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Overview
Comment:Fix issues on unix with opening database files via symlinks that are not in the current working directory. And with nested symlinks.
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SHA1:80398fd44fb232193450103808e1854e0eba5652
User & Date: dan 2016-01-25 17:04:48
Context
2016-01-25
18:05
Simplify the unixFullpathname() function. This adds a dependency on lstat(). check-in: f71249d3 user: dan tags: follow-symlinks
17:04
Fix issues on unix with opening database files via symlinks that are not in the current working directory. And with nested symlinks. check-in: 80398fd4 user: dan tags: follow-symlinks
15:57
Replace the OP_SetIfNotPos operator with OP_OffsetLimit in the VDBE, for simpler and smaller code. check-in: 7ac017a4 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/os_unix.c.

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#endif

/*
** Maximum supported path-length.
*/
#define MAX_PATHNAME 512






/* Always cast the getpid() return type for compatibility with
** kernel modules in VxWorks. */
#define osGetpid(X) (pid_t)getpid()

/*
** Only set the lastErrno if the error code is a real error and not 
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
................................................................................
    *pResOut = (0==osStat(zPath, &buf) && buf.st_size>0);
  }else{
    *pResOut = osAccess(zPath, W_OK|R_OK)==0;
  }
  return SQLITE_OK;
}


/*

** Turn a relative pathname into a full pathname. The relative path
** is stored as a nul-terminated string in the buffer pointed to by
** zPath. 



**
** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
** (in this case, MAX_PATHNAME bytes). The full-path is written to
** this buffer before returning.
*/
static int unixFullPathname(
  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
  const char *zPath,            /* Possibly relative input path */
  int nOut,                     /* Size of output buffer in bytes */

  char *zOut                    /* Output buffer */
){
  int nByte;

  /* It's odd to simulate an io-error here, but really this is just
  ** using the io-error infrastructure to test that SQLite handles this
  ** function failing. This function could fail if, for example, the
  ** current working directory has been unlinked.
  */
  SimulateIOError( return SQLITE_ERROR );

  assert( pVfs->mxPathname==MAX_PATHNAME );
  UNUSED_PARAMETER(pVfs);

#if defined(HAVE_READLINK)
  /* Attempt to resolve the path as if it were a symbolic link. If it is
  ** a symbolic link, the resolved path is stored in buffer zOut[]. Or, if
  ** the identified file is not a symbolic link or does not exist, then
  ** zPath is copied directly into zOut. Either way, nByte is left set to
  ** the size of the string copied into zOut[] in bytes.  */
  nByte = osReadlink(zPath, zOut, nOut-1);
  if( nByte<0 ){
    if( errno!=EINVAL && errno!=ENOENT ){
      return unixLogError(SQLITE_CANTOPEN_BKPT, "readlink", zPath);
    }
    sqlite3_snprintf(nOut, zOut, "%s", zPath);
    nByte = sqlite3Strlen30(zOut);
  }else{
    zOut[nByte] = '\0';
  }
#endif

  /* If buffer zOut[] now contains an absolute path there is nothing more
  ** to do. If it contains a relative path, do the following:
  **
  **   * move the relative path string so that it is at the end of th
  **     zOut[] buffer.
  **   * Call getcwd() to read the path of the current working directory 
  **     into the start of the zOut[] buffer.
................................................................................
  **     follows the '/'.
  **
  ** This code is written so that if the combination of the CWD and relative
  ** path are larger than the allocated size of zOut[] the CWD is silently
  ** truncated to make it fit. This is Ok, as SQLite refuses to open any
  ** file for which this function returns a full path larger than (nOut-8)
  ** bytes in size.  */

  testcase( nByte==nOut-5 );
  testcase( nByte==nOut-4 );
  if( zOut[0]!='/' && nByte<nOut-4 ){
    int nCwd;
    int nRem = nOut-nByte-1;
    memmove(&zOut[nRem], zOut, nByte+1);
    zOut[nRem-1] = '\0';
................................................................................
    assert( nCwd<=nRem-1 );
    zOut[nCwd] = '/';
    memmove(&zOut[nCwd+1], &zOut[nRem], nByte+1);
  }

  return SQLITE_OK;
}
































































































#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Interfaces for opening a shared library, finding entry points
** within the shared library, and closing the shared library.
*/







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#endif

/*
** Maximum supported path-length.
*/
#define MAX_PATHNAME 512

/*
** Maximum supported symbolic links
*/
#define SQLITE_MAX_SYMLINKS 100

/* Always cast the getpid() return type for compatibility with
** kernel modules in VxWorks. */
#define osGetpid(X) (pid_t)getpid()

/*
** Only set the lastErrno if the error code is a real error and not 
** a normal expected return code of SQLITE_BUSY or SQLITE_OK
................................................................................
    *pResOut = (0==osStat(zPath, &buf) && buf.st_size>0);
  }else{
    *pResOut = osAccess(zPath, W_OK|R_OK)==0;
  }
  return SQLITE_OK;
}


/*
** Buffer zOut contains a (possibly) relative pathname. Overwrite it with
** the corresponding full pathname.

**
** Parameter nOut is the allocated size of buffer zOut. nByte is the number
** of bytes in the nul-terminated string that it contains (not including
** the nul-terminator itself).
**


** Return SQLITE_OK if successful, or an SQLite error code otherwise.
*/
static int mkFullPathname(

  const char *zPath,              /* Use this path to log any errors */
  char *zOut,                     /* IN/OUT: Buffer to modify */
  int nByte,                      /* size of nul-terminated zOut in bytes */
  int nOut                        /* Allocated size of buffer zOut */
){






























  /* If buffer zOut[] now contains an absolute path there is nothing more
  ** to do. If it contains a relative path, do the following:
  **
  **   * move the relative path string so that it is at the end of th
  **     zOut[] buffer.
  **   * Call getcwd() to read the path of the current working directory 
  **     into the start of the zOut[] buffer.
................................................................................
  **     follows the '/'.
  **
  ** This code is written so that if the combination of the CWD and relative
  ** path are larger than the allocated size of zOut[] the CWD is silently
  ** truncated to make it fit. This is Ok, as SQLite refuses to open any
  ** file for which this function returns a full path larger than (nOut-8)
  ** bytes in size.  */
  assert( nByte<nOut );
  testcase( nByte==nOut-5 );
  testcase( nByte==nOut-4 );
  if( zOut[0]!='/' && nByte<nOut-4 ){
    int nCwd;
    int nRem = nOut-nByte-1;
    memmove(&zOut[nRem], zOut, nByte+1);
    zOut[nRem-1] = '\0';
................................................................................
    assert( nCwd<=nRem-1 );
    zOut[nCwd] = '/';
    memmove(&zOut[nCwd+1], &zOut[nRem], nByte+1);
  }

  return SQLITE_OK;
}

/*
** Turn a relative pathname into a full pathname. The relative path
** is stored as a nul-terminated string in the buffer pointed to by
** zPath. 
**
** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
** (in this case, MAX_PATHNAME bytes). The full-path is written to
** this buffer before returning.
*/
static int unixFullPathname(
  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
  const char *zPath,            /* Possibly relative input path */
  int nOut,                     /* Size of output buffer in bytes */
  char *zOut                    /* Output buffer */
){
#if !defined(HAVE_READLINK)
  sqlite3_snprintf(nOut, zOut, "%s", zIn);
  nByte = sqlite3Strlen30(zOut);
  return mkFullPathname(zPath, zOut, sqlite3Strlen30(zOut), nOut);
#else
  int rc = SQLITE_OK;
  int nByte;
  int nLink = 0;                /* Number of symbolic links followed so far */
  int bLink;                    /* True for a symbolic link */
  const char *zIn = zPath;      /* Input path for each iteration of loop */
  char *zDel = 0;

  assert( pVfs->mxPathname==MAX_PATHNAME );
  UNUSED_PARAMETER(pVfs);

  /* It's odd to simulate an io-error here, but really this is just
  ** using the io-error infrastructure to test that SQLite handles this
  ** function failing. This function could fail if, for example, the
  ** current working directory has been unlinked.
  */
  SimulateIOError( return SQLITE_ERROR );

  do {

    /* Attempt to resolve the path as if it were a symbolic link. If it is
    ** a symbolic link, the resolved path is stored in buffer zOut[]. Or, if
    ** the identified file is not a symbolic link or does not exist, then
    ** zPath is copied directly into zOut. Either way, nByte is left set to
    ** the size of the string copied into zOut[] in bytes.  */
    assert( (zDel==0 && zIn==zPath) || (zDel!=0 && zIn==zDel) );
    if( zDel ){
      assert( zIn==zDel );
      sqlite3_snprintf(nOut, zDel, "%s", zOut);
    }
    nByte = osReadlink(zIn, zOut, nOut-1);
    if( nByte<0 ){
      if( errno!=EINVAL && errno!=ENOENT ){
        rc = unixLogError(SQLITE_CANTOPEN_BKPT, "readlink", zPath);
      }else{
        sqlite3_snprintf(nOut, zOut, "%s", zIn);
        nByte = sqlite3Strlen30(zOut);
      }
      bLink = 0;
    }else if( ++nLink>SQLITE_MAX_SYMLINKS ){
      sqlite3_log(SQLITE_CANTOPEN, 
          "too many symbolic links (max=%d)", SQLITE_MAX_SYMLINKS
      );
      rc = SQLITE_CANTOPEN_BKPT;
    }else{
      zOut[nByte] = '\0';
      if( zOut[0]!='/' ){
        int n;
        for(n = sqlite3Strlen30(zIn); n>0 && zIn[n-1]!='/'; n--);
        if( nByte+n+1>nOut ){
          rc = SQLITE_CANTOPEN_BKPT;
        }else{
          memmove(&zOut[n], zOut, nByte+1);
          memcpy(zOut, zIn, n);
          nByte += n;
        }
      }
      if( zDel==0 ){
        zDel = sqlite3_malloc(nOut);
        if( zDel==0 ) rc = SQLITE_NOMEM;
        zIn = (const char*)zDel;
      }
      bLink = 1;
    }

    if( rc==SQLITE_OK ){
      rc = mkFullPathname(zPath, zOut, nByte, nOut);
    }
  }while( bLink && rc==SQLITE_OK );

  sqlite3_free(zDel);
  return rc;
#endif   /* HAVE_READLINK */
}


#ifndef SQLITE_OMIT_LOAD_EXTENSION
/*
** Interfaces for opening a shared library, finding entry points
** within the shared library, and closing the shared library.
*/

Changes to test/symlink.test.

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#-------------------------------------------------------------------------
# Test that journal and wal files are created next to the real file,
# not the symlink.
#
do_test 2.0 {
  catch { db close }
  catch { db2 close }
  forcedelete test.db test.db2
  sqlite3 db test.db
  execsql { CREATE TABLE t1(x) }
  file link test.db2 test.db






  sqlite3 db2 test.db2
  file exists test.db-journal
} 0

do_test 2.1 {
  execsql {
    BEGIN;
      INSERT INTO t1 VALUES(1);
  } db2
  file exists test.db-journal
} 1
do_test 2.2 {
  file exists test.db2-journal

} 0
do_test 2.3 {
  execsql {
    COMMIT;
    PRAGMA journal_mode = wal;
    INSERT INTO t1 VALUES(2);
  } db2
  file exists test.db-wal
} 1
do_test 2.4 {
  file exists test.db2-wal
} 0
do_execsql_test 2.5 {
  SELECT * FROM t1;
} {1 2}







# Try to open a ridiculously long pathname.  Bug found by
# Kostya Serebryany using libFuzzer on 2015-11-30.
#
do_test 3.1 {
  db close
  catch {sqlite3 db [string repeat [string repeat x 100]/ 6]} res
  set res
} {unable to open database file}






















































finish_test







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#-------------------------------------------------------------------------
# Test that journal and wal files are created next to the real file,
# not the symlink.
#
do_test 2.0 {
  catch { db close }
  catch { db2 close }
  forcedelete test.db test.db2 test.db3
  sqlite3 db test.db
  execsql { CREATE TABLE t1(x) }
  file link test.db2 test.db
  file link test.db3 test.db2
  set {} {}
} {}

foreach {tn f} {1 test.db2 2 test.db3} {
  do_test 2.$tn.1 {
    sqlite3 db2 $f
    file exists test.db-journal
  } 0

  do_test 2.$tn.2 {
    execsql {
      BEGIN;
        INSERT INTO t1 VALUES(1);
    } db2
    file exists test.db-journal
  } 1
  do_test 2.$tn.3 {

    list [file exists test2.db-journal] [file exists test3.db-journal]
  } {0 0}
  do_test 2.$tn.4 {
    execsql {
      COMMIT;
      PRAGMA journal_mode = wal;
      INSERT INTO t1 VALUES(2);
    } db2
    file exists test.db-wal
  } 1
  do_test 2.$tn.5 {
    list [file exists test2.db-wal] [file exists test3.db-wal]
  } {0 0}
  do_execsql_test 2.$tn.6 {
    SELECT * FROM t1;
  } {1 2}
  db2 close
  do_execsql_test 2.$tn.7 {
    DELETE FROM t1;
    PRAGMA journal_mode = delete;
  } delete
}

# Try to open a ridiculously long pathname.  Bug found by
# Kostya Serebryany using libFuzzer on 2015-11-30.
#
do_test 3.1 {
  db close
  catch {sqlite3 db [string repeat [string repeat x 100]/ 6]} res
  set res
} {unable to open database file}

#-------------------------------------------------------------------------
# Test that relative symlinks that are not located in the cwd work.
#
do_test 4.1 {
  forcedelete x y z
  file mkdir x
  file mkdir y
  file mkdir z
  sqlite3 db x/test.db
  file link y/test.db ../x/test.db
  file link z/test.db ../y/test.db
  execsql {
    PRAGMA journal_mode = wal;
    CREATE TABLE t1(x, y);
    INSERT INTO t1 VALUES('hello', 'world');
  }
} {wal}

do_test 4.2.1 {
  db close
  sqlite3 db y/test.db
  db eval { SELECT * FROM t1 }
} {hello world}
do_test 4.2.2 {
  list [file exists x/test.db-wal] [file exists y/test.db-wal]
} {1 0}

do_test 4.3.1 {
  db close
  sqlite3 db z/test.db
  db eval { SELECT * FROM t1 }
} {hello world}
do_test 4.3.2 {
  list [file exists x/test.db-wal] [file exists y/test.db-wal] \
       [file exists z/test.db-wal]
} {1 0 0}

do_test 4.4.0 {
  forcedelete w
  file mkdir w
  file link w/test.db [file join [pwd] x/test.db] 
  set {} {}
} {}
do_test 4.4.1 {
  db close
  breakpoint
  sqlite3 db w/test.db
  db eval { SELECT * FROM t1 }
} {hello world}
do_test 4.4.2 {
  list [file exists x/test.db-wal] [file exists w/test.db-wal]
} {1 0}

finish_test