stuffr-cli 0.25.1

//! zip's `ttyio.c`: the password prompt (`getp()`, the `ATH_BEO_UNX` one
//! that reads `/dev/tty` with echo off), and the random bytes of an
//! encryption header. zip's `ttyio.c` is unzip's (Apple's tree and
//! upstream's are the same file, and no Ubuntu patch touches it), so the
//! prompt's loop is unzip's port (`unzip::ttyio::getp_on`): the prompt on
//! standard error, a line read a byte at a time keeping `IZ_PWLEN + 1`
//! bytes, `(line too long--try again)` and the prompt again for a longer
//! one, a newline to standard error after each line. The terminal's mode
//! is put back on every path (`host::TtyMode`), also by zip's interrupt
//! handler (`host::install_zip_abort`), as `echon()` does.
//!
//! Under `Host::Sandbox` there is no terminal: [`getp`] answers as
//! `open()` of `/dev/tty` failing (the tests can type answers through
//! `TYPED`, test builds only).

use crate::compat::host::Host;
use crate::compat::unzip::ttyio::Password;

use super::Zr;

/// crypt.h:IZ_PWLEN: the password buffer is `IZ_PWLEN + 1` bytes.
pub(crate) const IZ_PWLEN: usize = 80;

#[cfg(test)]
thread_local! {
    /// The answers a sandboxed test types at the prompts, in order; none
    /// left is no terminal.
    pub(crate) static TYPED: std::cell::RefCell<std::collections::VecDeque<Vec<u8>>> =
        const { std::cell::RefCell::new(std::collections::VecDeque::new()) };
}

// port: ttyio.c:getp
/// `getp(prompt, buf, IZ_PWLEN+1)`: the answer typed at the controlling
/// terminal, `None` where the C returns `NULL` (no terminal to open; a
/// terminal that hangs up meanwhile, ruling T11-3 of unzip's port).
pub(crate) fn getp(z: &mut Zr, prompt: &[u8]) -> Option<Password> {
    if matches!(z.host, Host::Sandbox(_)) {
        #[cfg(test)]
        if let Some(answer) = TYPED.with(|t| t.borrow_mut().pop_front()) {
            let _ = z.err.write_all(prompt);
            let _ = z.err.write_all(b"\n");
            return Some(Password::new(&answer));
        }
        return None;
    }
    #[cfg(unix)]
    {
        use std::os::fd::{AsRawFd, FromRawFd, OwnedFd};
        // SAFETY: a NUL-terminated path; the descriptor, if any, is owned
        // by the `OwnedFd` below, which closes it (`close(f)`).
        let f = unsafe { libc::open(c"/dev/tty".as_ptr(), libc::O_RDONLY | libc::O_CLOEXEC) };
        if f == -1 {
            return None;
        }
        // SAFETY: `f` is a descriptor we just opened and own.
        let f = unsafe { OwnedFd::from_raw_fd(f) };
        crate::compat::unzip::ttyio::getp_on(&mut *z.err, f.as_raw_fd(), prompt, IZ_PWLEN + 1).ok()
    }
    #[cfg(not(unix))]
    {
        // no `/dev/tty` off unix: as when it cannot be opened
        let _ = prompt;
        None
    }
}

/// The ten random bytes of an encryption header (crypt.c:crypthead's
/// `rand()` draws), from the system: `getentropy()` (macOS and the BSDs),
/// `getrandom()` (Linux), else `/dev/urandom`; never a seeded `rand()`.
/// `Err` when the system gives none (the caller ends the run).
///
/// `getentropy` is declared for each of these targets by the `libc` crate
/// in Cargo.lock (0.2.189: `unix/bsd/apple`, `unix/bsd/freebsdlike` for
/// FreeBSD and DragonFly, `unix/bsd/netbsdlike` for NetBSD and OpenBSD).
#[cfg(unix)]
pub(crate) fn random_header() -> std::io::Result<[u8; 10]> {
    let mut b = [0u8; 10];
    #[cfg(any(
        target_vendor = "apple",
        target_os = "freebsd",
        target_os = "openbsd",
        target_os = "netbsd",
        target_os = "dragonfly"
    ))]
    // SAFETY: getentropy fills the 10 bytes of a buffer we own (at most
    // 256 may be asked for).
    if unsafe { libc::getentropy(b.as_mut_ptr().cast(), b.len()) } == 0 {
        return Ok(b);
    }
    #[cfg(any(target_os = "linux", target_os = "android"))]
    {
        let mut got = 0;
        while got < b.len() {
            // SAFETY: getrandom writes at most `len - got` bytes into the
            // part of our buffer not yet filled.
            let n = unsafe { libc::getrandom(b[got..].as_mut_ptr().cast(), b.len() - got, 0) };
            if n > 0 {
                got += n as usize;
            } else if n < 0
                && std::io::Error::last_os_error().kind() == std::io::ErrorKind::Interrupted
            {
                continue;
            } else {
                break;
            }
        }
        if got == b.len() {
            return Ok(b);
        }
    }
    use std::io::Read;
    std::fs::File::open("/dev/urandom").and_then(|mut f| f.read_exact(&mut b))?;
    Ok(b)
}

/// Off unix the system gives no generator this port reads: `Err`, and the
/// caller ends the run.
#[cfg(not(unix))]
pub(crate) fn random_header() -> std::io::Result<[u8; 10]> {
    Err(std::io::Error::from(std::io::ErrorKind::Unsupported))
}