1 files changed, 155 insertions, 110 deletions

diff --git a/C/XzIn.c b/C/XzIn.c
index b68af96..ba31636 100644
--- a/C/XzIn.c
+++ b/C/XzIn.c
@@ -1,38 +1,39 @@
 /* XzIn.c - Xz input
-2023-09-07 : Igor Pavlov : Public domain */
+: Igor Pavlov : Public domain */
 
 #include "Precomp.h"
 
 #include <string.h>
 
 #include "7zCrc.h"
-#include "CpuArch.h"
 #include "Xz.h"
+#include "CpuArch.h"
 
-/*
-#define XZ_FOOTER_SIG_CHECK(p) (memcmp((p), XZ_FOOTER_SIG, XZ_FOOTER_SIG_SIZE) == 0)
-*/
-#define XZ_FOOTER_SIG_CHECK(p) ((p)[0] == XZ_FOOTER_SIG_0 && (p)[1] == XZ_FOOTER_SIG_1)
-
+#define XZ_FOOTER_12B_ALIGNED16_SIG_CHECK(p) \
+    (GetUi16a((const Byte *)(const void *)(p) + 10) == \
+      (XZ_FOOTER_SIG_0 | (XZ_FOOTER_SIG_1 << 8)))
 
 SRes Xz_ReadHeader(CXzStreamFlags *p, ISeqInStreamPtr inStream)
 {
-  Byte sig[XZ_STREAM_HEADER_SIZE];
+  UInt32 data32[XZ_STREAM_HEADER_SIZE / 4];
   size_t processedSize = XZ_STREAM_HEADER_SIZE;
-  RINOK(SeqInStream_ReadMax(inStream, sig, &processedSize))
+  RINOK(SeqInStream_ReadMax(inStream, data32, &processedSize))
   if (processedSize != XZ_STREAM_HEADER_SIZE
-      || memcmp(sig, XZ_SIG, XZ_SIG_SIZE) != 0)
+      || memcmp(data32, XZ_SIG, XZ_SIG_SIZE) != 0)
     return SZ_ERROR_NO_ARCHIVE;
-  return Xz_ParseHeader(p, sig);
+  return Xz_ParseHeader(p, (const Byte *)(const void *)data32);
 }
 
-#define READ_VARINT_AND_CHECK(buf, pos, size, res) \
-  { const unsigned s = Xz_ReadVarInt(buf + pos, size - pos, res); \
+#define READ_VARINT_AND_CHECK(buf, size, res) \
+{ const unsigned s = Xz_ReadVarInt(buf, size, res); \
   if (s == 0) return SZ_ERROR_ARCHIVE; \
-  pos += s; }
+  size -= s; \
+  buf += s; \
+}
 
 SRes XzBlock_ReadHeader(CXzBlock *p, ISeqInStreamPtr inStream, BoolInt *isIndex, UInt32 *headerSizeRes)
 {
+  MY_ALIGN(4)
   Byte header[XZ_BLOCK_HEADER_SIZE_MAX];
   unsigned headerSize;
   *headerSizeRes = 0;
@@ -57,8 +58,12 @@ SRes XzBlock_ReadHeader(CXzBlock *p, ISeqInStreamPtr inStream, BoolInt *isIndex,
   return XzBlock_Parse(p, header);
 }
 
+
 #define ADD_SIZE_CHECK(size, val) \
-  { const UInt64 newSize = size + (val); if (newSize < size) return XZ_SIZE_OVERFLOW; size = newSize; }
+{ const UInt64 newSize = size + (val); \
+  if (newSize < size) return XZ_SIZE_OVERFLOW; \
+  size = newSize; \
+}
 
 UInt64 Xz_GetUnpackSize(const CXzStream *p)
 {
@@ -82,76 +87,85 @@ UInt64 Xz_GetPackSize(const CXzStream *p)
   return size;
 }
 
-/*
-SRes XzBlock_ReadFooter(CXzBlock *p, CXzStreamFlags f, ISeqInStreamPtr inStream)
-{
-  return SeqInStream_Read(inStream, p->check, XzFlags_GetCheckSize(f));
-}
-*/
 
-static SRes Xz_ReadIndex2(CXzStream *p, const Byte *buf, size_t size, ISzAllocPtr alloc)
+// input;
+//   CXzStream (p) is empty object.
+//   size != 0
+//   (size & 3) == 0
+//   (buf) is aligned for at least 4 bytes.
+// output:
+//   p->numBlocks is number of allocated items in p->blocks
+//   p->blocks[*] values must be ignored, if function returns error.
+static SRes Xz_ParseIndex(CXzStream *p, const Byte *buf, size_t size, ISzAllocPtr alloc)
 {
-  size_t numBlocks, pos = 1;
-  UInt32 crc;
-
+  size_t numBlocks;
   if (size < 5 || buf[0] != 0)
     return SZ_ERROR_ARCHIVE;
-
   size -= 4;
-  crc = CrcCalc(buf, size);
-  if (crc != GetUi32(buf + size))
-    return SZ_ERROR_ARCHIVE;
-
+  {
+    const UInt32 crc = CrcCalc(buf, size);
+    if (crc != GetUi32a(buf + size))
+      return SZ_ERROR_ARCHIVE;
+  }
+  buf++;
+  size--;
   {
     UInt64 numBlocks64;
-    READ_VARINT_AND_CHECK(buf, pos, size, &numBlocks64)
-    numBlocks = (size_t)numBlocks64;
-    if (numBlocks != numBlocks64 || numBlocks * 2 > size)
+    READ_VARINT_AND_CHECK(buf, size, &numBlocks64)
+    // (numBlocks64) is 63-bit value, so we can calculate (numBlocks64 * 2):
+    if (numBlocks64 * 2 > size)
       return SZ_ERROR_ARCHIVE;
+    if (numBlocks64 >= ((size_t)1 << (sizeof(size_t) * 8 - 1)) / sizeof(CXzBlockSizes))
+      return SZ_ERROR_MEM; // SZ_ERROR_ARCHIVE
+    numBlocks = (size_t)numBlocks64;
   }
-  
-  Xz_Free(p, alloc);
-  if (numBlocks != 0)
+  // Xz_Free(p, alloc); // it's optional, because (p) is empty already
+  if (numBlocks)
   {
-    size_t i;
-    p->numBlocks = numBlocks;
-    p->blocks = (CXzBlockSizes *)ISzAlloc_Alloc(alloc, sizeof(CXzBlockSizes) * numBlocks);
-    if (!p->blocks)
+    CXzBlockSizes *blocks = (CXzBlockSizes *)ISzAlloc_Alloc(alloc, sizeof(CXzBlockSizes) * numBlocks);
+    if (!blocks)
       return SZ_ERROR_MEM;
-    for (i = 0; i < numBlocks; i++)
+    p->blocks = blocks;
+    p->numBlocks = numBlocks;
+    // the caller will call Xz_Free() in case of error
+    do
     {
-      CXzBlockSizes *block = &p->blocks[i];
-      READ_VARINT_AND_CHECK(buf, pos, size, &block->totalSize)
-      READ_VARINT_AND_CHECK(buf, pos, size, &block->unpackSize)
-      if (block->totalSize == 0)
+      READ_VARINT_AND_CHECK(buf, size, &blocks->totalSize)
+      READ_VARINT_AND_CHECK(buf, size, &blocks->unpackSize)
+      if (blocks->totalSize == 0)
         return SZ_ERROR_ARCHIVE;
+      blocks++;
     }
+    while (--numBlocks);
   }
-  while ((pos & 3) != 0)
-    if (buf[pos++] != 0)
+  if (size >= 4)
+    return SZ_ERROR_ARCHIVE;
+  while (size)
+    if (buf[--size])
       return SZ_ERROR_ARCHIVE;
-  return (pos == size) ? SZ_OK : SZ_ERROR_ARCHIVE;
+  return SZ_OK;
 }
 
+
+/*
 static SRes Xz_ReadIndex(CXzStream *p, ILookInStreamPtr stream, UInt64 indexSize, ISzAllocPtr alloc)
 {
   SRes res;
   size_t size;
   Byte *buf;
-  if (indexSize > ((UInt32)1 << 31))
-    return SZ_ERROR_UNSUPPORTED;
+  if (indexSize >= ((size_t)1 << (sizeof(size_t) * 8 - 1)))
+    return SZ_ERROR_MEM; // SZ_ERROR_ARCHIVE
   size = (size_t)indexSize;
-  if (size != indexSize)
-    return SZ_ERROR_UNSUPPORTED;
   buf = (Byte *)ISzAlloc_Alloc(alloc, size);
   if (!buf)
     return SZ_ERROR_MEM;
   res = LookInStream_Read2(stream, buf, size, SZ_ERROR_UNSUPPORTED);
   if (res == SZ_OK)
-    res = Xz_ReadIndex2(p, buf, size, alloc);
+    res = Xz_ParseIndex(p, buf, size, alloc);
   ISzAlloc_Free(alloc, buf);
   return res;
 }
+*/
 
 static SRes LookInStream_SeekRead_ForArc(ILookInStreamPtr stream, UInt64 offset, void *buf, size_t size)
 {
@@ -160,84 +174,102 @@ static SRes LookInStream_SeekRead_ForArc(ILookInStreamPtr stream, UInt64 offset,
   /* return LookInStream_Read2(stream, buf, size, SZ_ERROR_NO_ARCHIVE); */
 }
 
+
+/*
+in:
+  (*startOffset) is position in (stream) where xz_stream must be finished.
+out:
+  if returns SZ_OK, then (*startOffset) is position in stream that shows start of xz_stream.
+*/
 static SRes Xz_ReadBackward(CXzStream *p, ILookInStreamPtr stream, Int64 *startOffset, ISzAllocPtr alloc)
 {
-  UInt64 indexSize;
-  Byte buf[XZ_STREAM_FOOTER_SIZE];
+  #define TEMP_BUF_SIZE  (1 << 10)
+  UInt32 buf32[TEMP_BUF_SIZE / 4];
   UInt64 pos = (UInt64)*startOffset;
 
-  if ((pos & 3) != 0 || pos < XZ_STREAM_FOOTER_SIZE)
+  if ((pos & 3) || pos < XZ_STREAM_FOOTER_SIZE)
     return SZ_ERROR_NO_ARCHIVE;
-
   pos -= XZ_STREAM_FOOTER_SIZE;
-  RINOK(LookInStream_SeekRead_ForArc(stream, pos, buf, XZ_STREAM_FOOTER_SIZE))
+  RINOK(LookInStream_SeekRead_ForArc(stream, pos, buf32, XZ_STREAM_FOOTER_SIZE))
   
-  if (!XZ_FOOTER_SIG_CHECK(buf + 10))
+  if (!XZ_FOOTER_12B_ALIGNED16_SIG_CHECK(buf32))
   {
-    UInt32 total = 0;
     pos += XZ_STREAM_FOOTER_SIZE;
-    
     for (;;)
     {
-      size_t i;
-      #define TEMP_BUF_SIZE (1 << 10)
-      Byte temp[TEMP_BUF_SIZE];
-      
-      i = (pos > TEMP_BUF_SIZE) ? TEMP_BUF_SIZE : (size_t)pos;
+      // pos != 0
+      // (pos & 3) == 0
+      size_t i = pos >= TEMP_BUF_SIZE ? TEMP_BUF_SIZE : (size_t)pos;
       pos -= i;
-      RINOK(LookInStream_SeekRead_ForArc(stream, pos, temp, i))
-      total += (UInt32)i;
-      for (; i != 0; i--)
-        if (temp[i - 1] != 0)
+      RINOK(LookInStream_SeekRead_ForArc(stream, pos, buf32, i))
+      i /= 4;
+      do
+        if (buf32[i - 1] != 0)
           break;
-      if (i != 0)
-      {
-        if ((i & 3) != 0)
-          return SZ_ERROR_NO_ARCHIVE;
-        pos += i;
-        break;
-      }
-      if (pos < XZ_STREAM_FOOTER_SIZE || total > (1 << 16))
+      while (--i);
+
+      pos += i * 4;
+      #define XZ_STREAM_BACKWARD_READING_PAD_MAX (1 << 16)
+      // here we don't support rare case with big padding for xz stream.
+      // so we have padding limit for backward reading.
+      if ((UInt64)*startOffset - pos > XZ_STREAM_BACKWARD_READING_PAD_MAX)
         return SZ_ERROR_NO_ARCHIVE;
+      if (i)
+        break;
     }
-    
+    // we try to open xz stream after skipping zero padding.
+    // ((UInt64)*startOffset == pos) is possible here!
     if (pos < XZ_STREAM_FOOTER_SIZE)
       return SZ_ERROR_NO_ARCHIVE;
     pos -= XZ_STREAM_FOOTER_SIZE;
-    RINOK(LookInStream_SeekRead_ForArc(stream, pos, buf, XZ_STREAM_FOOTER_SIZE))
-    if (!XZ_FOOTER_SIG_CHECK(buf + 10))
+    RINOK(LookInStream_SeekRead_ForArc(stream, pos, buf32, XZ_STREAM_FOOTER_SIZE))
+    if (!XZ_FOOTER_12B_ALIGNED16_SIG_CHECK(buf32))
       return SZ_ERROR_NO_ARCHIVE;
   }
   
-  p->flags = (CXzStreamFlags)GetBe16(buf + 8);
-
+  p->flags = (CXzStreamFlags)GetBe16a(buf32 + 2);
   if (!XzFlags_IsSupported(p->flags))
     return SZ_ERROR_UNSUPPORTED;
-
   {
     /* to eliminate GCC 6.3 warning:
        dereferencing type-punned pointer will break strict-aliasing rules */
-    const Byte *buf_ptr = buf;
-    if (GetUi32(buf_ptr) != CrcCalc(buf + 4, 6))
+    const UInt32 *buf_ptr = buf32;
+    if (GetUi32a(buf_ptr) != CrcCalc(buf32 + 1, 6))
       return SZ_ERROR_ARCHIVE;
   }
-
-  indexSize = ((UInt64)GetUi32(buf + 4) + 1) << 2;
-
-  if (pos < indexSize)
-    return SZ_ERROR_ARCHIVE;
-
-  pos -= indexSize;
-  RINOK(LookInStream_SeekTo(stream, pos))
-  RINOK(Xz_ReadIndex(p, stream, indexSize, alloc))
-
   {
-    UInt64 totalSize = Xz_GetPackSize(p);
-    if (totalSize == XZ_SIZE_OVERFLOW
-        || totalSize >= ((UInt64)1 << 63)
-        || pos < totalSize + XZ_STREAM_HEADER_SIZE)
+    const UInt64 indexSize = ((UInt64)GetUi32a(buf32 + 1) + 1) << 2;
+    if (pos < indexSize)
       return SZ_ERROR_ARCHIVE;
-    pos -= (totalSize + XZ_STREAM_HEADER_SIZE);
+    pos -= indexSize;
+    // v25.00: relaxed indexSize check. We allow big index table.
+    // if (indexSize > ((UInt32)1 << 31))
+    if (indexSize >= ((size_t)1 << (sizeof(size_t) * 8 - 1)))
+      return SZ_ERROR_MEM; // SZ_ERROR_ARCHIVE
+    RINOK(LookInStream_SeekTo(stream, pos))
+    // RINOK(Xz_ReadIndex(p, stream, indexSize, alloc))
+    {
+      SRes res;
+      const size_t size = (size_t)indexSize;
+      // if (size != indexSize) return SZ_ERROR_UNSUPPORTED;
+      Byte *buf = (Byte *)ISzAlloc_Alloc(alloc, size);
+      if (!buf)
+        return SZ_ERROR_MEM;
+      res = LookInStream_Read2(stream, buf, size, SZ_ERROR_UNSUPPORTED);
+      if (res == SZ_OK)
+        res = Xz_ParseIndex(p, buf, size, alloc);
+      ISzAlloc_Free(alloc, buf);
+      RINOK(res)
+    }
+  }
+  {
+    UInt64 total = Xz_GetPackSize(p);
+    if (total == XZ_SIZE_OVERFLOW || total >= ((UInt64)1 << 63))
+      return SZ_ERROR_ARCHIVE;
+    total += XZ_STREAM_HEADER_SIZE;
+    if (pos < total)
+      return SZ_ERROR_ARCHIVE;
+    pos -= total;
     RINOK(LookInStream_SeekTo(stream, pos))
     *startOffset = (Int64)pos;
   }
@@ -246,7 +278,6 @@ static SRes Xz_ReadBackward(CXzStream *p, ILookInStreamPtr stream, Int64 *startO
     CSecToRead secToRead;
     SecToRead_CreateVTable(&secToRead);
     secToRead.realStream = stream;
-
     RINOK(Xz_ReadHeader(&headerFlags, &secToRead.vt))
     return (p->flags == headerFlags) ? SZ_OK : SZ_ERROR_ARCHIVE;
   }
@@ -257,8 +288,7 @@ static SRes Xz_ReadBackward(CXzStream *p, ILookInStreamPtr stream, Int64 *startO
 
 void Xzs_Construct(CXzs *p)
 {
-  p->num = p->numAllocated = 0;
-  p->streams = 0;
+  Xzs_CONSTRUCT(p)
 }
 
 void Xzs_Free(CXzs *p, ISzAllocPtr alloc)
@@ -268,7 +298,7 @@ void Xzs_Free(CXzs *p, ISzAllocPtr alloc)
     Xz_Free(&p->streams[i], alloc);
   ISzAlloc_Free(alloc, p->streams);
   p->num = p->numAllocated = 0;
-  p->streams = 0;
+  p->streams = NULL;
 }
 
 UInt64 Xzs_GetNumBlocks(const CXzs *p)
@@ -307,34 +337,49 @@ UInt64 Xzs_GetPackSize(const CXzs *p)
 SRes Xzs_ReadBackward(CXzs *p, ILookInStreamPtr stream, Int64 *startOffset, ICompressProgressPtr progress, ISzAllocPtr alloc)
 {
   Int64 endOffset = 0;
+  // it's supposed that CXzs object is empty here.
+  // if CXzs object is not empty, it will add new streams to that non-empty object.
+  // Xzs_Free(p, alloc); // it's optional call to empty CXzs object.
   RINOK(ILookInStream_Seek(stream, &endOffset, SZ_SEEK_END))
   *startOffset = endOffset;
   for (;;)
   {
     CXzStream st;
     SRes res;
-    Xz_Construct(&st);
+    Xz_CONSTRUCT(&st)
     res = Xz_ReadBackward(&st, stream, startOffset, alloc);
+    // if (res == SZ_OK), then (*startOffset) is start offset of new stream if
+    // if (res != SZ_OK), then (*startOffset) is unchend or it's expected start offset of stream with error
     st.startOffset = (UInt64)*startOffset;
-    RINOK(res)
+    // we must store (st) object to array, or we must free (st) local object.
+    if (res != SZ_OK)
+    {
+      Xz_Free(&st, alloc);
+      return res;
+    }
     if (p->num == p->numAllocated)
     {
       const size_t newNum = p->num + p->num / 4 + 1;
       void *data = ISzAlloc_Alloc(alloc, newNum * sizeof(CXzStream));
       if (!data)
+      {
+        Xz_Free(&st, alloc);
         return SZ_ERROR_MEM;
+      }
       p->numAllocated = newNum;
       if (p->num != 0)
         memcpy(data, p->streams, p->num * sizeof(CXzStream));
       ISzAlloc_Free(alloc, p->streams);
       p->streams = (CXzStream *)data;
     }
+    // we use direct copying of raw data from local variable (st) to object in array.
+    // so we don't need to call Xz_Free(&st, alloc) after copying and after p->num++
     p->streams[p->num++] = st;
     if (*startOffset == 0)
-      break;
-    RINOK(LookInStream_SeekTo(stream, (UInt64)*startOffset))
+      return SZ_OK;
+    // seek operation is optional:
+    // RINOK(LookInStream_SeekTo(stream, (UInt64)*startOffset))
     if (progress && ICompressProgress_Progress(progress, (UInt64)(endOffset - *startOffset), (UInt64)(Int64)-1) != SZ_OK)
       return SZ_ERROR_PROGRESS;
   }
-  return SZ_OK;
 }