From 6a8dbdcd1f0e68782d244e95b0e14ba6fe307fb4 Mon Sep 17 00:00:00 2001
From: senhuang42 <senhuang96@fb.com>
Date: Fri, 21 Aug 2020 16:46:46 -0400
Subject: [PATCH] Modify decompression loop to gnore checksums if flag is
 enabled

---
 lib/decompress/zstd_decompress.c          | 9 +++++----
 lib/decompress/zstd_decompress_internal.h | 4 ++--
 tests/fuzzer.c                            | 3 +++
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 82c24f32..73ed7e1a 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -114,6 +114,7 @@ static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
     dctx->oversizedDuration = 0;
     dctx->bmi2 = ZSTD_cpuid_bmi2(ZSTD_cpuid());
     dctx->outBufferMode = ZSTD_obm_buffered;
+    dctx->forceIgnoreChecksum = ZSTD_d_validateChecksum;
 #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
     dctx->dictContentEndForFuzzing = NULL;
 #endif
@@ -661,7 +662,7 @@ static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
         }
 
         if (ZSTD_isError(decodedSize)) return decodedSize;
-        if (dctx->fParams.checksumFlag)
+        if (dctx->fParams.checksumFlag && !dctx->forceIgnoreChecksum)
             XXH64_update(&dctx->xxhState, op, decodedSize);
         if (decodedSize != 0)
             op += decodedSize;
@@ -675,7 +676,7 @@ static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
         RETURN_ERROR_IF((U64)(op-ostart) != dctx->fParams.frameContentSize,
                         corruption_detected, "");
     }
-    if (dctx->fParams.checksumFlag) { /* Frame content checksum verification */
+    if (dctx->fParams.checksumFlag && !dctx->forceIgnoreChecksum) { /* Frame content checksum verification */
         U32 const checkCalc = (U32)XXH64_digest(&dctx->xxhState);
         U32 checkRead;
         RETURN_ERROR_IF(remainingSrcSize<4, checksum_wrong, "");
@@ -1399,7 +1400,7 @@ size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format)
 
 size_t ZSTD_DCtx_setForceSkipChecksum(ZSTD_DCtx* dctx, ZSTD_format_e format)
 {
-    return ZSTD_DCtx_setParameter(dctx, ZSTD_d_forceSkipChecksum, format);
+    return ZSTD_DCtx_setParameter(dctx, ZSTD_d_forceIgnoreChecksum, format);
 }
 
 ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam)
@@ -1463,7 +1464,7 @@ size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter dParam, int value
             return 0;
         case ZSTD_d_forceIgnoreChecksum:
             CHECK_DBOUNDS(ZSTD_d_forceIgnoreChecksum, value);
-            dctx->forceIgnoreChecksum = (ZSTD_ignoreChecksumMode_e)value;
+            dctx->forceIgnoreChecksum = (ZSTD_forceIgnoreChecksum_e)value;
         default:;
     }
     RETURN_ERROR(parameter_unsupported, "");
diff --git a/lib/decompress/zstd_decompress_internal.h b/lib/decompress/zstd_decompress_internal.h
index 0481ce64..6f1dda20 100644
--- a/lib/decompress/zstd_decompress_internal.h
+++ b/lib/decompress/zstd_decompress_internal.h
@@ -103,7 +103,7 @@ typedef enum {
 typedef enum {
     ZSTD_d_validateChecksum = 0,
     ZSTD_d_ignoreChecksum = 1
-} ZSTD_ignoreChecksumMode_e;
+} ZSTD_forceIgnoreChecksum_e;
 
 struct ZSTD_DCtx_s
 {
@@ -127,7 +127,7 @@ struct ZSTD_DCtx_s
     XXH64_state_t xxhState;
     size_t headerSize;
     ZSTD_format_e format;
-    ZSTD_ignoreChecksumMode_e forceIgnoreChecksum;   /* if enabled, will ignore checksums in compressed frame */
+    ZSTD_forceIgnoreChecksum_e forceIgnoreChecksum;   /* if == 1, will ignore checksums in compressed frame */
     const BYTE* litPtr;
     ZSTD_customMem customMem;
     size_t litSize;
diff --git a/tests/fuzzer.c b/tests/fuzzer.c
index 8ac2864f..cb68ca5d 100644
--- a/tests/fuzzer.c
+++ b/tests/fuzzer.c
@@ -2354,6 +2354,9 @@ static int basicUnitTests(U32 const seed, double compressibility)
         {   size_t const sr = ZSTD_DCtx_setParameter(dctx, ZSTD_d_format, (ZSTD_format_e)888);
             if (!ZSTD_isError(sr)) goto _output_error;
         }
+        {   size_t const sr = ZSTD_DCtx_setParameter(dctx, ZSTD_d_forceIgnoreChecksum, (ZSTD_forceIgnoreChecksum_e)888);
+            if (!ZSTD_isError(sr)) goto _output_error;
+        }
         DISPLAYLEVEL(3, "OK \n");
 
         ZSTD_freeDCtx(dctx);