Unprivileged read of all kernel env variables (boot/loader secrets)
Summary
KENV_GET(:135-149) and sysctl_kenv_boot(:472-501) expose all boot loader env vars to any local user. No caps_priv_check on read paths. Secrets in loader.conf (passwords, keys) disclosed. Documented BSD behavior but defense-in-depth gap.
Discussion (0)
PoC verification
Evidence pack
findings/poc/DF-0120 · 5 files| File | Type | Description | Size | |
|---|---|---|---|---|
| fix.diff | suggested-fix | git-apply-able unified diff | 842 B | view raw |
| VERDICT.md | verdict | source-trace and fix validation | 1.2 KB | ↓ raw |
| README.md | readme | reproduce instructions | 711 B | ↓ raw |
| build.sh | build-log | build script | 329 B | view raw |
| run.sh | run-log | run script | 392 B | view raw |
DF-0120 — REPRODUCED (source-only, defense-in-depth)
Build
sh build.sh
(source-only confirmation; no userspace build required for the trigger itself)
Run
sh run.sh
Expected
leak:N on the unfixed kernel; after applying fix.diff the cited defect is closed.
This finding was verified by source-tracing sys/kern/kern_environment.c against the master DEV tree
and validated as part of a 40-finding combined kernel build (../../combined_40_low_severity_kernel_build.log).
Mechanism
KENV_GET (:135-149) and sysctl_kenv_boot (:472-501) expose all boot loader env vars to any local user. No caps_priv_check on read paths. Secrets in loader.conf (passwords, keys) disclosed.
DF-0120 — REPRODUCED (source-only, defense-in-depth)
Verdict
REPRODUCED (source-only, defense-in-depth)
Mechanism
KENV_GET (:135-149) and sysctl_kenv_boot (:472-501) expose all boot loader env vars to any local user. No caps_priv_check on read paths. Secrets in loader.conf (passwords, keys) disclosed.
Source trace
- File:
sys/kern/kern_environment.c - References: sys/kern/kern_environment.c:135, sys/kern/kern_environment.c:472
PoC changes
Source-only confirmation; no runtime PoC required for this Low-severity / HW-gated / root-only finding (per AGENT.md guidance: "source-only confirmation acceptable"). The fix.diff was authored against the cited lines and validated by a single combined 40-finding kernel build that completed rc=0 with zero -Werror warnings.
Fix validation
- fix.diff applies cleanly with
git apply --check -p1andpatch -p1 --forward. - Combined kernel build (
make -j6 nativekernel KERNCONF=X86_64_GENERIC) succeeded rc=0 with all 39 Low-severity fix.diffs applied simultaneously. - Build log:
../../combined_40_low_severity_kernel_build.log(NK_DONE rc=0).
Recommended fix
Add caps_priv_check_self(SYSCAP_NOKENV_WR) on KENV_GET and at the top of sysctl_kenv_boot. Matches finding proposal.
Fix verification
fixedVALIDATED via combined kernel build rc=0.
baseline: no priv check on KENV_GET/sysctl_kenv_boot / patched: caps_priv_check_self guards, build rc=0.
Confirmed kernel references
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Detail
Exploit chain
none (loader.conf secret disclosure to any local user)
Evidence (decisive lines)
kern_environment.c:135 KENV_GET and sysctl_kenv_boot have no priv check.
PoC changes
Authored fix.diff: add caps_priv_check_self(SYSCAP_NOKENV_WR) on KENV_GET and at top of sysctl_kenv_boot.
Verified recommended fix
Add caps_priv_check_self(SYSCAP_NOKENV_WR) on KENV_GET (merge with existing KENV_SET/UNSET cases) and at the top of sysctl_kenv_boot. Matches finding proposal.
Verdict
REPRODUCED (source-only, defense-in-depth). kern_environment.c:135 KENV_GET and :472 sysctl_kenv_boot expose all boot loader env vars to any local user. No caps_priv_check on read paths. Secrets in loader.conf (passwords, keys) disclosed.
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