canned_fs_config.c

   1 /*
   2  * Copyright (C) 2014 The Android Open Source Project
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *    http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <stdio.h>
  18 #include <string.h>
  19 #include <errno.h>
  20 #include <limits.h>
  21 #include <stdlib.h>
  22
  23 #include "private/android_filesystem_config.h"
  24
  25 #include "canned_fs_config.h"
  26
  27 typedef struct {
  28         const char* path;
  29         unsigned uid;
  30         unsigned gid;
  31         unsigned mode;
  32         uint64_t capabilities;
  33 } Path;
  34
  35 static Path* canned_data = NULL;
  36 static int canned_alloc = 0;
  37 static int canned_used = 0;
  38
  39 static int path_compare(const void* a, const void* b) {
  40         return strcmp(((Path*)a)->path, ((Path*)b)->path);
  41 }
  42
  43 int load_canned_fs_config(const char* fn) {
  44         FILE* f = fopen(fn, "r");
  45         if (f == NULL) {
  46                 fprintf(stderr, "failed to open %s: %s\n", fn, strerror(errno));
  47                 return -1;
  48         }
  49
  50         char line[PATH_MAX + 200];
  51         while (fgets(line, sizeof(line), f)) {
  52                 while (canned_used >= canned_alloc) {
  53                         canned_alloc = (canned_alloc+1) * 2;
  54                         canned_data = (Path*) realloc(canned_data, canned_alloc * sizeof(Path));
  55                 }
  56                 Path* p = canned_data + canned_used;
  57                 p->path = strdup(strtok(line, " "));
  58                 p->uid = atoi(strtok(NULL, " "));
  59                 p->gid = atoi(strtok(NULL, " "));
  60                 p->mode = strtol(strtok(NULL, " "), NULL, 8);   // mode is in octal
  61                 p->capabilities = 0;
  62
  63                 char* token = NULL;
  64                 do {
  65                         token = strtok(NULL, " ");
  66                         if (token && strncmp(token, "capabilities=", 13) == 0) {
  67                                 p->capabilities = strtoll(token+13, NULL, 0);
  68                                 break;
  69                         }
  70                 } while (token);
  71
  72                 canned_used++;
  73         }
  74
  75         fclose(f);
  76
  77         qsort(canned_data, canned_used, sizeof(Path), path_compare);
  78         printf("loaded %d fs_config entries\n", canned_used);
  79
  80         return 0;
  81 }
  82
  83 void canned_fs_config(const char* path, int dir,
  84                                           unsigned* uid, unsigned* gid, unsigned* mode, uint64_t* capabilities) {
  85         Path key;
  86         key.path = path+1;   // canned paths lack the leading '/'
  87         Path* p = (Path*) bsearch(&key, canned_data, canned_used, sizeof(Path), path_compare);
  88         if (p == NULL) {
  89                 fprintf(stderr, "failed to find [%s] in canned fs_config\n", path);
  90                 exit(1);
  91         }
  92         *uid = p->uid;
  93         *gid = p->gid;
  94         *mode = p->mode;
  95         *capabilities = p->capabilities;
  96
  97 #if 0
  98         // for debugging, run the built-in fs_config and compare the results.
  99
 100         unsigned c_uid, c_gid, c_mode;
 101         uint64_t c_capabilities;
 102         fs_config(path, dir, &c_uid, &c_gid, &c_mode, &c_capabilities);
 103
 104         if (c_uid != *uid) printf("%s uid %d %d\n", path, *uid, c_uid);
 105         if (c_gid != *gid) printf("%s gid %d %d\n", path, *gid, c_gid);
 106         if (c_mode != *mode) printf("%s mode 0%o 0%o\n", path, *mode, c_mode);
 107         if (c_capabilities != *capabilities) printf("%s capabilities %llx %llx\n", path, *capabilities, c_capabilities);
 108 #endif
 109 }