chroot implementation

Makefile

@@ -45,6 +45,7 @@ PROGS       := \
   whoami
 
 UNIX_PROGS := \
+  chroot \
   groups \
   hostid \
   hostname \

chroot/chroot.rs

@@ -0,0 +1,196 @@
+#![crate_id = "chroot#1.0.0"]
+/*
+ * This file is part of the uutils coreutils package.
+ *
+ * © Vsevolod Velichko <torkvemada@sorokdva.net>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+#![feature(macro_rules)]
+extern crate getopts;
+extern crate libc;
+extern crate debug;
+
+use getopts::{optflag, optopt, getopts, usage};
+use c_types::{get_pw_from_args, get_group};
+use libc::funcs::posix88::unistd::{execvp, setuid, setgid};
+
+#[path = "../common/util.rs"] mod util;
+#[path = "../common/c_types.rs"] mod c_types;
+
+extern {
+    fn chroot(path: *libc::c_char) -> libc::c_int;
+    fn setgroups(size: libc::c_int, list: *libc::uid_t) -> libc::c_int;
+}
+
+static NAME : &'static str = "chroot";
+static VERSION : &'static str = "1.0.0";
+
+#[allow(dead_code)]
+fn main () { std::os::set_exit_status(uumain(std::os::args())); }
+
+pub fn uumain(args: Vec<String>) -> int {
+    let program = args.get(0);
+
+    let options = [
+        optopt("u", "user", "User (ID or name) to switch before running the program", "USER"),
+        optopt("g", "group", "Group (ID or name) to switch to", "GROUP"),
+        optopt("G", "groups", "Comma-separated list of groups to switch to", "GROUP1,GROUP2…"),
+        optopt("", "userspec", "Colon-separated user and group to switch to. \
+                                Same as -u USER -g GROUP. \
+                                Userspec has higher preference than -u and/or -g", "USER:GROUP"),
+        optflag("h", "help", "Show help"),
+        optflag("V", "version", "Show program's version")
+    ];
+
+    let opts = match getopts(args.tail(), options) {
+        Ok(m) => {m}
+        Err(f) => {
+            println!("{}", f);
+            help_menu(program.as_slice(), options);
+            return 1
+        }
+    };
+
+    if opts.opt_present("V") { version(); return 0 }
+    if opts.opt_present("h") { help_menu(program.as_slice(), options); return 0 }
+
+    if opts.free.len() == 0 {
+        println!("Missing operand: NEWROOT");
+        println!("Try `{:s} --help` for more information.", program.as_slice());
+        return 1
+    }
+
+    let defaultShell : &'static str = "/bin/sh";
+    let defaultOption : &'static str = "-i";
+    let userShell = std::os::getenv("SHELL");
+
+    let newroot = Path::new(opts.free.get(0).as_slice());
+    if !newroot.is_dir() {
+        crash!(1, "cannot change root directory to `{}`: no such directory", newroot.display());
+    }
+
+    let command : Vec<&str> = match opts.free.len() {
+        1 => {
+            let shell : &str = match userShell {
+                None => {defaultShell}
+                Some(ref s) => {s.as_slice()}
+            };
+            vec!(shell, defaultOption)
+        }
+        _ => { opts.free.slice(1, opts.free.len()).iter().map(|x| x.as_slice()).collect() }
+    };
+
+    set_context(&newroot, &opts);
+
+    unsafe {
+        let executable = command.get(0).as_slice().to_c_str().unwrap();
+        let mut commandParts : Vec<*i8> = command.iter().map(|x| x.to_c_str().unwrap()).collect();
+        commandParts.push(std::ptr::null());
+        execvp(executable as *libc::c_char, commandParts.as_ptr() as **libc::c_char) as int
+    }
+}
+
+fn set_context(root: &Path, options: &getopts::Matches) {
+    let userspecStr = options.opt_str("userspec");
+    let userStr = options.opt_str("user").unwrap_or_default();
+    let groupStr = options.opt_str("group").unwrap_or_default();
+    let groupsStr = options.opt_str("groups").unwrap_or_default();
+    let userspec = match userspecStr {
+        Some(ref u) => {
+            let s : Vec<&str> = u.as_slice().split(':').collect();
+            if s.len() != 2 {
+                crash!(1, "invalid userspec: `{:s}`", u.as_slice())
+            };
+            s
+        }
+        None => { Vec::new() }
+    };
+    let user = if userspec.is_empty() { userStr.as_slice() } else { userspec.get(0).as_slice() };
+    let group = if userspec.is_empty() { groupStr.as_slice() } else { userspec.get(1).as_slice() };
+
+    enter_chroot(root);
+
+    set_groups(groupsStr.as_slice());
+    set_main_group(group);
+    set_user(user);
+}
+
+fn enter_chroot(root: &Path) {
+    let rootStr = root.display();
+    if !std::os::change_dir(root) {
+        crash!(1, "cannot chdir to {}", rootStr)
+    };
+    let err = unsafe {
+        chroot(".".to_c_str().unwrap() as *libc::c_char)
+    };
+    if err != 0 {
+        crash!(1, "cannot chroot to {}: {:s}", rootStr, strerror(err).as_slice())
+    };
+}
+
+fn set_main_group(group: &str) {
+    if !group.is_empty() {
+        let group_id = match get_group(group) {
+            None => { crash!(1, "no such group: {}", group) }
+            Some(g) => g.gr_gid
+        };
+        let err = unsafe { setgid(group_id) };
+        if err != 0 {
+            crash!(1, "cannot set gid to {:u}: {:s}", group_id, strerror(err).as_slice())
+        }
+    }
+}
+
+fn set_groups(groups: &str) {
+    if !groups.is_empty() {
+        let groupsVec : Vec<libc::uid_t> = FromIterator::from_iter(
+            groups.split(',').map(
+                |x| match get_group(x) {
+                    None => { crash!(1, "no such group: {}", x) }
+                    Some(g) => { g.gr_gid }
+                })
+            );
+        let err = unsafe {
+            setgroups(groupsVec.len() as libc::c_int,
+                      groupsVec.as_slice().as_ptr() as *libc::uid_t)
+        };
+        if err != 0 {
+            crash!(1, "cannot set groups: {:s}", strerror(err).as_slice())
+        }
+    }
+}
+
+fn set_user(user: &str) {
+    if !user.is_empty() {
+        let user_id = get_pw_from_args(&vec!(String::from_str(user))).unwrap().pw_uid;
+        let err = unsafe { setuid(user_id as libc::uid_t) };
+        if err != 0 {
+            crash!(1, "cannot set user to {:s}: {:s}", user, strerror(err).as_slice())
+        }
+    }
+}
+
+fn strerror(errno: i32) -> String {
+    unsafe {
+        let err = libc::funcs::c95::string::strerror(errno);
+        std::str::raw::from_c_str(err)
+    }
+}
+
+fn version() {
+    println!("{} v{}", NAME, VERSION)
+}
+
+fn help_menu(program: &str, options: &[getopts::OptGroup]) {
+    version();
+    println!("Usage:");
+    println!("  {:s} [OPTION]… NEWROOT [COMMAND [ARG]…]", program);
+    println!("");
+    print!("{:s}", usage(
+            "Run COMMAND with root directory set to NEWROOT.\n\
+             If COMMAND is not specified, it defaults to '${SHELL} -i'. \
+             If ${SHELL} is not set, /bin/sh is used.", options))
+}