pith/osdep/canaccess.c

   1 /*
   2  * ========================================================================
   3  * Copyright 2013-2022 Eduardo Chappa
   4  * Copyright 2006-2007 University of Washington
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * ========================================================================
  13  */
  14
  15 #include <system.h>
  16 #include "bldpath.h"
  17 #include "fnexpand.h"
  18 #include "../charconv/utf8.h"
  19 #include "../charconv/filesys.h"
  20 #include "canaccess.h"
  21
  22
  23 /*
  24  * Useful definitions
  25  */
  26 #ifdef  _WINDOWS
  27
  28 #define ACCESS_IN_CWD(F,M)      (can_access((F), (M)))
  29 #define PATH_SEP                ';'
  30 #define FILE_SEP                '\\'
  31
  32 #else  /* UNIX */
  33
  34 #define ACCESS_IN_CWD(F,M)      (-1)
  35 #define PATH_SEP                ':'
  36 #define FILE_SEP                '/'
  37
  38 #endif /* UNIX */
  39
  40
  41
  42 /*
  43  *     Check if we can access a file in a given way
  44  *
  45  * Args: file      -- The file to check
  46  *       mode      -- The mode ala the access() system call, see ACCESS_EXISTS
  47  *                    and friends in alpine.h.
  48  *
  49  * Result: returns 0 if the user can access the file according to the mode,
  50  *         -1 if he can't (and errno is set).
  51  *
  52  *
  53  */
  54 int
  55 can_access(char *file, int mode)
  56 {
  57 #ifdef  _WINDOWS
  58     struct stat buf;
  59
  60     /*
  61      * NOTE: The WinNT access call returns that every directory is readable and
  62      * writable. We actually want to know if the write is going to fail, so we
  63      * try it. We don't read directories in Windows so we skip implementing that.
  64      */
  65     if(mode & WRITE_ACCESS && file && !our_stat(file, &buf) && (buf.st_mode & S_IFMT) == S_IFDIR){
  66         char *testname;
  67         int   fd;
  68         size_t l = 0;
  69
  70         /*
  71          * We'd like to just call temp_nam here, since it creates a file
  72          * and does what we want. However, temp_nam calls us!
  73          */
  74         if((testname = malloc(MAXPATH * sizeof(char)))){
  75             strncpy(testname, file, MAXPATH-1);
  76             testname[MAXPATH-1] = '\0';
  77             if(testname[0] && testname[(l=strlen(testname))-1] != '\\' &&
  78                l+1 < MAXPATH){
  79                 l++;
  80                 strncat(testname, "\\", MAXPATH-strlen(testname)-1);
  81                 testname[MAXPATH-1] = '\0';
  82             }
  83
  84             if(l+8 < MAXPATH &&
  85                strncat(testname, "caXXXXXX", MAXPATH-strlen(testname)-1) && mktemp(testname)){
  86                 if((fd = our_open(testname, O_CREAT|O_EXCL|O_WRONLY|O_BINARY, 0600)) >= 0){
  87                     (void)close(fd);
  88                     our_unlink(testname);
  89                     free(testname);
  90                     /* success, drop through to access call */
  91                 }
  92                 else{
  93                     free(testname);
  94                     /* can't write in the directory */
  95                     return(-1);
  96                 }
  97             }
  98             else{
  99                 free(testname);
 100                 return(-1);
 101             }
 102         }
 103     }
 104     if(mode & EXECUTE_ACCESS)    /* Windows access has no execute mode */
 105       mode &= ~EXECUTE_ACCESS;   /* and crashes because of it */
 106 #endif /* WINDOWS */
 107
 108     return(our_access(file, mode));
 109 }
 110
 111
 112 /*----------------------------------------------------------------------
 113        Check if we can access a file in a given way in the given path
 114
 115    Args: path     -- The path to look for "file" in
 116          file      -- The file to check
 117          mode      -- The mode ala the access() system call, see ACCESS_EXISTS
 118                       and friends in alpine.h.
 119
 120  Result: returns 0 if the user can access the file according to the mode,
 121          -1 if he can't (and errno is set).
 122  ----*/
 123 int
 124 can_access_in_path(char *path, char *file, int mode)
 125 {
 126     char tmp[MAXPATH];
 127     int  rv = -1;
 128
 129     if(!path || !*path || is_rooted_path(file)){
 130         rv = can_access(file, mode);
 131     }
 132     else if(is_homedir_path(file)){
 133         strncpy(tmp, file, sizeof(tmp));
 134         tmp[sizeof(tmp)-1] = '\0';
 135         rv = fnexpand(tmp, sizeof(tmp)) ? can_access(tmp, mode) : -1;
 136     }
 137     else if((rv = ACCESS_IN_CWD(file,mode)) < 0){
 138         char path_copy[MAXPATH + 1], *p, *t;
 139
 140         if(strlen(path) < MAXPATH){
 141             strncpy(path_copy, path, sizeof(path_copy));
 142             path_copy[sizeof(path_copy)-1] = '\0';
 143
 144             for(p = path_copy; p && *p; p = t){
 145                 if((t = strchr(p, PATH_SEP)) != NULL)
 146                   *t++ = '\0';
 147
 148                 snprintf(tmp, sizeof(tmp), "%s%c%s", p, FILE_SEP, file);
 149                 if((rv = can_access(tmp, mode)) == 0)
 150                   break;
 151             }
 152         }
 153     }
 154
 155     return(rv);
 156 }