Merge pull request #18 from argentlabs/feature/contract_guardian

Contract guardian

Author: juniset

README.md

@@ -1,16 +1,21 @@
-# Argent Account on Starknet
+# Argent Account on StarkNet
 
-Preliminary work for an Argent Account on Starknet.
+*Warning: StarkNet is still in alpha, so is this project. In particular the `ArgentAccount.cairo` contract has not been audited yet and should not be used to store significant value.*
 
 ## High-Level Specification
 
-The account is a 2-of-2 custom multisig where the `signer` key is typically stored on the user's phone and the `guardian` key is managed by an off-chain service to enable fraud monitoring (e.g. trusted contacts, daily limits, etc). The user can always opt-out of the guardian service and manage the `guardian` key himself.
+The account is a 2-of-2 custom multisig where the `signer` key is typically stored on the user's phone and the `guardian` is an external contract that can validate the signatures of one or more keys. 
+The `guardian` acts both as a co-validator for typical operations of the wallet, and as the trusted actor that can recover the wallet in case the `signer` key is lost or compromised.
+These two features may have different key requirements (e.g. a single key for fraud monitoring, and a n-of-m setup for 'social' recovery) as encapsulated by the logic of the `guardian` contract.
 
-Normal operations of the wallet (`execute`, `change_signer` and `change_guardian`) require both signatures to be executed.
+By default the `guardian` has a single key managed by an off-chain service to enable fraud monitoring (e.g. trusted contacts, daily limits, etc) and recovery. The user can always opt-out of the guardian service and select a `guardian` contract with different key requirements.
 
-Each party alone can trigger the `escape` mode on the wallet if the other party is not cooperating or lost. An escape takes 7 days before being active, after which the non-cooperating party can be replaced. The wallet is asymmetric in favor of the `signer` who can override an escape triggered by the `guardian`.
+Normal operations of the wallet (`execute`, `change_signer`, `change_guardian`, `cancel_escape`) require the approval of both parties to be executed.
 
-A triggered escape can always be cancelled with both signatures.
+Each party alone can trigger the `escape` mode (a.k.a. recovery) on the wallet if the other party is not cooperating or lost. An escape takes 7 days before being active, after which the non-cooperating party can be replaced.
+The wallet is always asymmetric in favor of one of the party depending on the `weight` of the `guardian`. The favoured party can always override an escape triggered by the other party.
+
+A triggered escape can always be cancelled with the approval of both parties.
 
 We assume that the `signer` key is backed up such that the probability of the `signer` key being lost should be close to zero.
 

contracts/ArgentAccount.cairo

@@ -5,12 +5,26 @@ from starkware.cairo.common.cairo_builtins import HashBuiltin, SignatureBuiltin
 from starkware.cairo.common.signature import verify_ecdsa_signature
 from starkware.cairo.common.registers import get_fp_and_pc
 from starkware.cairo.common.alloc import alloc
+from starkware.cairo.common.memcpy import memcpy
 from starkware.cairo.common.math import assert_not_zero, assert_le, assert_nn
 from starkware.starknet.common.syscalls import call_contract, get_tx_signature, get_contract_address, get_caller_address
 from starkware.cairo.common.hash_state import (
     hash_init, hash_finalize, hash_update, hash_update_single
 )
 
+####################
+# INTERFACE
+####################
+
+@contract_interface
+namespace IGuardian:
+    func is_valid_signature(hash: felt, sig_len: felt, sig: felt*):
+    end
+
+    func weight() -> (weight: felt):
+    end
+end
+
 ####################
 # CONSTANTS
 ####################
@@ -104,6 +118,11 @@ func execute{
     # compute message hash
     let (message_hash) = get_message_hash(to, selector, calldata_len, calldata, nonce)
 
+    # rebind pointers
+    local syscall_ptr: felt* = syscall_ptr
+    local range_check_ptr = range_check_ptr
+    local pedersen_ptr: HashBuiltin* = pedersen_ptr
+
     if to == self:
         tempvar signer_condition = (selector - ESCAPE_GUARDIAN_SELECTOR) * (selector - TRIGGER_ESCAPE_GUARDIAN_SELECTOR)
         tempvar guardian_condition = (selector - ESCAPE_SIGNER_SELECTOR) * (selector - TRIGGER_ESCAPE_SIGNER_SELECTOR)
@@ -113,8 +132,10 @@ func execute{
             jmp do_execute
         end
         if guardian_condition == 0:
+            # add flag to indicate an escape
+            let (extended_sig) = add_escape_flag(sig, sig_len)
             # validate guardian signature
-            validate_guardian_signature(message_hash, sig, sig_len)
+            validate_guardian_signature(message_hash, extended_sig, sig_len + 1)
             jmp do_execute
         end
     end
@@ -130,7 +151,6 @@ func execute{
         calldata_size=calldata_len,
         calldata=calldata
     )
-
     return (response=response.retdata_size)
 end
 
@@ -142,7 +162,6 @@ func change_signer{
     } (
         new_signer: felt
     ):
-
     # only called via execute
     assert_only_self()
 
@@ -175,11 +194,27 @@ func trigger_escape_guardian{
         pedersen_ptr: HashBuiltin*,
         range_check_ptr
     } ():
-
+    alloc_locals
+    
     # only called via execute
     assert_only_self()
     # no escape when the guardian is not set
-    assert_guardian_set()
+    let (guardian) = assert_guardian_set()
+
+    # no escape if there is an escape by the guardian and guardian has weight > 1
+    let (current_escape) = _escape.read()
+    if current_escape.caller == guardian:
+        let (weight) = IGuardian.weight(contract_address=guardian)
+        # assert weight <= 1
+        assert_nn(1 - weight)
+        tempvar syscall_ptr: felt* = syscall_ptr
+        tempvar range_check_ptr = range_check_ptr
+        tempvar pedersen_ptr: HashBuiltin* = pedersen_ptr
+    else:
+        tempvar syscall_ptr: felt* = syscall_ptr
+        tempvar range_check_ptr = range_check_ptr
+        tempvar pedersen_ptr: HashBuiltin* = pedersen_ptr
+    end
 
     # store new escape
     let (block_timestamp) = _block_timestamp.read()
@@ -202,10 +237,19 @@ func trigger_escape_signer{
     # no escape when the guardian is not set
     let (guardian) = assert_guardian_set()
 
-    # no escape when there is an ongoing escape by the signer
+    # no escape if there is an escape by the signer and guardian has weight <= 1
     let (current_escape) = _escape.read()
-    if current_escape.active_at != 0:
-        assert current_escape.caller = guardian
+    if ((current_escape.caller - guardian) * current_escape.caller) != 0:
+        let (weight) = IGuardian.weight(contract_address=guardian)
+        # assert weight > 1
+        assert_nn(weight - 2)
+        tempvar syscall_ptr: felt* = syscall_ptr
+        tempvar range_check_ptr = range_check_ptr
+        tempvar pedersen_ptr: HashBuiltin* = pedersen_ptr
+    else:
+        tempvar syscall_ptr: felt* = syscall_ptr
+        tempvar range_check_ptr = range_check_ptr
+        tempvar pedersen_ptr: HashBuiltin* = pedersen_ptr
     end
 
     # store new escape
@@ -425,27 +469,39 @@ end
 func validate_guardian_signature{
         syscall_ptr: felt*, 
         pedersen_ptr: HashBuiltin*,
-        ecdsa_ptr : SignatureBuiltin*,
+        ecdsa_ptr: SignatureBuiltin*,
         range_check_ptr
     } (
         message: felt,
         signatures: felt*,
         signatures_len: felt
     ) -> ():
+    alloc_locals
     let (guardian) = _guardian.read()
     if guardian == 0:
         return()
     else:
         assert_nn(signatures_len - 2)
-        verify_ecdsa_signature(
-            message=message,
-            public_key=guardian,
-            signature_r=signatures[0],
-            signature_s=signatures[1])
+        IGuardian.is_valid_signature(contract_address=guardian, hash=message, sig_len=signatures_len, sig=signatures)
         return()
     end
 end
 
+func add_escape_flag{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (
+        sig: felt*,
+        sig_len: felt
+    ) -> (extended: felt*):
+    alloc_locals
+    let (local extended : felt*) = alloc()
+    memcpy(extended, sig, sig_len)
+    assert [extended+sig_len] = 'escape'
+    return(extended=extended)
+end
+
 func get_message_hash{
         syscall_ptr: felt*, 
         pedersen_ptr: HashBuiltin*,

contracts/guardians/SCSKGuardian.cairo

@@ -0,0 +1,94 @@
+%lang starknet
+%builtins pedersen range_check ecdsa
+
+from starkware.cairo.common.cairo_builtins import HashBuiltin, SignatureBuiltin
+from starkware.cairo.common.signature import verify_ecdsa_signature
+from starkware.cairo.common.hash import hash2
+from starkware.cairo.common.math import assert_not_zero, assert_nn
+from starkware.starknet.common.syscalls import get_tx_signature
+
+######################################
+# Single Common Stark Key Guardian
+######################################
+
+@storage_var
+func _signing_key() -> (res: felt):
+end
+
+@constructor
+func constructor{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (
+        signing_key: felt
+    ):
+    assert_not_zero(signing_key)
+    _signing_key.write(signing_key)
+    return ()
+end
+
+@external
+func set_signing_key{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        ecdsa_ptr: SignatureBuiltin*,
+        range_check_ptr
+    } (
+        new_signing_key: felt
+    ) -> ():
+
+    # get the signature
+    let (sig_len : felt, sig : felt*) = get_tx_signature()
+    # Verify the signature length.
+    assert_nn(sig_len - 2)
+    # Compute the hash of the message.
+    let (hash) = hash2{hash_ptr=pedersen_ptr}(new_signing_key, 0)
+    # get the existing signing key
+    let (signing_key) = _signing_key.read()
+    # verify the signature
+    verify_ecdsa_signature(
+        message=hash,
+        public_key=signing_key,
+        signature_r=sig[0],
+        signature_s=sig[1])
+    # set the new key
+    _signing_key.write(new_signing_key)
+    return()
+end
+
+@view
+func is_valid_signature{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        ecdsa_ptr: SignatureBuiltin*,
+        range_check_ptr
+    } (
+        hash: felt,
+        sig_len: felt,
+        sig: felt*
+    ) -> ():
+    assert_nn(sig_len - 2)
+    let (signing_key) = _signing_key.read()
+    verify_ecdsa_signature(
+        message=hash,
+        public_key=signing_key,
+        signature_r=sig[0],
+        signature_s=sig[1])
+    return()
+end
+
+@view
+func weight() -> (weight: felt):
+    return (weight=1)
+end
+
+@view
+func get_signing_key{
+        syscall_ptr: felt*, 
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } () -> (signing_key: felt):
+    let (signing_key) = _signing_key.read()
+    return (signing_key=signing_key)
+end

contracts/guardians/USDKGuardian.cairo

@@ -0,0 +1,107 @@
+%lang starknet
+%builtins pedersen range_check ecdsa
+
+from starkware.cairo.common.cairo_builtins import HashBuiltin, SignatureBuiltin
+from starkware.cairo.common.signature import verify_ecdsa_signature
+from starkware.cairo.common.math import assert_not_zero
+from starkware.starknet.common.syscalls import get_caller_address
+
+##############################################
+# User selected different single keys Guardian
+##############################################
+
+@storage_var
+func _signing_key(account : felt) -> (res: felt):
+end
+
+@storage_var
+func _escape_key(account : felt) -> (res: felt):
+end
+
+@view
+func is_valid_signature{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        ecdsa_ptr: SignatureBuiltin*,
+        range_check_ptr
+    } (
+        hash: felt,
+        sig_len: felt,
+        sig: felt*
+    ) -> ():
+    
+    let (account) = get_caller_address()
+    if sig_len == 3:
+        assert [sig + 2] = 'escape'
+        let (key) = _escape_key.read(account)
+        verify_ecdsa_signature(
+            message=hash,
+            public_key=key,
+            signature_r=sig[0],
+            signature_s=sig[1])
+        return()
+    end
+
+    if sig_len == 2:
+        let (key) = _signing_key.read(account)
+        verify_ecdsa_signature(
+            message=hash,
+            public_key=key,
+            signature_r=sig[0],
+            signature_s=sig[1])
+        return()
+    end
+    assert_not_zero(0)
+    return()
+end
+
+@view
+func weight() -> (weight: felt):
+    return (weight=1)
+end
+
+@external
+func set_signing_key{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (
+        key: felt
+    ) -> ():
+    let (account) = get_caller_address()
+    _signing_key.write(account, key)
+    return()
+end
+
+@external
+func set_escape_key{
+        syscall_ptr: felt*,
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (
+        key: felt
+    ) -> ():
+    let (account) = get_caller_address()
+    _escape_key.write(account, key)
+    return()
+end
+
+@view
+func get_signing_key{
+        syscall_ptr: felt*, 
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (account: felt) -> (signing_key: felt):
+    let (signing_key) = _signing_key.read(account)
+    return (signing_key=signing_key)
+end
+
+@view
+func get_escape_key{
+        syscall_ptr: felt*, 
+        pedersen_ptr: HashBuiltin*,
+        range_check_ptr
+    } (account: felt) -> (escape_key: felt):
+    let (escape_key) = _escape_key.read(account)
+    return (escape_key=escape_key)
+end