binutils: Add security patches #22272
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I have rebuilt binutils, CRT, GCC and binutils again in MINGW32, MINGW64 and UCRT64, and no error has been observed. Please examine this carefully. |
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Before this commit, the `.CRT` section (which contains pointers to image TLS callbacks) and the `.idata` section (which contains `__imp_` pointers to dllimport functions) that had been created by the GNU linker were writeable. As these functions to pointers are essential for programs to be functional, they could be exploited to inject malicious code, like the well-known IFUNC backdoor in XZ Utils. The Microsoft linker does not create these sections as writeable; instead, they seem to be merged into `.rdata` and are not modifiable, unless unprotected. LLD also does the same, suggesting these sections be merged into `.rdata`: https://github.com/llvm/llvm-project/blob/ebeb56af5f8f1ff9da8f5a7e98348f460d223de1/lld/COFF/Driver.cpp#L2034-L2048 This commit includes the following countermeasures: 1. Patch 3005 ensures the final `.CRT` and `.idata` sections (if any) will not be writeable in the final image. 2. Patch 3006 merges known sub-sections of `.CRT`, as well as `.ctors` and `.dtors` (which were merged into `.text` instead), into `.rdata`. Merging `.idata` into `.rdata` seems to prevent dllimport from working, so there's still an `.idata` section in the final image. See also: https://stackoverflow.com/questions/22651433/pe-idata-section Reference: https://sourceware.org/bugzilla/show_bug.cgi?id=32264 Signed-off-by: LIU Hao <[email protected]>
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Previous patch broke pseudo relocation, as 51247e1#diff-a641beeafacd689f0c4ac5f1141e724abbce202d57be6339df410b00401971f8R121-R131 |
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Also note that the pseudo relocator code which unprotects read-only memory was added in 2009, much later than the relocator itself: mingw-w64/mingw-w64@e209778 This might explain why those sections were required to be writeable. They no longer are. |
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Before this commit, the
.CRTsection (which contains pointers to image TLS callbacks) and the.idatasection (which contains__imp_pointers to dllimport functions) that had been created by the GNU linker were writeable.As these function pointers are essential for programs to be functional, they could be exploited to inject malicious code, like the well-known IFUNC backdoor in XZ Utils. The Microsoft linker does not create these sections as writeable; instead, they seem to be merged into
.rdataand are not modifiable, unless unprotected.LLD also does the same, suggesting these sections be merged into
.rdata: https://github.com/llvm/llvm-project/blob/ebeb56af5f8f1ff9da8f5a7e98348f460d223de1/lld/COFF/Driver.cpp#L2034-L2048This commit includes the following countermeasures:
.CRTand.idatasections (if any) will not be writeable in the final image..CRT, as well as.ctorsand.dtors(which were merged into.textinstead), into.rdata. Merging.idatainto.rdataseems to prevent dllimport from working, so there's still an.idatasection in the final image. See also: https://stackoverflow.com/questions/22651433/pe-idata-sectionReference: https://sourceware.org/bugzilla/show_bug.cgi?id=32264