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reject decoding strings that are passing the string block in size #1044

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merged 1 commit into from
Apr 29, 2024
Merged

reject decoding strings that are passing the string block in size #1044

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17 changes: 16 additions & 1 deletion androguard/core/axml/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -244,6 +244,13 @@ def _decode8(self, offset:int) -> str:
encoded_bytes, skip = self._decode_length(offset, 1)
offset += skip

# Two checks should happen here:
# a) offset + encoded_bytes surpassing the string_pool length and
# b) non-null terminated strings which should be rejected
# platform/frameworks/base/libs/androidfw/ResourceTypes.cpp#789
if len(self.m_charbuff) < (offset + encoded_bytes):
logger.warning(f"String size: {offset + encoded_bytes} is exceeding string pool size. Returning empty string.")
return ""
data = self.m_charbuff[offset: offset + encoded_bytes]

if self.m_charbuff[offset + encoded_bytes] != 0:
Expand All @@ -264,6 +271,14 @@ def _decode16(self, offset:int) -> str:
# The len is the string len in utf-16 units
encoded_bytes = str_len * 2

# Two checks should happen here:
# a) offset + encoded_bytes surpassing the string_pool length and
# b) non-null terminated strings which should be rejected
# platform/frameworks/base/libs/androidfw/ResourceTypes.cpp#789
if len(self.m_charbuff) < (offset + encoded_bytes):
logger.warning(f"String size: {offset + encoded_bytes} is exceeding string pool size. Returning empty string.")
return ""

data = self.m_charbuff[offset: offset + encoded_bytes]

if self.m_charbuff[offset + encoded_bytes:offset + encoded_bytes + 2] != b"\x00\x00":
Expand Down Expand Up @@ -835,7 +850,7 @@ def getAttributeName(self, index:int):
":")
if res != self.sb[name]:
self.packerwarning = True

if not res or res == ":":
# Attach the HEX Number, so for multiple missing attributes we do not run
# into problems.
Expand Down