s_zip/
reader.rs

1//! Streaming ZIP reader - reads ZIP files without loading entire central directory
2//!
3//! This is a minimal ZIP reader that can extract specific files from a ZIP archive
4//! without loading the entire central directory into memory.
5
6use crate::error::{Result, SZipError};
7use flate2::read::DeflateDecoder;
8use std::fs::File;
9use std::io::{BufReader, Read, Seek, SeekFrom};
10use std::path::Path;
11
12#[cfg(feature = "encryption")]
13use crate::encryption::{AesDecryptor, AesStrength};
14
15/// ZIP local file header signature
16const LOCAL_FILE_HEADER_SIGNATURE: u32 = 0x04034b50;
17
18/// ZIP central directory signature
19const CENTRAL_DIRECTORY_SIGNATURE: u32 = 0x02014b50;
20
21/// ZIP end of central directory signature
22const END_OF_CENTRAL_DIRECTORY_SIGNATURE: u32 = 0x06054b50;
23
24/// ZIP64 end of central directory record signature
25const ZIP64_END_OF_CENTRAL_DIRECTORY_SIGNATURE: u32 = 0x06064b50;
26
27// ZIP64 end of central directory locator signature (not used as a u32 constant)
28
29/// Entry in the ZIP central directory
30#[derive(Debug, Clone)]
31pub struct ZipEntry {
32    pub name: String,
33    pub compressed_size: u64,
34    pub uncompressed_size: u64,
35    pub compression_method: u16,
36    pub offset: u64,
37    #[cfg(feature = "encryption")]
38    pub is_encrypted: bool,
39}
40
41/// Streaming ZIP archive reader with adaptive buffering
42pub struct StreamingZipReader {
43    file: BufReader<File>,
44    entries: Vec<ZipEntry>,
45    #[cfg(feature = "encryption")]
46    password: Option<String>,
47}
48
49impl StreamingZipReader {
50    /// Open a ZIP file and read its central directory with default buffer size
51    pub fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
52        Self::open_with_buffer_size(path, None)
53    }
54
55    /// Open a ZIP file with custom buffer size for optimized reading
56    ///
57    /// Providing a buffer size hint can improve read performance:
58    /// - Small ZIPs (<10MB): 32KB buffer
59    /// - Medium ZIPs (<100MB): 128KB buffer  
60    /// - Large ZIPs (≥100MB): 512KB buffer (default)
61    ///
62    /// # Example
63    /// ```no_run
64    /// # use s_zip::StreamingZipReader;
65    /// # fn example() -> Result<(), Box<dyn std::error::Error>> {
66    /// // Optimize for large ZIP files
67    /// let reader = StreamingZipReader::open_with_buffer_size(
68    ///     "large_archive.zip",
69    ///     Some(1024 * 1024) // 1MB buffer for very large files
70    /// )?;
71    /// # Ok(())
72    /// # }
73    /// ```
74    pub fn open_with_buffer_size<P: AsRef<Path>>(
75        path: P,
76        buffer_size: Option<usize>,
77    ) -> Result<Self> {
78        let file = File::open(path)?;
79
80        // Use adaptive buffer size
81        let buf_size = buffer_size.unwrap_or(512 * 1024); // Default 512KB
82        let mut file = BufReader::with_capacity(buf_size, file);
83
84        // Find and read central directory
85        let entries = Self::read_central_directory(&mut file)?;
86
87        Ok(StreamingZipReader {
88            file,
89            entries,
90            #[cfg(feature = "encryption")]
91            password: None,
92        })
93    }
94
95    /// Set password for decrypting encrypted entries
96    #[cfg(feature = "encryption")]
97    pub fn set_password(&mut self, password: impl Into<String>) -> &mut Self {
98        self.password = Some(password.into());
99        self
100    }
101
102    /// Clear password
103    #[cfg(feature = "encryption")]
104    pub fn clear_password(&mut self) -> &mut Self {
105        self.password = None;
106        self
107    }
108
109    /// Get list of all entries in the ZIP
110    pub fn entries(&self) -> &[ZipEntry] {
111        &self.entries
112    }
113
114    /// Find an entry by name
115    pub fn find_entry(&self, name: &str) -> Option<&ZipEntry> {
116        self.entries.iter().find(|e| e.name == name)
117    }
118
119    /// Read an entry's decompressed data into a vector
120    pub fn read_entry(&mut self, entry: &ZipEntry) -> Result<Vec<u8>> {
121        // Seek to local file header
122        self.file.seek(SeekFrom::Start(entry.offset))?;
123
124        // Read and verify local file header
125        let signature = self.read_u32_le()?;
126        if signature != LOCAL_FILE_HEADER_SIGNATURE {
127            return Err(SZipError::InvalidFormat(
128                "Invalid local file header signature".to_string(),
129            ));
130        }
131
132        // Skip version
133        self.file.seek(SeekFrom::Current(2))?;
134
135        // Read flags to check for encryption
136        let flags = self.read_u16_le()?;
137        let is_encrypted = (flags & 0x01) != 0;
138
139        // Read compression method
140        let _compression_method = self.read_u16_le()?;
141
142        // Skip modification time and date, CRC-32
143        self.file.seek(SeekFrom::Current(8))?;
144
145        // Read compressed and uncompressed sizes (already known from central directory)
146        self.file.seek(SeekFrom::Current(8))?;
147
148        // Read filename length and extra field length
149        let filename_len = self.read_u16_le()? as i64;
150        let extra_len = self.read_u16_le()? as usize;
151
152        // Skip filename
153        self.file.seek(SeekFrom::Current(filename_len))?;
154
155        // Check for AES encryption in extra field
156        #[cfg(feature = "encryption")]
157        let encryption_info = if is_encrypted {
158            self.parse_aes_extra_field(extra_len)?
159        } else {
160            // Skip extra field if not encrypted
161            self.file.seek(SeekFrom::Current(extra_len as i64))?;
162            None
163        };
164
165        #[cfg(not(feature = "encryption"))]
166        {
167            if is_encrypted {
168                return Err(SZipError::InvalidFormat(
169                    "Encrypted entry found but encryption feature not enabled".to_string(),
170                ));
171            }
172            // Skip extra field
173            self.file.seek(SeekFrom::Current(extra_len as i64))?;
174        }
175
176        // Calculate actual data size (subtract salt, password verify, and auth code for encrypted entries)
177        #[cfg(feature = "encryption")]
178        let data_size = if let Some((strength, _, _)) = encryption_info {
179            // Subtract salt (already read), password verify (already read), and auth code (10 bytes at end)
180            entry
181                .compressed_size
182                .saturating_sub((strength.salt_size() + 2 + 10) as u64)
183        } else {
184            entry.compressed_size
185        };
186
187        #[cfg(not(feature = "encryption"))]
188        let data_size = entry.compressed_size;
189
190        // Now read the compressed data
191        let mut compressed_data = vec![0u8; data_size as usize];
192        self.file.read_exact(&mut compressed_data)?;
193
194        // Read auth code if encrypted
195        #[cfg(feature = "encryption")]
196        let auth_code = if encryption_info.is_some() {
197            let mut ac = vec![0u8; 10];
198            self.file.read_exact(&mut ac)?;
199            Some(ac)
200        } else {
201            None
202        };
203
204        // Decrypt if encrypted (Step 1: Decrypt compressed data)
205        #[cfg(feature = "encryption")]
206        let decryptor_opt = if let Some((strength, salt, pw_verify)) = encryption_info {
207            let password = self.password.as_ref().ok_or_else(|| {
208                SZipError::InvalidFormat("Encrypted entry but no password set".to_string())
209            })?;
210
211            // Create decryptor (password verification happens inside new())
212            let mut decryptor = AesDecryptor::new(password, strength, &salt, &pw_verify)?;
213
214            // Decrypt compressed data in-place
215            decryptor.decrypt(&mut compressed_data)?;
216
217            Some(decryptor)
218        } else {
219            None
220        };
221
222        // Decompress if needed (Step 2: Decompress decrypted data)
223        let data = if entry.compression_method == 8 {
224            // DEFLATE compression
225            let mut decoder = DeflateDecoder::new(&compressed_data[..]);
226            let mut decompressed = Vec::new();
227            decoder.read_to_end(&mut decompressed)?;
228            decompressed
229        } else if entry.compression_method == 0 {
230            // No compression (stored)
231            compressed_data
232        } else if entry.compression_method == 93 {
233            // Zstd compression
234            #[cfg(feature = "zstd-support")]
235            {
236                zstd::decode_all(&compressed_data[..])?
237            }
238            #[cfg(not(feature = "zstd-support"))]
239            {
240                return Err(SZipError::UnsupportedCompression(entry.compression_method));
241            }
242        } else {
243            return Err(SZipError::UnsupportedCompression(entry.compression_method));
244        };
245
246        // Verify HMAC authentication (Step 3: Update HMAC with plaintext and verify)
247        #[cfg(feature = "encryption")]
248        if let Some(mut decryptor) = decryptor_opt {
249            // Update HMAC with decompressed plaintext data
250            decryptor.update_hmac(&data);
251
252            // Verify authentication code
253            if let Some(ac) = auth_code {
254                decryptor.verify_auth_code(&ac)?;
255            }
256        }
257
258        Ok(data)
259    }
260
261    /// Read an entry by name
262    pub fn read_entry_by_name(&mut self, name: &str) -> Result<Vec<u8>> {
263        let entry = self
264            .find_entry(name)
265            .ok_or_else(|| SZipError::EntryNotFound(name.to_string()))?
266            .clone();
267
268        self.read_entry(&entry)
269    }
270
271    /// Get a streaming reader for an entry by name (for large files)
272    /// Returns a reader that decompresses data on-the-fly without loading everything into memory
273    pub fn read_entry_streaming_by_name(&mut self, name: &str) -> Result<Box<dyn Read + '_>> {
274        let entry = self
275            .find_entry(name)
276            .ok_or_else(|| SZipError::EntryNotFound(name.to_string()))?
277            .clone();
278
279        self.read_entry_streaming(&entry)
280    }
281
282    /// Get a streaming reader for an entry (for large files)
283    /// Returns a reader that decompresses data on-the-fly without loading everything into memory
284    pub fn read_entry_streaming(&mut self, entry: &ZipEntry) -> Result<Box<dyn Read + '_>> {
285        // Seek to local file header
286        self.file.seek(SeekFrom::Start(entry.offset))?;
287
288        // Read and verify local file header
289        let signature = self.read_u32_le()?;
290        if signature != LOCAL_FILE_HEADER_SIGNATURE {
291            return Err(SZipError::InvalidFormat(
292                "Invalid local file header signature".to_string(),
293            ));
294        }
295
296        // Skip version, flags, compression method
297        self.file.seek(SeekFrom::Current(6))?;
298
299        // Skip modification time and date, CRC-32
300        self.file.seek(SeekFrom::Current(8))?;
301
302        // Read compressed and uncompressed sizes
303        self.file.seek(SeekFrom::Current(8))?;
304
305        // Read filename length and extra field length
306        let filename_len = self.read_u16_le()? as i64;
307        let extra_len = self.read_u16_le()? as i64;
308
309        // Skip filename and extra field
310        self.file
311            .seek(SeekFrom::Current(filename_len + extra_len))?;
312
313        // Create a reader limited to compressed data size
314        let limited_reader = (&mut self.file).take(entry.compressed_size);
315
316        // Wrap with decompressor if needed
317        if entry.compression_method == 8 {
318            // DEFLATE compression
319            Ok(Box::new(DeflateDecoder::new(limited_reader)))
320        } else if entry.compression_method == 0 {
321            // No compression (stored)
322            Ok(Box::new(limited_reader))
323        } else if entry.compression_method == 93 {
324            // Zstd compression
325            #[cfg(feature = "zstd-support")]
326            {
327                Ok(Box::new(zstd::Decoder::new(limited_reader)?))
328            }
329            #[cfg(not(feature = "zstd-support"))]
330            {
331                Err(SZipError::UnsupportedCompression(entry.compression_method))
332            }
333        } else {
334            Err(SZipError::UnsupportedCompression(entry.compression_method))
335        }
336    }
337
338    /// Get a streaming reader for an entry by name
339    pub fn read_entry_by_name_streaming(&mut self, name: &str) -> Result<Box<dyn Read + '_>> {
340        let entry = self
341            .find_entry(name)
342            .ok_or_else(|| SZipError::EntryNotFound(name.to_string()))?
343            .clone();
344
345        self.read_entry_streaming(&entry)
346    }
347
348    /// Read the central directory from the ZIP file
349    fn read_central_directory(file: &mut BufReader<File>) -> Result<Vec<ZipEntry>> {
350        // Find end of central directory record
351        let eocd_offset = Self::find_eocd(file)?;
352
353        // Seek to EOCD
354        file.seek(SeekFrom::Start(eocd_offset))?;
355
356        // Read EOCD
357        let signature = Self::read_u32_le_static(file)?;
358        if signature != END_OF_CENTRAL_DIRECTORY_SIGNATURE {
359            return Err(SZipError::InvalidFormat(format!(
360                "Invalid end of central directory signature: 0x{:08x}",
361                signature
362            )));
363        }
364
365        // Skip disk number fields (4 bytes)
366        file.seek(SeekFrom::Current(4))?;
367
368        // Read number of entries on this disk (2 bytes)
369        let _entries_on_disk = Self::read_u16_le_static(file)?;
370
371        // Read total number of entries (2 bytes)
372
373        // These values may be placeholder 0xFFFF/0xFFFFFFFF when ZIP64 is used
374        let total_entries_16 = Self::read_u16_le_static(file)?;
375
376        // Read central directory size (4 bytes)
377        let cd_size_32 = Self::read_u32_le_static(file)?;
378
379        // Read central directory offset (4 bytes)
380        let cd_offset_32 = Self::read_u32_le_static(file)? as u64;
381
382        // Promote to u64 and handle ZIP64 if markers present
383        let mut total_entries = total_entries_16 as usize;
384        let mut cd_offset = cd_offset_32;
385        let _cd_size = cd_size_32 as u64;
386
387        if total_entries_16 == 0xFFFF || cd_size_32 == 0xFFFFFFFF || cd_offset_32 == 0xFFFFFFFF {
388            // Need to find ZIP64 EOCD locator and read ZIP64 EOCD record
389            let (zip64_total_entries, zip64_cd_size, zip64_cd_offset) =
390                Self::read_zip64_eocd(file, eocd_offset)?;
391            total_entries = zip64_total_entries as usize;
392            cd_offset = zip64_cd_offset;
393            // _cd_size can be used if needed (zip64_cd_size)
394            let _ = zip64_cd_size;
395        }
396
397        // Seek to central directory
398        file.seek(SeekFrom::Start(cd_offset))?;
399
400        // Read all central directory entries
401        let mut entries = Vec::with_capacity(total_entries);
402        for _ in 0..total_entries {
403            let signature = Self::read_u32_le_static(file)?;
404            if signature != CENTRAL_DIRECTORY_SIGNATURE {
405                break;
406            }
407
408            // Skip version made by, version needed
409            file.seek(SeekFrom::Current(4))?;
410
411            // Read flags (needed for encryption check)
412            #[cfg_attr(not(feature = "encryption"), allow(unused_variables))]
413            let flags = Self::read_u16_le_static(file)?;
414
415            let compression_method = Self::read_u16_le_static(file)?;
416
417            // Skip modification time, date, CRC-32
418            file.seek(SeekFrom::Current(8))?;
419
420            // Read sizes as 32-bit placeholders (may be 0xFFFFFFFF meaning ZIP64)
421            let compressed_size_32 = Self::read_u32_le_static(file)? as u64;
422            let uncompressed_size_32 = Self::read_u32_le_static(file)? as u64;
423            let filename_len = Self::read_u16_le_static(file)? as usize;
424            let extra_len = Self::read_u16_le_static(file)? as usize;
425            let comment_len = Self::read_u16_le_static(file)? as usize;
426
427            // Skip disk number, internal attributes, external attributes
428            file.seek(SeekFrom::Current(8))?;
429
430            let mut offset = Self::read_u32_le_static(file)? as u64;
431
432            // Read filename
433            let mut filename_buf = vec![0u8; filename_len];
434            file.read_exact(&mut filename_buf)?;
435            let name = String::from_utf8_lossy(&filename_buf).to_string();
436
437            // Read extra field so we can parse ZIP64 extra if present
438            let mut extra_buf = vec![0u8; extra_len];
439            if extra_len > 0 {
440                file.read_exact(&mut extra_buf)?;
441            }
442
443            // If sizes/offsets are 0xFFFFFFFF, parse ZIP64 extra field (0x0001)
444            let mut compressed_size = compressed_size_32;
445            let mut uncompressed_size = uncompressed_size_32;
446
447            if compressed_size_32 == 0xFFFFFFFF
448                || uncompressed_size_32 == 0xFFFFFFFF
449                || offset == 0xFFFFFFFF
450            {
451                // parse extra fields
452                let mut i = 0usize;
453                while i + 4 <= extra_buf.len() {
454                    let id = u16::from_le_bytes([extra_buf[i], extra_buf[i + 1]]);
455                    let data_len =
456                        u16::from_le_bytes([extra_buf[i + 2], extra_buf[i + 3]]) as usize;
457                    i += 4;
458                    if i + data_len > extra_buf.len() {
459                        break;
460                    }
461                    if id == 0x0001 {
462                        // ZIP64 extra field: contains values in order: original size, compressed size, relative header offset, disk start
463                        let mut cursor = 0usize;
464                        // read uncompressed size if placeholder present
465                        if uncompressed_size_32 == 0xFFFFFFFF && cursor + 8 <= data_len {
466                            uncompressed_size = u64::from_le_bytes([
467                                extra_buf[i + cursor],
468                                extra_buf[i + cursor + 1],
469                                extra_buf[i + cursor + 2],
470                                extra_buf[i + cursor + 3],
471                                extra_buf[i + cursor + 4],
472                                extra_buf[i + cursor + 5],
473                                extra_buf[i + cursor + 6],
474                                extra_buf[i + cursor + 7],
475                            ]);
476                            cursor += 8;
477                        }
478                        // read compressed size if placeholder present
479                        if compressed_size_32 == 0xFFFFFFFF && cursor + 8 <= data_len {
480                            compressed_size = u64::from_le_bytes([
481                                extra_buf[i + cursor],
482                                extra_buf[i + cursor + 1],
483                                extra_buf[i + cursor + 2],
484                                extra_buf[i + cursor + 3],
485                                extra_buf[i + cursor + 4],
486                                extra_buf[i + cursor + 5],
487                                extra_buf[i + cursor + 6],
488                                extra_buf[i + cursor + 7],
489                            ]);
490                            cursor += 8;
491                        }
492                        // read offset if placeholder present
493                        if offset == 0xFFFFFFFF && cursor + 8 <= data_len {
494                            offset = u64::from_le_bytes([
495                                extra_buf[i + cursor],
496                                extra_buf[i + cursor + 1],
497                                extra_buf[i + cursor + 2],
498                                extra_buf[i + cursor + 3],
499                                extra_buf[i + cursor + 4],
500                                extra_buf[i + cursor + 5],
501                                extra_buf[i + cursor + 6],
502                                extra_buf[i + cursor + 7],
503                            ]);
504                        }
505                        // we don't need disk start here
506                        break;
507                    }
508                    i += data_len;
509                }
510            }
511
512            // Skip comment
513            if comment_len > 0 {
514                file.seek(SeekFrom::Current(comment_len as i64))?;
515            }
516
517            entries.push(ZipEntry {
518                name,
519                compressed_size,
520                uncompressed_size,
521                compression_method,
522                offset,
523                #[cfg(feature = "encryption")]
524                is_encrypted: (flags & 0x01) != 0,
525            });
526        }
527
528        Ok(entries)
529    }
530
531    /// When EOCD indicates ZIP64 usage, find and read ZIP64 EOCD locator and record
532    fn read_zip64_eocd(file: &mut BufReader<File>, eocd_offset: u64) -> Result<(u64, u64, u64)> {
533        // Search backwards from EOCD for ZIP64 EOCD locator signature (50 4b 06 07)
534        let search_start = eocd_offset.saturating_sub(65557);
535        file.seek(SeekFrom::Start(search_start))?;
536        let mut buffer = Vec::new();
537        file.read_to_end(&mut buffer)?;
538
539        let mut locator_pos: Option<usize> = None;
540        for i in (0..buffer.len().saturating_sub(3)).rev() {
541            if buffer[i] == 0x50
542                && buffer[i + 1] == 0x4b
543                && buffer[i + 2] == 0x06
544                && buffer[i + 3] == 0x07
545            {
546                locator_pos = Some(i);
547                break;
548            }
549        }
550
551        let locator_pos = locator_pos
552            .ok_or_else(|| SZipError::InvalidFormat("ZIP64 EOCD locator not found".to_string()))?;
553
554        // Read locator fields from buffer
555        // locator layout: signature(4), number of the disk with the start of the zip64 eocd(4), relative offset of the zip64 eocd(8), total number of disks(4)
556        let rel_off_bytes = &buffer[locator_pos + 8..locator_pos + 16];
557        let zip64_eocd_offset = u64::from_le_bytes([
558            rel_off_bytes[0],
559            rel_off_bytes[1],
560            rel_off_bytes[2],
561            rel_off_bytes[3],
562            rel_off_bytes[4],
563            rel_off_bytes[5],
564            rel_off_bytes[6],
565            rel_off_bytes[7],
566        ]);
567
568        // Seek to ZIP64 EOCD record
569        file.seek(SeekFrom::Start(zip64_eocd_offset))?;
570
571        let sig = Self::read_u32_le_static(file)?;
572        if sig != ZIP64_END_OF_CENTRAL_DIRECTORY_SIGNATURE {
573            return Err(SZipError::InvalidFormat(format!(
574                "Invalid ZIP64 EOCD signature: 0x{:08x}",
575                sig
576            )));
577        }
578
579        // size of ZIP64 EOCD record (8 bytes)
580        let _size = {
581            let mut buf = [0u8; 8];
582            file.read_exact(&mut buf)?;
583            u64::from_le_bytes(buf)
584        };
585
586        // skip version made by (2), version needed (2), disk number (4), disk where central dir starts (4)
587        file.seek(SeekFrom::Current(12))?;
588
589        // total number of entries on this disk (8)
590        let total_entries = {
591            let mut buf = [0u8; 8];
592            file.read_exact(&mut buf)?;
593            u64::from_le_bytes(buf)
594        };
595
596        // total number of entries (8) - some implementations write both; ignore the second value
597        {
598            let mut buf = [0u8; 8];
599            file.read_exact(&mut buf)?;
600            // ignore u64::from_le_bytes(buf)
601        }
602
603        // central directory size (8)
604        let cd_size = {
605            let mut buf = [0u8; 8];
606            file.read_exact(&mut buf)?;
607            u64::from_le_bytes(buf)
608        };
609
610        // central directory offset (8)
611        let cd_offset = {
612            let mut buf = [0u8; 8];
613            file.read_exact(&mut buf)?;
614            u64::from_le_bytes(buf)
615        };
616
617        Ok((total_entries, cd_size, cd_offset))
618    }
619
620    /// Find the end of central directory record by scanning from the end of the file
621    fn find_eocd(file: &mut BufReader<File>) -> Result<u64> {
622        let file_size = file.seek(SeekFrom::End(0))?;
623
624        // EOCD is at least 22 bytes, search last 65KB (max comment size + EOCD)
625        let search_start = file_size.saturating_sub(65557);
626        file.seek(SeekFrom::Start(search_start))?;
627
628        let mut buffer = Vec::new();
629        file.read_to_end(&mut buffer)?;
630
631        // Search for EOCD signature from the end
632        for i in (0..buffer.len().saturating_sub(3)).rev() {
633            if buffer[i] == 0x50
634                && buffer[i + 1] == 0x4b
635                && buffer[i + 2] == 0x05
636                && buffer[i + 3] == 0x06
637            {
638                return Ok(search_start + i as u64);
639            }
640        }
641
642        Err(SZipError::InvalidFormat(
643            "End of central directory not found".to_string(),
644        ))
645    }
646
647    fn read_u16_le(&mut self) -> Result<u16> {
648        let mut buf = [0u8; 2];
649        self.file.read_exact(&mut buf)?;
650        Ok(u16::from_le_bytes(buf))
651    }
652
653    fn read_u32_le(&mut self) -> Result<u32> {
654        let mut buf = [0u8; 4];
655        self.file.read_exact(&mut buf)?;
656        Ok(u32::from_le_bytes(buf))
657    }
658
659    fn read_u16_le_static(file: &mut BufReader<File>) -> Result<u16> {
660        let mut buf = [0u8; 2];
661        file.read_exact(&mut buf)?;
662        Ok(u16::from_le_bytes(buf))
663    }
664
665    fn read_u32_le_static(file: &mut BufReader<File>) -> Result<u32> {
666        let mut buf = [0u8; 4];
667        file.read_exact(&mut buf)?;
668        Ok(u32::from_le_bytes(buf))
669    }
670
671    /// Parse AES encryption info from extra field
672    #[cfg(feature = "encryption")]
673    #[allow(clippy::type_complexity)]
674    fn parse_aes_extra_field(
675        &mut self,
676        extra_len: usize,
677    ) -> Result<Option<(AesStrength, Vec<u8>, [u8; 2])>> {
678        if extra_len == 0 {
679            return Ok(None);
680        }
681
682        let mut extra_buf = vec![0u8; extra_len];
683        self.file.read_exact(&mut extra_buf)?;
684
685        // Parse extra fields looking for AES extra (0x9901)
686        let mut i = 0usize;
687        while i + 4 <= extra_buf.len() {
688            let id = u16::from_le_bytes([extra_buf[i], extra_buf[i + 1]]);
689            let data_len = u16::from_le_bytes([extra_buf[i + 2], extra_buf[i + 3]]) as usize;
690            i += 4;
691
692            if i + data_len > extra_buf.len() {
693                break;
694            }
695
696            if id == 0x9901 {
697                // WinZip AES encryption extra field
698                // Layout: version(2) + vendor(2) + strength(2) + compression(2) + salt + pwverify(2)
699
700                if data_len < 7 {
701                    return Err(SZipError::InvalidFormat(
702                        "Invalid AES extra field".to_string(),
703                    ));
704                }
705
706                let strength_code = extra_buf[i + 4]; // AES strength is 1 byte, not 2!
707
708                let strength = match strength_code {
709                    0x03 => AesStrength::Aes256,
710                    _ => {
711                        return Err(SZipError::InvalidFormat(format!(
712                            "Unsupported AES strength: {}",
713                            strength_code
714                        )))
715                    }
716                };
717
718                // Read salt and password verification from actual file data (not extra field)
719                // Salt comes after the extra field, before compressed data
720                let salt_size = strength.salt_size();
721
722                let mut salt = vec![0u8; salt_size];
723                self.file.read_exact(&mut salt)?;
724
725                let mut pw_verify = [0u8; 2];
726                self.file.read_exact(&mut pw_verify)?;
727
728                return Ok(Some((strength, salt, pw_verify)));
729            }
730
731            i += data_len;
732        }
733
734        Ok(None)
735    }
736}
s_zip/reader.rs

s_zip/
reader.rs
