From 4c1d39b7a2bc9e58436da0bf85edf5cd74d5a882 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Thu, 12 Apr 2018 00:39:20 +0200
Subject: Properly force-clean for shortening bytesXX conversions.
---
Changelog.md | 1 +
libsolidity/codegen/CompilerUtils.cpp | 19 +++++++++----------
2 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/Changelog.md b/Changelog.md
index 91048cd5..0d436b6b 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -30,6 +30,7 @@ Bugfixes:
* Code Generator: Bugfix in modifier lookup in libraries.
* Code Generator: Implement packed encoding of external function types.
* Code Generator: Treat empty base constructor argument list as not provided.
+ * Code Generator: Properly force-clean bytesXX types for shortening conversions.
* Commandline interface: Fix error messages for imported files that do not exist.
* Commandline interface: Support ``--evm-version constantinople`` properly.
* DocString Parser: Fix error message for empty descriptions.
diff --git a/libsolidity/codegen/CompilerUtils.cpp b/libsolidity/codegen/CompilerUtils.cpp
index b4550153..4af7d905 100644
--- a/libsolidity/codegen/CompilerUtils.cpp
+++ b/libsolidity/codegen/CompilerUtils.cpp
@@ -684,19 +684,17 @@ void CompilerUtils::convertType(
// clear for conversion to longer bytes
solAssert(targetTypeCategory == Type::Category::FixedBytes, "Invalid type conversion requested.");
FixedBytesType const& targetType = dynamic_cast<FixedBytesType const&>(_targetType);
- if (targetType.numBytes() > typeOnStack.numBytes() || _cleanupNeeded)
+ if (typeOnStack.numBytes() == 0 || targetType.numBytes() == 0)
+ m_context << Instruction::POP << u256(0);
+ else if (targetType.numBytes() > typeOnStack.numBytes() || _cleanupNeeded)
{
- if (typeOnStack.numBytes() == 0)
- m_context << Instruction::POP << u256(0);
- else
- {
- m_context << ((u256(1) << (256 - typeOnStack.numBytes() * 8)) - 1);
- m_context << Instruction::NOT << Instruction::AND;
- }
+ int bytes = min(typeOnStack.numBytes(), targetType.numBytes());
+ m_context << ((u256(1) << (256 - bytes * 8)) - 1);
+ m_context << Instruction::NOT << Instruction::AND;
}
}
- }
break;
+ }
case Type::Category::Enum:
solAssert(_targetType == _typeOnStack || targetTypeCategory == Type::Category::Integer, "");
if (enumOverflowCheckPending)
@@ -798,8 +796,9 @@ void CompilerUtils::convertType(
bytesConstRef data(value);
if (targetTypeCategory == Type::Category::FixedBytes)
{
+ int const numBytes = dynamic_cast<FixedBytesType const&>(_targetType).numBytes();
solAssert(data.size() <= 32, "");
- m_context << h256::Arith(h256(data, h256::AlignLeft));
+ m_context << (h256::Arith(h256(data, h256::AlignLeft)) & (~(u256(-1) >> (8 * numBytes))));
}
else if (targetTypeCategory == Type::Category::Array)
{
--
cgit v1.2.3
From 0201492bbfb18ecc73f34d10e76dc0ee8395de73 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Fri, 13 Apr 2018 02:14:18 +0100
Subject: Remove redundant cleanup for abi.encode.
---
libsolidity/codegen/ExpressionCompiler.cpp | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index ed5af42e..3cf46a9d 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -1023,7 +1023,6 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
solAssert(function.kind() == FunctionType::Kind::ABIEncodeWithSelector, "");
}
- // Cleanup actually does not clean on shrinking the type.
utils().convertType(*dataOnStack, FixedBytesType(4), true);
// stack: <memory pointer> <selector>
@@ -1034,7 +1033,7 @@ bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
let data_start := add(mem_ptr, 0x20)
let data := mload(data_start)
let mask := )" + mask + R"(
- mstore(data_start, or(and(data, mask), and(selector, not(mask))))
+ mstore(data_start, or(and(data, mask), selector))
})", {"mem_ptr", "selector"});
m_context << Instruction::POP;
}
--
cgit v1.2.3
From bf57500e250c0ebaed4b608626245dde4b423ba1 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Fri, 13 Apr 2018 17:34:35 +0200
Subject: Tests for bytes cleanup.
---
test/libsolidity/SolidityEndToEndTest.cpp | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index cbeca215..e1727ee0 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -8807,6 +8807,24 @@ BOOST_AUTO_TEST_CASE(cleanup_bytes_types)
ABI_CHECK(callContractFunction("f(bytes2,uint16)", string("abc"), u256(0x040102)), encodeArgs(0));
}
+BOOST_AUTO_TEST_CASE(cleanup_bytes_types_shortening)
+{
+ char const* sourceCode = R"(
+ contract C {
+ function f() pure returns (bytes32 r) {
+ bytes4 x = 0xffffffff;
+ bytes2 y = bytes2(x);
+ assembly { r := y }
+ // At this point, r and y both store four bytes, but
+ // y is properly cleaned before the equality check
+ require(y == bytes2(0xffff));
+ }
+ }
+ )";
+ compileAndRun(sourceCode, 0, "C");
+ ABI_CHECK(callContractFunction("f()"), encodeArgs("\xff\xff\xff\xff"));
+}
+
BOOST_AUTO_TEST_CASE(skip_dynamic_types)
{
// The EVM cannot provide access to dynamically-sized return values, so we have to skip them.
@@ -11322,6 +11340,10 @@ BOOST_AUTO_TEST_CASE(abi_encode)
y[0] = "e";
require(y[0] == "e");
}
+ function f4() returns (bytes) {
+ bytes4 x = "abcd";
+ return abi.encode(bytes2(x));
+ }
}
)";
compileAndRun(sourceCode, 0, "C");
@@ -11329,6 +11351,7 @@ BOOST_AUTO_TEST_CASE(abi_encode)
ABI_CHECK(callContractFunction("f1()"), encodeArgs(0x20, 0x40, 1, 2));
ABI_CHECK(callContractFunction("f2()"), encodeArgs(0x20, 0xa0, 1, 0x60, 2, 3, "abc"));
ABI_CHECK(callContractFunction("f3()"), encodeArgs(0x20, 0xa0, 1, 0x60, 2, 3, "abc"));
+ ABI_CHECK(callContractFunction("f4()"), encodeArgs(0x20, 0x20, "ab"));
}
BOOST_AUTO_TEST_CASE(abi_encode_v2)
--
cgit v1.2.3
From a9c16b8c3976dbd2c386586cdf143150a4266ac0 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Mon, 16 Apr 2018 12:46:48 +0200
Subject: Add documentation.
---
docs/assembly.rst | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/docs/assembly.rst b/docs/assembly.rst
index 705cd1b8..978e71e3 100644
--- a/docs/assembly.rst
+++ b/docs/assembly.rst
@@ -405,6 +405,16 @@ changes during the call, and thus references to local variables will be wrong.
}
}
+.. note::
+ If you access variables of a type that spans less than 256 bits
+ (for example ``uint64``, ``address``, ``bytes16`` or ``byte``),
+ you cannot make any assumptions about bits not part of the
+ encoding of the type. Especially, do not assume them to be zero.
+ To be safe, always clear the data properly before you use it
+ in a context where this is important:
+ ``uint32 x = f(); assembly { x := and(x, 0xffffffff) /* now use x */ }``
+ To clean signed types, you can use the ``signextend`` opcode.
+
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