pith/osdep/canaccess.c

   1 #if !defined(lint) && !defined(DOS)
   2 static char rcsid[] = "$Id: canaccess.c 769 2007-10-24 00:15:40Z hubert@u.washington.edu $";
   3 #endif
   4
   5 /*
   6  * ========================================================================
   7  * Copyright 2006-2007 University of Washington
   8  * Copyright 2013-2014 Eduardo Chappa
   9  *
  10  * Licensed under the Apache License, Version 2.0 (the "License");
  11  * you may not use this file except in compliance with the License.
  12  * You may obtain a copy of the License at
  13  *
  14  *     http://www.apache.org/licenses/LICENSE-2.0
  15  *
  16  * ========================================================================
  17  */
  18
  19 #include <system.h>
  20 #include "bldpath.h"
  21 #include "fnexpand.h"
  22 #include "../charconv/utf8.h"
  23 #include "../charconv/filesys.h"
  24 #include "canaccess.h"
  25
  26
  27 /*
  28  * Useful definitions
  29  */
  30 #ifdef  _WINDOWS
  31
  32 #define ACCESS_IN_CWD(F,M)      (can_access((F), (M)))
  33 #define PATH_SEP                ';'
  34 #define FILE_SEP                '\\'
  35
  36 #else  /* UNIX */
  37
  38 #define ACCESS_IN_CWD(F,M)      (-1)
  39 #define PATH_SEP                ':'
  40 #define FILE_SEP                '/'
  41
  42 #endif /* UNIX */
  43
  44
  45
  46 /*
  47  *     Check if we can access a file in a given way
  48  *
  49  * Args: file      -- The file to check
  50  *       mode      -- The mode ala the access() system call, see ACCESS_EXISTS
  51  *                    and friends in alpine.h.
  52  *
  53  * Result: returns 0 if the user can access the file according to the mode,
  54  *         -1 if he can't (and errno is set).
  55  *
  56  *
  57  */
  58 int
  59 can_access(char *file, int mode)
  60 {
  61 #ifdef  _WINDOWS
  62     struct stat buf;
  63
  64     /*
  65      * NOTE: The WinNT access call returns that every directory is readable and
  66      * writable. We actually want to know if the write is going to fail, so we
  67      * try it. We don't read directories in Windows so we skip implementing that.
  68      */
  69     if(mode & WRITE_ACCESS && file && !our_stat(file, &buf) && (buf.st_mode & S_IFMT) == S_IFDIR){
  70         char *testname;
  71         int   fd;
  72         size_t l = 0;
  73
  74         /*
  75          * We'd like to just call temp_nam here, since it creates a file
  76          * and does what we want. However, temp_nam calls us!
  77          */
  78         if((testname = malloc(MAXPATH * sizeof(char)))){
  79             strncpy(testname, file, MAXPATH-1);
  80             testname[MAXPATH-1] = '\0';
  81             if(testname[0] && testname[(l=strlen(testname))-1] != '\\' &&
  82                l+1 < MAXPATH){
  83                 l++;
  84                 strncat(testname, "\\", MAXPATH-strlen(testname)-1);
  85                 testname[MAXPATH-1] = '\0';
  86             }
  87
  88             if(l+8 < MAXPATH &&
  89                strncat(testname, "caXXXXXX", MAXPATH-strlen(testname)-1) && mktemp(testname)){
  90                 if((fd = our_open(testname, O_CREAT|O_EXCL|O_WRONLY|O_BINARY, 0600)) >= 0){
  91                     (void)close(fd);
  92                     our_unlink(testname);
  93                     free(testname);
  94                     /* success, drop through to access call */
  95                 }
  96                 else{
  97                     free(testname);
  98                     /* can't write in the directory */
  99                     return(-1);
 100                 }
 101             }
 102             else{
 103                 free(testname);
 104                 return(-1);
 105             }
 106         }
 107     }
 108     if(mode & EXECUTE_ACCESS)    /* Windows access has no execute mode */
 109       mode &= ~EXECUTE_ACCESS;   /* and crashes because of it */
 110 #endif /* WINDOWS */
 111
 112     return(our_access(file, mode));
 113 }
 114
 115
 116 /*----------------------------------------------------------------------
 117        Check if we can access a file in a given way in the given path
 118
 119    Args: path     -- The path to look for "file" in
 120          file      -- The file to check
 121          mode      -- The mode ala the access() system call, see ACCESS_EXISTS
 122                       and friends in alpine.h.
 123
 124  Result: returns 0 if the user can access the file according to the mode,
 125          -1 if he can't (and errno is set).
 126  ----*/
 127 int
 128 can_access_in_path(char *path, char *file, int mode)
 129 {
 130     char tmp[MAXPATH];
 131     int  rv = -1;
 132
 133     if(!path || !*path || is_rooted_path(file)){
 134         rv = can_access(file, mode);
 135     }
 136     else if(is_homedir_path(file)){
 137         strncpy(tmp, file, sizeof(tmp));
 138         tmp[sizeof(tmp)-1] = '\0';
 139         rv = fnexpand(tmp, sizeof(tmp)) ? can_access(tmp, mode) : -1;
 140     }
 141     else if((rv = ACCESS_IN_CWD(file,mode)) < 0){
 142         char path_copy[MAXPATH + 1], *p, *t;
 143
 144         if(strlen(path) < MAXPATH){
 145             strncpy(path_copy, path, sizeof(path_copy));
 146             path_copy[sizeof(path_copy)-1] = '\0';
 147
 148             for(p = path_copy; p && *p; p = t){
 149                 if((t = strchr(p, PATH_SEP)) != NULL)
 150                   *t++ = '\0';
 151
 152                 snprintf(tmp, sizeof(tmp), "%s%c%s", p, FILE_SEP, file);
 153                 if((rv = can_access(tmp, mode)) == 0)
 154                   break;
 155             }
 156         }
 157     }
 158
 159     return(rv);
 160 }