diff --git a/src/header/tar/mod.rs b/src/header/tar/mod.rs index 92e51a5efc..010b9c59e0 100644 --- a/src/header/tar/mod.rs +++ b/src/header/tar/mod.rs @@ -1,10 +1,20 @@ -/// tar.h implementation for Redox, following https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/tar.h.html +//! tar.h implementation for Redox, following POSIX.1-1990 specification +//! and https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/tar.h.html + +//! +//! This module provides functionality for working with tar archives, including +//! header creation, validation, and manipulation. It implements the POSIX.1-1990 +//! ustar format. + use core::slice; -/// Archive block size -pub const BLOCKSIZE: usize = 512; // Block size in bytes +#[cfg(test)] +mod tests; -/// Default record size (512 blocks) +/// Block size for tar archives (512 bytes). +pub const BLOCKSIZE: usize = 512; + +/// Default record size for tar archives (10KB, consisting of 20 blocks). pub const RECORDSIZE: usize = BLOCKSIZE * 20; // 10KB (default for tar archives) /// Field lengths in tar headers @@ -67,31 +77,13 @@ pub const GNUTYPE_LONGNAME: u8 = b'L'; // Long file name pub const GNUTYPE_LONGLINK: u8 = b'K'; // Long link name pub const GNUTYPE_SPARSE: u8 = b'S'; // Sparse file -pub struct TarHeaderBuilder { - header: TarHeader, -} - -impl TarHeaderBuilder { - pub fn new() -> Self { - let mut header = TarHeader::default(); - header.magic.copy_from_slice(TMAGIC.as_bytes()); - header.version.copy_from_slice(TVERSION.as_bytes()); - Self { header } - } - - pub fn name(mut self, name: &str) -> Result { - self.header.name = TarHeader::to_null_terminated_field::(name)?; - Ok(self) - } - - pub fn build(self) -> TarHeader { - self.header - } -} - +/// Represents a tar archive header following the POSIX ustar format. +/// +/// The header contains metadata about a file in a tar archive, including +/// its name, size, permissions, and other attributes. All text fields are +/// null-terminated. #[repr(C)] #[derive(Debug, Clone, Copy)] -/// tar header structure, from POSIX 1003.1-1990. pub struct TarHeader { // Byte offset - usage pub name: [u8; NAME_SIZE], // 0 - File name @@ -113,9 +105,42 @@ pub struct TarHeader { pub padding: [u8; 12], // 500 - Padding to make 512 bytes } +pub struct TarHeaderBuilder { + header: TarHeader, +} + +impl TarHeaderBuilder { + /// Creates a new `TarHeaderBuilder` with default values. + pub fn new() -> Self { + let mut header = TarHeader::default(); + header.magic.copy_from_slice(TMAGIC.as_bytes()); + header.version.copy_from_slice(TVERSION.as_bytes()); + Self { header } + } + + /// Sets the name field in the tar header. + /// + /// # Arguments + /// + /// * `name` - A string slice that holds the name of the file. + /// + /// # Errors + /// + /// Returns `TarError::FieldTooLong` if the name exceeds the maximum allowed length. + pub fn name(mut self, name: &str) -> Result { + self.header.name = TarHeader::to_null_terminated_field::(name)?; + Ok(self) + } + + /// Builds and returns the `TarHeader`. + pub fn build(self) -> TarHeader { + self.header + } +} + impl Default for TarHeader { fn default() -> Self { - Self { + let mut header = Self { name: [0; NAME_SIZE], mode: [0; MODE_SIZE], uid: [0; UID_SIZE], @@ -133,60 +158,114 @@ impl Default for TarHeader { devminor: [0; DEVMINOR_SIZE], prefix: [0; PREFIX_SIZE], padding: [0; 12], + }; + + // Set default magic and version + let magic_bytes = TMAGIC.as_bytes(); // "ustar" + header.magic[..magic_bytes.len()].copy_from_slice(magic_bytes); + + // POSIX ustar magic expects a trailing null + // TMAGIC = "ustar" (5 chars) + '\0' = 6 chars total + if TMAGLEN == 6 { + header.magic[5] = 0; } + + // Set the version field to "00" + let version_bytes = TVERSION.as_bytes(); // "00" + header.version[..version_bytes.len()].copy_from_slice(version_bytes); + + header } } impl TarHeader { - /// Converts a byte array field to a string, trimming null bytes. + /// Converts a byte array field to a UTF-8 string, trimming null bytes. + /// + /// # Returns + /// + /// * `Some(&str)` - If the field contains valid UTF-8 data + /// * `None` - If the field contains invalid UTF-8 data pub fn to_str(field: &[u8]) -> Option<&str> { let end = field.iter().position(|&b| b == 0).unwrap_or(field.len()); core::str::from_utf8(&field[..end]).ok() } - /// Converts a string to a null-terminated byte array for a field. + /// Converts a string to a null-terminated byte array suitable for a tar header field. + /// + /// # Arguments + /// + /// * `s` - The string to convert + /// + /// # Returns + /// + /// * `Ok([u8; N])` - The null-terminated byte array + /// * `Err(TarError)` - If the string is too long for the field pub fn to_null_terminated_field(s: &str) -> Result<[u8; N], TarError> { let mut field = [0u8; N]; let bytes = s.as_bytes(); - if bytes.len() >= N { + + // Reserve one byte for the null terminator + if bytes.len() + 1 > N { return Err(TarError::FieldTooLong); } + field[..bytes.len()].copy_from_slice(bytes); + field[bytes.len()] = 0; // Null terminator + Ok(field) } - /// Validate the checksum + /// Calculates the checksum of the header according to the POSIX specification. + /// + /// The checksum is calculated by summing all bytes in the header, with the + /// checksum field itself treated as eight spaces (ASCII 32). + /// + /// # Returns + /// + /// The calculated checksum value + pub fn calculate_checksum(&self) -> usize { + let mut header_copy = *self; + // Replace chksum field with spaces + header_copy.chksum.fill(b' '); + + let bytes = + unsafe { slice::from_raw_parts(&header_copy as *const _ as *const u8, HEADER_SIZE) }; + + bytes.iter().map(|&b| b as usize).sum() + } + + /// Validates the header's stored checksum against a calculated checksum. + /// + /// # Returns + /// + /// * `Ok(())` - If the checksum is valid + /// * `Err(TarError)` - If the checksum is invalid or malformed pub fn validate(&self) -> Result<(), TarError> { - let recorded_checksum = match TarHeader::to_str(&self.chksum) { - Some(cs) => { - usize::from_str_radix(cs.trim_end(), 8).map_err(|_| TarError::InvalidChecksum)? - } + let recorded_str = match TarHeader::to_str(&self.chksum) { + Some(cs) => cs.trim_end(), None => return Err(TarError::InvalidChecksum), }; - // Calculate actual checksum - let mut header_copy = *self; - - // Set checksum field to spaces for calculation - header_copy.chksum.fill(b' '); - - let actual_checksum: usize = unsafe { - core::slice::from_raw_parts(&header_copy as *const _ as *const u8, HEADER_SIZE) - } - .iter() - .map(|&x| x as usize) - .sum(); + let recorded_checksum = + usize::from_str_radix(recorded_str, 8).map_err(|_| TarError::InvalidChecksum)?; + let actual_checksum = self.calculate_checksum(); if actual_checksum != recorded_checksum { return Err(TarError::InvalidChecksum); } Ok(()) } + /// Creates a new TarHeaderBuilder for constructing a TarHeader. pub fn builder() -> TarHeaderBuilder { TarHeaderBuilder::new() } + /// Returns a human-readable description of the file type. + /// + /// # Returns + /// + /// A string slice describing the type of file represented by this header. pub fn file_type(&self) -> &'static str { match self.typeflag { REGTYPE | AREGTYPE => "Regular File", @@ -200,17 +279,20 @@ impl TarHeader { _ => "Unknown", } } - - } #[derive(Debug)] pub enum TarError { + /// The checksum in the tar header is invalid. InvalidChecksum, + /// An I/O error occurred. IoError, + /// The tar header is invalid. InvalidHeader, + /// The type flag in the tar header is unknown. UnknownTypeFlag(u8), - InvalidEncoding, // Check for UTF-8 conversion errors - FieldTooLong, // Checks when input strings exceed field sizes + /// An error occurred during UTF-8 conversion. + InvalidEncoding, + /// The input string exceeds the maximum allowed field size. + FieldTooLong, } - diff --git a/src/header/tar/tests.rs b/src/header/tar/tests.rs new file mode 100644 index 0000000000..51a60c31be --- /dev/null +++ b/src/header/tar/tests.rs @@ -0,0 +1,81 @@ +#[cfg(test)] +mod tests { + use super::*; + use crate::header::tar::{TarError, TarHeader, DIRTYPE, NAME_SIZE, SYMTYPE}; + + #[test] + fn test_header_checksum() { + let mut header = TarHeader::default(); + + // Set fields to valid octal strings for mode, size, mtime + // mode: 0000644 (octal), commonly used in tar archives + header.mode = *b"0000644\0"; + + // size: 12 chars total, octal "000000000123" fits exactly + // (no null terminator needed if fully used) + header.size = *b"000000000123"; + + // mtime: 12 chars total, octal time "00000001234\0" + // Counting chars: '0'(1)'0'(2)'0'(3)'0'(4)'0'(5)'0'(6)'0'(7)'1'(8)'2'(9)'3'(10)'4'(11)'\0'(12) + header.mtime = *b"00000001234\0"; + + // Calculate the checksum + let checksum = header.calculate_checksum(); + + // According to tar specification, the checksum field should contains + // an octal number followed by a null and a space if possible. + // For an 8-byte field: 6 octal digits, a null, and a space : + // + // Example: "000000\0 " (sum in octal) + let checksum_str = format!("{:06o}\0 ", checksum); + header.chksum.copy_from_slice(checksum_str.as_bytes()); + + assert!(header.validate().is_ok()); + } + + #[test] + fn test_header_builder() { + let header = TarHeader::builder().name("test/file.txt").unwrap().build(); + + // The builder sets a null terminator after "test/file.txt" + let expected = { + let mut arr = [0u8; NAME_SIZE]; + arr[.."test/file.txt".len()].copy_from_slice(b"test/file.txt"); + arr["test/file.txt".len()] = 0; + arr + }; + + assert_eq!(header.name, expected); + } + + #[test] + fn test_field_too_long() { + // NAME_SIZE = 100, so a string longer than 99 chars fails + let long_string = "a".repeat(200); + let result = TarHeader::to_null_terminated_field::(&long_string); + + assert!(matches!(result, Err(TarError::FieldTooLong))); + } + + #[test] + fn test_invalid_checksum() { + let mut header = TarHeader::default(); + + // Set chksum to something invalid + header.chksum = *b"99999999"; // Not a valid octal, likely fails + + assert!(header.validate().is_err()); + } + + #[test] + fn test_file_type() { + let mut header = TarHeader::default(); + assert_eq!(header.file_type(), "Regular File"); + + header.typeflag = DIRTYPE; + assert_eq!(header.file_type(), "Directory"); + + header.typeflag = SYMTYPE; + assert_eq!(header.file_type(), "Symbolic Link"); + } +}