sudo: check ownership and setuid bit

[japaric]

closes #331

[github-actions[bot]]

Number of dependencies and binary size impact report

Metric	main	PR #703	Delta
Direct dependencies	3	3	-
Total dependencies	4	4	-
Binary size	989.1 KiB	989.1 KiB	-
Text size	575 KiB	575.7 KiB	+0.1%

Dependencies diff

```diff └─ sudo-rs [v0.2.0-dev.20230711] ├─ glob [v0.3.1] ├─ libc [v0.2.147] └─ log [v0.4.19] ```

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.07 :warning:

Comparison is base (8f10ef5) 57.37% compared to head (b842bda) 57.30%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #703 +/- ## ========================================== - Coverage 57.37% 57.30% -0.07% ========================================== Files 68 68 Lines 9091 9102 +11 ========================================== Hits 5216 5216 - Misses 3875 3886 +11 ``` | [Impacted Files](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety) | Coverage Δ | | |---|---|---| | [src/common/error.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL2NvbW1vbi9lcnJvci5ycw==) | `14.70% <0.00%> (-0.45%)` | :arrow_down: | | [src/sudo/mod.rs](https://app.codecov.io/gh/memorysafety/sudo-rs/pull/703?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=memorysafety#diff-c3JjL3N1ZG8vbW9kLnJz) | `0.00% <0.00%> (ø)` | |

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.