Issue #24259: tarfile now raises a ReadError if an archive is truncated inside a data segment.

1 files changed, 15 insertions, 7 deletions

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 6d8d36c..5f1a979 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -225,7 +225,7 @@ def calc_chksums(buf):
     signed_chksum = 256 + sum(struct.unpack_from("148b8x356b", buf))
     return unsigned_chksum, signed_chksum
 
-def copyfileobj(src, dst, length=None):
+def copyfileobj(src, dst, length=None, exception=OSError):
     """Copy length bytes from fileobj src to fileobj dst.
        If length is None, copy the entire content.
     """
@@ -240,13 +240,13 @@ def copyfileobj(src, dst, length=None):
     for b in range(blocks):
         buf = src.read(BUFSIZE)
         if len(buf) < BUFSIZE:
-            raise OSError("end of file reached")
+            raise exception("unexpected end of data")
         dst.write(buf)
 
     if remainder != 0:
         buf = src.read(remainder)
         if len(buf) < remainder:
-            raise OSError("end of file reached")
+            raise exception("unexpected end of data")
         dst.write(buf)
     return
 
@@ -690,7 +690,10 @@ class _FileInFile(object):
             length = min(size, stop - self.position)
             if data:
                 self.fileobj.seek(offset + (self.position - start))
-                buf += self.fileobj.read(length)
+                b = self.fileobj.read(length)
+                if len(b) != length:
+                    raise ReadError("unexpected end of data")
+                buf += b
             else:
                 buf += NUL * length
             size -= length
@@ -2132,9 +2135,9 @@ class TarFile(object):
             if tarinfo.sparse is not None:
                 for offset, size in tarinfo.sparse:
                     target.seek(offset)
-                    copyfileobj(source, target, size)
+                    copyfileobj(source, target, size, ReadError)
             else:
-                copyfileobj(source, target, tarinfo.size)
+                copyfileobj(source, target, tarinfo.size, ReadError)
             target.seek(tarinfo.size)
             target.truncate()
 
@@ -2244,8 +2247,13 @@ class TarFile(object):
             self.firstmember = None
             return m
 
+        # Advance the file pointer.
+        if self.offset != self.fileobj.tell():
+            self.fileobj.seek(self.offset - 1)
+            if not self.fileobj.read(1):
+                raise ReadError("unexpected end of data")
+
         # Read the next block.
-        self.fileobj.seek(self.offset)
         tarinfo = None
         while True:
             try: