[Bug 2127766] Re: snap run --strace doesn't work with sudo-rs [sudo -E not supported]

[Maciej Borzecki]

2.72 on 26.04:

root at u1:~# snap version
snap          2.72+ubuntu26.04.1
snapd         2.72+ubuntu26.04.1
series        16
ubuntu        26.04
kernel        6.17.0-6-generic
architecture  amd64
root at u1:~# snap install hello
2025-12-03T12:36:04Z INFO Waiting for automatic snapd restart...
hello 2.10 from Canonical✓ installed
root at u1:~# su - ubuntu
ubuntu at u1:~$ snap run hello
Hello, world!
ubuntu at u1:~$ snap run --strace hello
warning: preserving the entire environment is not supported, `-E` is ignored
error: exit status 1

2.73 on 26.04:

ubuntu at u1:~$ snap version
snap          2.73+ubuntu26.04.1
snapd         2.73+ubuntu26.04.1
series        16
ubuntu        26.04
kernel        6.17.0-6-generic
architecture  amd64
ubuntu at u1:~$ dpkg -l sudo-rs
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version         Architecture Description
+++-==============-===============-============-======================================
ii  sudo-rs        0.2.10-1ubuntu1 amd64        Rust-based sudo and su implementations

ubuntu at u1:~$ snap run --strace hello
/usr/bin/strace: Process 3032 attached
--- stopped by SIGSTOP ---
--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=3023, si_uid=1000} ---
[pid  3032] execve("/snap/hello/42/snap/command-chain/snapcraft-runner", ["/snap/hello/42/snap/command-chai"..., "/snap/hello/42/bin/hello"], 0xc000158780 /* 37 vars */ <unfinished ...>
[pid  3042] <... futex resumed>)        = ?
[pid  3042] +++ exited with 0 +++
[pid  3041] +++ exited with 0 +++
<... execve resumed>)                   = 0
brk(NULL)                               = 0x63b0d576a000
arch_prctl(0x3001 /* ARCH_??? */, 0x7fffff1f07f0) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
....
fstat(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(0x88, 0), ...}) = 0
write(1, "Hello, world!\n", 14Hello, world!
)         = 14
close(1)                                = 0
close(2)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++


Can confirm the workaround is applied with snapd 2.73.

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https://bugs.launchpad.net/bugs/2127766

Title:
  snap run --strace doesn't work with sudo-rs [sudo -E not supported]

Status in snapd:
  Fix Committed
Status in rust-sudo-rs package in Ubuntu:
  Won't Fix
Status in snapd package in Ubuntu:
  New

Bug description:
  [SRU] 2.73:
  https://bugs.launchpad.net/ubuntu/+source/snapd/+bug/2132084

  [ Impact ]

  Only impacts Ubuntu 25.10+
  With sudo-rs, -E` is ignored, which breaks snapd run --strace.

  [ Test Plan ]

  1. Reproduce with snapd snap < 2.73

  - Ensure sudo-rs installed
  - Run: snap run --strace <snap>.<app>
  - Expect: warning: preserving the entire environment is not supported, `-E` is ignored

  2. Prove fixed with snapd snap 2.73

  - Ensure sudo-rs installed
  - Run: snap run --strace <snap>.<app>
  - Expect: No warning

  ---original---

  sudo-rs became the default sudo in 25.10, which broke this snap run
  --strace,

  $ snap run --strace <snap>.<app>
  warning: preserving the entire environment is not supported, `-E` is ignored
  [sudo: authenticate] Password:
  error: exit status 1

  It does work if I switch back to GNU Coreutils' sudo. The reason being
  many required environment variables are no longer passed through, and
  the strace fails due to SNAP_INSTANCE_NAME not being set, before we
  get to execve'ing the snap application itself.

  I commented on this use case in the sudo-rs issue tracker:
  https://github.com/trifectatechfoundation/sudo-rs/issues/1299

  Maybe snapd needs to have a whitelist of environment variables?

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