src/StoreMetaUnpacker.cc

   1 /*
   2  * Copyright (C) 1996-2018 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section 20    Storage Manager Swapfile Unpacker */
  10
  11 #include "squid.h"
  12 #include "base/TextException.h"
  13 #include "Debug.h"
  14 #include "defines.h"
  15 #include "StoreMeta.h"
  16 #include "StoreMetaUnpacker.h"
  17
  18 int const StoreMetaUnpacker::MinimumBufferLength = sizeof(char) + sizeof(int);
  19
  20 /// useful for meta stored in pre-initialized (with zeros) db files
  21 bool
  22 StoreMetaUnpacker::isBufferZero()
  23 {
  24     // We could memcmp the entire buffer, but it is probably safe enough
  25     // to test a few bytes because if we do not detect a corrupted entry
  26     // it is not a big deal. Empty entries are not isBufferSane anyway.
  27     const int depth = 10;
  28     if (buflen < depth)
  29         return false; // cannot be sure enough
  30
  31     for (int i = 0; i < depth; ++i) {
  32         if (buf[i])
  33             return false;
  34     }
  35     return true;
  36 }
  37
  38 void
  39 StoreMetaUnpacker::checkBuffer()
  40 {
  41     assert(buf); // paranoid; already checked in the constructor
  42     if (buf[0] != static_cast<char>(STORE_META_OK))
  43         throw TexcHere("store entry metadata is corrupted");
  44     /*
  45      * sanity check on 'buflen' value.  It should be at least big
  46      * enough to hold one type and one length.
  47      */
  48     getBufferLength();
  49     if (*hdr_len < MinimumBufferLength)
  50         throw TexcHere("store entry metadata is too small");
  51     if (*hdr_len > buflen)
  52         throw TexcHere("store entry metadata is too big");
  53 }
  54
  55 void
  56 StoreMetaUnpacker::getBufferLength()
  57 {
  58     memcpy(hdr_len, &buf[1], sizeof(int));
  59 }
  60
  61 StoreMetaUnpacker::StoreMetaUnpacker(char const *aBuffer, ssize_t aLen, int *anInt) :
  62     buf(aBuffer),
  63     buflen(aLen),
  64     hdr_len(anInt),
  65     position(1 + sizeof(int)),
  66     type('\0'),
  67     length(0),
  68     tail(NULL)
  69 {
  70     assert(aBuffer != NULL);
  71 }
  72
  73 void
  74 StoreMetaUnpacker::getType()
  75 {
  76     type = buf[position];
  77     ++position;
  78 }
  79
  80 void
  81 StoreMetaUnpacker::getLength()
  82 {
  83     memcpy(&length, &buf[position], sizeof(int));
  84     position += sizeof(int);
  85 }
  86
  87 bool
  88 StoreMetaUnpacker::doOneEntry()
  89 {
  90     getType();
  91     getLength();
  92
  93     if (position + length > *hdr_len) {
  94         debugs(20, DBG_CRITICAL, "storeSwapMetaUnpack: overflow!");
  95         debugs(20, DBG_CRITICAL, "\ttype=" << type << ", length=" << length << ", *hdr_len=" << *hdr_len << ", offset=" << position);
  96         return false;
  97     }
  98
  99     StoreMeta *newNode = StoreMeta::Factory(type, length, &buf[position]);
 100
 101     if (newNode)
 102         tail = StoreMeta::Add (tail, newNode);
 103
 104     position += length;
 105
 106     return true;
 107 }
 108
 109 bool
 110 StoreMetaUnpacker::moreToProcess() const
 111 {
 112     return *hdr_len - position - MinimumBufferLength >= 0;
 113 }
 114
 115 StoreMeta *
 116 StoreMetaUnpacker::createStoreMeta ()
 117 {
 118     tlv *TLV = NULL;
 119     tail = &TLV;
 120     assert(hdr_len != NULL);
 121
 122     checkBuffer();
 123
 124     getBufferLength();
 125
 126     assert (position == 1 + sizeof(int));
 127
 128     while (moreToProcess()) {
 129         if (!doOneEntry())
 130             break;
 131     }
 132
 133     if (!TLV)
 134         throw TexcHere("store entry metadata is empty");
 135
 136     assert(TLV);
 137     return TLV;
 138 }
 139