Add pw module for user and group information;

which - check if our user can exec found file

src/cmd/bootstrap/mod.rs

@@ -246,20 +246,7 @@ impl BootstrapCmd for dyn Cmd {
         let mut path = PathBuf::from(prefix);
         let binpath = self.path();
         match binpath {
-            Some(crate::Path::Bin) => path.push("bin"),
-            Some(crate::Path::Sbin) => path.push("sbin"),
-            Some(crate::Path::UsrBin) => {
-                if usr {
-                    path.push("usr");
-                }
-                path.push("bin");
-            }
-            Some(crate::Path::UsrSbin) => {
-                if usr {
-                    path.push("usr");
-                }
-                path.push("sbin");
-            }
+            Some(p) => path.push(p.to_str(usr)),
             None => return None,
         }
         path.push(self.name());

src/cmd/which/mod.rs

@@ -62,7 +62,23 @@ fn which(command: &str, path: &[&str]) -> Option<String> {
             if let Ok(exe) = File::open(&file) {
                 if let Ok(meta) = exe.metadata() {
                     let mode = meta.mode();
-                    if mode & 0o111 != 0 {
+                    let myuid = unsafe {
+                        libc::geteuid()
+                    };
+                    let mygroups = crate::pw::get_gids();
+                    // we own the file and it has u+x
+                    if myuid == meta.uid() && mode & 0o100 != 0 {
+                        return Some(format!("{}", file.display()));
+                    // file has ug+x
+                    } else if mode & 0o110 != 0 {
+                        if let Ok(groups) = mygroups {
+                            // one of our groups owns the file
+                            if groups.contains(&meta.gid()) {
+                                return Some(format!("{}", file.display()));
+                            }
+                        }
+                    // the file has uga+x
+                    } else if mode & 0o111 != 0 {
                         return Some(format!("{}", file.display()));
                     }
                 }

src/lib.rs

@@ -4,6 +4,8 @@ use std::{env, error::Error, path::PathBuf, process, string::ToString};
 pub mod cmd;
 pub use cmd::Cmd;
 pub mod math;
+/// User and group related functionality
+pub mod pw;
 
 #[derive(Debug, Clone, Copy)]
 pub enum Path {
@@ -13,6 +15,19 @@ pub enum Path {
     UsrSbin,
 }
 
+impl Path {
+    pub fn to_str(&self, usr: bool) -> &'static str {
+        match self {
+            Self::Bin => "bin",
+            Self::UsrBin if usr => "usr/bin",
+            Self::UsrBin => "bin",
+            Self::Sbin => "sbin",
+            Self::UsrSbin if usr => "usr/sbin",
+            Self::UsrSbin => "sbin",
+        }
+    }
+}
+
 #[must_use]
 pub fn progname() -> Option<String> {
     env::args()

src/pw/mod.rs

@@ -0,0 +1,70 @@
+use std::{error::Error, ffi::CStr, num};
+
+pub fn get_username<'a>() -> Result<&'a str, std::str::Utf8Error> {
+    let user = unsafe {
+        let uid = libc::getuid();
+        let pw = libc::getpwuid(uid);
+        let name = (*pw).pw_name;
+        CStr::from_ptr(name)
+    };
+    user.to_str()
+}
+
+pub fn get_eusername<'a>() -> Result<&'a str, std::str::Utf8Error> {
+    let user = unsafe {
+        let uid = libc::geteuid();
+        let pw = libc::getpwuid(uid);
+        let name = (*pw).pw_name;
+        CStr::from_ptr(name)
+    };
+    user.to_str()
+}
+
+pub fn get_grpname<'a>() -> Result<&'a str, std::str::Utf8Error> {
+    let group = unsafe {
+        let gid = libc::getgid();
+        let gr = libc::getgrgid(gid);
+        let name = (*gr).gr_name;
+        CStr::from_ptr(name)
+    };
+    group.to_str()
+}
+
+pub fn get_egrpname<'a>() -> Result<&'a str, std::str::Utf8Error> {
+    let group = unsafe {
+        let gid = libc::getegid();
+        let gr = libc::getgrgid(gid);
+        let name = (*gr).gr_name;
+        CStr::from_ptr(name)
+    };
+    group.to_str()
+}
+
+pub fn get_gids() -> Result<Vec<u32>, num::TryFromIntError> {
+    let mut buf: Vec<libc::gid_t>;
+    unsafe {
+        buf = vec![0; 1];
+        let num = libc::getgroups(0, buf.as_mut_ptr());
+        buf = vec![0; num.try_into()?];
+        let _num = libc::getgroups(num, buf.as_mut_ptr());
+        buf.push(libc::getegid());
+    };
+    buf.dedup();
+    Ok(buf)
+}
+
+pub fn get_group_names() -> Result<Vec<String>, Box<dyn Error>> {
+    let gids = get_gids()?;
+    let mut names = vec![];
+    for id in gids {
+        let name = unsafe {
+                let gr = libc::getgrgid(id);
+                let name = (*gr).gr_name;
+                // if we don't take ownership here the OS can (and will)
+                // reuse the memory
+                CStr::from_ptr(name).to_str()?.to_string()
+        };
+        names.push(name);
+    }
+    Ok(names)
+}