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utf8string: detect overlong encodings

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- also, stronger tests for utf8string
This commit is contained in:
Simon Cruanes 2018-03-06 23:50:49 -06:00
parent fe88bafe77
commit ea4a4e4ffb
1 changed files with 27 additions and 12 deletions
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39
src/core/CCUtf8_string.ml
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@ -37,15 +37,20 @@ exception Malformed of string * int
@raise Malformed if an invalid substring is met *)
let next_ (type a) (st : Dec.t) ~(yield:uchar -> a) ~(stop:unit -> a) () : a =
let open Dec in
let malformed st = raise (Malformed (st.s,st.i)) in
(* read a multi-byte character.
@param acc the accumulator (containing the first byte of the char)
@param n_bytes number of bytes to read (i.e. [width char - 1]) *)
let read_multi n_bytes acc =
@param acc the accumulator (containing the first byte of the char)
@param n_bytes number of bytes to read (i.e. [width char - 1])
@param overlong minimal bound on second byte (to detect overlong encoding)
*)
let read_multi ?(overlong=0) n_bytes acc =
(* inner loop j = 1..jmax *)
let rec aux j acc =
let c = Char.code st.s.[ st.i + j] in
(* check that c is in 0b10xxxxxx *)
if c lsr 6 <> 0b10 then raise (Malformed (st.s,st.i));
if c lsr 6 <> 0b10 then malformed st;
(* overlong encoding? *)
if j=1 && overlong<>0 && (c land 0b111111) < overlong then malformed st;
(* except for first, each char gives 6 bits *)
let next = (acc lsl 6) lor (c land 0b111111) in
if j = n_bytes then (
@ -54,7 +59,7 @@ let next_ (type a) (st : Dec.t) ~(yield:uchar -> a) ~(stop:unit -> a) () : a =
st.i <- st.i + j + 1; (* +1 for first char *)
yield (Uchar.unsafe_of_int next)
) else (
raise (Malformed (st.s,st.i))
malformed st;
)
) else (
aux (j+1) next
@ -66,7 +71,7 @@ let next_ (type a) (st : Dec.t) ~(yield:uchar -> a) ~(stop:unit -> a) () : a =
aux 1 acc (* start with j=1, first char is already proccessed! *)
) else (
(* char is truncated *)
raise (Malformed (st.s,st.i))
malformed st;
)
in
if st.i >= st.len then (
@ -80,11 +85,18 @@ let next_ (type a) (st : Dec.t) ~(yield:uchar -> a) ~(stop:unit -> a) () : a =
st.i <- 1 + st.i;
yield (Uchar.of_int @@ Char.code c) (* 0xxxxxxx *)
| '\194' .. '\223' -> read_multi 1 ((Char.code c) land 0b11111) (* 110yyyyy *)
| '\224' .. '\239' -> read_multi 2 ((Char.code c) land 0b1111) (* 1110zzzz *)
| '\240' .. '\244' -> read_multi 3 ((Char.code c) land 0b111) (* 11110uuu *)
| '\225' .. '\239' -> read_multi 2 ((Char.code c) land 0b1111) (* 1110zzzz *)
| '\241' .. '\244' -> read_multi 3 ((Char.code c) land 0b111) (* 11110uuu *)
| '\224' ->
(* overlong: if next byte is < than [0b001000000] then the char
would fit in 1 byte *)
read_multi ~overlong:0b00100000 2 ((Char.code c) land 0b1111) (* 1110zzzz *)
| '\240' ->
(* overlong: if next byte is < than [0b000100000] then the char
would fit in 2 bytes *)
read_multi ~overlong:0b00010000 3 ((Char.code c) land 0b111) (* 11110uuu *)
| '\128' .. '\193' (* 192,193 are forbidden *)
| '\245' .. '\255' ->
raise (Malformed (st.s,st.i))
| '\245' .. '\255' -> malformed st;
)
let to_gen ?(idx=0) str : uchar gen =
@ -248,6 +260,9 @@ let uutf_to_seq s f =
(*$T
not (is_valid "\192\181")
not (is_valid "\193\143")
not (is_valid "\224\151\167")
not (is_valid "\224\137\165")
is_valid "\240\151\189\163"
*)
(*$QR & ~long_factor:40
@ -272,7 +287,7 @@ let uutf_to_seq s f =
(* compare with uutf *)
(*$QR & ~long_factor:40 ~count:10_000
(*$QR & ~long_factor:40 ~count:100_000
Q.string (fun s ->
let v1 = is_valid s in
let v2 = uutf_is_valid s in
@ -281,7 +296,7 @@ let uutf_to_seq s f =
)
*)
(*$QR & ~long_factor:40 ~count:10_000
(*$QR & ~long_factor:40 ~count:100_000
Q.string (fun s ->
Q.assume (is_valid s && uutf_is_valid s);
let pp s = Q.Print.(list pp_uchar) s in