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Merge pull request #235 from hannesm/no-handcrafted-asn1
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tests, mirage-crypto-ec: use asn1-combinators again
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@hannesm
hannesm authored Jun 9, 2024
2 parents 448ad35 + 0bfa81d commit 8ac86fa
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Showing 3 changed files with 27 additions and 131 deletions.
1 change: 1 addition & 0 deletions mirage-crypto-ec.opam
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Expand Up @@ -36,6 +36,7 @@ depends: [
"ppx_deriving_yojson" {with-test}
"ppx_deriving" {with-test}
"yojson" {with-test & >= "1.6.0"}
"asn1-combinators" {with-test & >= "0.3.1"}
]
conflicts: [
"ocaml-freestanding"
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2 changes: 1 addition & 1 deletion tests/dune
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Expand Up @@ -57,7 +57,7 @@
ecdsa_secp384r1_sha384_test.json ecdsa_secp384r1_sha512_test.json
ecdh_secp521r1_test.json ecdsa_secp521r1_sha512_test.json
x25519_test.json eddsa_test.json)
(libraries alcotest mirage-crypto-ec wycheproof digestif)
(libraries alcotest mirage-crypto-ec wycheproof digestif asn1-combinators)
(package mirage-crypto-ec))

(tests
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155 changes: 25 additions & 130 deletions tests/test_ec_wycheproof.ml
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Expand Up @@ -15,138 +15,33 @@ let string_get_uint8 d off =
let hex = Alcotest.testable Wycheproof.pp_hex Wycheproof.equal_hex

module Asn = struct
(* This is a handcrafted asn1 parser, sufficient for the wycheproof tests.
The underlying reason is to avoid a dependency on asn1-grammars and
mirage-crypto-pk (which depends on gmp and zarith, and are cumbersome to
build on windows with CL.EXE). *)

let guard p e = if p then Ok () else Error e

let decode_len start_off buf =
let len = string_get_uint8 buf start_off in
if len >= 0x80 then
let bytes = len - 0x80 in
let rec g acc off =
if off = bytes then
Ok (acc, bytes + start_off + 1)
else
let this = string_get_uint8 buf (start_off + 1 + off) in
let* () = guard (off = 0 && this >= 0x80) "badly encoded length" in
let acc' = acc lsl 8 + this in
let* () = guard (acc <= acc') "decode_len overflow in acc" in
g (acc lsl 8 + string_get_uint8 buf (start_off + 1 + off)) (succ off)
in
g 0 0
else
Ok (len, start_off + 1)

let decode_seq data =
let* () = guard (String.length data > 2) "decode_seq: data too short" in
let tag = string_get_uint8 data 0 in
let* () = guard (tag = 0x30) "decode_seq: bad tag (should be 0x30)" in
let* len, off = decode_len 1 data in
let* () = guard (String.length data - off >= len) "decode_seq: too short" in
Ok (String.sub data off len,
if String.length data - off > len then
Some (String.sub data (off + len) (String.length data - len - off))
else
None)

let decode_2_oid data =
let decode_one off =
let tag = string_get_uint8 data off in
let* () = guard (tag = 0x06) "decode_oid: bad tag (should be 0x06)" in
let len = string_get_uint8 data (off + 1) in
let* () = guard (String.length data - 2 - off >= len) "decode_oid: data too short" in
Ok (String.sub data (off + 2) len, off + 2 + len)
in
let* first, off = decode_one 0 in
let* second, off = decode_one off in
let* () = guard (off = String.length data) "decode_oid: leftover data" in
Ok (first, second)

let decode_bit_string data =
let tag = string_get_uint8 data 0 in
let* () = guard (tag = 0x03) "decode_bit_string: bad tag (expected 0x03)" in
let* len, off = decode_len 1 data in
let* () = guard (String.length data - off = len) "decode_bit_string: leftover or too short data" in
let unused = string_get_uint8 data off in
let* () = guard (unused = 0) "unused is not 0" in
Ok (String.sub data (off + 1) (len - 1))

let decode_int_pair data =
let decode_int off =
let* () = guard (String.length data - off > 2) "decode_int: data too short" in
let tag = string_get_uint8 data off in
let* () = guard (tag = 0x02) "decode_int: bad tag (should be 0x02)" in
let len = string_get_uint8 data (off + 1) in
let* () = guard (String.length data - off - 2 >= len) "decode_int: too short" in
let fix_one = if string_get_uint8 data (off + 2) = 0x00 then 1 else 0 in
let* () = guard (string_get_uint8 data (off + 2) land 0x80 = 0) "decode_int: negative number" in
let* () =
if String.length data > off + 3 && fix_one = 1 then
guard (string_get_uint8 data (off + 3) <> 0x00) "decode_int: leading extra 0 byte"
else
Ok ()
in
Ok (String.sub data (fix_one + off + 2) (len - fix_one), off + len + 2)
in
let* first, off = decode_int 0 in
let* second, off = decode_int off in
let* () = guard (off = String.length data) "decode_int: leftover data" in
Ok (first, second)

let encode_oid = function
| first :: second :: rt ->
let oct1 = 40 * first + second in
let octs = concat_map (fun x ->
let fst = x / 16384
and snd = x / 128
and thr = x mod 128
in
assert (fst < 128);
(if fst > 0 then [ 128 (* set high bit *) + fst ] else []) @
(if snd > 0 then [ 128 + snd ] else []) @
[ thr ])
rt
in
String.init (1 + List.length octs) (function
| 0 -> char_of_int oct1
| n -> char_of_int (List.nth octs (pred n)))
| _ -> assert false

let parse_point curve s =
let ec_public_key = encode_oid [ 1 ; 2 ; 840; 10045; 2; 1 ] in
let prime_oid = encode_oid (match curve with
| "secp256r1" -> [ 1 ; 2 ; 840; 10045; 3; 1; 7 ]
| "secp384r1" -> [ 1 ; 3 ; 132; 0; 34 ]
| "secp521r1" -> [ 1 ; 3 ; 132; 0; 35 ]
| _ -> assert false)
let seq2 a b = Asn.S.(sequence2 (required a) (required b)) in
let term = Asn.S.(seq2 (seq2 oid oid) bit_string_octets) in
let ec_public_key = Asn.OID.(base 1 2 <|| [ 840; 10045; 2; 1 ]) in
let prime_oid = match curve with
| "secp256r1" -> Asn.OID.(base 1 2 <|| [ 840; 10045; 3; 1; 7 ])
| "secp384r1" -> Asn.OID.(base 1 3 <|| [ 132; 0; 34 ])
| "secp521r1" -> Asn.OID.(base 1 3 <|| [ 132; 0; 35 ])
| _ -> assert false
in
let* r = decode_seq s in
match r with
| _data, Some _ -> Error "expected no leftover"
| data, None ->
let* r = decode_seq data in
match r with
| _oids, None -> Error "expected some data"
| oids, Some data ->
let* oid1, oid2 = decode_2_oid oids in
let* data = decode_bit_string data in
if not (String.equal oid1 ec_public_key) then
Error "ASN1: wrong oid 1"
else if not (String.equal oid2 prime_oid) then
Error "ASN1: wrong oid 2"
else
Ok data

let parse_signature s =
let* r = decode_seq s in
match r with
| _data, Some _ -> Error "expected no leftover"
| data, None ->
let* r, s = decode_int_pair data in
Ok (r, s)
match Asn.decode (Asn.codec Asn.ber term) s with
| Error _ -> Error "ASN1 parse error"
| Ok (((oid1, oid2), data), rest) ->
if String.length rest <> 0 then Error "ASN1 leftover"
else if not (Asn.OID.equal oid1 ec_public_key) then
Error "ASN1: wrong oid 1"
else if not (Asn.OID.equal oid2 prime_oid) then Error "ASN1: wrong oid 2"
else Ok data

let parse_signature cs =
let asn = Asn.S.(sequence2 (required unsigned_integer) (required unsigned_integer)) in
match Asn.(decode (codec der asn) cs) with
| Error _ -> Error "ASN1 parse error"
| Ok (r_s, rest) ->
if String.length rest <> 0 then Error "ASN1 leftover"
else
Ok r_s
end

let to_string_result ~pp_error = function
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