archive: allow preserving ownerships when unpacking

.github/workflows/main.yml

@@ -31,6 +31,9 @@ jobs:
       shell: bash
     - run: cargo test
     - run: cargo test --no-default-features
+    - name: Run cargo test with root
+      run: sudo -E $(which cargo) test
+      if: ${{ matrix.os == 'ubuntu-latest' }}
 
   rustfmt:
     name: Rustfmt

src/archive.rs

@@ -24,6 +24,7 @@ pub struct ArchiveInner<R: ?Sized> {
     pos: Cell<u64>,
     unpack_xattrs: bool,
     preserve_permissions: bool,
+    preserve_ownerships: bool,
     preserve_mtime: bool,
     overwrite: bool,
     ignore_zeros: bool,
@@ -54,6 +55,7 @@ impl<R: Read> Archive<R> {
             inner: ArchiveInner {
                 unpack_xattrs: false,
                 preserve_permissions: false,
+                preserve_ownerships: false,
                 preserve_mtime: true,
                 overwrite: true,
                 ignore_zeros: false,
@@ -126,6 +128,15 @@ impl<R: Read> Archive<R> {
         self.inner.preserve_permissions = preserve;
     }
 
+    /// Indicate whether numeric ownership ids (like uid and gid on Unix)
+    /// are preserved when unpacking this entry.
+    ///
+    /// This flag is disabled by default and is currently only implemented on
+    /// Unix.
+    pub fn set_preserve_ownerships(&mut self, preserve: bool) {
+        self.inner.preserve_ownerships = preserve;
+    }
+
     /// Indicate whether files and symlinks should be overwritten on extraction.
     pub fn set_overwrite(&mut self, overwrite: bool) {
         self.inner.overwrite = overwrite;
@@ -308,6 +319,7 @@ impl<'a> EntriesFields<'a> {
             preserve_permissions: self.archive.inner.preserve_permissions,
             preserve_mtime: self.archive.inner.preserve_mtime,
             overwrite: self.archive.inner.overwrite,
+            preserve_ownerships: self.archive.inner.preserve_ownerships,
         };
 
         // Store where the next entry is, rounding up by 512 bytes (the size of

src/entry.rs

@@ -38,6 +38,7 @@ pub struct EntryFields<'a> {
     pub data: Vec<EntryIo<'a>>,
     pub unpack_xattrs: bool,
     pub preserve_permissions: bool,
+    pub preserve_ownerships: bool,
     pub preserve_mtime: bool,
     pub overwrite: bool,
 }
@@ -444,13 +445,36 @@ impl<'a> EntryFields<'a> {
 
     /// Returns access to the header of this entry in the archive.
     fn unpack(&mut self, target_base: Option<&Path>, dst: &Path) -> io::Result<Unpacked> {
+        fn set_perms_ownerships(
+            dst: &Path,
+            f: Option<&mut std::fs::File>,
+            header: &Header,
+            perms: bool,
+            ownerships: bool,
+        ) -> io::Result<()> {
+            // ownerships need to be set first to avoid stripping SUID bits in the permissions ...
+            if ownerships {
+                set_ownerships(dst, &f, header.uid()?, header.gid()?)?;
+            }
+            // ... then set permissions, SUID bits set here is kept
+            if let Ok(mode) = header.mode() {
+                set_perms(dst, f, mode, perms)?;
+            }
+
+            Ok(())
+        }
+
         let kind = self.header.entry_type();
 
         if kind.is_dir() {
             self.unpack_dir(dst)?;
-            if let Ok(mode) = self.header.mode() {
-                set_perms(dst, None, mode, self.preserve_permissions)?;
-            }
+            set_perms_ownerships(
+                dst,
+                None,
+                &self.header,
+                self.preserve_permissions,
+                self.preserve_ownerships,
+            )?;
             return Ok(Unpacked::__Nonexhaustive);
         } else if kind.is_hard_link() || kind.is_symlink() {
             let src = match self.link_name()? {
@@ -553,9 +577,13 @@ impl<'a> EntryFields<'a> {
         // Only applies to old headers.
         if self.header.as_ustar().is_none() && self.path_bytes().ends_with(b"/") {
             self.unpack_dir(dst)?;
-            if let Ok(mode) = self.header.mode() {
-                set_perms(dst, None, mode, self.preserve_permissions)?;
-            }
+            set_perms_ownerships(
+                dst,
+                None,
+                &self.header,
+                self.preserve_permissions,
+                self.preserve_ownerships,
+            )?;
             return Ok(Unpacked::__Nonexhaustive);
         }
 
@@ -632,14 +660,83 @@ impl<'a> EntryFields<'a> {
                 })?;
             }
         }
-        if let Ok(mode) = self.header.mode() {
-            set_perms(dst, Some(&mut f), mode, self.preserve_permissions)?;
-        }
+        set_perms_ownerships(
+            dst,
+            Some(&mut f),
+            &self.header,
+            self.preserve_permissions,
+            self.preserve_ownerships,
+        )?;
         if self.unpack_xattrs {
             set_xattrs(self, dst)?;
         }
         return Ok(Unpacked::File(f));
 
+        fn set_ownerships(
+            dst: &Path,
+            f: &Option<&mut std::fs::File>,
+            uid: u64,
+            gid: u64,
+        ) -> Result<(), TarError> {
+            _set_ownerships(dst, f, uid, gid).map_err(|e| {
+                TarError::new(
+                    format!(
+                        "failed to set ownerships to uid={:?}, gid={:?} \
+                         for `{}`",
+                        uid,
+                        gid,
+                        dst.display()
+                    ),
+                    e,
+                )
+            })
+        }
+
+        #[cfg(unix)]
+        fn _set_ownerships(
+            dst: &Path,
+            f: &Option<&mut std::fs::File>,
+            uid: u64,
+            gid: u64,
+        ) -> io::Result<()> {
+            use std::os::unix::prelude::*;
+
+            match f {
+                Some(f) => unsafe {
+                    let fd = f.as_raw_fd();
+                    if libc::fchown(fd, uid as u32, gid as u32) != 0 {
+                        Err(io::Error::last_os_error())
+                    } else {
+                        Ok(())
+                    }
+                },
+                None => unsafe {
+                    let path = std::ffi::CString::new(dst.as_os_str().as_bytes()).map_err(|e| {
+                        io::Error::new(
+                            io::ErrorKind::Other,
+                            format!("path contains null character: {:?}", e),
+                        )
+                    })?;
+                    if libc::lchown(path.as_ptr(), uid as u32, gid as u32) != 0 {
+                        Err(io::Error::last_os_error())
+                    } else {
+                        Ok(())
+                    }
+                },
+            }
+        }
+
+        // Windows does not support posix numeric ownership IDs
+        #[cfg(any(windows, target_arch = "wasm32"))]
+        fn _set_ownerships(
+            _: &Path,
+            _: &Option<&mut std::fs::File>,
+            _: u64,
+            _: u64,
+        ) -> io::Result<()> {
+            Ok(())
+        }
+
         fn set_perms(
             dst: &Path,
             f: Option<&mut std::fs::File>,

tests/all.rs

@@ -1385,3 +1385,57 @@ fn header_size_overflow() {
         err
     );
 }
+
+#[test]
+#[cfg(unix)]
+fn ownership_preserving() {
+    use std::os::unix::prelude::*;
+
+    let mut rdr = Vec::new();
+    let mut ar = Builder::new(&mut rdr);
+    let data: &[u8] = &[];
+    let mut header = Header::new_gnu();
+    // file 1 with uid = 580800000, gid = 580800000
+    header.set_gid(580800000);
+    header.set_uid(580800000);
+    t!(header.set_path("iamuid580800000"));
+    header.set_size(0);
+    header.set_cksum();
+    t!(ar.append(&header, data));
+    // file 2 with uid = 580800001, gid = 580800000
+    header.set_uid(580800001);
+    t!(header.set_path("iamuid580800001"));
+    header.set_cksum();
+    t!(ar.append(&header, data));
+    // file 3 with uid = 580800002, gid = 580800002
+    header.set_gid(580800002);
+    header.set_uid(580800002);
+    t!(header.set_path("iamuid580800002"));
+    header.set_cksum();
+    t!(ar.append(&header, data));
+    t!(ar.finish());
+
+    let rdr = Cursor::new(t!(ar.into_inner()));
+    let td = t!(TempBuilder::new().prefix("tar-rs").tempdir());
+    let mut ar = Archive::new(rdr);
+    ar.set_preserve_ownerships(true);
+
+    if unsafe { libc::getuid() } == 0 {
+        assert!(ar.unpack(td.path()).is_ok());
+        // validate against premade files
+        // iamuid580800001 has this ownership: 580800001:580800000
+        let meta = std::fs::metadata(td.path().join("iamuid580800000")).unwrap();
+        assert_eq!(meta.uid(), 580800000);
+        assert_eq!(meta.gid(), 580800000);
+        let meta = std::fs::metadata(td.path().join("iamuid580800001")).unwrap();
+        assert_eq!(meta.uid(), 580800001);
+        assert_eq!(meta.gid(), 580800000);
+        let meta = std::fs::metadata(td.path().join("iamuid580800002")).unwrap();
+        assert_eq!(meta.uid(), 580800002);
+        assert_eq!(meta.gid(), 580800002);
+    } else {
+        // it's not possible to unpack tar while preserving ownership
+        // without root permissions
+        assert!(ar.unpack(td.path()).is_err());
+    }
+}