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Merge #1139
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1139: Add `Users` and `Group` related functions r=asomers a=otavio

This was a collaborative work between Johannes Schilling
<[email protected]>, Fredrick Brennan <[email protected]>
and myself.

This PR is a split-off from #864 so we merge ready parts first. Next, we work on the iterators.

Signed-off-by: Otavio Salvador <[email protected]>

Co-authored-by: Otavio Salvador <[email protected]>
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@bors @otavio
bors[bot] and otavio authored Nov 1, 2019
2 parents 6b57a5a + b14415a commit cfc550f
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4 changes: 4 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
- Added `mkfifoat`
([#1133](https://github.com/nix-rust/nix/pull/1133))

- Added `User::from_uid`, `User::from_name`, `User::from_gid` and
`Group::from_name`,
([#1139](https://github.com/nix-rust/nix/pull/1139))

### Changed
- `sys::socket::recvfrom` now returns
`Result<(usize, Option<SockAddr>)>` instead of `Result<(usize, SockAddr)>`.
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254 changes: 253 additions & 1 deletion src/unistd.rs
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Expand Up @@ -7,7 +7,7 @@ use fcntl::FcntlArg::F_SETFD;
use libc::{self, c_char, c_void, c_int, c_long, c_uint, size_t, pid_t, off_t,
uid_t, gid_t, mode_t, PATH_MAX};
use std::{fmt, mem, ptr};
use std::ffi::{CStr, OsString, OsStr};
use std::ffi::{CString, CStr, OsString, OsStr};
use std::os::unix::ffi::{OsStringExt, OsStrExt};
use std::os::unix::io::RawFd;
use std::path::PathBuf;
Expand Down Expand Up @@ -2424,3 +2424,255 @@ pub fn access<P: ?Sized + NixPath>(path: &P, amode: AccessFlags) -> Result<()> {
})?;
Errno::result(res).map(drop)
}

/// Representation of a User, based on `libc::passwd`
///
/// The reason some fields in this struct are `String` and others are `CString` is because some
/// fields are based on the user's locale, which could be non-UTF8, while other fields are
/// guaranteed to conform to [`NAME_REGEX`](https://serverfault.com/a/73101/407341), which only
/// contains ASCII.
#[derive(Debug, Clone, PartialEq)]
pub struct User {
/// Username
pub name: String,
/// User password (probably encrypted)
pub passwd: CString,
/// User ID
pub uid: Uid,
/// Group ID
pub gid: Gid,
/// User information
#[cfg(not(target_os = "android"))]
pub gecos: CString,
/// Home directory
pub dir: PathBuf,
/// Path to shell
pub shell: PathBuf,
/// Login class
#[cfg(not(any(target_os = "android", target_os = "linux")))]
pub class: CString,
/// Last password change
#[cfg(not(any(target_os = "android", target_os = "linux")))]
pub change: libc::time_t,
/// Expiration time of account
#[cfg(not(any(target_os = "android", target_os = "linux")))]
pub expire: libc::time_t
}

impl From<&libc::passwd> for User {
fn from(pw: &libc::passwd) -> User {
unsafe {
User {
name: CStr::from_ptr((*pw).pw_name).to_string_lossy().into_owned(),
passwd: CString::new(CStr::from_ptr((*pw).pw_passwd).to_bytes()).unwrap(),
#[cfg(not(target_os = "android"))]
gecos: CString::new(CStr::from_ptr((*pw).pw_gecos).to_bytes()).unwrap(),
dir: PathBuf::from(OsStr::from_bytes(CStr::from_ptr((*pw).pw_dir).to_bytes())),
shell: PathBuf::from(OsStr::from_bytes(CStr::from_ptr((*pw).pw_shell).to_bytes())),
uid: Uid::from_raw((*pw).pw_uid),
gid: Gid::from_raw((*pw).pw_gid),
#[cfg(not(any(target_os = "android", target_os = "linux")))]
class: CString::new(CStr::from_ptr((*pw).pw_class).to_bytes()).unwrap(),
#[cfg(not(any(target_os = "android", target_os = "linux")))]
change: (*pw).pw_change,
#[cfg(not(any(target_os = "android", target_os = "linux")))]
expire: (*pw).pw_expire
}
}
}
}

impl User {
fn from_anything<F>(f: F) -> Result<Option<Self>>
where
F: Fn(*mut libc::passwd,
*mut libc::c_char,
libc::size_t,
*mut *mut libc::passwd) -> libc::c_int
{
let buflimit = 16384;
let bufsize = match sysconf(SysconfVar::GETPW_R_SIZE_MAX) {
Ok(Some(n)) => n as usize,
Ok(None) | Err(_) => buflimit as usize,
};

let mut cbuf = Vec::with_capacity(bufsize);
let mut pwd = mem::MaybeUninit::<libc::passwd>::uninit();
let mut res = ptr::null_mut();

loop {
let error = f(pwd.as_mut_ptr(), cbuf.as_mut_ptr(), cbuf.capacity(), &mut res);
if error == 0 {
if res.is_null() {
return Ok(None);
} else {
let pwd = unsafe { pwd.assume_init() };
return Ok(Some(User::from(&pwd)));
}
} else if Errno::last() == Errno::ERANGE {
// Trigger the internal buffer resizing logic.
reserve_double_buffer_size(&mut cbuf, buflimit)?;
} else {
return Err(Error::Sys(Errno::last()));
}
}
}

/// Get a user by UID.
///
/// Internally, this function calls
/// [getpwuid_r(3)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getpwuid_r.html)
///
/// # Examples
///
/// ```
/// use nix::unistd::{Uid, User};
/// // Returns an Result<Option<User>>, thus the double unwrap.
/// let res = User::from_uid(Uid::from_raw(0)).unwrap().unwrap();
/// assert!(res.name == "root");
/// ```
pub fn from_uid(uid: Uid) -> Result<Option<Self>> {
User::from_anything(|pwd, cbuf, cap, res| {
unsafe { libc::getpwuid_r(uid.0, pwd, cbuf, cap, res) }
})
}

/// Get a user by name.
///
/// Internally, this function calls
/// [getpwnam_r(3)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getpwuid_r.html)
///
/// # Examples
///
/// ```
/// use nix::unistd::User;
/// // Returns an Result<Option<User>>, thus the double unwrap.
/// let res = User::from_name("root").unwrap().unwrap();
/// assert!(res.name == "root");
/// ```
pub fn from_name(name: &str) -> Result<Option<Self>> {
let name = CString::new(name).unwrap();
User::from_anything(|pwd, cbuf, cap, res| {
unsafe { libc::getpwnam_r(name.as_ptr(), pwd, cbuf, cap, res) }
})
}
}

/// Representation of a Group, based on `libc::group`
#[derive(Debug, Clone, PartialEq)]
pub struct Group {
/// Group name
pub name: String,
/// Group ID
pub gid: Gid,
/// List of Group members
pub mem: Vec<String>
}

impl From<&libc::group> for Group {
fn from(gr: &libc::group) -> Group {
unsafe {
Group {
name: CStr::from_ptr((*gr).gr_name).to_string_lossy().into_owned(),
gid: Gid::from_raw((*gr).gr_gid),
mem: Group::members((*gr).gr_mem)
}
}
}
}

impl Group {
unsafe fn members(mem: *mut *mut c_char) -> Vec<String> {
let mut ret = Vec::new();

for i in 0.. {
let u = mem.offset(i);
if (*u).is_null() {
break;
} else {
let s = CStr::from_ptr(*u).to_string_lossy().into_owned();
ret.push(s);
}
}

ret
}

fn from_anything<F>(f: F) -> Result<Option<Self>>
where
F: Fn(*mut libc::group,
*mut libc::c_char,
libc::size_t,
*mut *mut libc::group) -> libc::c_int
{
let buflimit = 16384;
let bufsize = match sysconf(SysconfVar::GETGR_R_SIZE_MAX) {
Ok(Some(n)) => n as usize,
Ok(None) | Err(_) => buflimit as usize,
};

let mut cbuf = Vec::with_capacity(bufsize);
let mut grp = mem::MaybeUninit::<libc::group>::uninit();
let mut res = ptr::null_mut();

loop {
let error = f(grp.as_mut_ptr(), cbuf.as_mut_ptr(), cbuf.capacity(), &mut res);
if error == 0 {
if res.is_null() {
return Ok(None);
} else {
let grp = unsafe { grp.assume_init() };
return Ok(Some(Group::from(&grp)));
}
} else if Errno::last() == Errno::ERANGE {
// Trigger the internal buffer resizing logic.
reserve_double_buffer_size(&mut cbuf, buflimit)?;
} else {
return Err(Error::Sys(Errno::last()));
}
}
}

/// Get a group by GID.
///
/// Internally, this function calls
/// [getgrgid_r(3)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getpwuid_r.html)
///
/// # Examples
///
// Disable this test on all OS except Linux as root group may not exist.
#[cfg_attr(not(target_os = "linux"), doc = " ```no_run")]
#[cfg_attr(target_os = "linux", doc = " ```")]
/// use nix::unistd::{Gid, Group};
/// // Returns an Result<Option<Group>>, thus the double unwrap.
/// let res = Group::from_gid(Gid::from_raw(0)).unwrap().unwrap();
/// assert!(res.name == "root");
/// ```
pub fn from_gid(gid: Gid) -> Result<Option<Self>> {
Group::from_anything(|grp, cbuf, cap, res| {
unsafe { libc::getgrgid_r(gid.0, grp, cbuf, cap, res) }
})
}

/// Get a group by name.
///
/// Internally, this function calls
/// [getgrnam_r(3)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getpwuid_r.html)
///
/// # Examples
///
// Disable this test on all OS except Linux as root group may not exist.
#[cfg_attr(not(target_os = "linux"), doc = " ```no_run")]
#[cfg_attr(target_os = "linux", doc = " ```")]
/// use nix::unistd::Group;
/// // Returns an Result<Option<Group>>, thus the double unwrap.
/// let res = Group::from_name("root").unwrap().unwrap();
/// assert!(res.name == "root");
/// ```
pub fn from_name(name: &str) -> Result<Option<Self>> {
let name = CString::new(name).unwrap();
Group::from_anything(|grp, cbuf, cap, res| {
unsafe { libc::getgrnam_r(name.as_ptr(), grp, cbuf, cap, res) }
})
}
}

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