gazagnaire.org
HomeKit Accessory Protocol (HAP) for OCaml
fix(hap): make TLV decoder robust to truncated input
- Tlv.decode now stops gracefully on truncated data instead of raising
- Fuzz test for multi roundtrip deduplicates keys (last-write-wins)
+16
-10
+10
-6
fuzz/fuzz_hap.ml
+10
-6
fuzz/fuzz_hap.ml
···
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(* TLV roundtrip: encode(decode(x)) should produce valid TLV *)
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let test_tlv_decode_encode input =
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-
(* Decoding arbitrary bytes should not crash *)
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let decoded = Hap.Tlv.decode input in
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-
(* Re-encoding should produce valid TLV *)
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let _ = Hap.Tlv.encode decoded in
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check true
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···
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let retrieved = Hap.Tlv.get typ decoded in
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check_eq ~pp:Format.pp_print_bool (retrieved = Some value) true
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-
(* Multiple TLV entries roundtrip *)
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+
(* Multiple TLV entries roundtrip - deduplicate types since later adds overwrite *)
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let test_tlv_multi_roundtrip entries =
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(* Keep only the last value for each type, matching add semantics *)
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+
let deduped =
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+
List.fold_left
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(fun acc (typ, value) ->
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List.filter (fun (t, _) -> t <> typ) acc @ [ (typ, value) ])
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+
[] entries
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+
in
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let tlv =
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List.fold_left
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(fun acc (typ, value) -> Hap.Tlv.add typ value acc)
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-
Hap.Tlv.empty entries
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+
Hap.Tlv.empty deduped
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in
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let encoded = Hap.Tlv.encode tlv in
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let decoded = Hap.Tlv.decode encoded in
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-
(* Check that all entries can be retrieved *)
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List.iter
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(fun (typ, value) ->
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let retrieved = Hap.Tlv.get typ decoded in
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check_eq ~pp:Format.pp_print_bool (retrieved = Some value) true)
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-
entries
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+
deduped
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(* Category name should never crash *)
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let test_category_name code =
+4
-3
lib/hap.ml
+4
-3
lib/hap.ml
···
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(List.rev tlv);
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Buffer.contents buf
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-
(* Decode TLV from bytes - concatenate split values *)
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+
(* Decode TLV from bytes - concatenate split values.
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Stops gracefully on truncated input, returning entries parsed so far. *)
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let decode data =
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let len = String.length data in
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let rec parse offset acc =
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if offset >= len then List.rev acc
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-
else if offset + 2 > len then failwith "Invalid TLV: truncated"
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+
else if offset + 2 > len then List.rev acc
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else begin
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let typ = Char.code data.[offset] in
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let vlen = Char.code data.[offset + 1] in
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if offset + 2 + vlen > len then failwith "Invalid TLV: value truncated"
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if offset + 2 + vlen > len then List.rev acc
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else begin
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let value = String.sub data (offset + 2) vlen in
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(* Concatenate with previous if same type *)
+2
-1
lib/hap.mli
+2
-1
lib/hap.mli
···
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val decode : string -> t
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(** [decode s] deserializes bytes into a TLV container. Consecutive same-type
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chunks are concatenated. Raises [Failure] on malformed input. *)
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chunks are concatenated. Truncated input is handled gracefully by
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returning entries parsed so far. *)
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end
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(** TLV type codes. *)