def visitFunctionCallExpr(self, ast: FunctionCallExpr):
if isinstance(ast.func, BuiltinFunction):
self.handle_builtin_function_call(ast, ast.func)
elif ast.is_cast:
if not isinstance(ast.func.target, EnumDefinition):
raise NotImplementedError(
'User type casts only implemented for enums')
ast.annotated_type = self.handle_cast(
ast.args[0], ast.func.target.annotated_type.type_name)
elif isinstance(ast.func, LocationExpr):
ft = ast.func.annotated_type.type_name
if len(ft.parameters) != len(ast.args):
raise TypeException("Wrong number of arguments", ast.func)
# Check arguments
for i in range(len(ast.args)):
ast.args[i] = self.get_rhs(ast.args[i],
ft.parameters[i].annotated_type)
# Set expression type to return type
if len(ft.return_parameters) == 1:
ast.annotated_type = ft.return_parameters[
0].annotated_type.clone()
else:
# TODO maybe not None label in the future
ast.annotated_type = AnnotatedTypeName(
TupleType([t.annotated_type
for t in ft.return_parameters]), None)
else:
raise TypeException('Invalid function call', ast)
def handle_homomorphic_builtin_function_call(self, ast: FunctionCallExpr,
func: BuiltinFunction):
# First - same as non-homomorphic - check that argument types conform to op signature
if not func.is_eq():
for arg, t in zip(ast.args, func.input_types()):
if not arg.instanceof_data_type(t):
raise TypeMismatchException(t,
arg.annotated_type.type_name,
arg)
homomorphic_func = func.select_homomorphic_overload(
ast.args, ast.analysis)
if homomorphic_func is None:
raise TypeException(
f'Operation \'{func.op}\' requires all arguments to be accessible, '
f'i.e. @all or provably equal to @me', ast)
# We could perform homomorphic operations on-chain by using some Solidity arbitrary precision math library.
# For now, keep it simple and evaluate homomorphic operations in Python and check the result in the circuit.
func.is_private = True
ast.annotated_type = homomorphic_func.output_type()
func.homomorphism = ast.annotated_type.homomorphism
expected_arg_types = homomorphic_func.input_types()
# Check that the argument types are correct
ast.args[:] = map(lambda arg, arg_pt: self.get_rhs(arg, arg_pt),
ast.args, expected_arg_types)
def visitAssignmentExpr(self, ctx: SolidityParser.AssignmentExprContext):
if not self.is_expr_stmt(ctx):
raise SyntaxException('Assignments are only allowed as statements', ctx, self.code)
lhs = self.visit(ctx.lhs)
rhs = self.visit(ctx.rhs)
assert ctx.op.text[-1] == '='
op = ctx.op.text[:-1] if ctx.op.text != '=' else ''
if op:
# If the assignment contains an additional operator -> replace lhs = rhs with lhs = lhs 'op' rhs
rhs = FunctionCallExpr(BuiltinFunction(op).override(line=ctx.op.line, column=ctx.op.column), [self.visit(ctx.lhs), rhs])
rhs.line = ctx.rhs.start.line
rhs.column = ctx.rhs.start.column + 1
return ast.AssignmentStatement(lhs, rhs, op)
def _handle_crement_expr(self, ctx, kind: str):
if not self.is_expr_stmt(ctx):
raise SyntaxException(f'{kind}-crement expressions are only allowed as statements', ctx, self.code)
op = '+' if ctx.op.text == '++' else '-'
one = NumberLiteralExpr(1)
one.line = ctx.op.line
one.column = ctx.op.column + 1
fct = FunctionCallExpr(BuiltinFunction(op).override(line=ctx.op.line, column=ctx.op.column), [self.visit(ctx.expr), one])
fct.line = ctx.op.line
fct.column = ctx.op.column + 1
return ast.AssignmentStatement(self.visit(ctx.expr), fct, f'{kind}{ctx.op.text}')
def visitFunctionCallExpr(self, ctx: SolidityParser.FunctionCallExprContext):
func = self.visit(ctx.func)
args = self.handle_field(ctx.args)
if isinstance(func, IdentifierExpr):
if func.idf.name == 'reveal':
if len(args) != 2:
raise SyntaxException(f'Invalid number of arguments for reveal: {args}', ctx.args, self.code)
return ReclassifyExpr(args[0], args[1])
return FunctionCallExpr(func, args)
def handle_builtin_function_call(self, ast: FunctionCallExpr,
func: BuiltinFunction):
if func.is_parenthesis():
ast.annotated_type = ast.args[0].annotated_type
return
all_args_all_or_me = all(
map(lambda x: x.annotated_type.is_accessible(ast.analysis),
ast.args))
is_public_ite = func.is_ite() and ast.args[0].annotated_type.is_public(
)
if all_args_all_or_me or is_public_ite:
self.handle_unhom_builtin_function_call(ast, func)
else:
self.handle_homomorphic_builtin_function_call(ast, func)
def visitFunctionCallExpr(self, ctx: SolidityParser.FunctionCallExprContext):
func = self.visit(ctx.func)
args = self.handle_field(ctx.args)
if isinstance(func, IdentifierExpr):
if func.idf.name == 'reveal':
if len(args) != 2:
raise SyntaxException(f'Invalid number of arguments for reveal: {args}', ctx.args, self.code)
return ReclassifyExpr(args[0], args[1], None)
elif func.idf.name in self.rehom_expressions:
name = func.idf.name
homomorphism = self.rehom_expressions[name]
if len(args) != 1:
raise SyntaxException(f'Invalid number of arguments for {name}: {args}', ctx.args, self.code)
return RehomExpr(args[0], homomorphism)
return FunctionCallExpr(func, args)
def visitFunctionCallExpr(self, ast: FunctionCallExpr):
self.visitAST(ast)
if isinstance(ast.func, LocationExpr):
# for now no reference types -> only state could have been modified
fdef = ast.func.target
rlen = len(ast.read_values)
ast.read_values.update({
v
for v in fdef.read_values
if isinstance(v.target, StateVariableDeclaration)
})
self.fixed_point_reached &= rlen == len(ast.read_values)
# update modified values if any
mlen = len(ast.modified_values)
for v in fdef.modified_values:
if isinstance(v.target, StateVariableDeclaration):
ast.modified_values[v] = None
self.fixed_point_reached &= mlen == len(ast.modified_values)
def handle_builtin_function_call(self, ast: FunctionCallExpr,
func: BuiltinFunction):
# handle special cases
if func.is_ite():
cond_t = ast.args[0].annotated_type
# Ensure that condition is boolean
if not cond_t.type_name.implicitly_convertible_to(
TypeName.bool_type()):
raise TypeMismatchException(TypeName.bool_type(),
cond_t.type_name, ast.args[0])
res_t = ast.args[1].annotated_type.type_name.combined_type(
ast.args[2].annotated_type.type_name, True)
if cond_t.is_private():
# Everything is turned private
func.is_private = True
a = res_t.annotate(Expression.me_expr())
else:
p = ast.args[1].annotated_type.combined_privacy(
ast.analysis, ast.args[2].annotated_type)
a = res_t.annotate(p)
ast.args[1] = self.get_rhs(ast.args[1], a)
ast.args[2] = self.get_rhs(ast.args[2], a)
ast.annotated_type = a
return
elif func.is_parenthesis():
ast.annotated_type = ast.args[0].annotated_type
return
# Check that argument types conform to op signature
parameter_types = func.input_types()
if not func.is_eq():
for arg, t in zip(ast.args, parameter_types):
if not arg.instanceof_data_type(t):
raise TypeMismatchException(t,
arg.annotated_type.type_name,
arg)
t1 = ast.args[0].annotated_type.type_name
t2 = None if len(
ast.args) == 1 else ast.args[1].annotated_type.type_name
if len(ast.args) == 1:
arg_t = 'lit' if ast.args[
0].annotated_type.type_name.is_literal else t1
else:
assert len(ast.args) == 2
is_eq_with_tuples = func.is_eq() and isinstance(t1, TupleType)
arg_t = t1.combined_type(t2, convert_literals=is_eq_with_tuples)
# Infer argument and output types
if arg_t == 'lit':
res = func.op_func(
*[arg.annotated_type.type_name.value for arg in ast.args])
if isinstance(res, bool):
assert func.output_type() == TypeName.bool_type()
out_t = BooleanLiteralType(res)
else:
assert func.output_type() == TypeName.number_type()
out_t = NumberLiteralType(res)
if func.is_eq():
arg_t = t1.to_abstract_type().combined_type(
t2.to_abstract_type(), True)
elif func.output_type() == TypeName.bool_type():
out_t = TypeName.bool_type()
else:
out_t = arg_t
assert arg_t is not None and (arg_t != 'lit' or not func.is_eq())
private_args = any(map(self.has_private_type, ast.args))
if private_args:
assert arg_t != 'lit'
if func.can_be_private():
if func.is_shiftop():
if not ast.args[1].annotated_type.type_name.is_literal:
raise TypeException(
'Private shift expressions must use a constant (literal) shift amount',
ast.args[1])
if ast.args[1].annotated_type.type_name.value < 0:
raise TypeException('Cannot shift by negative amount',
ast.args[1])
if func.is_bitop() or func.is_shiftop():
for arg in ast.args:
if arg.annotated_type.type_name.elem_bitwidth == 256:
raise TypeException(
'Private bitwise and shift operations are only supported for integer types < 256 bit, '
'please use a smaller type', arg)
if func.is_arithmetic():
for a in ast.args:
if a.annotated_type.type_name.elem_bitwidth == 256:
issue_compiler_warning(
func, 'Possible field prime overflow',
'Private arithmetic 256bit operations overflow at FIELD_PRIME.\n'
'If you need correct overflow behavior, use a smaller integer type.'
)
break
elif func.is_comp():
for a in ast.args:
if a.annotated_type.type_name.elem_bitwidth == 256:
issue_compiler_warning(
func, 'Possible private comparison failure',
'Private 256bit comparison operations will fail for values >= 2^252.\n'
'If you cannot guarantee that the value stays in range, you must use '
'a smaller integer type to ensure correctness.'
)
break
func.is_private = True
p = Expression.me_expr()
else:
raise TypeException(
f'Operation \'{func.op}\' does not support private operands',
ast)
else:
p = None
if arg_t != 'lit':
# Add implicit casts for arguments
arg_pt = arg_t.annotate(p)
if func.is_shiftop() and p is not None:
ast.args[0] = self.get_rhs(ast.args[0], arg_pt)
else:
ast.args[:] = map(
lambda argument: self.get_rhs(argument, arg_pt), ast.args)
ast.annotated_type = out_t.annotate(p)
def create_external_wrapper_body(int_fct: ConstructorOrFunctionDefinition,
ext_circuit: CircuitHelper,
original_params: List[Parameter],
requires_proof: bool) -> Block:
"""
Return Block with external wrapper function body.
:param int_fct: corresponding internal function
:param ext_circuit: [SIDE EFFECT] circuit helper of the external wrapper function
:param original_params: list of transformed function parameters without additional parameters added due to transformation
:return: body with wrapper code
"""
has_priv_args = any(
[p.annotated_type.is_cipher() for p in original_params])
stmts = []
if has_priv_args:
ext_circuit._require_public_key_for_label_at(
None, Expression.me_expr())
if cfg.is_symmetric_cipher():
# Make sure msg.sender's key pair is available in the circuit
assert any(isinstance(k, MeExpr) for k in ext_circuit.requested_global_keys) \
or has_priv_args, "requires verification => both sender keys required"
stmts += ext_circuit.request_private_key()
# Verify that out parameter has correct size
stmts += [
RequireStatement(
IdentifierExpr(cfg.zk_out_name).dot('length').binop(
'==', NumberLiteralExpr(ext_circuit.out_size_trans)))
]
# IdentifierExpr for array var holding serialized public circuit inputs
in_arr_var = IdentifierExpr(cfg.zk_in_name).as_type(
Array(AnnotatedTypeName.uint_all()))
# Find index of me's public key in requested_global_keys
glob_me_key_index = -1
for idx, e in enumerate(ext_circuit.requested_global_keys):
if isinstance(e, MeExpr):
glob_me_key_index = idx
break
# Request static public keys
offset = 0
key_req_stmts = []
if ext_circuit.requested_global_keys:
# Ensure that me public key is stored starting at in[0]
keys = [key for key in ext_circuit.requested_global_keys]
if glob_me_key_index != -1:
(keys[0], keys[glob_me_key_index]) = (keys[glob_me_key_index],
keys[0])
tmp_key_var = Identifier('_tmp_key')
key_req_stmts.append(
tmp_key_var.decl_var(AnnotatedTypeName.key_type()))
for key_owner in keys:
idf, assignment = ext_circuit.request_public_key(
key_owner, ext_circuit.get_glob_key_name(key_owner))
assignment.lhs = IdentifierExpr(tmp_key_var.clone())
key_req_stmts.append(assignment)
# Manually add to circuit inputs
key_req_stmts.append(
in_arr_var.slice(offset, cfg.key_len).assign(
IdentifierExpr(tmp_key_var.clone()).slice(
0, cfg.key_len)))
offset += cfg.key_len
assert offset == ext_circuit.in_size
# Check encrypted parameters
param_stmts = []
for p in original_params:
""" * of T_e rule 8 """
if p.annotated_type.is_cipher():
assign_stmt = in_arr_var.slice(
offset, cfg.cipher_payload_len).assign(
IdentifierExpr(p.idf.clone()).slice(
0, cfg.cipher_payload_len))
ext_circuit.ensure_parameter_encryption(assign_stmt, p)
# Manually add to circuit inputs
param_stmts.append(assign_stmt)
offset += cfg.cipher_payload_len
if cfg.is_symmetric_cipher():
# Populate sender field of encrypted parameters
copy_stmts = []
for p in original_params:
if p.annotated_type.is_cipher():
sender_key = in_arr_var.index(0)
idf = IdentifierExpr(p.idf.clone()).as_type(
p.annotated_type.clone())
lit = ArrayLiteralExpr([
idf.clone().index(i)
for i in range(cfg.cipher_payload_len)
] + [sender_key])
copy_stmts.append(
VariableDeclarationStatement(
VariableDeclaration([], p.annotated_type.clone(),
p.idf.clone(), 'memory'), lit))
if copy_stmts:
param_stmts += [
Comment(),
Comment(
'Copy from calldata to memory and set sender field')
] + copy_stmts
assert glob_me_key_index != -1, "Symmetric cipher but did not request me key"
# Declare in array
new_in_array_expr = NewExpr(
AnnotatedTypeName(TypeName.dyn_uint_array()),
[NumberLiteralExpr(ext_circuit.in_size_trans)])
in_var_decl = in_arr_var.idf.decl_var(TypeName.dyn_uint_array(),
new_in_array_expr)
stmts.append(in_var_decl)
stmts.append(Comment())
stmts += Comment.comment_wrap_block('Request static public keys',
key_req_stmts)
stmts += Comment.comment_wrap_block(
'Backup private arguments for verification', param_stmts)
# Call internal function
args = [IdentifierExpr(param.idf.clone()) for param in original_params]
internal_call = FunctionCallExpr(
IdentifierExpr(int_fct.idf.clone()).override(target=int_fct), args)
internal_call.sec_start_offset = ext_circuit.priv_in_size
if int_fct.requires_verification:
ext_circuit.call_function(internal_call)
args += [
in_arr_var.clone(),
NumberLiteralExpr(ext_circuit.in_size),
IdentifierExpr(cfg.zk_out_name),
NumberLiteralExpr(ext_circuit.out_size)
]
if int_fct.return_parameters:
stmts += Comment.comment_list("Declare return variables", [
VariableDeclarationStatement(deep_copy(vd))
for vd in int_fct.return_var_decls
])
in_call = TupleExpr([
IdentifierExpr(vd.idf.clone())
for vd in int_fct.return_var_decls
]).assign(internal_call)
else:
in_call = ExpressionStatement(internal_call)
stmts.append(Comment("Call internal function"))
stmts.append(in_call)
stmts.append(Comment())
# Call verifier
if requires_proof:
verifier = IdentifierExpr(
cfg.get_contract_var_name(
ext_circuit.verifier_contract_type.code()))
verifier_args = [
IdentifierExpr(cfg.proof_param_name),
IdentifierExpr(cfg.zk_in_name),
IdentifierExpr(cfg.zk_out_name)
]
verify = ExpressionStatement(
verifier.call(cfg.verification_function_name, verifier_args))
stmts.append(
StatementList(
[Comment('Verify zk proof of execution'), verify],
excluded_from_simulation=True))
# Add return statement at the end if necessary
if int_fct.return_parameters:
stmts.append(
ReturnStatement(
TupleExpr([
IdentifierExpr(vd.idf.clone())
for vd in int_fct.return_var_decls
])))
return Block(stmts)
def visitIteExpr(self, ctx: SolidityParser.IteExprContext):
f = BuiltinFunction('ite')
cond = self.visit(ctx.cond)
then_expr = self.visit(ctx.then_expr)
else_expr = self.visit(ctx.else_expr)
return FunctionCallExpr(f, [cond, then_expr, else_expr])
def _visitBinaryExpr(self, ctx):
lhs = self.visit(ctx.lhs)
rhs = self.visit(ctx.rhs)
f = BuiltinFunction(ctx.op.text).override(line=ctx.op.line, column=ctx.op.column)
return FunctionCallExpr(f, [lhs, rhs])
def visitBitwiseNotExpr(self, ctx: SolidityParser.BitwiseNotExprContext):
f = BuiltinFunction('~').override(line=ctx.start.line, column=ctx.start.column)
expr = self.visit(ctx.expr)
return FunctionCallExpr(f, [expr])
def visitSignExpr(self, ctx: SolidityParser.SignExprContext):
f = BuiltinFunction('sign' + ctx.op.text).override(line=ctx.op.line, column=ctx.op.column)
expr = self.visit(ctx.expr)
return FunctionCallExpr(f, [expr])
def visitParenthesisExpr(self, ctx: SolidityParser.ParenthesisExprContext):
f = BuiltinFunction('parenthesis').override(line=ctx.start.line, column=ctx.start.column)
expr = self.visit(ctx.expr)
return FunctionCallExpr(f, [expr])
def test_builtin_code(self):
f = BuiltinFunction('+')
c = FunctionCallExpr(f, [NumberLiteralExpr(0), NumberLiteralExpr(0)])
self.assertEqual(c.code(), '0 + 0')
def create_external_wrapper_body(int_fct: ConstructorOrFunctionDefinition, ext_circuit: CircuitHelper,
original_params: List[Parameter], requires_proof: bool) -> Block:
"""
Return Block with external wrapper function body.
:param int_fct: corresponding internal function
:param ext_circuit: [SIDE EFFECT] circuit helper of the external wrapper function
:param original_params: list of transformed function parameters without additional parameters added due to transformation
:return: body with wrapper code
"""
priv_args = [p for p in original_params if p.annotated_type.is_cipher()]
args_backends = OrderedDict.fromkeys([p.annotated_type.type_name.crypto_params for p in priv_args])
stmts = []
for crypto_params in args_backends:
assert crypto_params in int_fct.used_crypto_backends
# If there are any private arguments with homomorphism 'hom', we need the public key for that crypto backend
ext_circuit._require_public_key_for_label_at(None, Expression.me_expr(), crypto_params)
for crypto_params in cfg.all_crypto_params():
if crypto_params.is_symmetric_cipher():
if (MeExpr(), crypto_params) in ext_circuit.requested_global_keys or crypto_params in args_backends:
# Make sure msg.sender's key pair is available in the circuit
stmts += ext_circuit.request_private_key(crypto_params)
# Verify that out parameter has correct size
stmts += [RequireStatement(IdentifierExpr(cfg.zk_out_name).dot('length').binop('==', NumberLiteralExpr(ext_circuit.out_size_trans)))]
# IdentifierExpr for array var holding serialized public circuit inputs
in_arr_var = IdentifierExpr(cfg.zk_in_name).as_type(Array(AnnotatedTypeName.uint_all()))
# Request static public keys
offset = 0
key_req_stmts = []
me_key_idx: Dict[CryptoParams, int] = {}
if ext_circuit.requested_global_keys:
# Ensure that me public key is stored starting at in[0]
keys = [key for key in ext_circuit.requested_global_keys]
tmp_keys = {}
for crypto_params in int_fct.used_crypto_backends:
tmp_key_var = Identifier(f'_tmp_key_{crypto_params.identifier_name}')
key_req_stmts.append(tmp_key_var.decl_var(AnnotatedTypeName.key_type(crypto_params)))
tmp_keys[crypto_params] = tmp_key_var
for (key_owner, crypto_params) in keys:
tmp_key_var = tmp_keys[crypto_params]
idf, assignment = ext_circuit.request_public_key(crypto_params, key_owner, ext_circuit.get_glob_key_name(key_owner, crypto_params))
assignment.lhs = IdentifierExpr(tmp_key_var.clone())
key_req_stmts.append(assignment)
# Remember me-keys for later use in symmetrically encrypted keys
if key_owner == MeExpr():
assert crypto_params not in me_key_idx
me_key_idx[crypto_params] = offset
# Manually add to circuit inputs
key_len = crypto_params.key_len
key_req_stmts.append(in_arr_var.slice(offset, key_len).assign(IdentifierExpr(tmp_key_var.clone()).slice(0, key_len)))
offset += key_len
assert offset == ext_circuit.in_size
# Check encrypted parameters
param_stmts = []
for p in original_params:
""" * of T_e rule 8 """
if p.annotated_type.is_cipher():
cipher_payload_len = p.annotated_type.type_name.crypto_params.cipher_payload_len
assign_stmt = in_arr_var.slice(offset, cipher_payload_len).assign(IdentifierExpr(p.idf.clone()).slice(0, cipher_payload_len))
ext_circuit.ensure_parameter_encryption(assign_stmt, p)
# Manually add to circuit inputs
param_stmts.append(assign_stmt)
offset += cipher_payload_len
# Populate sender field of parameters encrypted with a symmetric cipher
copy_stmts = []
for p in original_params:
if p.annotated_type.is_cipher():
c = p.annotated_type.type_name
assert isinstance(c, CipherText)
if c.crypto_params.is_symmetric_cipher():
sender_key = in_arr_var.index(me_key_idx[c.crypto_params])
idf = IdentifierExpr(p.idf.clone()).as_type(p.annotated_type.clone())
cipher_payload_len = cfg.get_crypto_params(p.annotated_type.homomorphism).cipher_payload_len
lit = ArrayLiteralExpr([idf.clone().index(i) for i in range(cipher_payload_len)] + [sender_key])
copy_stmts.append(VariableDeclarationStatement(VariableDeclaration([], p.annotated_type.clone(), p.idf.clone(), 'memory'), lit))
if copy_stmts:
param_stmts += [Comment(), Comment('Copy from calldata to memory and set sender field')] + copy_stmts
# Declare in array
new_in_array_expr = NewExpr(AnnotatedTypeName(TypeName.dyn_uint_array()), [NumberLiteralExpr(ext_circuit.in_size_trans)])
in_var_decl = in_arr_var.idf.decl_var(TypeName.dyn_uint_array(), new_in_array_expr)
stmts.append(in_var_decl)
stmts.append(Comment())
stmts += Comment.comment_wrap_block('Request static public keys', key_req_stmts)
stmts += Comment.comment_wrap_block('Backup private arguments for verification', param_stmts)
# Call internal function
args = [IdentifierExpr(param.idf.clone()) for param in original_params]
internal_call = FunctionCallExpr(IdentifierExpr(int_fct.idf.clone()).override(target=int_fct), args)
internal_call.sec_start_offset = ext_circuit.priv_in_size
if int_fct.requires_verification:
ext_circuit.call_function(internal_call)
args += [in_arr_var.clone(), NumberLiteralExpr(ext_circuit.in_size),
IdentifierExpr(cfg.zk_out_name), NumberLiteralExpr(ext_circuit.out_size)]
if int_fct.return_parameters:
stmts += Comment.comment_list("Declare return variables", [VariableDeclarationStatement(deep_copy(vd)) for vd in int_fct.return_var_decls])
in_call = TupleExpr([IdentifierExpr(vd.idf.clone()) for vd in int_fct.return_var_decls]).assign(internal_call)
else:
in_call = ExpressionStatement(internal_call)
stmts.append(Comment("Call internal function"))
stmts.append(in_call)
stmts.append(Comment())
# Call verifier
if requires_proof and not cfg.disable_verification:
verifier = IdentifierExpr(cfg.get_contract_var_name(ext_circuit.verifier_contract_type.code()))
verifier_args = [IdentifierExpr(cfg.proof_param_name), IdentifierExpr(cfg.zk_in_name), IdentifierExpr(cfg.zk_out_name)]
verify = ExpressionStatement(verifier.call(cfg.verification_function_name, verifier_args))
stmts.append(StatementList([Comment('Verify zk proof of execution'), verify], excluded_from_simulation=True))
# Add return statement at the end if necessary
if int_fct.return_parameters:
stmts.append(ReturnStatement(TupleExpr([IdentifierExpr(vd.idf.clone()) for vd in int_fct.return_var_decls])))
return Block(stmts)
def evaluate_stmt_in_circuit(self, ast: Statement) -> AssignmentStatement:
"""
Evaluate an entire statement privately.
This works by turning the statement into an assignment statement where the
* lhs is a tuple of all external locations (defined outside statement), which are modified inside the statement
* rhs is the return value of an inlined function call expression to a virtual function where body = the statement + return statement \
which returns a tuple of the most recent SSA version of all modified locations
Note: Modifying external locations which are not owned by @me inside the statement is illegal (would leak information).
Note: At the moment, this is only used for if statements with a private condition.
:param ast: the statement to evaluate inside the circuit
:return: AssignmentStatement as described above
"""
astmt = ExpressionStatement(NumberLiteralExpr(0))
for var in ast.modified_values:
if var.in_scope_at(ast):
astmt = AssignmentStatement(None, None)
break
astmt.before_analysis = ast.before_analysis
# External values written inside statement -> function return values
ret_params = []
for var in ast.modified_values:
if var.in_scope_at(ast):
# side effect affects location outside statement and has privacy @me
assert ast.before_analysis.same_partition(
var.privacy, Expression.me_expr())
assert isinstance(
var.target,
(Parameter, VariableDeclaration, StateVariableDeclaration))
t = var.target.annotated_type.zkay_type
if not t.type_name.is_primitive_type():
raise NotImplementedError(
'Reference types inside private if statements are not supported'
)
ret_t = AnnotatedTypeName(t.type_name, Expression.me_expr(),
t.homomorphism) # t, but @me
ret_param = IdentifierExpr(var.target.idf.clone(),
ret_t).override(target=var.target)
ret_param.statement = astmt
ret_params.append(ret_param)
# Build the imaginary function
fdef = ConstructorOrFunctionDefinition(
Identifier('<stmt_fct>'), [], ['private'], [
Parameter([], ret.annotated_type, ret.target.idf)
for ret in ret_params
], Block([ast, ReturnStatement(TupleExpr(ret_params))]))
fdef.original_body = fdef.body
fdef.body.parent = fdef
fdef.parent = ast
# inline "Call" to the imaginary function
fcall = FunctionCallExpr(
IdentifierExpr('<stmt_fct>').override(target=fdef), [])
fcall.statement = astmt
ret_args = self.inline_function_call_into_circuit(fcall)
# Move all return values out of the circuit
if not isinstance(ret_args, TupleExpr):
ret_args = TupleExpr([ret_args])
for ret_arg in ret_args.elements:
ret_arg.statement = astmt
ret_arg_outs = [
self._get_circuit_output_for_private_expression(
ret_arg, Expression.me_expr(),
ret_param.annotated_type.homomorphism)
for ret_param, ret_arg in zip(ret_params, ret_args.elements)
]
# Create assignment statement
if ret_params:
astmt.lhs = TupleExpr(
[ret_param.clone() for ret_param in ret_params])
astmt.rhs = TupleExpr(ret_arg_outs)
return astmt
else:
assert isinstance(astmt, ExpressionStatement)
return astmt
def join(then_idf, else_idf):
"""Return new temporary HybridArgumentIdf with value cond ? then_idf : else_idf."""
rhs = FunctionCallExpr(BuiltinFunction('ite'), [true_cond_for_other_branch.clone(), then_idf, else_idf]).as_type(val.t)
return create_val_for_name_and_expr_fct(key.name, rhs)
def visitFunctionCallExpr(self, ast: FunctionCallExpr):
if isinstance(ast.func, BuiltinFunction):
if ast.func.is_private:
"""
Modified Rule (12) builtin functions with private operands are evaluated inside the circuit.
A private expression on its own (like an IdentifierExpr referring to a private variable) is not enough to trigger a
boundary crossing (assignment of private variables is a public operation).
"""
return self.gen.evaluate_expr_in_circuit(ast, Expression.me_expr())
else:
"""
Rule (10) with additional short-circuit handling.
Builtin operations on public operands are normally left untransformed, but if the builtin function has
short-circuiting semantics, guard conditions must be added if any of the public operands contains
nested private expressions.
"""
# handle short-circuiting
if ast.func.has_shortcircuiting() and any(map(contains_private_expr, ast.args[1:])):
op = ast.func.op
guard_var = self.gen.add_to_circuit_inputs(ast.args[0])
ast.args[0] = guard_var.get_loc_expr(ast)
if op == 'ite':
ast.args[1] = self.visit_guarded_expression(guard_var, True, ast.args[1])
ast.args[2] = self.visit_guarded_expression(guard_var, False, ast.args[2])
elif op == '||':
ast.args[1] = self.visit_guarded_expression(guard_var, False, ast.args[1])
elif op == '&&':
ast.args[1] = self.visit_guarded_expression(guard_var, True, ast.args[1])
return ast
return self.visit_children(ast)
elif ast.is_cast:
"""Casts are handled either in public or inside the circuit depending on the privacy of the casted expression."""
assert isinstance(ast.func.target, EnumDefinition)
if ast.args[0].evaluate_privately:
return self.gen.evaluate_expr_in_circuit(ast, Expression.me_expr())
else:
return self.visit_children(ast)
else:
"""
Handle normal function calls (outside private expression case).
The called functions are allowed to have side effects,
if the function does not require verification it can even be recursive.
"""
assert isinstance(ast.func, LocationExpr)
ast = self.visit_children(ast)
if ast.func.target.requires_verification_when_external:
# Reroute the function call to the corresponding internal function if the called function was split into external/internal.
if not isinstance(ast.func, IdentifierExpr):
raise NotImplementedError()
ast.func.idf.name = cfg.get_internal_name(ast.func.target)
if ast.func.target.requires_verification:
# If the target function has an associated circuit, make this function's circuit aware of the call.
self.gen.call_function(ast)
elif ast.func.target.has_side_effects and self.gen is not None:
# Invalidate modified state variables for the current circuit
for val in ast.modified_values:
if val.key is None and isinstance(val.target, StateVariableDeclaration):
self.gen.invalidate_idf(val.target.idf)
# The call will be present as a normal function call in the output solidity code.
return ast