| # foomatic_shell: mini-shell used by foomatic-rip |
| |
| This is a simple mini-shell that is used by `foomatic-rip` to execute small |
| scripts included in some PPD files. |
| |
| Some PPD files from foomatic provides small shell scripts that must be run in |
| order to process documents sent to a printer. The script is often customized in |
| runtime. This approach is quite flexible but also introduces security |
| vulnerability. Originally, `foomatic-rip` uses default OS shell to execute the |
| script. In ChromeOS, `foomatic-rip` calls `foomatic_shell` instead (from this |
| package). |
| |
| `foomatic_shell` executes given shell script in controlled environment to |
| mitigate the security risk. It supports pipes and backticks operator |
| (generating command by a subshell). Only very limited set of commands is |
| allowed, `foomatic_shell` enforces also some restrictions on command line |
| parameters. |
| |
| ## Appendix: FOOMATIC_VERIFY_MODE |
| |
| When the environment variable `FOOMATIC_VERIFY_MODE` is set, |
| `foomatic_shell` goes into no-op mode. It carries out command |
| verification as normal but does not run the overall pipeline. For |
| example, [this environment variable is set in the printer.TestPPDs tast |
| test.][tast-foomatic-verify-mode]. |
| |
| [tast-foomatic-verify-mode]: https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/HEAD/src/chromiumos/tast/local/bundles/cros/printer/test_ppds.go |
