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Inline lambdas in packets
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Wow, this is a fair bit of work, but it seems to behave correctly in at least some cases.  Several packets still aren't working, but this is still significant progress.
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@Pokechu22
Pokechu22 committed Feb 17, 2022
1 parent 9b9ace8 commit 9f01cf0
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Showing 2 changed files with 299 additions and 96 deletions.
117 changes: 101 additions & 16 deletions burger/toppings/packetinstructions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,10 @@
from jawa.transforms import simple_swap

from .topping import Topping
from burger.util import stringify_invokedynamic
from burger.util import InvokeDynamicInfo

SUB_INS_EPSILON = .01
PACKETBUF_NAME = "packetbuffer" # Used to specially identify the PacketBuffer we care about

class PacketInstructionsTopping(Topping):
"""Provides the instructions used to construct network packets."""
Expand Down Expand Up @@ -131,7 +134,7 @@ def act(aggregate, classloader, verbose=False):

@staticmethod
def operations(classloader, classname, classes, verbose, args=None,
methodname=None, arg_names=("this", "packetbuffer")):
methodname=None, arg_names=("this", PACKETBUF_NAME)):
"""Gets the instructions of the specified method"""

# Find the writing method
Expand Down Expand Up @@ -232,7 +235,7 @@ def operations(classloader, classname, classes, verbose, args=None,
type=_PIT.TYPES[name],
field=arguments[0]))
stack.append(obj)
elif len(name) == 1 and isinstance(obj, StackOperand) and obj.value == "packetbuffer":
elif len(name) == 1 and isinstance(obj, StackOperand) and obj.value == PACKETBUF_NAME:
# Checking len(name) == 1 is used to see if it's a Minecraft
# method (due to obfuscation). Netty methods have real
# (and thus longer) names.
Expand Down Expand Up @@ -340,22 +343,88 @@ def operations(classloader, classname, classes, verbose, args=None,
descriptor.args[1].name == "java/util/function/BiConsumer":
# Loop that calls the consumer with the packetbuffer
# and value for each value in collection
# TODO: Disambiguate names it and itv if there are multiple loops
operations.append(Operation(instruction.pos, "write",
type="varint",
field=field.value + ".size()"))
operations.append(Operation(instruction.pos, "store",
type="Iterator",
var="it",
value=field.value + ".iterator()"))
operations.append(Operation(instruction.pos, "loop",
condition="it.hasNext()"))
info = arguments[1]
assert isinstance(info, InvokeDynamicInfo)
assert len(info.method_desc.args) >= 2 # May be more if locals are referenced
operations.append(Operation(instruction.pos, "store",
type=info.method_desc.args[-1].name.replace("/", "."),
var="itv", value="it.next()"))
operations += _PIT.sub_operations2(
classloader, cf, classes, instruction,
info.method_class + ".class", info.method_name,
info.method_desc.descriptor, verbose,
info.stored_args + [PACKETBUF_NAME, "itv"]
)
# Jank: the part of the program that converts loop+endloop
# to a nested setup sorts the operations.
# Thus, if instruction.pos is used, sub_operations
# adds epsilon to each sub-instruction, making them
# come after the endloop.
# Assume that 1 - SUB_INS_EPSILON (e.g. .99) will put
# the endloop past everything.
operations.append(Operation(instruction.pos + 1 - SUB_INS_EPSILON, "endloop"))
else:
raise Exception("Unexpected descriptor " + desc)
elif num_arguments == 3:
if arg_type == "java/util/Map" and \
descriptor.args[1].name == "java/util/function/BiConsumer" and \
descriptor.args[1].name == "java/util/function/BiConsumer":
# Loop that calls the consumers with the packetbuffer
# and key, and then packetbuffer and value, for each
# (key, value) pair in the map.
# TODO: Disambiguate names it and itv if there are multiple loops
operations.append(Operation(instruction.pos, "write",
type="varint",
field=field.value + ".size()"))
operations.append(Operation(instruction.pos, "store",
type="Iterator",
var="it",
value=field.value + ".iterator()"))
# TODO: inline the referenced function - would require
# changing how stringify_invokedynamic works
target = arguments[1][:arguments[1].find(":")]
name2 = arguments[1][arguments[1].rfind(":")+1:]
operations.append(Operation(instruction.pos, "loop",
condition="it.hasNext()"))
operations.append(Operation(instruction.pos, "interfacecall",
type="dynamic",
target=target, name=name,
method=name, field=target,
args="buf, it.next()"))
operations.append(Operation(instruction.pos, "endloop"))
key_info = arguments[1]
val_info = arguments[2]
assert isinstance(key_info, InvokeDynamicInfo)
assert isinstance(val_info, InvokeDynamicInfo)
# TODO: these are violated
assert len(key_info.method_desc.args) >= 2 # May be more if locals are referenced
assert len(val_info.method_desc.args) >= 2 # May be more if locals are referenced
key_type = key_info.method_desc.args[-1].name.replace("/", ".")
val_type = val_info.method_desc.args[-1].name.replace("/", ".")
operations.append(Operation(instruction.pos, "store",
type="Map.Entry<" + key_type + ", " + val_type + ">",
var="itv", value="it.next()"))
operations += _PIT.sub_operations2(
classloader, cf, classes, instruction,
key_info.method_class + ".class", key_info.method_name,
key_info.method_desc.descriptor, verbose,
key_info.stored_args + [PACKETBUF_NAME, "itv.getKey()"]
)
# TODO: Does the SUB_INS_EPSILON work correctly here?
operations += _PIT.sub_operations2(
classloader, cf, classes, instruction,
val_info.method_class + ".class", val_info.method_name,
val_info.method_desc.descriptor, verbose,
val_info.stored_args + [PACKETBUF_NAME, "itv.getValue()"]
)
# Jank: the part of the program that converts loop+endloop
# to a nested setup sorts the operations.
# Thus, if instruction.pos is used, sub_operations
# adds epsilon to each sub-instruction, making them
# come after the endloop.
# Assume that 1 - SUB_INS_EPSILON (e.g. .99) will put
# the endloop past everything.
operations.append(Operation(instruction.pos + 1 - SUB_INS_EPSILON, "endloop"))
else:
raise Exception("Unexpected descriptor " + desc)
else:
Expand Down Expand Up @@ -420,7 +489,7 @@ def operations(classloader, classname, classes, verbose, args=None,
break

elif mnemonic == "invokedynamic":
stack.append(stringify_invokedynamic(stack, instruction, cf))
InvokeDynamicInfo(instruction, cf).apply_to_stack(stack)

# Conditional statements and loops
elif mnemonic.startswith("if"):
Expand Down Expand Up @@ -663,20 +732,36 @@ def sub_operations(classloader, cf, classes, instruction, verbose,
invoked_class = operand.c + ".class"
name = operand.name
descriptor = operand.descriptor
args = method_descriptor(descriptor).args_descriptor
return _PIT.sub_operations2(classloader, cf, classes, instruction,
invoked_class, name, descriptor, verbose, arg_names)

@staticmethod
def sub_operations2(classloader, cf, classes, instruction, invoked_class,
name, descriptor, verbose, arg_names=[""]):
"""Gets the instructions of a different class"""
cache_key = "%s/%s/%s/%s" % (invoked_class, name,
descriptor, _PIT.join(arg_names, ","))

if cache_key in _PIT.CACHE:
cache = _PIT.CACHE[cache_key]
operations = [op.clone() for op in cache]
else:
args = method_descriptor(descriptor).args_descriptor
operations = _PIT.operations(classloader, invoked_class, classes, verbose,
args, name, arg_names)

# Sort operations by position, and try to ensure all of them fit between
# two normal instructions. Note that since operations are renumbered
# on each use of sub_operations, this is safe (recursive calls to
# sub_operations will produce [1.01, 1.02, 1.03, 1.04], not
# [1.01, 1.0101, 1.0102, 1.02] or [1.01, 1.02, 1.03, 1.02]).
position = 0
for operation in _PIT.ordered_operations(operations):
position += 0.01
position += SUB_INS_EPSILON
# However, it will break if the position gets too large, as then
# something like [1.01, 1.02, ..., 1.99, 2.00, 2.01, 2] could occur.
# If this happens, just shrink SUB_INS_EPSILON.
assert(position < 1)
operation.position = instruction.pos + (position)

_PIT.CACHE[cache_key] = operations
Expand Down
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