anti-debug 0.3.0

#![doc = include_str!("../README.md")]
#![warn(missing_docs)]

/// Checks if a debugger is currently attached to the process.
///
/// This function performs platform-specific checks to detect
/// whether a debugger is actively attached to the current process.
///
/// # Platform-specific Behavior
///
/// - **Windows**: Uses `IsDebuggerPresent`.
///   When the `deep-detect` feature is enabled, additionally checks
///   `CheckRemoteDebuggerPresent` and `NtQueryInformationProcess`.
/// - **Linux/Android**: Checks the `TracerPid` field in `/proc/self/status`.
/// - **macOS**: Uses `proc_pidinfo` to retrieve `proc_bsdinfo` and checks the `pbi_flags` field.
/// - **Other platforms**: Compilation error.
///
/// # Return Value
///
/// Returns `Ok(true)` if a debugger is detected, `Ok(false)` if no debugger is present,
/// or `Err(std::io::Error)` if the check could not be performed due to a system error.
///
/// # Examples
///
/// ```rust
/// # fn main() {
/// match anti_debug::is_debugger_present() {
///     Ok(true) => println!("Debugger detected!"),
///     Ok(false) => println!("No debugger present"),
///     Err(e) => println!("Error checking for debugger: {}", e),
/// }
/// # }
/// ```
///
/// # Notes
///
/// - This detection can be bypassed by skilled attackers using advanced anti-anti-debugging techniques
/// - Some debuggers may not be detected depending on their attachment method
/// - The check is performed at the moment the function is called and may not reflect
///   subsequent attachment/detachment of debuggers
pub fn is_debugger_present() -> Result<bool, std::io::Error> {
    #[cfg(target_os = "windows")] {
        // Check with `IsDebuggerPresent`.
        unsafe {
            let result = windows_sys::Win32::System::Diagnostics::Debug::IsDebuggerPresent();
            if result != windows_sys::Win32::Foundation::FALSE {
                return Ok(true);
            }
        }
        // Check with `CheckRemoteDebuggerPresent`.
        #[cfg(feature = "deep-detect")]
        unsafe {
            let mut p_debugger_present = windows_sys::Win32::Foundation::FALSE;
            let result = windows_sys::Win32::System::Diagnostics::Debug::CheckRemoteDebuggerPresent(
                windows_sys::Win32::System::Threading::GetCurrentProcess(),
                &mut p_debugger_present,
            );
            if result == windows_sys::Win32::Foundation::FALSE {
                return Err(std::io::Error::last_os_error());
            }
            if p_debugger_present != windows_sys::Win32::Foundation::FALSE {
                return Ok(true);
            }
        }
        // Check with `NtQueryInformationProcess`.
        #[cfg(feature = "deep-detect")]
        unsafe {
            let mut p_debug_port = 0i32;
            let result = windows_sys::Wdk::System::Threading::NtQueryInformationProcess(
                windows_sys::Win32::System::Threading::GetCurrentProcess(),
                windows_sys::Wdk::System::Threading::ProcessDebugPort,
                &mut p_debug_port as *mut _ as _,
                size_of::<i32>() as _,
                &mut 0,
            );
            let result = windows_sys::Win32::Foundation::RtlNtStatusToDosError(result);
            if result != 0 {
                return Err(std::io::Error::from_raw_os_error(result as _));
            }
            if p_debug_port != 0 {
                return Ok(true);
            }
        }
        Ok(false)
    }
    #[cfg(any(target_os = "linux", target_os = "android"))] {
        // Check with `/proc/self/status`.
        {
            let proc = std::fs::read_to_string("/proc/self/status")?;
            let pid = proc
                .lines()
                .filter_map(|line| line.strip_prefix("TracerPid:"))
                .filter_map(|pid| pid.trim().parse::<i32>().ok())
                .next()
                .ok_or_else(|| std::io::Error::new(std::io::ErrorKind::InvalidData, "invalid pid format"))?;
            if pid != 0 {
                return Ok(true);
            }
        }
        Ok(false)
    }
    #[cfg(target_os = "macos")] {
        // Check with `proc_pidinfo`.
        {
            let pid = std::process::id() as i32;
            let result = libproc::proc_pid::pidinfo::<libproc::bsd_info::BSDInfo>(pid, 0);
            let proc_bsdinfo = match result {
                Ok(proc_bsdinfo) => proc_bsdinfo,
                Err(_message) => return Err(std::io::Error::last_os_error()),
            };
            const PROC_FLAG_TRACED: u32 = 2; // use libproc::osx_libproc_bindings::PROC_FLAG_TRACED;
            if proc_bsdinfo.pbi_flags & PROC_FLAG_TRACED != 0 { return Ok(true); }
        }
        Ok(false)
    }
    #[cfg(not(any(
        target_os = "windows",
        target_os = "linux",
        target_os = "android",
        target_os = "macos",
    )))]
    compile_error!("Anti-Debug doesn't support current platform.")
}

/// Attempts to prevent debuggers from attaching to the current process.
///
/// This function performs platform-specific operations to prevent debuggers
/// from attaching to the current process.
///
/// # Platform-specific Behavior
///
/// - **Windows/Linux/Android**: There is no way to prevent the debugger from attaching in the future.
///   Checks if a debugger is currently attached using [`is_debugger_present`].
///   If a debugger is detected, returns an error.
/// - **macOS**: Uses `ptrace` with the `PT_DENY_ATTACH` flag.
/// - **Other platforms**: Compilation error.
///
/// # Return Value
///
/// - Returns `Ok(())` if:
///   - On Windows/Linux/Android: No debugger is currently attached.
///   - On macOS: The `ptrace(PT_DENY_ATTACH)` call succeeded.
/// - Returns `Err(std::io::Error)` if:
///   - On Windows/Linux/Android: A debugger is currently attached.
///   - On macOS: The `ptrace` system call failed.
///   - Any platform-specific system call fails.
///
/// # Examples
///
/// ```rust
/// # fn main() {
/// if let Err(e) = anti_debug::deny_attach() {
///     println!("Debugger protection failed: {}", e);
/// }
/// # }
/// ```
///
/// # Notes
///
/// - This detection can be bypassed by skilled attackers using advanced anti-anti-debugging techniques
/// - Some debuggers may not be detected depending on their attachment method
/// - On Windows/Linux/Android, this is a detection-based approach. i.e. passive detection
pub fn deny_attach() -> Result<(), std::io::Error> {
    #[cfg(any(target_os = "windows", target_os = "linux", target_os = "android"))] {
        if is_debugger_present()? {
            return Err(std::io::Error::new(std::io::ErrorKind::AlreadyExists, "Debugger present."));
        }
        Ok(())
    }
    #[cfg(target_os = "macos")] {
        // Deny with `ptrace`.
        unsafe {
            let result = libc::ptrace(libc::PT_DENY_ATTACH, 0, std::ptr::null_mut(), 0);
            if result == -1 { return Err(std::io::Error::last_os_error()); }
        }
        Ok(())
    }
    #[cfg(not(any(
        target_os = "windows",
        target_os = "linux",
        target_os = "android",
        target_os = "macos",
    )))]
    compile_error!("Anti-Debug doesn't support current platform.")
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_is_debugger_present() {
        assert!(!super::is_debugger_present().unwrap_or(false));
        assert!(!super::is_debugger_present().unwrap_or(false));
        assert!(!super::is_debugger_present().unwrap_or(false));
    }

    #[test]
    fn test_deny_attach() {
        super::deny_attach().unwrap();
        super::deny_attach().unwrap();
        super::deny_attach().unwrap();
    }
}