Fixes security issues in libTIFF's handling of LZW-encoded
images.  The use of uninitialized data could lead to a buffer
underflow and a crash or arbitrary code execution.

CVE-ID: CVE-2008-2327
Security bug: https://bugs.gentoo.org/show_bug.cgi?id=234080

Index: tiff-3.8.2/libtiff/tif_lzw.c
===================================================================
--- tiff-3.8.2.orig/libtiff/tif_lzw.c
+++ tiff-3.8.2/libtiff/tif_lzw.c
@@ -237,6 +237,12 @@ LZWSetupDecode(TIFF* tif)
                     sp->dec_codetab[code].length = 1;
                     sp->dec_codetab[code].next = NULL;
                 } while (code--);
+		/*
+		* Zero-out the unused entries
+		*/
+		_TIFFmemset(&sp->dec_codetab[CODE_CLEAR], 0,
+		(CODE_FIRST-CODE_CLEAR)*sizeof (code_t));
+
 	}
 	return (1);
 }
@@ -408,12 +414,19 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize
 			break;
 		if (code == CODE_CLEAR) {
 			free_entp = sp->dec_codetab + CODE_FIRST;
+			_TIFFmemset(free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
 			nbits = BITS_MIN;
 			nbitsmask = MAXCODE(BITS_MIN);
 			maxcodep = sp->dec_codetab + nbitsmask-1;
 			NextCode(tif, sp, bp, code, GetNextCode);
 			if (code == CODE_EOI)
 				break;
+			if (code == CODE_CLEAR) {
+				TIFFErrorExt(tif->tif_clientdata, tif->tif_name,
+				"LZWDecode: Corrupted LZW table at scanline %d",
+				tif->tif_row);
+				return (0);
+			}
 			*op++ = (char)code, occ--;
 			oldcodep = sp->dec_codetab + code;
 			continue;
@@ -604,12 +617,19 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0,
 			break;
 		if (code == CODE_CLEAR) {
 			free_entp = sp->dec_codetab + CODE_FIRST;
+			_TIFFmemset(free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
 			nbits = BITS_MIN;
 			nbitsmask = MAXCODE(BITS_MIN);
 			maxcodep = sp->dec_codetab + nbitsmask;
 			NextCode(tif, sp, bp, code, GetNextCodeCompat);
 			if (code == CODE_EOI)
 				break;
+			if (code == CODE_CLEAR) {
+				TIFFErrorExt(tif->tif_clientdata, tif->tif_name,
+				"LZWDecode: Corrupted LZW table at scanline %d",
+				tif->tif_row);
+				return (0);
+			}
 			*op++ = code, occ--;
 			oldcodep = sp->dec_codetab + code;
 			continue;