9ed20568e7
This commit introduces basic annotations for `std::basic_string`,
mirroring the approach used in `std::vector` and `std::deque`.
Initially, only long strings with the default allocator will be
annotated. Short strings (_SSO - short string optimization_) and strings
with non-default allocators will be annotated in the near future, with
separate commits dedicated to enabling them. The process will be similar
to the workflow employed for enabling annotations in `std::deque`.
**Please note**: these annotations function effectively only when libc++
and libc++abi dylibs are instrumented (with ASan). This aligns with the
prevailing behavior of Memory Sanitizer.
To avoid breaking everything, this commit also appends
`_LIBCPP_INSTRUMENTED_WITH_ASAN` to `__config_site` whenever libc++ is
compiled with ASan. If this macro is not defined, string annotations are
not enabled. However, linking a binary that does **not** annotate
strings with a dynamic library that annotates strings, is not permitted.
Originally proposed here: https://reviews.llvm.org/D132769
Related patches on Phabricator:
- Turning on annotations for short strings:
https://reviews.llvm.org/D147680
- Turning on annotations for all allocators:
https://reviews.llvm.org/D146214
This PR is a part of a series of patches extending AddressSanitizer C++
container overflow detection capabilities by adding annotations, similar
to those existing in `std::vector` and `std::deque` collections. These
enhancements empower ASan to effectively detect instances where the
instrumented program attempts to access memory within a collection's
internal allocation that remains unused. This includes cases where
access occurs before or after the stored elements in `std::deque`, or
between the `std::basic_string`'s size (including the null terminator)
and capacity bounds.
The introduction of these annotations was spurred by a real-world
software bug discovered by Trail of Bits, involving an out-of-bounds
memory access during the comparison of two strings using the
`std::equals` function. This function was taking iterators
(`iter1_begin`, `iter1_end`, `iter2_begin`) to perform the comparison,
using a custom comparison function. When the `iter1` object exceeded the
length of `iter2`, an out-of-bounds read could occur on the `iter2`
object. Container sanitization, upon enabling these annotations, would
effectively identify and flag this potential vulnerability.
This Pull Request introduces basic annotations for `std::basic_string`.
Long strings exhibit structural similarities to `std::vector` and will
be annotated accordingly. Short strings are already implemented, but
will be turned on separately in a forthcoming commit. Look at [a
comment](https://github.com/llvm/llvm-project/pull/72677#issuecomment-1850554465)
below to read about SSO issues at current moment.
Due to the functionality introduced in
[D132522](dd1b7b797a),
the `__sanitizer_annotate_contiguous_container` function now offers
compatibility with all allocators. However, enabling this support will
be done in a subsequent commit. For the time being, only strings with
the default allocator will be annotated.
If you have any questions, please email:
- advenam.tacet@trailofbits.com
- disconnect3d@trailofbits.com
56 lines
2.1 KiB
C++
56 lines
2.1 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// <string>
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// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
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// To silence a GCC warning-turned-error re. `BadAlloc::value_type`.
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// ADDITIONAL_COMPILE_FLAGS: -Wno-unused-local-typedefs
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// template<ranges::input_range R,
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// class Allocator = allocator<ranges::range_value_t<R>>>
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// basic_string(from_range_t, R&&, Allocator = Allocator())
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// -> basic_string<ranges::range_value_t<R>, char_traits<ranges::range_value_t<R>>,
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// Allocator>; // C++23
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//
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// The deduction guide shall not participate in overload resolution if Allocator
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// is a type that does not qualify as an allocator (in addition to the `input_range` concept being satisfied by `R`).
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#include <array>
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#include <string>
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#include "deduction_guides_sfinae_checks.h"
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#include "test_allocator.h"
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#include "asan_testing.h"
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int main(int, char**) {
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using Char = char16_t;
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{
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std::basic_string c(std::from_range, std::array<Char, 0>());
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static_assert(std::is_same_v<decltype(c), std::basic_string<Char>>);
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LIBCPP_ASSERT(is_string_asan_correct(c));
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}
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{
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using Alloc = test_allocator<Char>;
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std::basic_string c(std::from_range, std::array<Char, 0>(), Alloc());
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static_assert(std::is_same_v<decltype(c), std::basic_string<Char, std::char_traits<Char>, Alloc>>);
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LIBCPP_ASSERT(is_string_asan_correct(c));
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}
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// Note: defining `value_type` is a workaround because one of the deduction guides will end up instantiating
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// `basic_string`, and that would fail with a hard error if the given allocator doesn't define `value_type`.
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struct BadAlloc {
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using value_type = char;
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};
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SequenceContainerDeductionGuidesSfinaeAway<std::basic_string, std::basic_string<char>, BadAlloc>();
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return 0;
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}
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