sudo: `-u longusername` fails when effective group id cannot be resolved into a group name

[Jorge Aparicio]

relevant test

sudo-rs/test-framework/sudo-compliance-tests/src/sudo/misc.rs

Lines 205 to 225 in 0b9207b

 fn long_username() -> Result<()> { 
     // `useradd` limits usernames to 32 characters 
     // directly write to `/etc/passwd` to work around this limitation 
     let username = "a".repeat(33); 
     let env = Env(SUDOERS_ALL_ALL_NOPASSWD).build()?; 
  
     Command::new("sh") 
         .arg("-c") 
         .arg(format!( 
             "echo {username}:x:1000:1000::/tmp:/bin/sh >> /etc/passwd" 
         )) 
         .output(&env)? 
         .assert_success()?; 
  
     Command::new("sudo") 
         .arg("-u") 
         .arg(username) 
         .arg("true") 
         .output(&env)? 
         .assert_success() 
 } 

useradd does not work with usernames with usernames longer than 32 characters. this issue is only observed with usernames longer than 32 characters. when editing /etc/passwd (instead of useradd) is used to create the user

[Jorge Aparicio]

the above test does not update /etc/groups, i.e. it does not assign a primary group to the new user. this makes the groups command fail:

root@a22ac8003931:/tmp# groups aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa : groups: cannot find name for group ID 1001
1001
root@a22ac8003931:/tmp# echo $?
1

I think sudo-rs is failing because it's trying to resolve the group ID into a group name whereas ogsudo is not while still being able to execute the complete pipeline.