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Overview
Comment:Fix further buffer overreads triggered by passing corrupt records to the sqlite_dbdata module.
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SHA3-256: dbc6a9f7f67256dea96d3245e7bec145ba65d64adf322e18f1f3ac9556b4e0b6
User & Date: dan 2019-05-09 15:07:46
Context
2019-05-09
15:51
Fix another corruption related buffer overread in the sqlite_dbdata module. check-in: 5cd728fb user: dan tags: trunk
15:07
Fix further buffer overreads triggered by passing corrupt records to the sqlite_dbdata module. check-in: dbc6a9f7 user: dan tags: trunk
14:15
Have ".recover" handle cases where the sqlite_master table contains malformed SQL statements. check-in: e736da9c user: dan tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to ext/misc/dbdata.c.

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        int bHasRowid = 0;
        int nPointer = 0;
        sqlite3_int64 nPayload = 0;
        sqlite3_int64 nHdr = 0;
        int iHdr;
        int U, X;
        int nLocal;

  
        switch( pCsr->aPage[iOff] ){
          case 0x02:
            nPointer = 4;
            break;
          case 0x0a:
            break;
................................................................................
          default:
            /* This is not a b-tree page with records on it. Continue. */
            pCsr->iCell = pCsr->nCell;
            break;
        }

        if( pCsr->iCell>=pCsr->nCell ){
          sqlite3_free(pCsr->aPage);
          pCsr->aPage = 0;
          if( pCsr->bOnePage ) return SQLITE_OK;
          pCsr->iPgno++;
          continue;

        }
  
        iOff += 8 + nPointer + pCsr->iCell*2;



        iOff = get_uint16(&pCsr->aPage[iOff]);
  

        /* For an interior node cell, skip past the child-page number */
        iOff += nPointer;
  
        /* Load the "byte of payload including overflow" field */



        iOff += dbdataGetVarint(&pCsr->aPage[iOff], &nPayload);
  

        /* If this is a leaf intkey cell, load the rowid */
        if( bHasRowid ){
          iOff += dbdataGetVarint(&pCsr->aPage[iOff], &pCsr->iIntkey);
        }
  
        /* Allocate space for payload */
        pCsr->pRec = (u8*)sqlite3_malloc64(nPayload);
        if( pCsr->pRec==0 ) return SQLITE_NOMEM;
        pCsr->nRec = nPayload;
  

        U = pCsr->nPage;
        if( bHasRowid ){
          X = U-35;
        }else{
          X = ((U-12)*64/255)-23;
        }
        if( nPayload<=X ){
          nLocal = nPayload;
        }else{
          int M, K;
          M = ((U-12)*32/255)-23;
          K = M+((nPayload-M)%(U-4));
          if( K<=X ){
            nLocal = K;
          }else{
            nLocal = M;
          }
        }
  












        /* Load the nLocal bytes of payload */
        memcpy(pCsr->pRec, &pCsr->aPage[iOff], nLocal);
        iOff += nLocal;
  
        /* Load content from overflow pages */
        if( nPayload>nLocal ){
          sqlite3_int64 nRem = nPayload - nLocal;
          unsigned int pgnoOvfl = get_uint32(&pCsr->aPage[iOff]);
          while( nRem>0 ){
            u8 *aOvfl = 0;
            int nOvfl = 0;
            int nCopy;
            rc = dbdataLoadPage(pCsr, pgnoOvfl, &aOvfl, &nOvfl);
            assert( rc!=SQLITE_OK || nOvfl==pCsr->nPage );
            if( rc!=SQLITE_OK ) return rc;
  
            nCopy = U-4;
            if( nCopy>nRem ) nCopy = nRem;
            memcpy(&pCsr->pRec[nPayload-nRem], &aOvfl[4], nCopy);
            nRem -= nCopy;
  
            pgnoOvfl = get_uint32(aOvfl);
            sqlite3_free(aOvfl);
          }
        }
  
        iHdr = dbdataGetVarint(pCsr->pRec, &nHdr);
        pCsr->nHdr = nHdr;
        pCsr->pHdrPtr = &pCsr->pRec[iHdr];
        pCsr->pPtr = &pCsr->pRec[pCsr->nHdr];
        pCsr->iField = (bHasRowid ? -1 : 0);










      }else{
        pCsr->iField++;
        if( pCsr->iField>0 ){
          sqlite3_int64 iType;
          pCsr->pHdrPtr += dbdataGetVarint(pCsr->pHdrPtr, &iType);
          pCsr->pPtr += dbdataValueBytes(iType);
        }







>







 







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        int bHasRowid = 0;
        int nPointer = 0;
        sqlite3_int64 nPayload = 0;
        sqlite3_int64 nHdr = 0;
        int iHdr;
        int U, X;
        int nLocal;
        int bNextPage = 0;
  
        switch( pCsr->aPage[iOff] ){
          case 0x02:
            nPointer = 4;
            break;
          case 0x0a:
            break;
................................................................................
          default:
            /* This is not a b-tree page with records on it. Continue. */
            pCsr->iCell = pCsr->nCell;
            break;
        }

        if( pCsr->iCell>=pCsr->nCell ){

          bNextPage = 1;



        }else{
  

          iOff += 8 + nPointer + pCsr->iCell*2;
          if( iOff>pCsr->nPage ){
            bNextPage = 1;
          }else{
            iOff = get_uint16(&pCsr->aPage[iOff]);
          }
    
          /* For an interior node cell, skip past the child-page number */
          iOff += nPointer;
    
          /* Load the "byte of payload including overflow" field */
          if( bNextPage || iOff>pCsr->nPage ){
            bNextPage = 1;
          }else{
            iOff += dbdataGetVarint(&pCsr->aPage[iOff], &nPayload);
          }
    
          /* If this is a leaf intkey cell, load the rowid */
          if( bHasRowid && !bNextPage && iOff<pCsr->nPage ){
            iOff += dbdataGetVarint(&pCsr->aPage[iOff], &pCsr->iIntkey);
          }
    





          /* Figure out how much data to read from the local page */
          U = pCsr->nPage;
          if( bHasRowid ){
            X = U-35;
          }else{
            X = ((U-12)*64/255)-23;
          }
          if( nPayload<=X ){
            nLocal = nPayload;
          }else{
            int M, K;
            M = ((U-12)*32/255)-23;
            K = M+((nPayload-M)%(U-4));
            if( K<=X ){
              nLocal = K;
            }else{
              nLocal = M;
            }
          }

          if( bNextPage || nLocal+iOff>pCsr->nPage ){
            bNextPage = 1;
          }else{

            /* Allocate space for payload. And a bit more to catch small buffer
            ** overruns caused by attempting to read a varint or similar from 
            ** near the end of a corrupt record.  */
            pCsr->pRec = (u8*)sqlite3_malloc64(nPayload+100);
            if( pCsr->pRec==0 ) return SQLITE_NOMEM;
            memset(pCsr->pRec, 0, nPayload+100);
            pCsr->nRec = nPayload;

            /* Load the nLocal bytes of payload */
            memcpy(pCsr->pRec, &pCsr->aPage[iOff], nLocal);
            iOff += nLocal;

            /* Load content from overflow pages */
            if( nPayload>nLocal ){
              sqlite3_int64 nRem = nPayload - nLocal;
              unsigned int pgnoOvfl = get_uint32(&pCsr->aPage[iOff]);
              while( nRem>0 ){
                u8 *aOvfl = 0;
                int nOvfl = 0;
                int nCopy;
                rc = dbdataLoadPage(pCsr, pgnoOvfl, &aOvfl, &nOvfl);
                assert( rc!=SQLITE_OK || nOvfl==pCsr->nPage );
                if( rc!=SQLITE_OK ) return rc;

                nCopy = U-4;
                if( nCopy>nRem ) nCopy = nRem;
                memcpy(&pCsr->pRec[nPayload-nRem], &aOvfl[4], nCopy);
                nRem -= nCopy;

                pgnoOvfl = get_uint32(aOvfl);
                sqlite3_free(aOvfl);
              }
            }
    
            iHdr = dbdataGetVarint(pCsr->pRec, &nHdr);
            pCsr->nHdr = nHdr;
            pCsr->pHdrPtr = &pCsr->pRec[iHdr];
            pCsr->pPtr = &pCsr->pRec[pCsr->nHdr];
            pCsr->iField = (bHasRowid ? -1 : 0);
          }
        }

        if( bNextPage ){
          sqlite3_free(pCsr->aPage);
          pCsr->aPage = 0;
          if( pCsr->bOnePage ) return SQLITE_OK;
          pCsr->iPgno++;
          continue;
        }
      }else{
        pCsr->iField++;
        if( pCsr->iField>0 ){
          sqlite3_int64 iType;
          pCsr->pHdrPtr += dbdataGetVarint(pCsr->pHdrPtr, &iType);
          pCsr->pPtr += dbdataValueBytes(iType);
        }