pxar: encoder: warn on lacking read permissions instead of fail.

If during creation of the archive, files/dirs with lacking read permissions are
encountered, the user is displayed a warning and the archive is created without
including the file/dir.
Previously this resulted in an error and the archive creation failed.

In order to implement this also for the .pxarexclude files, the Error type of
MatchPattern::from_file() and MatchPattern::from_line() was adopted accordingly.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

TODO.rst

@@ -1,8 +1,6 @@
 TODO list for Proxmox Backup
 ============================
 
-* do not abort host backups on file permission errors
-
 * proxmox-backup-client: verify server cert (save/compare last saved cert fingerprint)
 
 Suggestions

src/pxar/encoder.rs

@@ -697,6 +697,14 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
                 (Some((buffer, stat)), excludes)
             }
             Ok(None) => (None, Vec::new()),
+            Err(nix::Error::Sys(Errno::EACCES)) => {
+                // No permission to read .pxarexclude, ignore its contents.
+                eprintln!(
+                    "ignoring match patterns in {:?}: open file failed - EACCES",
+                    self.full_path().join(".pxarexclude"),
+                );
+                (None, Vec::new())
+            }
             Err(err) => bail!("error while reading exclude file - {}", err),
         };
         for excl in &excludes {
@@ -777,6 +785,7 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
             let start_pos = self.writer_pos;
 
             if filename.as_bytes() == b".pxarexclude" {
+                // pxar_exclude is none in case of error EACCES.
                 if let Some((ref content, ref stat)) = pxar_exclude {
                     let filefd = match nix::fcntl::openat(
                         rawfd,
@@ -789,6 +798,14 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
                             self.report_vanished_file(&self.full_path())?;
                             continue;
                         }
+                        Err(nix::Error::Sys(Errno::EACCES)) => {
+                            let filename_osstr = std::ffi::OsStr::from_bytes(filename.to_bytes());
+                            eprintln!(
+                                "skipping {:?}: open file failed - EACCES",
+                                self.full_path().join(filename_osstr),
+                            );
+                            continue;
+                        }
                         Err(err) => {
                             let filename_osstr = std::ffi::OsStr::from_bytes(filename.to_bytes());
                             bail!(
@@ -810,8 +827,8 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
                         catalog.add_file(&filename, stat.st_size as u64, stat.st_mtime as u64)?;
                     }
                     self.encode_pxar_exclude(filefd, stat, child_magic, content)?;
-                    continue;
                 }
+                continue;
             }
 
             if is_root && filename.as_bytes() == b".pxarexclude-cli" {
@@ -846,6 +863,14 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
                         self.relative_path.pop();
                         continue;
                     }
+                    Err(nix::Error::Sys(Errno::EACCES)) => {
+                        eprintln!(
+                            "skipping {:?}: open dir failed - EACCES",
+                            self.full_path(),
+                        );
+                        self.relative_path.pop();
+                        continue;
+                    }
                     Err(err) => bail!("open dir {:?} failed - {}", self.full_path(), err),
                 };
 
@@ -901,6 +926,14 @@ impl<'a, W: Write, C: BackupCatalogWriter> Encoder<'a, W, C> {
                             self.relative_path.pop();
                             continue;
                         }
+                        Err(nix::Error::Sys(Errno::EACCES)) => {
+                            eprintln!(
+                                "skipping {:?}: open file failed - EACCES",
+                                self.full_path(),
+                            );
+                            self.relative_path.pop();
+                            continue;
+                        }
                         Err(err) => bail!("open file {:?} failed - {}", self.full_path(), err),
                     };
 

src/pxar/match_pattern.rs

@@ -97,18 +97,19 @@ impl MatchPattern {
     pub fn from_file<P: ?Sized + NixPath>(
         parent_fd: RawFd,
         filename: &P,
-    ) -> Result<Option<(Vec<MatchPattern>, Vec<u8>, FileStat)>, Error> {
+    ) -> Result<Option<(Vec<MatchPattern>, Vec<u8>, FileStat)>, nix::Error> {
         let stat = match stat::fstatat(parent_fd, filename, AtFlags::AT_SYMLINK_NOFOLLOW) {
             Ok(stat) => stat,
             Err(nix::Error::Sys(Errno::ENOENT)) => return Ok(None),
-            Err(err) => bail!("stat failed - {}", err),
+            Err(err) => return Err(err),
         };
 
         let filefd = fcntl::openat(parent_fd, filename, OFlag::O_NOFOLLOW, Mode::empty())?;
         let mut file = unsafe { File::from_raw_fd(filefd) };
 
         let mut content_buffer = Vec::new();
-        let _bytes = file.read_to_end(&mut content_buffer)?;
+        let _bytes = file.read_to_end(&mut content_buffer)
+            .map_err(|_| Errno::EIO)?;
 
         let mut match_pattern = Vec::new();
         for line in content_buffer.split(|&c| c == b'\n') {
@@ -129,8 +130,8 @@ impl MatchPattern {
     /// Pattern starting with '!' are interpreted as negative match pattern.
     /// Pattern with trailing `/` match only against directories.
     /// `.` as well as `..` and any pattern containing `\0` are invalid and will
-    /// result in an error.
-    pub fn from_line(line: &[u8]) -> Result<Option<MatchPattern>, Error> {
+    /// result in an error with Errno::EINVAL.
+    pub fn from_line(line: &[u8]) -> Result<Option<MatchPattern>, nix::Error> {
         let mut input = line;
 
         if input.starts_with(b"#") {
@@ -160,7 +161,7 @@ impl MatchPattern {
         }
 
         if input.is_empty() || input == b"." || input == b".." || input.contains(&b'\0') {
-            bail!("invalid path component encountered");
+            return Err(nix::Error::Sys(Errno::EINVAL));
         }
 
         Ok(Some(MatchPattern {