Cleanup use of java.util.Inflater, fixing rare infinite loops

The native implementation of inflate() can set finished to return
true at the same time as it copies the last bytes into the buffer.

Check for finished on each iteration, terminating as soon as libz
knows the stream was completely inflated.

If not finished, it is likely input is required before the next
native call could do any useful work. Most invocations are passing
in a buffer large enough to store the entire result. A partial return
from inflate() will need more input before it can continue. Checking
right away that needsInput() is true saves a native call to determine
no bytes can be inflated without more input.

This should fix a rare infinite loop condition inside of inflation
when an object ends exactly at the end of a block boundary, and
the next block contains only the 20 byte trailing SHA-1.

When the stream is finished each new attempt to inflate() returns
n == 0, as no additional bytes were output. The needsInput() test
tries to add the length of the footer block to itself, but then loops
back around an reloads the same block as the block is smaller than
a full block size. A zero length input is set to the inflater,
which triggers needsInput() condition again.

Change-Id: I95d02bfeab4bf995a254d49166b4ae62d1f21346

1 files changed, 13 insertions, 18 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java
index c3fdacc27a..633554a96f 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/PackParser.java
@@ -1653,24 +1653,19 @@ public abstract class PackParser {
 				int n = 0;
 				while (n < cnt) {
 					int r = inf.inflate(dst, pos + n, cnt - n);
-					if (r == 0) {
-						if (inf.finished())
-							break;
-						if (inf.needsInput()) {
-							onObjectData(src, buf, p, bAvail);
-							use(bAvail);
-
-							p = fill(src, 1);
-							inf.setInput(buf, p, bAvail);
-						} else {
-							throw new CorruptObjectException(
-									MessageFormat
-											.format(
-													JGitText.get().packfileCorruptionDetected,
-													JGitText.get().unknownZlibError));
-						}
-					} else {
-						n += r;
+					n += r;
+					if (inf.finished())
+						break;
+					if (inf.needsInput()) {
+						onObjectData(src, buf, p, bAvail);
+						use(bAvail);
+
+						p = fill(src, 1);
+						inf.setInput(buf, p, bAvail);
+					} else if (r == 0) {
+						throw new CorruptObjectException(MessageFormat.format(
+								JGitText.get().packfileCorruptionDetected,
+								JGitText.get().unknownZlibError));
 					}
 				}
 				actualSize += n;