[pbs-devel] [PATCH proxmox-backup v3] fix #2998: encode mtime as i64 instead of u64

[Dominik Csapak <d.csapak@proxmox.com>]

saves files mtime as i64 instead of u64 which enables backup of
files with negative mtime

the catalog_decode_i64 is compatible to encoded u64 values (if < 2^63)
but not reverse, so all "old" catalogs can be read with the new
decoder, but catalogs that contain negative mtimes will decode wrongly
on older clients

also remove the arbitrary maximum value of 2^63 - 1 for
encode_u64 (we just use up to 10 bytes now) and correctly
decode them and update the comments accordingly

adds also test for i64 encode/decode and for compatibility between
u64 encode and i64 decode

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
changes from v2:
* add tests
* handle i64::MIN correctly
 src/backup/catalog.rs | 135 ++++++++++++++++++++++++++++++++++++++----
 src/pxar/catalog.rs   |   2 +-
 src/pxar/create.rs    |   2 +-
 3 files changed, 126 insertions(+), 13 deletions(-)

diff --git a/src/backup/catalog.rs b/src/backup/catalog.rs
index d1f519e5..b500fb93 100644
--- a/src/backup/catalog.rs
+++ b/src/backup/catalog.rs
@@ -78,7 +78,7 @@ pub struct DirEntry {
 #[derive(Clone, Debug, PartialEq)]
 pub enum DirEntryAttribute {
     Directory { start: u64 },
-    File { size: u64, mtime: u64 },
+    File { size: u64, mtime: i64 },
     Symlink,
     Hardlink,
     BlockDevice,
@@ -89,7 +89,7 @@ pub enum DirEntryAttribute {
 
 impl DirEntry {
 
-    fn new(etype: CatalogEntryType, name: Vec<u8>, start: u64, size: u64, mtime:u64) -> Self {
+    fn new(etype: CatalogEntryType, name: Vec<u8>, start: u64, size: u64, mtime: i64) -> Self {
         match etype {
             CatalogEntryType::Directory => {
                 DirEntry { name, attr: DirEntryAttribute::Directory { start } }
@@ -184,7 +184,7 @@ impl DirInfo {
                 catalog_encode_u64(writer, name.len() as u64)?;
                 writer.write_all(name)?;
                 catalog_encode_u64(writer, *size)?;
-                catalog_encode_u64(writer, *mtime)?;
+                catalog_encode_i64(writer, *mtime)?;
             }
             DirEntry { name, attr: DirEntryAttribute::Symlink } => {
                 writer.write_all(&[CatalogEntryType::Symlink as u8])?;
@@ -234,7 +234,7 @@ impl DirInfo {
         Ok((self.name, data))
     }
 
-    fn parse<C: FnMut(CatalogEntryType, &[u8], u64, u64, u64) -> Result<bool, Error>>(
+    fn parse<C: FnMut(CatalogEntryType, &[u8], u64, u64, i64) -> Result<bool, Error>>(
         data: &[u8],
         mut callback: C,
     ) -> Result<(), Error> {
@@ -265,7 +265,7 @@ impl DirInfo {
                 }
                 CatalogEntryType::File => {
                     let size = catalog_decode_u64(&mut cursor)?;
-                    let mtime = catalog_decode_u64(&mut cursor)?;
+                    let mtime = catalog_decode_i64(&mut cursor)?;
                     callback(etype, name, 0, size, mtime)?
                 }
                 _ => {
@@ -362,7 +362,7 @@ impl <W: Write> BackupCatalogWriter for CatalogWriter<W> {
         Ok(())
     }
 
-    fn add_file(&mut self, name: &CStr, size: u64, mtime: u64) -> Result<(), Error> {
+    fn add_file(&mut self, name: &CStr, size: u64, mtime: i64) -> Result<(), Error> {
         let dir = self.dirstack.last_mut().ok_or_else(|| format_err!("outside root"))?;
         let name = name.to_bytes().to_vec();
         dir.entries.push(DirEntry { name, attr: DirEntryAttribute::File { size, mtime } });
@@ -587,14 +587,77 @@ impl <R: Read + Seek> CatalogReader<R> {
     }
 }
 
+/// Serialize i64 as short, variable length byte sequence
+///
+/// Stores 7 bits per byte, Bit 8 indicates the end of the sequence (when not set).
+/// If the value is negative, we end with a zero byte (0x00).
+pub fn catalog_encode_i64<W: Write>(writer: &mut W, v: i64) -> Result<(), Error> {
+    let mut enc = Vec::new();
+
+    let mut d = if v < 0 {
+        (-1 * (v + 1)) as u64 + 1 // also handles i64::MIN
+    } else {
+        v as u64
+    };
+
+    loop {
+        if d < 128 {
+            if v < 0 {
+                enc.push(128 | d as u8);
+                enc.push(0u8);
+            } else {
+                enc.push(d as u8);
+            }
+            break;
+        }
+        enc.push((128 | (d & 127)) as u8);
+        d = d >> 7;
+    }
+    writer.write_all(&enc)?;
+
+    Ok(())
+}
+
+/// Deserialize i64 from variable length byte sequence
+///
+/// We currently read maximal 11 bytes, which give a maximum of 70 bits + sign.
+/// this method is compatible with catalog_encode_u64 iff the
+/// value encoded is <= 2^63 (values > 2^63 cannot be represented in an i64)
+pub fn catalog_decode_i64<R: Read>(reader: &mut R) -> Result<i64, Error> {
+
+    let mut v: u64 = 0;
+    let mut buf = [0u8];
+
+    for i in 0..11 { // only allow 11 bytes (70 bits + sign marker)
+        if buf.is_empty() {
+            bail!("decode_i64 failed - unexpected EOB");
+        }
+        reader.read_exact(&mut buf)?;
+
+        let t = buf[0];
+
+        if t == 0 {
+            if v == 0 {
+                return Ok(0);
+            }
+            return Ok(((v - 1) as i64 * -1) - 1); // also handles i64::MIN
+        } else if t < 128 {
+            v |= (t as u64) << (i*7);
+            return Ok(v as i64);
+        } else {
+            v |= ((t & 127) as u64) << (i*7);
+        }
+    }
+
+    bail!("decode_i64 failed - missing end marker");
+}
+
 /// Serialize u64 as short, variable length byte sequence
 ///
 /// Stores 7 bits per byte, Bit 8 indicates the end of the sequence (when not set).
-/// We limit values to a maximum of 2^63.
 pub fn catalog_encode_u64<W: Write>(writer: &mut W, v: u64) -> Result<(), Error> {
     let mut enc = Vec::new();
 
-    if (v & (1<<63)) != 0 { bail!("catalog_encode_u64 failed - value >= 2^63"); }
     let mut d = v;
     loop {
         if d < 128 {
@@ -611,13 +674,14 @@ pub fn catalog_encode_u64<W: Write>(writer: &mut W, v: u64) -> Result<(), Error>
 
 /// Deserialize u64 from variable length byte sequence
 ///
-/// We currently read maximal 9 bytes, which give a maximum of 63 bits.
+/// We currently read maximal 10 bytes, which give a maximum of 70 bits,
+/// but we currently only encode up to 64 bits
 pub fn catalog_decode_u64<R: Read>(reader: &mut R) -> Result<u64, Error> {
 
     let mut v: u64 = 0;
     let mut buf = [0u8];
 
-    for i in 0..9 { // only allow 9 bytes (63 bits)
+    for i in 0..10 { // only allow 10 bytes (70 bits)
         if buf.is_empty() {
             bail!("decode_u64 failed - unexpected EOB");
         }
@@ -652,9 +716,58 @@ fn test_catalog_u64_encoder() {
         assert!(decoded == value);
     }
 
+    test_encode_decode(u64::MIN);
+    test_encode_decode(126);
+    test_encode_decode((1<<12)-1);
+    test_encode_decode((1<<20)-1);
+    test_encode_decode((1<<50)-1);
+    test_encode_decode(u64::MAX);
+}
+
+#[test]
+fn test_catalog_i64_encoder() {
+
+    fn test_encode_decode(value: i64) {
+
+        let mut data = Vec::new();
+        catalog_encode_i64(&mut data, value).unwrap();
+
+        let slice = &mut &data[..];
+        let decoded = catalog_decode_i64(slice).unwrap();
+
+        assert!(decoded == value);
+    }
+
+    test_encode_decode(0);
+    test_encode_decode(-0);
+    test_encode_decode(126);
+    test_encode_decode(-126);
+    test_encode_decode((1<<12)-1);
+    test_encode_decode(-(1<<12)-1);
+    test_encode_decode((1<<20)-1);
+    test_encode_decode(-(1<<20)-1);
+    test_encode_decode(i64::MIN);
+    test_encode_decode(i64::MAX);
+}
+
+#[test]
+fn test_catalog_i64_compatibility() {
+
+    fn test_encode_decode(value: u64) {
+
+        let mut data = Vec::new();
+        catalog_encode_u64(&mut data, value).unwrap();
+
+        let slice = &mut &data[..];
+        let decoded = catalog_decode_i64(slice).unwrap() as u64;
+
+        assert!(decoded == value);
+    }
+
+    test_encode_decode(u64::MIN);
     test_encode_decode(126);
     test_encode_decode((1<<12)-1);
     test_encode_decode((1<<20)-1);
     test_encode_decode((1<<50)-1);
-    test_encode_decode((1<<63)-1);
+    test_encode_decode(u64::MAX);
 }
diff --git a/src/pxar/catalog.rs b/src/pxar/catalog.rs
index 96b42427..02b57dfa 100644
--- a/src/pxar/catalog.rs
+++ b/src/pxar/catalog.rs
@@ -9,7 +9,7 @@ use std::ffi::CStr;
 pub trait BackupCatalogWriter {
     fn start_directory(&mut self, name: &CStr) -> Result<(), Error>;
     fn end_directory(&mut self) -> Result<(), Error>;
-    fn add_file(&mut self, name: &CStr, size: u64, mtime: u64) -> Result<(), Error>;
+    fn add_file(&mut self, name: &CStr, size: u64, mtime: i64) -> Result<(), Error>;
     fn add_symlink(&mut self, name: &CStr) -> Result<(), Error>;
     fn add_hardlink(&mut self, name: &CStr) -> Result<(), Error>;
     fn add_block_device(&mut self, name: &CStr) -> Result<(), Error>;
diff --git a/src/pxar/create.rs b/src/pxar/create.rs
index 74c49050..6ba6f15c 100644
--- a/src/pxar/create.rs
+++ b/src/pxar/create.rs
@@ -535,7 +535,7 @@ impl<'a, 'b> Archiver<'a, 'b> {
 
                 let file_size = stat.st_size as u64;
                 if let Some(ref mut catalog) = self.catalog {
-                    catalog.add_file(c_file_name, file_size, stat.st_mtime as u64)?;
+                    catalog.add_file(c_file_name, file_size, stat.st_mtime)?;
                 }
 
                 let offset: LinkOffset =
-- 
2.20.1