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Diffstat (limited to 'sid.ml')
| -rw-r--r-- | sid.ml | 199 |
1 files changed, 199 insertions, 0 deletions
@@ -0,0 +1,199 @@ +module U64 = Stdint.Uint64 +module U32 = Stdint.Uint32 + +type sid = + { sid_ident_auth : U64.t (* 6 B *) + ; sid_sub_auths : U32.t array (* max. 15 × *) + } +and sub_auths = U32.t array + +let sub_auth_max = 15 + +let sizeof_sub_auth = 4 + +let create_unsafe sa ia = + { sid_ident_auth = ia + ; sid_sub_auths = sa } + +(* There isn’t much to validate to begin with except for the hard cap on + the number of subauths. *) +let create ?(sa=[||]) ia = + if Array.length sa > max_subauth_count then None else + Some (create_unsafe sa ia) + +exception Nope + +let equal_sub_auths saa sab = + try + Array.iter2 + (fun saa sab -> if U32.compare saa sab <> 0 then raise Nope) + saa sab; + true + with Nope -> false + +let equal a b = + U64.compare a.sid_ident_auth b.sid_ident_auth = 0 + && Array.length a.sid_sub_auths = Array.length b.sid_sub_auths + && equal_sub_auths a.sid_sub_auths b.sid_sub_auths + +module type Xtract = sig + type t + val nth_byte : t -> int -> int +end + +module MkExtract (INTTYPE : Stdint.Int) = struct + type t = INTTYPE.t + + let ilsr = INTTYPE.shift_left + let iland = INTTYPE.logand + let ixff = INTTYPE.of_string "255" + + let nth_byte n i = + (ilsr n i) |> iland ixff |> INTTYPE.to_int +end + +module U32Extract = MkExtract (U32) +module U64Extract = MkExtract (U64) + +module StringFmt = struct + + let expect_char s c p = + if s.[p] = c then () else + raise + (Invalid_argument + (Printf.sprintf + "Invalid SID [%s]: expected ‘%c’ at position %d, found ‘%c’" + s c p s.[p])) + + let is_digit c = '0' <= c && c <= '9' + + let read_decimal_string f s p = + let n = String.length s in + assert (p < n); + let p' = ref p in + let b = Buffer.create 16 in + while !p' < n && is_digit s.[!p'] do + Buffer.add_char b s.[!p']; + incr p' + done; + let nb = Buffer.length b in + if nb = 0 then + raise (Invalid_argument + (Printf.sprintf + "Invalid SID [%s]: expected decimal at position %d" s p)) + else + p + nb, + f (Buffer.contents b) + + let read_decimal_u64 = read_decimal_string U64.of_string + let read_decimal_u32 = read_decimal_string U32.of_string + + (* + * The spec ([MS-DTYP]): + * + * 2.4.2.1: SID= "S-1-" IdentifierAuthority 1*SubAuthority + *) + let decode s = + let n = String.length s in + if n <= 4 then + raise + (Invalid_argument + (Printf.sprintf + "Invalid SID: ‘%s’ too short to be a SID in string format" s)) + else + expect_char s 'S' 0; + expect_char s '-' 1; + expect_char s '1' 2; + expect_char s '-' 3; + let p = 4 in + let p, ia = read_decimal_u64 s p in + let sa = ref [] and p' = ref p in + while !p' < n && List.length !sa < sub_auth_max do + expect_char s '-' !p'; + let np, d = read_decimal_u32 s (!p' + 1) in + sa := d :: !sa; + p' := np + done; + { sid_ident_auth = ia + ; sid_sub_auths = Array.of_list (List.rev !sa) + } + + let from_string_res s = + try Ok (decode s) with Invalid_argument msg -> Error msg + + let from_string_opt s = + try Some (decode s) with Invalid_argument _ -> None + + let fmt_ident_auth b ia = + Buffer.add_string b (U64.to_string ia) + + let fmt_sub_auths b sas = + Array.iter + (fun sa -> + Buffer.add_char b '-'; + Buffer.add_string b (U32.to_string sa)) + sas + + let encode s = + let b = Buffer.create 16 in + Buffer.add_string b "S-1-"; + fmt_ident_auth b s.sid_ident_auth; + fmt_sub_auths b s.sid_sub_auths; + Buffer.contents b + +end (* [module StringFmt] *) + +module PacketRep = struct (* [MS-DTYP] 2.4.22 *) + + let encode s = + let nsa = Array.length s.sid_sub_auths in + let l = 8 + nsa * sizeof_sub_auth in + let b = Buffer.create l in + + assert (0 <= nsa && nsa <= 15); + + let pushbyte c = char_of_int c |> Buffer.add_char b in + + pushbyte 1; + pushbyte nsa; + + let getia n = + pushbyte (U64.to_int (U64.shift_right s.sid_ident_auth n) land 0xff) + in (* big endian!, cf. [MS-DTYP] 2.4.1.1 *) + getia 5; getia 4; getia 3; getia 2; getia 1; getia 0; + + let getsa sa n = pushbyte (U32.to_int (U32.shift_right sa n) land 0xff) in + Array.iter + (fun sa -> getsa sa 0; getsa sa 1; getsa sa 2; getsa sa 3) + s.sid_sub_auths; + Bytes.unsafe_of_string (Buffer.contents b) + +end (* [module PacketRep] *) + +module WellKnown = struct + (* + * see also + * https://docs.microsoft.com/en-us/windows/desktop/secauthz/well-known-sids + *) + + let null = create_unsafe [| U32.zero |] U64.zero + let everyone = create_unsafe [| U32.zero |] U64.one + let world = everyone + let local = create_unsafe [| U32.zero |] (U64.of_int 2) + let creator_owner_id = create_unsafe [| U32.zero |] (U64.of_int 3) + let creator_group_id = create_unsafe [| U32.one |] (U64.of_int 3) + let elite = create_unsafe [| U32.of_int 3 ; U32.of_int 3; U32.of_int 7 |] U64.one + + module Prefix = struct + let security_null_sid_authority ?(sa=[||]) () = create ~sa (U64.of_int 0) + let security_world_sid_authority ?(sa=[||]) () = create ~sa (U64.of_int 1) + let security_local_sid_authority ?(sa=[||]) () = create ~sa (U64.of_int 2) + let security_creator_sid_authority ?(sa=[||]) () = create ~sa (U64.of_int 3) + let security_nt_authority ?(sa=[||]) () = create ~sa (U64.of_int 5) + end +end + +let of_string = StringFmt.decode +let to_string = StringFmt.encode + +type t = sid |