patch.hpp

   1 /* patcyh - you should pronounce it like patch
   2  * Copyright (C) 2015  Jay Freeman (saurik)
   3 */
   4
   5 /* GNU General Public License, Version 3 {{{ */
   6 /*
   7  * Cydia is free software: you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published
   9  * by the Free Software Foundation, either version 3 of the License,
  10  * or (at your option) any later version.
  11  *
  12  * Cydia is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with Cydia.  If not, see <http://www.gnu.org/licenses/>.
  19 **/
  20 /* }}} */
  21
  22 #ifndef PATCH_HPP
  23 #define PATCH_HPP
  24
  25 #include <string>
  26
  27 #include <dlfcn.h>
  28
  29 #include <sys/mman.h>
  30 #include <sys/types.h>
  31 #include <sys/stat.h>
  32
  33 #include <mach-o/loader.h>
  34
  35 #define LIBUICACHE "/usr/lib/libpatcyh.dylib"
  36
  37 static void *(*$memmem)(const void *, size_t, const void *, size_t) = reinterpret_cast<void *(*)(const void *, size_t, const void *, size_t)>(dlsym(RTLD_DEFAULT, "memmem"));
  38
  39 template <typename Header>
  40 static bool PatchInstall(bool uninstall, void *data) {
  41     Header *header(reinterpret_cast<Header *>(data));
  42
  43     load_command *command(reinterpret_cast<load_command *>(header + 1));
  44     for (size_t i(0); i != header->ncmds; ++i, command = reinterpret_cast<load_command *>(reinterpret_cast<uint8_t *>(command) + command->cmdsize)) {
  45         if (command->cmdsize > sizeof(Header) + header->sizeofcmds - (reinterpret_cast<uint8_t *>(command) - reinterpret_cast<uint8_t *>(header))) {
  46             fprintf(stderr, "load command is to long to fit in header\n");
  47             return false;
  48         }
  49
  50         if (command->cmd != LC_LOAD_DYLIB)
  51             continue;
  52
  53         dylib_command *load(reinterpret_cast<dylib_command *>(command));
  54         const char *name(reinterpret_cast<char *>(command) + load->dylib.name.offset);
  55         if (strcmp(name, LIBUICACHE) != 0)
  56             continue;
  57
  58         if (!uninstall)
  59             return true;
  60
  61         if (i != header->ncmds - 1) {
  62             fprintf(stderr, "load command not in final position %zd %zd\n", i, header->ncmds);
  63             return false;
  64         }
  65
  66         if (reinterpret_cast<uint8_t *>(command) + command->cmdsize != reinterpret_cast<uint8_t *>(header + 1) + header->sizeofcmds) {
  67             fprintf(stderr, "load command header size integrity fail\n");
  68             return false;
  69         }
  70
  71         --header->ncmds;
  72         header->sizeofcmds -= command->cmdsize;
  73         memset(command, 0, command->cmdsize);
  74
  75         return true;
  76     }
  77
  78     if (reinterpret_cast<uint8_t *>(command) != reinterpret_cast<uint8_t *>(header + 1) + header->sizeofcmds) {
  79         fprintf(stderr, "load command header size integrity fail\n");
  80         return false;
  81     }
  82
  83     if (uninstall)
  84         return true;
  85
  86     dylib_command *load(reinterpret_cast<dylib_command *>(command));
  87     memset(load, 0, sizeof(*load));
  88     load->cmd = LC_LOAD_DYLIB;
  89
  90     load->cmdsize = sizeof(*load) + sizeof(LIBUICACHE);
  91     load->cmdsize = (load->cmdsize + 15) / 16 * 16;
  92     memset(load + 1, 0, load->cmdsize - sizeof(*load));
  93
  94     dylib *dylib(&load->dylib);
  95     dylib->name.offset = sizeof(*load);
  96     memcpy(load + 1, LIBUICACHE, sizeof(LIBUICACHE));
  97
  98     ++header->ncmds;
  99     header->sizeofcmds += load->cmdsize;
 100
 101     return true;
 102 }
 103
 104 static bool Patch(const std::string &path, const std::string &service, bool uninstall, bool abort) {
 105     if (!abort && system("ldid --") != 0) {
 106         fprintf(stderr, "this package requires ldid to be installed\n");
 107         return false;
 108     }
 109
 110     int fd(open(path.c_str(), O_RDWR));
 111     if (fd == -1)
 112         return false;
 113
 114     struct stat stat;
 115     if (fstat(fd, &stat) == -1) {
 116         close(fd);
 117         return false;
 118     }
 119
 120     size_t size(stat.st_size);
 121     void *data(mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
 122     close(fd);
 123     if (data == MAP_FAILED)
 124         return false;
 125
 126     bool changed(false);
 127     uint32_t magic(*reinterpret_cast<uint32_t *>(data));
 128     switch (magic) {
 129         case MH_MAGIC:
 130             changed = PatchInstall<mach_header>(uninstall, data);
 131             break;
 132         case MH_MAGIC_64:
 133             changed = PatchInstall<mach_header_64>(uninstall, data);
 134             break;
 135         default:
 136             fprintf(stderr, "unknown header magic on installd: %08x\n", magic);
 137             return false;
 138     }
 139
 140     munmap(data, size);
 141
 142     if (changed) {
 143         system(("ldid -s " + path + "").c_str());
 144         system(("cp -af " + path + " " + path + "_").c_str());
 145         system(("mv -f " + path + "_ " + path + "").c_str());
 146         system(("launchctl stop " + service + "").c_str());
 147     }
 148
 149     return true;
 150 }
 151
 152
 153 static bool PatchInstall(bool uninstall, bool abort) {
 154     return Patch("/usr/libexec/installd", "com.apple.mobile.installd", uninstall, abort);
 155 }
 156
 157 static bool PatchLaunch(bool uninstall, bool abort) {
 158     return Patch("/usr/libexec/lsd", "com.apple.lsd", uninstall, abort);
 159 }
 160
 161 #endif//PATCH_HPP