albatross_log: skip unknown entries

This commit is contained in:
Hannes Mehnert 2020-07-29 15:12:35 +02:00
parent 1b1164166b
commit a5265c9a44

View file

@ -46,32 +46,7 @@
that decoder on the sub-buffer. The following implements this.
let seq_hd cs =
(* we assume a ASN.1 DER/BER encoded sequence starting in cs:
- 0x30
- length (definite length field - not 0x80)
- <data> (of length length)
retrieve data to decode only the first element: <data>, which is cs offset
(at least 2, 0x30 0xLL), and length encoded before
*)
guard (Cstruct.len cs > 2) (`Msg "too short") >>= fun () ->
guard (Cstruct.get_uint8 cs 0 = 0x30) (`Msg "not a sequence") >>= fun () ->
let l1 = Cstruct.get_uint8 cs 1 in
(if l1 < 0x80 then
Ok (2, l1)
else if l1 = 0x80 then
Error (`Msg "indefinite length")
else
let octets = l1 land 0x7F in
guard (Cstruct.len cs > octets + 2) (`Msg "data too short") >>= fun () ->
let rec go off acc =
if off = octets then
Ok (2 + octets, acc)
else
go (succ off) (Cstruct.get_uint8 cs (off + 2) + acc lsl 8)
in
go 0 0) >>= fun (off, l) ->
guard (Cstruct.len cs >= l + off) (`Msg "buffer too small") >>= fun () ->
decode_seq_len cs >>= fun (l, off) ->
Ok (Cstruct.sub cs off l)
let decode_version cs =
@ -93,6 +68,32 @@ open Rresult.R.Infix
let guard p err = if p then Ok () else Error err
let decode_seq_len cs =
(* we assume a ASN.1 DER/BER encoded sequence starting in cs:
- 0x30
- length (definite length field - not 0x80)
- <data> (of length length)
*)
guard (Cstruct.len cs > 2) (`Msg "buffer too short") >>= fun () ->
guard (Cstruct.get_uint8 cs 0 = 0x30) (`Msg "not a sequence") >>= fun () ->
let l1 = Cstruct.get_uint8 cs 1 in
(if l1 < 0x80 then
Ok (2, l1)
else if l1 = 0x80 then
Error (`Msg "indefinite length")
else
let octets = l1 land 0x7F in
guard (Cstruct.len cs > octets + 2) (`Msg "data too short") >>= fun () ->
let rec go off acc =
if off = octets then
Ok (2 + octets, acc)
else
go (succ off) (Cstruct.get_uint8 cs (off + 2) + acc lsl 8)
in
go 0 0) >>= fun (off, l) ->
guard (Cstruct.len cs >= l + off) (`Msg "buffer too small") >>= fun () ->
Ok (l, off)
let decode_strict codec cs =
match Asn.decode codec cs with
| Ok (a, cs) ->
@ -711,6 +712,10 @@ let log_disk_of_cstruct, log_disk_to_cstruct =
let log_to_disk entry = log_disk_to_cstruct (current, entry)
let skip_seq cs =
decode_seq_len cs >>= fun (l, off) ->
Ok (Cstruct.shift cs (l + off))
let logs_of_disk buf =
let rec next acc buf =
match log_disk_of_cstruct buf with
@ -719,7 +724,9 @@ let logs_of_disk buf =
next (entry :: acc) cs
| Error (`Parse msg) ->
Logs.warn (fun m -> m "parse error %s while parsing log" msg) ;
acc (* ignore *)
match skip_seq buf with
| Ok cs' -> next acc cs'
| Error _ -> acc (* ignore *)
in
next [] buf