cksum: Check --length before --check

[RenjiSann]

(Found with fuzzer)

args: ["cksum", "-l", "158", "-c", "-a", "crc", "/tmp/shlsgiqaxn"]                                                                                                                                                                                                                          
Running test ["cksum", "-l", "158", "-c", "-a", "crc", "/tmp/shlsgiqaxn"]                                                                                                                                                                                                                   
Test Type: cksum                                                                                                                                                                                                                                                                            
Input: ["-l", "158", "-c", "-a", "crc", "/tmp/shlsgiqaxn"]                                                                                                                                                                                                                                  
Rust stderr: --check is not supported with --algorithm={bsd,sysv,crc}                                                                                                                                                                                                                       
GNU stderr: --length is only supported with --algorithm=blake2b                                                                                                                                                                                                                             
Diff=                                                                                                                                                                                                                                                                                       
---check is not supported with --algorithm={bsd,sysv,crc}                                                                                                                                                                                                                                   
+--length is only supported with --algorithm=blake2b                                                                                                                                                                                                                                        
                                                                                                                                                                                                                                                                                            
Discrepancy detected: stderr differs                                                                                                                                                                                                                                                        
Test completed with discrepancies for cksum: ["-l", "158", "-c", "-a", "crc", "/tmp/shlsgiqaxn"]

Basically, cksum should check that --length is allowed before checking if --check is.

[RenjiSann]

@sylvestre this can be set as a good first issue IMO

[Felle33]

Hello, I would like to solve this issue, although it is the first time I contribute to open source projects (so sorry in advance if I make some mistakes). I read the DEVELOPMENT.md and CONTRIBUTING.md files and followed the guidelines to install the environment.
I would like to reproduce the bug, but I am not sure how to do it.

[RenjiSann]

Hello, I would like to solve this issue, although it is the first time I contribute to open source projects (so sorry in advance if I make some mistakes). I read the DEVELOPMENT.md and CONTRIBUTING.md files and followed the guidelines to install the environment. I would like to reproduce the bug, but I am not sure how to do it.

Hi @Felle33 ! thanks for being interested in fixing this.
The steps to reproduce the error are simple. There is basically no preparation work other than building the cksum util.
To do so, you can figure out the cargo command, but I never remember it and I personnally use the make wrapper to do it

make UTILS="cksum"

Once done, your cksum binary will be at target/debug/cksum.

You should observe the following behavior when running it with the problematic arguments

./target/debug/cksum -l 158 -c -a crc /tmp/xxx
--check is not supported with --algorithm={bsd,sysv,crc}

Note: The /tmp/xxx file content or existence actually doesn't matter because flag sanitization happens before file checking.

Now, you can compare this to the GNU cksum. You may use your OS' coreutils if it's the version 9.5, which is the version we're trying to match in uutils (check this with cksum --version). Otherwise, you will need to run the script ./util/build-gnu.sh and follow its instructions to build the GNU cksum binary from source (IIRC, once built, you will find the binary at ../gnu/src/cksum).
With GNU's implementation, you should observe the following behavior when running it with the problematic arguments:

./target/debug/cksum -l 158 -c -a crc /tmp/xxx
--length is only supported with --algorithm=blake2b

I hope that's detailed enough for you, feel free to reach out to me here on the issue, or on the discord server if you have any other question regarding your development environment ^^

[cakebaker]

@RenjiSann good explanation :)

[Felle33]

@RenjiSann thanks for the support :)