Source file baking.ml

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open Alpha_context
open Misc
open Misc.Syntax

type error += Invalid_fitness_gap of int64 * int64 (* `Permanent *)

type error += Timestamp_too_early of Timestamp.t * Timestamp.t

(* `Permanent *)

type error += Unexpected_endorsement (* `Permanent *)

type error +=
  | Invalid_block_signature of Block_hash.t * Signature.Public_key_hash.t

(* `Permanent *)

type error += Invalid_signature (* `Permanent *)

type error += Invalid_stamp (* `Permanent *)

let () =
  register_error_kind
    `Permanent
    ~id:"baking.timestamp_too_early"
    ~title:"Block forged too early"
    ~description:
      "The block timestamp is before the first slot for this baker at this \
       level"
    ~pp:(fun ppf (r, p) ->
      Format.fprintf
        ppf
        "Block forged too early (%a is before %a)"
        Time.pp_hum
        p
        Time.pp_hum
        r)
    Data_encoding.(
      obj2 (req "minimum" Time.encoding) (req "provided" Time.encoding))
    (function Timestamp_too_early (r, p) -> Some (r, p) | _ -> None)
    (fun (r, p) -> Timestamp_too_early (r, p)) ;
  register_error_kind
    `Permanent
    ~id:"baking.invalid_fitness_gap"
    ~title:"Invalid fitness gap"
    ~description:"The gap of fitness is out of bounds"
    ~pp:(fun ppf (m, g) ->
      Format.fprintf ppf "The gap of fitness %Ld is not between 0 and %Ld" g m)
    Data_encoding.(obj2 (req "maximum" int64) (req "provided" int64))
    (function Invalid_fitness_gap (m, g) -> Some (m, g) | _ -> None)
    (fun (m, g) -> Invalid_fitness_gap (m, g)) ;
  register_error_kind
    `Permanent
    ~id:"baking.invalid_block_signature"
    ~title:"Invalid block signature"
    ~description:"A block was not signed with the expected private key."
    ~pp:(fun ppf (block, pkh) ->
      Format.fprintf
        ppf
        "Invalid signature for block %a. Expected: %a."
        Block_hash.pp_short
        block
        Signature.Public_key_hash.pp_short
        pkh)
    Data_encoding.(
      obj2
        (req "block" Block_hash.encoding)
        (req "expected" Signature.Public_key_hash.encoding))
    (function
      | Invalid_block_signature (block, pkh) -> Some (block, pkh) | _ -> None)
    (fun (block, pkh) -> Invalid_block_signature (block, pkh)) ;
  register_error_kind
    `Permanent
    ~id:"baking.invalid_signature"
    ~title:"Invalid block signature"
    ~description:"The block's signature is invalid"
    ~pp:(fun ppf () -> Format.fprintf ppf "Invalid block signature")
    Data_encoding.empty
    (function Invalid_signature -> Some () | _ -> None)
    (fun () -> Invalid_signature) ;
  register_error_kind
    `Permanent
    ~id:"baking.insufficient_proof_of_work"
    ~title:"Insufficient block proof-of-work stamp"
    ~description:"The block's proof-of-work stamp is insufficient"
    ~pp:(fun ppf () -> Format.fprintf ppf "Insufficient proof-of-work stamp")
    Data_encoding.empty
    (function Invalid_stamp -> Some () | _ -> None)
    (fun () -> Invalid_stamp) ;
  register_error_kind
    `Permanent
    ~id:"baking.unexpected_endorsement"
    ~title:"Endorsement from unexpected delegate"
    ~description:
      "The operation is signed by a delegate without endorsement rights."
    ~pp:(fun ppf () ->
      Format.fprintf
        ppf
        "The endorsement is signed by a delegate without endorsement rights.")
    Data_encoding.unit
    (function Unexpected_endorsement -> Some () | _ -> None)
    (fun () -> Unexpected_endorsement)

let minimal_time c priority pred_timestamp =
  let priority = Int32.of_int priority in
  let rec cumsum_time_between_blocks acc durations p =
    if Compare.Int32.( <= ) p 0l then ok acc
    else
      match durations with
      | [] ->
          cumsum_time_between_blocks acc [Period.one_minute] p
      | [last] ->
          Period.mult p last >>? fun period -> Timestamp.(acc +? period)
      | first :: durations ->
          Timestamp.(acc +? first)
          >>? fun acc ->
          let p = Int32.pred p in
          cumsum_time_between_blocks acc durations p
  in
  cumsum_time_between_blocks
    pred_timestamp
    (Constants.time_between_blocks c)
    (Int32.succ priority)

let earlier_predecessor_timestamp ctxt level =
  let current = Level.current ctxt in
  let current_timestamp = Timestamp.current ctxt in
  let gap = Level.diff level current in
  let step = List.hd (Constants.time_between_blocks ctxt) in
  if Compare.Int32.(gap < 1l) then
    failwith "Baking.earlier_block_timestamp: past block."
  else
    Period.mult (Int32.pred gap) step
    >>? fun delay -> Timestamp.(current_timestamp +? delay)

let check_timestamp c priority pred_timestamp =
  minimal_time c priority pred_timestamp
  >>? fun minimal_time ->
  let timestamp = Alpha_context.Timestamp.current c in
  record_trace
    (Timestamp_too_early (minimal_time, timestamp))
    Timestamp.(timestamp -? minimal_time)

let check_baking_rights c {Block_header.priority; _} pred_timestamp =
  let level = Level.current c in
  Roll.baking_rights_owner c level ~priority
  >>=? fun delegate ->
  Lwt.return
    ( check_timestamp c priority pred_timestamp
    >|? fun block_delay -> (delegate, block_delay) )

type error += Incorrect_priority (* `Permanent *)

type error += Incorrect_number_of_endorsements (* `Permanent *)

let () =
  register_error_kind
    `Permanent
    ~id:"incorrect_priority"
    ~title:"Incorrect priority"
    ~description:"Block priority must be non-negative."
    ~pp:(fun ppf () ->
      Format.fprintf ppf "The block priority must be non-negative.")
    Data_encoding.unit
    (function Incorrect_priority -> Some () | _ -> None)
    (fun () -> Incorrect_priority)

let () =
  let description =
    "The number of endorsements must be non-negative and at most the \
     endorsers_per_block constant."
  in
  register_error_kind
    `Permanent
    ~id:"incorrect_number_of_endorsements"
    ~title:"Incorrect number of endorsements"
    ~description
    ~pp:(fun ppf () -> Format.fprintf ppf "%s" description)
    Data_encoding.unit
    (function Incorrect_number_of_endorsements -> Some () | _ -> None)
    (fun () -> Incorrect_number_of_endorsements)

let rec reward_for_priority reward_per_prio prio =
  match reward_per_prio with
  | [] ->
      (* Empty reward list in parameters means no rewards *)
      Tez.zero
  | [last] ->
      last
  | first :: rest ->
      if Compare.Int.(prio <= 0) then first
      else reward_for_priority rest (pred prio)

let baking_reward ctxt ~block_priority ~included_endorsements =
  error_unless Compare.Int.(block_priority >= 0) Incorrect_priority
  >>? fun () ->
  error_unless
    Compare.Int.(
      included_endorsements >= 0
      && included_endorsements <= Constants.endorsers_per_block ctxt)
    Incorrect_number_of_endorsements
  >>? fun () ->
  let reward_per_endorsement =
    reward_for_priority
      (Constants.baking_reward_per_endorsement ctxt)
      block_priority
  in
  Tez.(reward_per_endorsement *? Int64.of_int included_endorsements)

let endorsing_reward ctxt ~block_priority num_slots =
  error_unless Compare.Int.(block_priority >= 0) Incorrect_priority
  >>? fun () ->
  let reward_per_endorsement =
    reward_for_priority (Constants.endorsement_reward ctxt) block_priority
  in
  Tez.(reward_per_endorsement *? Int64.of_int num_slots)

let baking_priorities c level =
  let rec f priority =
    Roll.baking_rights_owner c level ~priority
    >|=? fun delegate -> LCons (delegate, fun () -> f (succ priority))
  in
  f 0

let endorsement_rights ctxt level =
  fold_left_s
    (fun acc slot ->
      Roll.endorsement_rights_owner ctxt level ~slot
      >|=? fun pk ->
      let pkh = Signature.Public_key.hash pk in
      let right =
        match Signature.Public_key_hash.Map.find_opt pkh acc with
        | None ->
            (pk, [slot], false)
        | Some (pk, slots, used) ->
            (pk, slot :: slots, used)
      in
      Signature.Public_key_hash.Map.add pkh right acc)
    Signature.Public_key_hash.Map.empty
    (0 --> (Constants.endorsers_per_block ctxt - 1))

let check_endorsement_rights ctxt chain_id (op : Kind.endorsement Operation.t)
    =
  let current_level = Level.current ctxt in
  let (Single (Endorsement {level; _})) = op.protocol_data.contents in
  ( if Raw_level.(succ level = current_level.level) then
    return (Alpha_context.allowed_endorsements ctxt)
  else endorsement_rights ctxt (Level.from_raw ctxt level) )
  >>=? fun endorsements ->
  match
    Signature.Public_key_hash.Map.fold (* no find_first *)
      (fun pkh (pk, slots, used) acc ->
        match Operation.check_signature pk chain_id op with
        | Error _ ->
            acc
        | Ok () ->
            Some (pkh, slots, used))
      endorsements
      None
  with
  | None ->
      fail Unexpected_endorsement
  | Some v ->
      return v

let select_delegate delegate delegate_list max_priority =
  let rec loop acc l n =
    if Compare.Int.(n >= max_priority) then return (List.rev acc)
    else
      let (LCons (pk, t)) = l in
      let acc =
        if
          Signature.Public_key_hash.equal
            delegate
            (Signature.Public_key.hash pk)
        then n :: acc
        else acc
      in
      t () >>=? fun t -> loop acc t (succ n)
  in
  loop [] delegate_list 0

let first_baking_priorities ctxt ?(max_priority = 32) delegate level =
  baking_priorities ctxt level
  >>=? fun delegate_list -> select_delegate delegate delegate_list max_priority

let check_hash hash stamp_threshold =
  let bytes = Block_hash.to_bytes hash in
  let word = MBytes.get_int64 bytes 0 in
  Compare.Uint64.(word <= stamp_threshold)

let check_header_proof_of_work_stamp shell contents stamp_threshold =
  let hash =
    Block_header.hash
      {shell; protocol_data = {contents; signature = Signature.zero}}
  in
  check_hash hash stamp_threshold

let check_proof_of_work_stamp ctxt block =
  let proof_of_work_threshold = Constants.proof_of_work_threshold ctxt in
  if
    check_header_proof_of_work_stamp
      block.Block_header.shell
      block.protocol_data.contents
      proof_of_work_threshold
  then return_unit
  else fail Invalid_stamp

let check_signature block chain_id key =
  let check_signature key
      {Block_header.shell; protocol_data = {contents; signature}} =
    let unsigned_header =
      Data_encoding.Binary.to_bytes_exn
        Block_header.unsigned_encoding
        (shell, contents)
    in
    Signature.check
      ~watermark:(Block_header chain_id)
      key
      signature
      unsigned_header
  in
  if check_signature key block then return_unit
  else
    fail
      (Invalid_block_signature
         (Block_header.hash block, Signature.Public_key.hash key))

let max_fitness_gap _ctxt = 1L

let check_fitness_gap ctxt (block : Block_header.t) =
  let current_fitness = Fitness.current ctxt in
  Fitness.to_int64 block.shell.fitness
  >>? fun announced_fitness ->
  let gap = Int64.sub announced_fitness current_fitness in
  if Compare.Int64.(gap <= 0L || max_fitness_gap ctxt < gap) then
    error (Invalid_fitness_gap (max_fitness_gap ctxt, gap))
  else ok_unit

let last_of_a_cycle ctxt l =
  Compare.Int32.(
    Int32.succ l.Level.cycle_position = Constants.blocks_per_cycle ctxt)

let dawn_of_a_new_cycle ctxt =
  let level = Level.current ctxt in
  if last_of_a_cycle ctxt level then return_some level.cycle else return_none

let minimum_allowed_endorsements ctxt ~block_delay =
  let minimum = Constants.initial_endorsers ctxt in
  let delay_per_missing_endorsement =
    Period.to_seconds (Constants.delay_per_missing_endorsement ctxt)
  in
  let reduced_time_constraint =
    let delay = Period.to_seconds block_delay in
    if Compare.Int64.(delay_per_missing_endorsement = 0L) then delay
    else Int64.div delay delay_per_missing_endorsement
  in
  if Compare.Int64.(Int64.of_int minimum < reduced_time_constraint) then 0
  else minimum - Int64.to_int reduced_time_constraint

let minimal_valid_time ctxt ~priority ~endorsing_power =
  let predecessor_timestamp = Timestamp.current ctxt in
  minimal_time ctxt priority predecessor_timestamp
  >>? fun minimal_time ->
  let minimal_required_endorsements = Constants.initial_endorsers ctxt in
  let delay_per_missing_endorsement =
    Constants.delay_per_missing_endorsement ctxt
  in
  let missing_endorsements =
    Compare.Int.max 0 (minimal_required_endorsements - endorsing_power)
  in
  Period.mult (Int32.of_int missing_endorsements) delay_per_missing_endorsement
  >|? fun delay -> Time.add minimal_time (Period.to_seconds delay)