sc_rollup_inbox_repr.ml
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(* *)
(* Open Source License *)
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(**
A Merkelized inbox represents a list of messages. This list
is decomposed into sublists of messages, one for each non-empty Tezos
level greater than the level of the Last Cemented Commitment (LCC).
This module is designed to:
1. provide a space-efficient representation for proofs of inbox
inclusions (only for inboxes obtained at the end of block
validation) ;
2. offer an efficient function to add a new batch of messages in the
inbox at the current level.
To solve (1), we use a proof tree H which is implemented by a sparse
merkelized skip list allowing for compact inclusion proofs (See
{!skip_list_repr.ml}).
To solve (2), we maintain a separate proof tree C witnessing the
contents of messages of the current level.
The protocol maintains the hashes of the head of H, and the root hash of C.
The rollup node needs to maintain a full representation for C and a
partial representation for H back to the level of the LCC.
*)
type error += Invalid_level_add_messages of Raw_level_repr.t
type error += Inbox_proof_error of string
type error += Tried_to_add_zero_messages
type error += Empty_upper_level of Raw_level_repr.t
let () =
let open Data_encoding in
register_error_kind
`Permanent
~id:"sc_rollup_inbox.invalid_level_add_messages"
~title:"Internal error: Trying to add a message to an inbox from the past"
~description:
"An inbox can only accept messages for its current level or for the next \
levels."
(obj1 (req "level" Raw_level_repr.encoding))
(function Invalid_level_add_messages level -> Some level | _ -> None)
(fun level -> Invalid_level_add_messages level) ;
register_error_kind
`Permanent
~id:"sc_rollup_inbox.inbox_proof_error"
~title:
"Internal error: error occurred during proof production or validation"
~description:"An inbox proof error."
~pp:(fun ppf e -> Format.fprintf ppf "Inbox proof error: %s" e)
(obj1 (req "error" string))
(function Inbox_proof_error e -> Some e | _ -> None)
(fun e -> Inbox_proof_error e) ;
register_error_kind
`Permanent
~id:"sc_rollup_inbox.add_zero_messages"
~title:"Internal error: trying to add zero messages"
~description:
"Message adding functions must be called with a positive number of \
messages"
~pp:(fun ppf _ -> Format.fprintf ppf "Tried to add zero messages")
empty
(function Tried_to_add_zero_messages -> Some () | _ -> None)
(fun () -> Tried_to_add_zero_messages) ;
register_error_kind
`Permanent
~id:"sc_rollup_inbox.empty_upper_level"
~title:"Internal error: No payload found in a [Level_crossing] proof"
~description:
"Failed to find any message in the [upper_level] of a [Level_crossing] \
proof"
(obj1 (req "upper_level" Raw_level_repr.encoding))
(function Empty_upper_level upper_level -> Some upper_level | _ -> None)
(fun upper_level -> Empty_upper_level upper_level)
module Int64_map = Map.Make (Int64)
(* 32 *)
let hash_prefix = "\003\250\174\238\208" (* scib1(55) *)
module Hash = struct
let prefix = "scib1"
let encoded_size = 55
module H =
Blake2B.Make
(Base58)
(struct
let name = "inbox_hash"
let title = "The hash of an inbox of a smart contract rollup"
let b58check_prefix = hash_prefix
(* defaults to 32 *)
let size = None
end)
include H
let () = Base58.check_encoded_prefix b58check_encoding prefix encoded_size
let of_context_hash context_hash =
Context_hash.to_bytes context_hash |> of_bytes_exn
let to_context_hash hash = to_bytes hash |> Context_hash.of_bytes_exn
include Path_encoding.Make_hex (H)
end
module Skip_list_parameters = struct
let basis = 2
end
module Skip_list = Skip_list_repr.Make (Skip_list_parameters)
let hash_skip_list_cell cell =
let current_level_hash = Skip_list.content cell in
let back_pointers_hashes = Skip_list.back_pointers cell in
Hash.to_bytes current_level_hash
:: List.map Hash.to_bytes back_pointers_hashes
|> Hash.hash_bytes
module V1 = struct
type history_proof = (Hash.t, Hash.t) Skip_list.cell
let equal_history_proof = Skip_list.equal Hash.equal Hash.equal
let history_proof_encoding : history_proof Data_encoding.t =
Skip_list.encoding Hash.encoding Hash.encoding
let pp_history_proof fmt history =
let history_hash = hash_skip_list_cell history in
Format.fprintf
fmt
"@[hash : %a@;%a@]"
Hash.pp
history_hash
(Skip_list.pp ~pp_content:Hash.pp ~pp_ptr:Hash.pp)
history
(** Construct an inbox [history] with a given [capacity]. If you
are running a rollup node, [capacity] needs to be large enough to
remember any levels for which you may need to produce proofs. *)
module History =
Bounded_history_repr.Make
(struct
let name = "inbox_history"
end)
(Hash)
(struct
type t = history_proof
let pp = pp_history_proof
let equal = equal_history_proof
let encoding = history_proof_encoding
end)
(*
At a given level, an inbox is composed of metadata of type [t] and
[current_level], a [tree] representing the messages of the current level
(held by the [Raw_context.t] in the protocol).
The metadata contains :
- [rollup] : the address of the rollup ;
- [level] : the inbox level ;
- [message_counter] : the number of messages in the [level]'s inbox ;
the number of messages that have not been consumed by a commitment cementing ;
- [nb_messages_in_commitment_period] :
the number of messages during the commitment period ;
- [starting_level_of_current_commitment_period] :
the level marking the beginning of the current commitment period ;
- [current_level_hash] : the root hash of [current_level] ;
- [old_levels_messages] : a witness of the inbox history.
When new messages are appended to the current level inbox, the
metadata stored in the context may be related to an older level.
In that situation, an archival process is applied to the metadata.
This process saves the [current_level_hash] in the
[old_levels_messages] and empties [current_level]. It then
initialises a new level tree for the new messages---note that any
intermediate levels are simply skipped. See
{!Make_hashing_scheme.archive_if_needed} for details.
*)
type t = {
rollup : Sc_rollup_repr.t;
level : Raw_level_repr.t;
nb_messages_in_commitment_period : int64;
starting_level_of_current_commitment_period : Raw_level_repr.t;
message_counter : Z.t;
(* Lazy to avoid hashing O(n^2) time in [add_messages] *)
current_level_hash : unit -> Hash.t;
old_levels_messages : history_proof;
}
let equal inbox1 inbox2 =
(* To be robust to addition of fields in [t]. *)
let {
rollup;
level;
nb_messages_in_commitment_period;
starting_level_of_current_commitment_period;
message_counter;
current_level_hash;
old_levels_messages;
} =
inbox1
in
Sc_rollup_repr.Address.equal rollup inbox2.rollup
&& Raw_level_repr.equal level inbox2.level
&& Compare.Int64.(
equal
nb_messages_in_commitment_period
inbox2.nb_messages_in_commitment_period)
&& Raw_level_repr.(
equal
starting_level_of_current_commitment_period
inbox2.starting_level_of_current_commitment_period)
&& Z.equal message_counter inbox2.message_counter
&& Hash.equal (current_level_hash ()) (inbox2.current_level_hash ())
&& equal_history_proof old_levels_messages inbox2.old_levels_messages
let pp fmt
{
rollup;
level;
nb_messages_in_commitment_period;
starting_level_of_current_commitment_period;
message_counter;
current_level_hash;
old_levels_messages;
} =
Format.fprintf
fmt
"@[<hov 2>{ rollup = %a@;\
level = %a@;\
current messages hash = %a@;\
nb_messages_in_commitment_period = %s@;\
starting_level_of_current_commitment_period = %a@;\
message_counter = %a@;\
old_levels_messages = %a@;\
}@]"
Sc_rollup_repr.Address.pp
rollup
Raw_level_repr.pp
level
Hash.pp
(current_level_hash ())
(Int64.to_string nb_messages_in_commitment_period)
Raw_level_repr.pp
starting_level_of_current_commitment_period
Z.pp_print
message_counter
pp_history_proof
old_levels_messages
let inbox_level inbox = inbox.level
let old_levels_messages inbox = inbox.old_levels_messages
let current_level_hash inbox = inbox.current_level_hash ()
let old_levels_messages_encoding =
Skip_list.encoding Hash.encoding Hash.encoding
let encoding =
Data_encoding.(
conv
(fun {
rollup;
message_counter;
nb_messages_in_commitment_period;
starting_level_of_current_commitment_period;
level;
current_level_hash;
old_levels_messages;
} ->
( rollup,
message_counter,
nb_messages_in_commitment_period,
starting_level_of_current_commitment_period,
level,
current_level_hash (),
old_levels_messages ))
(fun ( rollup,
message_counter,
nb_messages_in_commitment_period,
starting_level_of_current_commitment_period,
level,
current_level_hash,
old_levels_messages ) ->
{
rollup;
message_counter;
nb_messages_in_commitment_period;
starting_level_of_current_commitment_period;
level;
current_level_hash = (fun () -> current_level_hash);
old_levels_messages;
})
(obj7
(req "rollup" Sc_rollup_repr.encoding)
(req "message_counter" n)
(req "nb_messages_in_commitment_period" int64)
(req
"starting_level_of_current_commitment_period"
Raw_level_repr.encoding)
(req "level" Raw_level_repr.encoding)
(req "current_level_hash" Hash.encoding)
(req "old_levels_messages" old_levels_messages_encoding)))
let number_of_messages_during_commitment_period inbox =
inbox.nb_messages_in_commitment_period
let start_new_commitment_period inbox level =
{
inbox with
starting_level_of_current_commitment_period = level;
nb_messages_in_commitment_period = 0L;
}
let starting_level_of_current_commitment_period inbox =
inbox.starting_level_of_current_commitment_period
let refresh_commitment_period ~commitment_period ~level inbox =
let start = starting_level_of_current_commitment_period inbox in
let freshness = Raw_level_repr.diff level start in
let open Int32 in
let open Compare.Int32 in
if freshness >= commitment_period then (
let nb_periods =
to_int ((mul (div freshness commitment_period)) commitment_period)
in
let new_starting_level = Raw_level_repr.(add start nb_periods) in
assert (Raw_level_repr.(new_starting_level <= level)) ;
assert (
rem (Raw_level_repr.diff new_starting_level start) commitment_period
= 0l) ;
start_new_commitment_period inbox new_starting_level)
else inbox
end
type versioned = V1 of V1.t
let versioned_encoding =
let open Data_encoding in
union
[
case
~title:"V1"
(Tag 0)
V1.encoding
(function V1 inbox -> Some inbox)
(fun inbox -> V1 inbox);
]
include V1
let of_versioned = function V1 inbox -> inbox [@@inline]
let to_versioned inbox = V1 inbox [@@inline]
let key_of_message ix =
["message"; Data_encoding.Binary.to_string_exn Data_encoding.n ix]
let level_key = ["level"]
let number_of_messages_key = ["number_of_messages"]
type serialized_proof = bytes
let serialized_proof_encoding = Data_encoding.bytes
module type Merkelized_operations = sig
type inbox_context
type tree
val hash_level_tree : tree -> Hash.t
val new_level_tree : inbox_context -> Raw_level_repr.t -> tree Lwt.t
val add_messages :
inbox_context ->
History.t ->
t ->
Raw_level_repr.t ->
Sc_rollup_inbox_message_repr.serialized list ->
tree option ->
(tree * History.t * t) tzresult Lwt.t
val add_messages_no_history :
inbox_context ->
t ->
Raw_level_repr.t ->
Sc_rollup_inbox_message_repr.serialized list ->
tree option ->
(tree * t) tzresult Lwt.t
val get_message_payload :
tree -> Z.t -> Sc_rollup_inbox_message_repr.serialized option Lwt.t
val form_history_proof :
inbox_context ->
History.t ->
t ->
tree option ->
(History.t * history_proof) tzresult Lwt.t
val take_snapshot : t -> history_proof
type inclusion_proof
val inclusion_proof_encoding : inclusion_proof Data_encoding.t
val pp_inclusion_proof : Format.formatter -> inclusion_proof -> unit
val number_of_proof_steps : inclusion_proof -> int
val verify_inclusion_proof :
inclusion_proof -> history_proof -> history_proof -> bool
type proof
val pp_proof : Format.formatter -> proof -> unit
val to_serialized_proof : proof -> serialized_proof
val of_serialized_proof : serialized_proof -> proof option
val verify_proof :
Raw_level_repr.t * Z.t ->
history_proof ->
proof ->
Sc_rollup_PVM_sig.inbox_message option tzresult Lwt.t
val produce_proof :
inbox_context ->
History.t ->
history_proof ->
Raw_level_repr.t * Z.t ->
(proof * Sc_rollup_PVM_sig.inbox_message option) tzresult Lwt.t
val empty : inbox_context -> Sc_rollup_repr.t -> Raw_level_repr.t -> t Lwt.t
module Internal_for_tests : sig
val eq_tree : tree -> tree -> bool
val produce_inclusion_proof :
History.t ->
history_proof ->
history_proof ->
inclusion_proof option tzresult
val serialized_proof_of_string : string -> serialized_proof
end
end
module type P = sig
module Tree : Context.TREE with type key = string list and type value = bytes
type t = Tree.t
type tree = Tree.tree
val commit_tree : Tree.t -> string list -> Tree.tree -> unit Lwt.t
val lookup_tree : Tree.t -> Hash.t -> tree option Lwt.t
type proof
val proof_encoding : proof Data_encoding.t
val proof_before : proof -> Hash.t
val verify_proof :
proof -> (tree -> (tree * 'a) Lwt.t) -> (tree * 'a) option Lwt.t
val produce_proof :
Tree.t -> tree -> (tree -> (tree * 'a) Lwt.t) -> (proof * 'a) option Lwt.t
end
module Make_hashing_scheme (P : P) :
Merkelized_operations with type tree = P.tree and type inbox_context = P.t =
struct
module Tree = P.Tree
type inbox_context = P.t
type tree = P.tree
let hash_level_tree level_tree = Hash.of_context_hash (Tree.hash level_tree)
let set_level tree level =
let level_bytes =
Data_encoding.Binary.to_bytes_exn Raw_level_repr.encoding level
in
Tree.add tree level_key level_bytes
let find_level tree =
let open Lwt_syntax in
let+ level_bytes = Tree.(find tree level_key) in
Option.bind
level_bytes
(Data_encoding.Binary.of_bytes_opt Raw_level_repr.encoding)
let set_number_of_messages tree number_of_messages =
let number_of_messages_bytes =
Data_encoding.Binary.to_bytes_exn Data_encoding.n number_of_messages
in
Tree.add tree number_of_messages_key number_of_messages_bytes
(** Initialise the merkle tree for a new level in the inbox. We have
to include the [level] in this structure so that it cannot be
forged by a malicious rollup node. *)
let new_level_tree ctxt level =
let open Lwt_syntax in
let tree = Tree.empty ctxt in
let* tree = set_number_of_messages tree Z.zero in
set_level tree level
let add_message inbox payload level_tree =
let open Lwt_tzresult_syntax in
let message_index = inbox.message_counter in
let message_counter = Z.succ message_index in
let*! level_tree =
Tree.add
level_tree
(key_of_message message_index)
(Bytes.of_string
(payload : Sc_rollup_inbox_message_repr.serialized :> string))
in
let*! level_tree = set_number_of_messages level_tree message_counter in
let nb_messages_in_commitment_period =
Int64.succ inbox.nb_messages_in_commitment_period
in
let inbox =
{
starting_level_of_current_commitment_period =
inbox.starting_level_of_current_commitment_period;
current_level_hash = inbox.current_level_hash;
rollup = inbox.rollup;
level = inbox.level;
old_levels_messages = inbox.old_levels_messages;
message_counter;
nb_messages_in_commitment_period;
}
in
return (level_tree, inbox)
let get_message_payload level_tree message_index =
let open Lwt_syntax in
let key = key_of_message message_index in
let* bytes = Tree.(find level_tree key) in
return
@@ Option.map
(fun bs ->
Sc_rollup_inbox_message_repr.unsafe_of_string (Bytes.to_string bs))
bytes
(** [no_history] creates an empty history with [capacity] set to
zero---this makes the [remember] function a no-op. We want this
behaviour in the protocol because we don't want to store
previous levels of the inbox. *)
let no_history = History.empty ~capacity:0L
let take_snapshot inbox =
let prev_cell = inbox.old_levels_messages in
let prev_cell_ptr = hash_skip_list_cell prev_cell in
Skip_list.next ~prev_cell ~prev_cell_ptr (current_level_hash inbox)
let key_of_level level =
let level_bytes =
Data_encoding.Binary.to_bytes_exn Raw_level_repr.encoding level
in
Bytes.to_string level_bytes
let commit_tree ctxt tree inbox_level =
let key = [key_of_level inbox_level] in
P.commit_tree ctxt key tree
let form_history_proof ctxt history inbox level_tree =
let open Lwt_tzresult_syntax in
let*! () =
let*! tree =
match level_tree with
| Some tree -> Lwt.return tree
| None -> new_level_tree ctxt inbox.level
in
commit_tree ctxt tree inbox.level
in
let prev_cell = inbox.old_levels_messages in
let prev_cell_ptr = hash_skip_list_cell prev_cell in
let*? history = History.remember prev_cell_ptr prev_cell history in
let cell =
Skip_list.next ~prev_cell ~prev_cell_ptr (current_level_hash inbox)
in
return (history, cell)
(** [archive_if_needed ctxt history inbox new_level level_tree]
is responsible for ensuring that the {!add_messages} function
below has a correctly set-up [level_tree] to which to add the
messages. If [new_level] is a higher level than the current inbox,
we create a new inbox level tree at that level in which to start
adding messages, and archive the earlier levels depending on the
[history] parameter's [capacity]. If [level_tree] is [None] (this
happens when the inbox is first created) we similarly create a new
empty level tree with the right [level] key.
This function and {!form_history_proof} are the only places we
begin new level trees. *)
let archive_if_needed ctxt history inbox new_level level_tree =
let open Lwt_result_syntax in
if Raw_level_repr.(inbox.level = new_level) then
match level_tree with
| Some tree -> return (history, inbox, tree)
| None ->
let*! tree = new_level_tree ctxt new_level in
return (history, inbox, tree)
else
let* history, old_levels_messages =
form_history_proof ctxt history inbox level_tree
in
let*! tree = new_level_tree ctxt new_level in
let inbox =
{
starting_level_of_current_commitment_period =
inbox.starting_level_of_current_commitment_period;
current_level_hash = inbox.current_level_hash;
rollup = inbox.rollup;
nb_messages_in_commitment_period =
inbox.nb_messages_in_commitment_period;
old_levels_messages;
level = new_level;
message_counter = Z.zero;
}
in
return (history, inbox, tree)
let add_messages ctxt history inbox level payloads level_tree =
let open Lwt_tzresult_syntax in
let* () =
fail_when
(match payloads with [] -> true | _ -> false)
Tried_to_add_zero_messages
in
let* () =
fail_when
Raw_level_repr.(level < inbox.level)
(Invalid_level_add_messages level)
in
let* history, inbox, level_tree =
archive_if_needed ctxt history inbox level level_tree
in
let* level_tree, inbox =
List.fold_left_es
(fun (level_tree, inbox) payload ->
add_message inbox payload level_tree)
(level_tree, inbox)
payloads
in
let current_level_hash () = hash_level_tree level_tree in
return (level_tree, history, {inbox with current_level_hash})
let add_messages_no_history ctxt inbox level payloads level_tree =
let open Lwt_tzresult_syntax in
let+ level_tree, _, inbox =
add_messages ctxt no_history inbox level payloads level_tree
in
(level_tree, inbox)
(* An [inclusion_proof] is a path in the Merkelized skip list
showing that a given inbox history is a prefix of another one.
This path has a size logarithmic in the difference between the
levels of the two inboxes.
[Irmin.Proof.{tree_proof, stream_proof}] could not be reused here
because there is no obvious encoding of sequences in these data
structures with the same guarantee about the size of proofs. *)
type inclusion_proof = history_proof list
let inclusion_proof_encoding =
let open Data_encoding in
list history_proof_encoding
let pp_inclusion_proof fmt proof =
Format.pp_print_list pp_history_proof fmt proof
let number_of_proof_steps proof = List.length proof
let lift_ptr_path deref ptr_path =
let rec aux accu = function
| [] -> Some (List.rev accu)
| x :: xs -> Option.bind (deref x) @@ fun c -> aux (c :: accu) xs
in
aux [] ptr_path
let verify_inclusion_proof proof a b =
let assoc = List.map (fun c -> (hash_skip_list_cell c, c)) proof in
let path = List.split assoc |> fst in
let deref =
let open Hash.Map in
let map = of_seq (List.to_seq assoc) in
fun ptr -> find_opt ptr map
in
let cell_ptr = hash_skip_list_cell b in
let target_ptr = hash_skip_list_cell a in
Skip_list.valid_back_path
~equal_ptr:Hash.equal
~deref
~cell_ptr
~target_ptr
path
type proof =
(* See the main docstring for this type (in the mli file) for
definitions of the three proof parameters [starting_point],
[message] and [snapshot]. In the below we deconstruct
[starting_point] into [(l, n)] where [l] is a level and [n] is a
message index.
In a [Single_level] proof, [level] is the skip list cell for the
level [l], [inc] is an inclusion proof of [level] into
[snapshot] and [message_proof] is a tree proof showing that
[exists level_tree .
(hash_level_tree level_tree = level.content)
AND (payload_and_level n level_tree = (_, (message, l)))]
Note: in the case that [message] is [None] this shows that
there's no value at the index [n]; in this case we also must
check that [level] equals [snapshot] (otherwise, we'd need a
[Level_crossing] proof instead. *)
| Single_level of {
level : history_proof;
inc : inclusion_proof;
message_proof : P.proof;
}
(* See the main docstring for this type (in the mli file) for
definitions of the three proof parameters [starting_point],
[message] and [snapshot]. In the below we deconstruct
[starting_point] as [(l, n)] where [l] is a level and [n] is a
message index.
In a [Level_crossing] proof, [lower] is the skip list cell for
the level [l] and [upper] must be the skip list cell that comes
immediately after it in [snapshot]. If the inbox has been
constructed correctly using the functions in this module that
will be the next non-empty level in the inbox.
[inc] is an inclusion proof of [upper] into [snapshot].
[upper_level] is the level of [upper].
The tree proof [lower_message_proof] shows the following:
[exists level_tree .
(hash_level_tree level_tree = lower.content)
AND (payload_and_level n level_tree = (_, (None, l)))]
in other words, there is no message at index [n] in
level [l]. This means that level has been fully read.
The tree proof [upper_message_proof] shows the following:
[exists level_tree .
(hash_level_tree level_tree = upper.content)
AND (payload_and_level 0 level_tree = (_, (message, upper_level)))]
in other words, if we look in the next non-empty level the
message at index zero is [message]. *)
| Level_crossing of {
lower : history_proof;
upper : history_proof;
inc : inclusion_proof;
lower_message_proof : P.proof;
upper_message_proof : P.proof;
upper_level : Raw_level_repr.t;
}
let pp_proof fmt proof =
match proof with
| Single_level {level; _} ->
let hash = Skip_list.content level in
Format.fprintf fmt "Single_level inbox proof at %a" Hash.pp hash
| Level_crossing {lower; upper; upper_level; _} ->
let lower_hash = Skip_list.content lower in
let upper_hash = Skip_list.content upper in
Format.fprintf
fmt
"Level_crossing inbox proof between %a and %a (upper_level %a)"
Hash.pp
lower_hash
Hash.pp
upper_hash
Raw_level_repr.pp
upper_level
let proof_encoding =
let open Data_encoding in
union
~tag_size:`Uint8
[
case
~title:"Single_level"
(Tag 0)
(obj3
(req "level" history_proof_encoding)
(req "inclusion_proof" inclusion_proof_encoding)
(req "message_proof" P.proof_encoding))
(function
| Single_level {level; inc; message_proof} ->
Some (level, inc, message_proof)
| _ -> None)
(fun (level, inc, message_proof) ->
Single_level {level; inc; message_proof});
case
~title:"Level_crossing"
(Tag 1)
(obj6
(req "lower" history_proof_encoding)
(req "upper" history_proof_encoding)
(req "inclusion_proof" inclusion_proof_encoding)
(req "lower_message_proof" P.proof_encoding)
(req "upper_message_proof" P.proof_encoding)
(req "upper_level" Raw_level_repr.encoding))
(function
| Level_crossing
{
lower;
upper;
inc;
lower_message_proof;
upper_message_proof;
upper_level;
} ->
Some
( lower,
upper,
inc,
lower_message_proof,
upper_message_proof,
upper_level )
| _ -> None)
(fun ( lower,
upper,
inc,
lower_message_proof,
upper_message_proof,
upper_level ) ->
Level_crossing
{
lower;
upper;
inc;
lower_message_proof;
upper_message_proof;
upper_level;
});
]
let of_serialized_proof = Data_encoding.Binary.of_bytes_opt proof_encoding
let to_serialized_proof = Data_encoding.Binary.to_bytes_exn proof_encoding
let proof_error reason =
let open Lwt_tzresult_syntax in
fail (Inbox_proof_error reason)
let check p reason = unless p (fun () -> proof_error reason)
(** Utility function that checks the inclusion proof [inc] for any
inbox proof.
In the case of a [Single_level] proof this is just an inclusion
proof between [level] and the inbox snapshot targeted the proof.
In the case of a [Level_crossing] proof [inc] must be an inclusion
proof between [upper] and the inbox snapshot. In this case we must
additionally check that [lower] is the immediate predecessor of
[upper] in the inbox skip list. NB: there may be many 'inbox
levels' apart, but if the intervening levels are empty they will
be immediate neighbours in the skip list because it misses empty
levels out. *)
let check_inclusions proof snapshot =
check
(match proof with
| Single_level {inc; level; _} ->
verify_inclusion_proof inc level snapshot
| Level_crossing {inc; lower; upper; _} -> (
let prev_cell = Skip_list.back_pointer upper 0 in
match prev_cell with
| None -> false
| Some p ->
verify_inclusion_proof inc upper snapshot
&& Hash.equal p (hash_skip_list_cell lower)))
"invalid inclusions"
(** To construct or verify a tree proof we need a function of type
[tree -> (tree, result) Lwt.t]
where [result] is some data extracted from the tree that we care
about proving. [payload_and_level n] is such a function, used for
checking both the inbox level specified inside the tree and the
message at a particular index, [n].
For this function, the [result] is
[(payload, level) : string option * Raw_level_repr.t option]
where [payload] is [None] if there was no message at the index.
The [level] part of the result will only be [None] if the [tree]
is not in the correct format for an inbox level. This should not
happen if the [tree] was correctly initialised with
[new_level_tree]. *)
let payload_and_level n tree =
let open Lwt_syntax in
let* payload = get_message_payload tree n in
let* level = find_level tree in
return (tree, (payload, level))
(** Utility function that handles all the verification needed for a
particular message proof at a particular level. It calls
[P.verify_proof], but also checks the proof has the correct
[P.proof_before] hash and the [level] stored inside the tree is
the expected one. *)
let check_message_proof message_proof level_hash (l, n) label =
let open Lwt_tzresult_syntax in
let* () =
check
(Hash.equal level_hash (P.proof_before message_proof))
(Format.sprintf "message_proof (%s) does not match history" label)
in
let*! result = P.verify_proof message_proof (payload_and_level n) in
match result with
| None -> proof_error (Format.sprintf "message_proof is invalid (%s)" label)
| Some (_, (_, None)) ->
proof_error
(Format.sprintf "badly encoded level in message_proof (%s)" label)
| Some (_, (payload_opt, Some proof_level)) ->
let* () =
check
(Raw_level_repr.equal proof_level l)
(Format.sprintf "incorrect level in message_proof (%s)" label)
in
return payload_opt
let verify_proof (l, n) snapshot proof =
assert (Z.(geq n zero)) ;
let open Lwt_tzresult_syntax in
let* () = check_inclusions proof snapshot in
match proof with
| Single_level p -> (
let level_hash = Skip_list.content p.level in
let* payload_opt =
check_message_proof p.message_proof level_hash (l, n) "single level"
in
match payload_opt with
| None ->
if equal_history_proof snapshot p.level then return None
else proof_error "payload is None but proof.level not top level"
| Some payload ->
return
@@ Some
Sc_rollup_PVM_sig.
{inbox_level = l; message_counter = n; payload})
| Level_crossing p -> (
let lower_level_hash = Skip_list.content p.lower in
let* should_be_none =
check_message_proof
p.lower_message_proof
lower_level_hash
(l, n)
"lower"
in
let* () =
match should_be_none with
| None -> return ()
| Some _ -> proof_error "more messages to read in lower level"
in
let upper_level_hash = Skip_list.content p.upper in
let* payload_opt =
check_message_proof
p.upper_message_proof
upper_level_hash
(p.upper_level, Z.zero)
"upper"
in
match payload_opt with
| None ->
(* [check_inclusions] checks at least two important properties:
1. [p.lower_level] is different from [p.upper_level]
2. [p.upper_level] is included in the snapshot
If [p.upper_level] is included in the snapshot, the level was
created by the protocol. If the protocol created a level tree
at [p.upper_level] it *must* contain at least one message.
So, if [p.upper_level] exists, at the index [Z.zero] (fetched
here), a payload *must* exist.
This code is then dead as long as we store only the nonempty
inboxes.
*)
fail (Empty_upper_level p.upper_level)
| Some payload ->
return
@@ Some
Sc_rollup_PVM_sig.
{
inbox_level = p.upper_level;
message_counter = Z.zero;
payload;
})
(** Utility function; we convert all our calls to be consistent with
[Lwt_tzresult_syntax]. *)
let option_to_result e lwt_opt =
let open Lwt_syntax in
let* opt = lwt_opt in
match opt with None -> proof_error e | Some x -> return (ok x)
let produce_proof ctxt history inbox (l, n) =
let open Lwt_tzresult_syntax in
let deref ptr = History.find ptr history in
let compare hash =
let*! tree = P.lookup_tree ctxt hash in
match tree with
| None -> Lwt.return (-1)
| Some tree -> (
let open Lwt_syntax in
let+ level = find_level tree in
match level with
| None -> -1
| Some level -> Raw_level_repr.compare level l)
in
let*! result = Skip_list.search ~deref ~compare ~cell:inbox in
let* inc, level =
match result with
| Skip_list.{rev_path; last_cell = Found level} ->
return (List.rev rev_path, level)
| {last_cell = Nearest _; _}
| {last_cell = No_exact_or_lower_ptr; _}
| {last_cell = Deref_returned_none; _} ->
(* We are only interested to the result where [search] than a
path to the cell we were looking for. All the other cases
should be considered as an error. *)
proof_error
(Format.asprintf
"Skip_list.search failed to find a valid path: %a"
(Skip_list.pp_search_result ~pp_cell:pp_history_proof)
result)
in
let* level_tree =
option_to_result
"could not find level_tree in the inbox_context"
(P.lookup_tree ctxt (Skip_list.content level))
in
let* message_proof, (payload_opt, _) =
option_to_result
"failed to produce message proof for level_tree"
(P.produce_proof ctxt level_tree (payload_and_level n))
in
match payload_opt with
| Some payload ->
return
( Single_level {level; inc; message_proof},
Some
Sc_rollup_PVM_sig.{inbox_level = l; message_counter = n; payload}
)
| None -> (
if equal_history_proof inbox level then
return (Single_level {level; inc; message_proof}, None)
else
let target_index = Skip_list.index level + 1 in
let cell_ptr = hash_skip_list_cell inbox in
let*? history = History.remember cell_ptr inbox history in
let deref ptr = History.find ptr history in
let* inc =
option_to_result
"failed to find path to upper level"
(Lwt.return
(Skip_list.back_path ~deref ~cell_ptr ~target_index
|> Option.map (lift_ptr_path deref)
|> Option.join))
in
let* upper =
option_to_result
"back_path returned empty list"
(Lwt.return (List.last_opt inc))
in
let* upper_level_tree =
option_to_result
"could not find upper_level_tree in the inbox_context"
(P.lookup_tree ctxt (Skip_list.content upper))
in
let* upper_message_proof, (payload_opt, upper_level_opt) =
option_to_result
"failed to produce message proof for upper_level_tree"
(P.produce_proof ctxt upper_level_tree (payload_and_level Z.zero))
in
let* upper_level =
option_to_result
"upper_level_tree was misformed---could not find level"
(Lwt.return upper_level_opt)
in
match payload_opt with
| None ->
proof_error "if upper_level_tree exists, the payload must exist"
| Some payload ->
let input_given =
Some
Sc_rollup_PVM_sig.
{
inbox_level = upper_level;
message_counter = Z.zero;
payload;
}
in
return
( Level_crossing
{
lower = level;
upper;
inc;
lower_message_proof = message_proof;
upper_message_proof;
upper_level;
},
input_given ))
let empty context rollup level =
let open Lwt_syntax in
assert (Raw_level_repr.(level <> Raw_level_repr.root)) ;
let pre_genesis_level = Raw_level_repr.root in
let* initial_level = new_level_tree context pre_genesis_level in
let* () = commit_tree context initial_level pre_genesis_level in
let initial_hash = hash_level_tree initial_level in
return
{
rollup;
level;
message_counter = Z.zero;
nb_messages_in_commitment_period = 0L;
starting_level_of_current_commitment_period = level;
current_level_hash = (fun () -> initial_hash);
old_levels_messages = Skip_list.genesis initial_hash;
}
module Internal_for_tests = struct
let eq_tree = Tree.equal
let produce_inclusion_proof history a b =
let open Tzresult_syntax in
let cell_ptr = hash_skip_list_cell b in
let target_index = Skip_list.index a in
let* history = History.remember cell_ptr b history in
let deref ptr = History.find ptr history in
Skip_list.back_path ~deref ~cell_ptr ~target_index
|> Option.map (lift_ptr_path deref)
|> Option.join |> return
let serialized_proof_of_string x = Bytes.of_string x
end
end
include (
Make_hashing_scheme (struct
module Tree = struct
include Context.Tree
type t = Context.t
type tree = Context.tree
type value = bytes
type key = string list
end
type t = Context.t
type tree = Context.tree
let commit_tree _ctxt _key _tree =
(* This is a no-op in the protocol inbox implementation *)
Lwt.return ()
let lookup_tree _ctxt _hash =
(* We cannot find the tree without a full inbox_context *)
Lwt.return None
type proof = Context.Proof.tree Context.Proof.t
let proof_encoding = Context.Proof_encoding.V1.Tree32.tree_proof_encoding
let proof_before proof =
match proof.Context.Proof.before with
| `Value hash | `Node hash -> Hash.of_context_hash hash
let verify_proof p f =
Lwt.map Result.to_option (Context.verify_tree_proof p f)
let produce_proof _ _ _ =
(* We cannot produce a proof without full inbox_context *)
Lwt.return None
end) :
Merkelized_operations
with type tree = Context.tree
and type inbox_context = Context.t)
type inbox = t
