3023,9 +3026,15 @@ mod tests {
assert!(!is_utf8([0xf0, 0x82, 0x82, 0xac]));
assert!(!is_utf8([0xf4, 0x90, 0x80, 0x80]));

// deny surrogates
assert!(!is_utf8([0xED, 0xA0, 0x80]));
assert!(!is_utf8([0xED, 0xBF, 0xBF]));

assert!(is_utf8([0xC2, 0x80]));
assert!(is_utf8([0xDF, 0xBF]));
assert!(is_utf8([0xE0, 0xA0, 0x80]));
assert!(is_utf8([0xED, 0x9F, 0xBF]));
assert!(is_utf8([0xEE, 0x80, 0x80]));
assert!(is_utf8([0xEF, 0xBF, 0xBF]));
assert!(is_utf8([0xF0, 0x90, 0x80, 0x80]));
assert!(is_utf8([0xF4, 0x8F, 0xBF, 0xBF]));
Expand Down