guix: Pointer Authentication and Branch Target Identification for aarch64 Linux #24123

fanquake · 2022-01-21T13:43:03Z

Arm Pointer Authentication (PAC) is a method of hardening code from Return Oriented Programming (ROP) attacks. It uses a tag in a pointer to sign and verify pointers. Branch Target Identification (BTI) is another code hardening method, where the branch/jump target is identified with a special landing pad instruction. Outside of some system support in glibc+kernel, packages gain the additional hardening by compiling with the -mbranch-protection=flag available in recent versions of GCC. In particular -mbranch-protection=standard enables both BTI and PAC, with backwards compatible to armv8.0 code sequences that activate on v8.3 (PAC) & v8.5 (BTI) enabled Arm machines. (taken from Fedora).

Creation of a BTI enabled binary also requires that everything being linked in be BTI enabled. This means you currently cannot, for example, cross-compile using a Ubuntu based aarch64 toolchain, if you're wanting to use this feature. This can be shown using -Wl,z,force-bti, which will emit warnings for linked objects that are not BTI enabled (this is used in configure to detect when to disable using the flags). i.e:

int main() { return 0; }

# aarch64-linux-gnu-g++ (Ubuntu 13.2.0-23ubuntu4) 13.2.0
aarch64-linux-gnu-g++ test.cpp -mbranch-protection=standard -Wl,-z,force-bti
/usr/lib/gcc-cross/aarch64-linux-gnu/13/../../../../aarch64-linux-gnu/bin/ld: /usr/lib/gcc-cross/aarch64-linux-gnu/13/../../../../aarch64-linux-gnu/lib/../lib/Scrt1.o: warning: BTI turned on by -z force-bti when all inputs do not have BTI in NOTE section.

Closes #19075.

DrahtBot · 2022-01-21T19:58:15Z

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Concept ACK	hebasto, laanwj, kristapsk

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Conflicts

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#25573 ([POC] guix: produce a fully -static-pie bitcoind by fanquake)
#25391 (guix: Use LTO to build releases by fanquake)

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hebasto · 2022-01-22T22:25:52Z

Concept ACK.

From reading docs it's still unclear to me whether -mbranch-protection=standard implies -mbranch-protection=bti?

$ ./test/lint/lint-git-commit-check.sh 
The subject line of commit hash f799135959461079a220c5ddc97ea9a6b0056b2b is followed by a non-empty line. Subject lines should always be followed by a blank line.

laanwj · 2022-01-25T16:00:02Z

Concept ACK.

We might want to wait with doing this until hardware supporting BTI and PAC is available to test on, though.

configure.ac

DrahtBot · 2022-05-17T19:05:22Z

Guix builds

File	commit `225e5b5` (master)	commit `6e02029` (master and this pull)
SHA256SUMS.part	`1b58b80ca65983b3...`	`60902da13322462a...`
*-aarch64-linux-gnu-debug.tar.gz	`26b50f702207b949...`	`da73c81f36ba2f4f...`
*-aarch64-linux-gnu.tar.gz	`93156ddbf46f81df...`	`49d87e2a6f62f992...`
*-arm-linux-gnueabihf-debug.tar.gz	`448908d67e456427...`	`6995a4237a002a65...`
*-arm-linux-gnueabihf.tar.gz	`595189752c32bf97...`	`b3aadb2d8f165b42...`
*-arm64-apple-darwin-unsigned.dmg	`8fe9a774204a88c7...`	`068c1b89b9bacaef...`
*-arm64-apple-darwin-unsigned.tar.gz	`293f411c2dc51edb...`	`c09afa12e0677dc9...`
*-arm64-apple-darwin.tar.gz	`abca1d81d437a08a...`	`c15b198b2d1f03fc...`
*-powerpc64-linux-gnu-debug.tar.gz	`1744beebac78a5d6...`	`18afbab08627bbd0...`
*-powerpc64-linux-gnu.tar.gz	`ec4d4712136dc767...`	`564780d6229517f2...`
*-powerpc64le-linux-gnu-debug.tar.gz	`ac1890b8743df6a5...`	`08950113d8f8a24a...`
*-powerpc64le-linux-gnu.tar.gz	`b0ebc5e4120bf000...`	`5033d195b6c3a5f7...`
*-riscv64-linux-gnu-debug.tar.gz	`702be3dc495a5a10...`	`06fb203fb1b5161a...`
*-riscv64-linux-gnu.tar.gz	`ad1394d672c7b965...`	`be8de64710848522...`
*-win64-debug.zip	`5464743530003d4d...`	`c9e8d9c625b5eb35...`
*-win64-setup-unsigned.exe	`955c755466eb2b07...`	`7ef06802748bdc8f...`
*-win64-unsigned.tar.gz	`0126640c2d061f14...`	`146ee2330f8ddfa4...`
*-win64.zip	`5b07889e2dce9103...`	`4e2f315a1f35caee...`
*-x86_64-apple-darwin-unsigned.dmg	`c5526437a0193c3b...`	`2c0af2ea1cd7545d...`
*-x86_64-apple-darwin-unsigned.tar.gz	`e1d81f18176fab2e...`	`6bc18c838e5fff4f...`
*-x86_64-apple-darwin.tar.gz	`d34e5f7fe086c51f...`	`64b3270b92cd3128...`
*-x86_64-linux-gnu-debug.tar.gz	`acb6561a5919c80f...`	`6f25c5199f7623a8...`
*-x86_64-linux-gnu.tar.gz	`00bb67a5b4e29ca3...`	`8645814c4e7e8c7e...`
*.tar.gz	`ab4e54f5d920eb45...`	`9c521162a3ecfd6e...`
guix_build.log	`68d9a71f1973680b...`	`754faf723b062cbf...`
guix_build.log.diff		`85fe222476c6b46f...`

fanquake · 2022-06-28T10:43:34Z

I've changed the approach here, and this is now based on #25437 and parts of #25484.

This adds --enable-standard-branch-protection to the configure flags when building GCC, which turns on the usage of branch-protection features by default. I've also added a commit that switches to using glibc 2.33 for the aarch64 build. glibc 2.32 was the first to ship with support for aarch64 branch protection features when built with a compatible compiler (see commit message for details). We couldn't actually use this for Guix builds, because it would break out back compat requires (the symbol checks fail), so this is still just for demonstration.

kristapsk · 2022-06-28T10:54:57Z

Concept ACK

fanquake · 2024-05-16T04:26:27Z

Rebased on #29987.

DrahtBot · 2024-06-26T17:49:01Z

🚧 At least one of the CI tasks failed. Make sure to run all tests locally, according to the
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Possibly this is due to a silent merge conflict (the changes in this pull request being
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_{Debug: https://github.com/bitcoin/bitcoin/runs/26712572542}

fanquake · 2024-08-23T12:25:40Z

Rebased on master and dropped a commit, also bumped the glibc 2.33 branch to the latest commit. Still based on #30433, but the main blocker here remains the glibc bump.

fanquake · 2024-08-23T12:28:47Z

For now, the Guix built bins could be inspected with:

# bitcoin/guix-build-30af1c56da93/output/aarch64-linux-gnu/bitcoin-30af1c56da93/bin# readelf -n * | grep "AArch64"
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC
      Properties: AArch64 feature: BTI, PAC

hebasto · 2024-08-27T14:20:33Z

It would be helpful if someone with BTI-enabled hardware could test the binaries and verified BTI during runtime.

Unfortunately, I'm unable to do it by myself, as my hardware supports only PAC, not BTI.

…ags for aarch64-linux 001b1cf build: use standard branch-protection for aarch64-linux (fanquake) Pull request description: Use `-mbranch-protection=standard` when targetting `*aarch64-*-linux*`. Part of #24123, but this flag can already be used on a best effort basis. Note that this flag is also already used by default, in the toolchain, on various distros (i.e Fedora). ACKs for top commit: hebasto: ACK 001b1cf. TheCharlatan: ACK 001b1cf Tree-SHA512: 2d7ae60f59921a62d51139cb0fd5cecbed4f63266564b2623b7d160f5b0c2c42c78ef8aeff787f485eccc46a9ffd5da70023ec093df6add7c982e0d48a1601b5

glibc 2.32 was the first to ship with support for branch protection when compiled with a compatible compiler. glibc 2.32 release notes: https://lwn.net/Articles/828210/ * AArch64 now supports standard branch protection security hardening in glibc when it is built with a GCC that is configured with --enable-standard-branch-protection (or if -mbranch-protection=standard flag is passed when building both GCC target libraries and glibc, in either case a custom GCC is needed). This includes branch target identification (BTI) and pointer authentication for return addresses (PAC-RET). They require armv8.5-a and armv8.3-a architecture extensions respectively for the protection to be effective, otherwise the used instructions are nops. User code can use PAC-RET without libc support, but BTI requires a libc that is built with BTI support, otherwise runtime objects linked into user code will not be BTI compatible. `__libc_single_threaded` added as it is now exported from at least `bitcoin-wallet` and `test_bitcoin`.

fanquake · 2024-09-13T15:27:29Z

Rebased for #30433, and updated to add an export allowance for __libc_single_threaded.

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guix: Pointer Authentication and Branch Target Identification for aarch64 Linux #24123

guix: Pointer Authentication and Branch Target Identification for aarch64 Linux #24123

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guix: Pointer Authentication and Branch Target Identification for aarch64 Linux #24123

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guix: Pointer Authentication and Branch Target Identification for aarch64 Linux #24123

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