systemd: make home directory readable by systemd-coredump

In systemd/systemd@924453c ProtectHome was set to true for systemd-coredump in order to reduce risk, since an attacker could craft a malicious binary in order to compromise systemd-coredump. At that point the object analysis was done in the main systemd-coredump process. Because of this systemd-coredump is unable to product symbolicated call-stacks for binaries running under /home ("n/a" is shown instead of function names). However, later in systemd/systemd@61aea45 systemd-coredump was changed to do the object analysis in a forked process, covering those security concerns. Let's set ProtectHome to read-only so that systemd-coredump produces symbolicated call-stacks for processes running under /home. Note: it still does not work in /tmp (because of PrivateTmp=yes) and in /root (for unknown reasons). Before the change (with minidebuginfo enabled): root@qemux86-64:~# /home/sleep 1000 & [1] 426 root@qemux86-64:~# kill -11 $(pidof sleep) root@qemux86-64:~# coredumpctl info PID: 426 (sleep) UID: 0 (root) GID: 0 (root) Signal: 11 (SEGV) Timestamp: Fri 2024-09-06 17:25:18 UTC (3s ago) Command Line: /home/sleep 1000 Executable: /home/sleep Control Group: /system.slice/system-serial\x2dgetty.slice/[email protected] Unit: [email protected] Slice: system-serial\x2dgetty.slice Boot ID: 44ef4ddfaad249ceaa29d1e9f330d3b5 Machine ID: fb279f18f2c849c59768754c7a274ee3 Hostname: qemux86-64 Storage: /var/lib/systemd/coredump/core.sleep.0.44ef4ddfaad249ceaa29d1e9f330d3b5.426.1725643518000000.zst (present) Size on Disk: 16.5K Message: Process 426 (sleep) of user 0 dumped core. Stack trace of thread 426: #0 0x00007f365f3849a7 clock_nanosleep (libc.so.6 + 0xd49a7) #1 0x00007f365f38f667 __nanosleep (libc.so.6 + 0xdf667) #2 0x0000561fee703737 n/a (/home/sleep + 0x7737) #3 0x000000003a6227c5 n/a (n/a + 0x0) ELF object binary architecture: AMD x86-64 [1]+ Segmentation fault (core dumped) /home/sleep 1000 After the change (with minidebuginfo enabled): root@qemux86-64:~# /home/sleep 1000 & [1] 450 root@qemux86-64:~# kill -11 $(pidof sleep) root@qemux86-64:~# coredumpctl info PID: 450 (sleep) UID: 0 (root) GID: 0 (root) Signal: 11 (SEGV) Timestamp: Fri 2024-09-06 17:30:12 UTC (4s ago) Command Line: /home/sleep 1000 Executable: /home/sleep Control Group: /system.slice/system-serial\x2dgetty.slice/[email protected] Unit: [email protected] Slice: system-serial\x2dgetty.slice Boot ID: 44ef4ddfaad249ceaa29d1e9f330d3b5 Machine ID: fb279f18f2c849c59768754c7a274ee3 Hostname: qemux86-64 Storage: /var/lib/systemd/coredump/core.sleep.0.44ef4ddfaad249ceaa29d1e9f330d3b5.450.1725643812000000.zst (present) Size on Disk: 16.5K Message: Process 450 (sleep) of user 0 dumped core. Stack trace of thread 450: #0 0x00007f795dd689a7 clock_nanosleep (libc.so.6 + 0xd49a7) #1 0x00007f795dd73667 __nanosleep (libc.so.6 + 0xdf667) #2 0x0000561965c9d737 rpl_nanosleep (sleep + 0x7737) #3 0x0000561965c9d0c1 xnanosleep (sleep + 0x70c1) #4 0x0000561965c985c8 main (sleep + 0x25c8) #5 0x00007f795dcba01b __libc_start_call_main (libc.so.6 + 0x2601b) #6 0x00007f795dcba0d9 __libc_start_main (libc.so.6 + 0x260d9) #7 0x0000561965c98685 _start (sleep + 0x2685) ELF object binary architecture: AMD x86-64 [1]+ Segmentation fault (core dumped) /home/sleep 1000 (From OE-Core rev: 3c37bf8e4844d676dde3d7ce6ad5b7de32196975) Signed-off-by: Etienne Cordonnier <[email protected]> Signed-off-by: Richard Purdie <[email protected]>
yoctoproject · Sep 9, 2024 · 556e848 · 556e848
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commit 556e848
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diff --git a/meta/recipes-core/systemd/systemd/0003-coredump-set-ProtectHome-to-read-only.patch b/meta/recipes-core/systemd/systemd/0003-coredump-set-ProtectHome-to-read-only.patch
@@ -0,0 +1,38 @@
+From 4ac1755be2d6c141fae7e57c42936e507c5b54e3 Mon Sep 17 00:00:00 2001
+From: Etienne Cordonnier <[email protected]>
+Date: Fri, 6 Sep 2024 10:36:28 +0200
+Subject: [PATCH] coredump: set ProtectHome to read-only
+
+In https://github.com/systemd/systemd/pull/5283/commits/924453c22599cc246746a0233b2f52a27ade0819
+ProtectHome was set to true for systemd-coredump in order to reduce risk, since an attacker could craft a malicious binary in order to compromise systemd-coredump.
+At that point the object analysis was done in the main systemd-coredump process.
+Because of this systemd-coredump is unable to product symbolicated call-stacks for binaries running under /home ("n/a" is shown instead of function names).
+
+However, later in https://github.com/systemd/systemd/commit/61aea456c12c54f49c4a76259af130e576130ce9 systemd-coredump was changed to do the object analysis in a forked process,
+covering those security concerns.
+
+Let's set ProtectHome to read-only so that systemd-coredump produces symbolicated call-stacks for processes running under /home.
+
+Upstream-Status: Backport [https://github.com/systemd/systemd/commit/4ac1755be2d6c141fae7e57c42936e507c5b54e3]
+
+Signed-off-by: Etienne Cordonnier <[email protected]>
+---
+ units/[email protected] | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/units/[email protected] b/units/[email protected]
+index 012c60d2f6..fa3206d07b 100644
+--- a/units/[email protected]
++++ b/units/[email protected]
+@@ -28,7 +28,7 @@ PrivateDevices=yes
+ PrivateNetwork=yes
+ PrivateTmp=yes
+ ProtectControlGroups=yes
+-ProtectHome=yes
++ProtectHome=read-only
+ ProtectHostname=yes
+ ProtectKernelModules=yes
+ ProtectKernelTunables=yes
+-- 
+2.43.0
+
diff --git a/meta/recipes-core/systemd/systemd_256.5.bb b/meta/recipes-core/systemd/systemd_256.5.bb
@@ -28,6 +28,7 @@ SRC_URI += " \
            file://systemd-pager.sh \
            file://0001-binfmt-Don-t-install-dependency-links-at-install-tim.patch \
            file://0002-implment-systemd-sysv-install-for-OE.patch \
+           file://0003-coredump-set-ProtectHome-to-read-only.patch \
            "
 
 # patches needed by musl