Add support for PAX Format, Version 1.0

src/archive.rs

@@ -9,9 +9,10 @@ use std::path::Path;
 
 use crate::entry::{EntryFields, EntryIo};
 use crate::error::TarError;
+use crate::header::{SparseEntry, BLOCK_SIZE};
 use crate::other;
 use crate::pax::pax_extensions_size;
-use crate::{Entry, GnuExtSparseHeader, GnuSparseHeader, Header};
+use crate::{Entry, GnuExtSparseHeader, Header};
 
 /// A top-level representation of an archive file.
 ///
@@ -256,6 +257,7 @@ impl<'a, R: Read> Iterator for Entries<'a, R> {
     }
 }
 
+#[allow(unused_assignments)]
 impl<'a> EntriesFields<'a> {
     fn next_entry_raw(
         &mut self,
@@ -277,14 +279,14 @@ impl<'a> EntriesFields<'a> {
             // Otherwise, check if we are ignoring zeros and continue, or break as if this is the
             // end of the archive.
             if !header.as_bytes().iter().all(|i| *i == 0) {
-                self.next += 512;
+                self.next += BLOCK_SIZE as u64;
                 break;
             }
 
             if !self.archive.inner.ignore_zeros {
                 return Ok(None);
             }
-            self.next += 512;
+            self.next += BLOCK_SIZE as u64;
             header_pos = self.next;
         }
 
@@ -325,11 +327,11 @@ impl<'a> EntriesFields<'a> {
         // Store where the next entry is, rounding up by 512 bytes (the size of
         // a header);
         let size = size
-            .checked_add(511)
+            .checked_add(BLOCK_SIZE as u64 - 1)
             .ok_or_else(|| other("size overflow"))?;
         self.next = self
             .next
-            .checked_add(size & !(512 - 1))
+            .checked_add(size & !(BLOCK_SIZE as u64 - 1))
             .ok_or_else(|| other("size overflow"))?;
 
         Ok(Some(ret.into_entry()))
@@ -394,26 +396,68 @@ impl<'a> EntriesFields<'a> {
                 if let Some(pax_extensions_ref) = &pax_extensions {
                     pax_size = pax_extensions_size(pax_extensions_ref);
                 }
+                // This entry has two headers.
+                // Keep pax_extensions for the next ustar header.
+                processed -= 1;
                 continue;
             }
 
             let mut fields = EntryFields::from(entry);
-            fields.long_pathname = gnu_longname;
-            fields.long_linkname = gnu_longlink;
             fields.pax_extensions = pax_extensions;
+            // False positive: unused assignment
+            // https://github.com/rust-lang/rust/issues/22630
+            pax_extensions = None; // Reset pax_extensions after use
+            fields.long_pathname = if is_recognized_header && fields.is_pax_sparse() {
+                fields.pax_sparse_name()
+            } else {
+                gnu_longname
+            };
+            fields.long_linkname = gnu_longlink;
             self.parse_sparse_header(&mut fields)?;
             return Ok(Some(fields.into_entry()));
         }
     }
 
     fn parse_sparse_header(&mut self, entry: &mut EntryFields<'a>) -> io::Result<()> {
-        if !entry.header.entry_type().is_gnu_sparse() {
+        if !entry.is_pax_sparse() && !entry.header.entry_type().is_gnu_sparse() {
             return Ok(());
         }
-        let gnu = match entry.header.as_gnu() {
-            Some(gnu) => gnu,
-            None => return Err(other("sparse entry type listed but not GNU header")),
-        };
+        let mut sparse_map = Vec::<SparseEntry>::new();
+        let mut real_size = 0;
+        if entry.is_pax_sparse() {
+            real_size = entry.pax_sparse_realsize()?;
+            let mut num_bytes_read = 0;
+            let mut reader = io::BufReader::with_capacity(BLOCK_SIZE, &self.archive.inner);
+            let mut read_decimal_line = || -> io::Result<u64> {
+                let mut str = String::new();
+                num_bytes_read += reader.read_line(&mut str)?;
+                str.strip_suffix("\n")
+                    .and_then(|s| s.parse::<u64>().ok())
+                    .ok_or_else(|| other("failed to read a decimal line"))
+            };
+
+            let num_entries = read_decimal_line()?;
+            for _ in 0..num_entries {
+                let offset = read_decimal_line()?;
+                let size = read_decimal_line()?;
+                sparse_map.push(SparseEntry { offset, size });
+            }
+            let rem = BLOCK_SIZE - (num_bytes_read % BLOCK_SIZE);
+            entry.size -= (num_bytes_read + rem) as u64;
+        } else if entry.header.entry_type().is_gnu_sparse() {
+            let gnu = match entry.header.as_gnu() {
+                Some(gnu) => gnu,
+                None => return Err(other("sparse entry type listed but not GNU header")),
+            };
+            real_size = gnu.real_size()?;
+            for block in gnu.sparse.iter() {
+                if !block.is_empty() {
+                    let offset = block.offset()?;
+                    let size = block.length()?;
+                    sparse_map.push(SparseEntry { offset, size });
+                }
+            }
+        }
 
         // Sparse files are represented internally as a list of blocks that are
         // read. Blocks are either a bunch of 0's or they're data from the
@@ -442,13 +486,8 @@ impl<'a> EntriesFields<'a> {
             let data = &mut entry.data;
             let reader = &self.archive.inner;
             let size = entry.size;
-            let mut add_block = |block: &GnuSparseHeader| -> io::Result<_> {
-                if block.is_empty() {
-                    return Ok(());
-                }
-                let off = block.offset()?;
-                let len = block.length()?;
-                if len != 0 && (size - remaining) % 512 != 0 {
+            let mut add_block = |off: u64, len: u64| -> io::Result<_> {
+                if len != 0 && (size - remaining) % BLOCK_SIZE as u64 != 0 {
                     return Err(other(
                         "previous block in sparse file was not \
                          aligned to 512-byte boundary",
@@ -474,25 +513,27 @@ impl<'a> EntriesFields<'a> {
                 data.push(EntryIo::Data(reader.take(len)));
                 Ok(())
             };
-            for block in gnu.sparse.iter() {
-                add_block(block)?
+            for block in sparse_map {
+                add_block(block.offset, block.size)?
             }
-            if gnu.is_extended() {
+            if entry.header.as_gnu().map(|gnu| gnu.is_extended()) == Some(true) {
                 let mut ext = GnuExtSparseHeader::new();
                 ext.isextended[0] = 1;
                 while ext.is_extended() {
                     if !try_read_all(&mut &self.archive.inner, ext.as_mut_bytes())? {
                         return Err(other("failed to read extension"));
                     }
 
-                    self.next += 512;
+                    self.next += BLOCK_SIZE as u64;
                     for block in ext.sparse.iter() {
-                        add_block(block)?;
+                        if !block.is_empty() {
+                            add_block(block.offset()?, block.length()?)?;
+                        }
                     }
                 }
             }
         }
-        if cur != gnu.real_size()? {
+        if cur != real_size {
             return Err(other(
                 "mismatch in sparse file chunks and \
                  size in header",

src/entry.rs

@@ -285,6 +285,46 @@ impl<'a> EntryFields<'a> {
         self.read_to_end(&mut v).map(|_| v)
     }
 
+    pub fn is_pax_sparse(&mut self) -> bool {
+        if let Some(ref pax) = self.pax_extensions {
+            let mut extensions = PaxExtensions::new(pax).filter_map(|f| f.ok());
+            return extensions
+                .find(|f| f.key_bytes() == b"GNU.sparse.major" && f.value_bytes() == b"1")
+                .is_some()
+                && extensions
+                    .find(|f| f.key_bytes() == b"GNU.sparse.minor" && f.value_bytes() == b"0")
+                    .is_some();
+        }
+        false
+    }
+
+    pub fn pax_sparse_name(&mut self) -> Option<Vec<u8>> {
+        if let Some(ref pax) = self.pax_extensions {
+            return PaxExtensions::new(pax)
+                .filter_map(|f| f.ok())
+                .find(|f| f.key_bytes() == b"GNU.sparse.name")
+                .map(|f| f.value_bytes().to_vec());
+        }
+        None
+    }
+
+    pub fn pax_sparse_realsize(&mut self) -> io::Result<u64> {
+        if let Some(ref pax) = self.pax_extensions {
+            let pax = PaxExtensions::new(pax)
+                .filter_map(|f| f.ok())
+                .find(|f| f.key_bytes() == b"GNU.sparse.realsize")
+                .map(|f| f.value_bytes());
+            if let Some(field) = pax {
+                let str =
+                    std::str::from_utf8(&field).map_err(|_| other("failed to read string"))?;
+                return str
+                    .parse::<u64>()
+                    .map_err(|_| other("failed to parse the real size"));
+            }
+        }
+        Err(other("PAX extension GNU.sparse.realsize not found"))
+    }
+
     fn path(&self) -> io::Result<Cow<Path>> {
         bytes2path(self.path_bytes())
     }

src/header.rs

@@ -16,11 +16,13 @@ use std::str;
 use crate::other;
 use crate::EntryType;
 
+pub const BLOCK_SIZE: usize = 512;
+
 /// Representation of the header of an entry in an archive
 #[repr(C)]
 #[allow(missing_docs)]
 pub struct Header {
-    bytes: [u8; 512],
+    bytes: [u8; BLOCK_SIZE],
 }
 
 /// Declares the information that should be included when filling a Header
@@ -110,6 +112,12 @@ pub struct GnuHeader {
     pub pad: [u8; 17],
 }
 
+/// Description of a spare entry.
+pub struct SparseEntry {
+    pub offset: u64,
+    pub size: u64,
+}
+
 /// Description of the header of a spare entry.
 ///
 /// Specifies the offset/number of bytes of a chunk of data in octal.

tests/all.rs

@@ -1089,6 +1089,19 @@ fn sparse_with_trailing() {
     assert_eq!(&s[0x100_000..], "1MB through\n");
 }
 
+#[test]
+fn pax_sparse() {
+    let rdr = Cursor::new(tar!("pax_sparse.tar"));
+    let mut ar = Archive::new(rdr);
+    let td = t!(TempBuilder::new().prefix("tar-rs").tempdir());
+    t!(ar.unpack(td.path()));
+
+    let mut s = String::new();
+    t!(t!(File::open(td.path().join("sparse_begin.txt"))).read_to_string(&mut s));
+    assert_eq!(&s[..5], "test\n");
+    assert!(s[5..].chars().all(|x| x == '\u{0}'));
+}
+
 #[test]
 fn path_separators() {
     let mut ar = Builder::new(Vec::new());