[25842c161] Prevent zero-length compress actions in [zlib] streaming API.

2 files changed, 24 insertions, 15 deletions

diff --git a/generic/tclZlib.c b/generic/tclZlib.c
index ba3e9cb..6f1d225 100644
--- a/generic/tclZlib.c
+++ b/generic/tclZlib.c
@@ -1164,6 +1164,14 @@ Tcl_ZlibStreamPut(
 	zshPtr->stream.next_in = Tcl_GetByteArrayFromObj(data, &size);
 	zshPtr->stream.avail_in = size;
 
+	/*
+	 * Must not do a zero-length compress. [Bug 25842c161]
+	 */
+
+	if (size == 0) {
+	    return TCL_OK;
+	}
+
 	if (HaveDictToSet(zshPtr)) {
 	    e = SetDeflateDictionary(&zshPtr->stream, zshPtr->compDictObj);
 	    if (e != Z_OK) {
@@ -1186,32 +1194,27 @@ Tcl_ZlibStreamPut(
 	zshPtr->stream.next_out = (Bytef *) dataTmp;
 
 	e = deflate(&zshPtr->stream, flush);
-	if ((e==Z_OK || e==Z_BUF_ERROR) && (zshPtr->stream.avail_out == 0)) {
-	    if (outSize - zshPtr->stream.avail_out > 0) {
-		/*
-		 * Output buffer too small.
-		 */
-
-		obj = Tcl_NewByteArrayObj((unsigned char *) dataTmp,
-			outSize - zshPtr->stream.avail_out);
+	while (e == Z_BUF_ERROR) {
+	    /*
+	     * Output buffer too small to hold the data being generated; so
+	     * put a new buffer into place after saving the old generated
+	     * data to the outData list.
+	     */
 
-		/*
-		 * Now append the compressed data to the outData list.
-		 */
+	    obj = Tcl_NewByteArrayObj((unsigned char *) dataTmp, outSize);
+	    Tcl_ListObjAppendElement(NULL, zshPtr->outData, obj);
 
-		Tcl_ListObjAppendElement(NULL, zshPtr->outData, obj);
-	    }
 	    if (outSize < 0xFFFF) {
 		outSize = 0xFFFF;	/* There may be *lots* of data left to
 					 * output... */
-		ckfree(dataTmp);
-		dataTmp = ckalloc(outSize);
+		dataTmp = ckrealloc(dataTmp, outSize);
 	    }
 	    zshPtr->stream.avail_out = outSize;
 	    zshPtr->stream.next_out = (Bytef *) dataTmp;
 
 	    e = deflate(&zshPtr->stream, flush);
 	}
+
 	if (e != Z_OK && !(flush==Z_FINISH && e==Z_STREAM_END)) {
 	    if (zshPtr->interp) {
 		ConvertError(zshPtr->interp, e, zshPtr->stream.adler);
diff --git a/tests/zlib.test b/tests/zlib.test
index b1d43fb..7a486ba 100644
--- a/tests/zlib.test
+++ b/tests/zlib.test
@@ -132,6 +132,12 @@ test zlib-7.6 {zlib stream} zlib {
     $s close
     lappend result $data
 } {{} 69f34b6a abcdeEDCBA..}
+test zlib-7.7 {zlib stream: Bug 25842c161} -constraints zlib -body {
+    set s [zlib stream deflate]
+    $s put {}
+} -cleanup {
+    catch {$s close}
+} -result ""
 
 test zlib-8.1 {zlib transformation} -constraints zlib -setup {
     set file [makeFile {} test.gz]