Added UPX_MAGIC2_LE32 as an additional magic number for the original

packheader as stored in the stubs.

committer: mfx <mfx> 979754722 +0000

src/packhead.cpp

@@ -99,7 +99,7 @@ int PackHeader::getPackHeaderSize() const
 
 
 /*************************************************************************
-//
+// see stub/header.ash
 **************************************************************************/
 
 void PackHeader::putPackHeader(upx_bytep p)
@@ -108,32 +108,34 @@ void PackHeader::putPackHeader(upx_bytep p)
     throwBadLoader();
 #else
     assert(get_le32(p) == UPX_MAGIC_LE32);
-    int size = 0;
+    if (get_le32(p+4) != UPX_MAGIC2_LE32)
+    {
+        printf("%x %x\n", get_le32(p+4), UPX_MAGIC2_LE32);
+        throwBadLoader();
+    }
 
-    p[4] = (unsigned char) version;
+    int size = 0;
-    p[5] = (unsigned char) format;
+    int old_chksum = 0;
-    p[6] = (unsigned char) method;
-    p[7] = (unsigned char) level;
 
     // the new variable length header
     if (format < 128)
     {
-        set_le32(p+8,u_adler);
-        set_le32(p+12,c_adler);
         if (format == UPX_F_DOS_COM || format == UPX_F_DOS_SYS)
         {
+            size = 22;
+            old_chksum = get_packheader_checksum(p, size - 1);
             set_le16(p+16,u_len);
             set_le16(p+18,c_len);
             p[20] = (unsigned char) filter;
-            size = 22;
         }
         else if (format == UPX_F_DOS_EXE)
         {
+            size = 27;
+            old_chksum = get_packheader_checksum(p, size - 1);
             set_le24(p+16,u_len);
             set_le24(p+19,c_len);
             set_le24(p+22,u_file_size);
             p[25] = (unsigned char) filter;
-            size = 27;
         }
         else if (format == UPX_F_DOS_EXEH)
         {
@@ -141,17 +143,22 @@ void PackHeader::putPackHeader(upx_bytep p)
         }
         else
         {
+            size = 32;
+            old_chksum = get_packheader_checksum(p, size - 1);
             set_le32(p+16,u_len);
             set_le32(p+20,c_len);
             set_le32(p+24,u_file_size);
             p[28] = (unsigned char) filter;
             p[29] = (unsigned char) filter_cto;
             p[30] = 0;
-            size = 32;
         }
+        set_le32(p+8,u_adler);
+        set_le32(p+12,c_adler);
     }
     else
     {
+        size = 32;
+        old_chksum = get_packheader_checksum(p, size - 1);
         set_be32(p+8,u_len);
         set_be32(p+12,c_len);
         set_be32(p+16,u_adler);
@@ -160,11 +167,25 @@ void PackHeader::putPackHeader(upx_bytep p)
         p[28] = (unsigned char) filter;
         p[29] = (unsigned char) filter_cto;
         p[30] = 0;
-        size = 32;
     }
 
-    // store header_checksum
+    p[4] = (unsigned char) version;
+    p[5] = (unsigned char) format;
+    p[6] = (unsigned char) method;
+    p[7] = (unsigned char) level;
+
+    // header_checksum
     assert(size == getPackHeaderSize());
+    // check old header_checksum
+    if (p[size - 1] != 0)
+    {
+        if (p[size - 1] != old_chksum)
+        {
+            printf("old_checksum: %d %d\n", p[size - 1], old_chksum);
+            throwBadLoader();
+        }
+    }
+    // store new header_checksum
     p[size - 1] = get_packheader_checksum(p, size - 1);
 #endif /* UNUPX */
 }

src/stub/header.ash

@@ -28,11 +28,16 @@
 
 ; ------------- HEADER -------------    ;     __UPX1HEAD__
 
-                db      'UPX!'          ;  0  magic
+                db      85,80,88,33     ;  0  UPX_MAGIC_LE32
+ %if 0
                 db      0               ;  4  version
-                db      0               ;  5  type (com,sys,...)
+                db      0               ;  5  format
                 db      0               ;  6  compression method
                 db      0               ;  7  compression level
+ %else
+        ; another magic for PackHeader::putPackHeader
+                db      161,216,208,213 ;     UPX_MAGIC2_LE32
+ %endif
                 dd      0               ;  8  uncompressed adler32
                 dd      0               ; 12  compressed adler32
 
@@ -52,9 +57,9 @@
                 dd      0               ; 20  compressed len
                 dd      0               ; 24  original file size
                 db      0               ; 28  filter id
-                db      0               ; 29  cto (for filters 0x21..0x29)
+                db      0               ; 29  filter cto
                 db      0               ;  unsused
-                db      0               ; 31  header checksum
+                db      45              ; 31  header checksum
  %endif
 
 

src/stub/l_tos.s

@@ -288,8 +288,11 @@ clear_bss_end:
 
                 align4
 
-                dc.b    'UPX!'          ; magic
+                ; 32 bytes - #include "header.ash"
-                dc.l    0,0,0,0,0,0,0   ; 28 bytes - #include "header.ash"
+                dc.b    85,80,88,33         ; UPX_MAGIC_LE32
+                dc.b    161,216,208,213     ; UPX_MAGIC2_LE32
+                dc.l    0,0,0,0,0           ; 20 bytes
+                dc.b    0,0,0,45
 
 
         ; end of text segment - size is a multiple of 4

src/unupx.h

@@ -88,6 +88,7 @@ typedef unsigned upx_uint32;
 
 
 #define UPX_MAGIC_LE32      0x21585055          /* "UPX!" */
+#define UPX_MAGIC2_LE32     0xD5D0D8A1
 
 
 /*************************************************************************