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 <dlfcn.h>
  26
  27 #include <sys/mman.h>
  28 #include <sys/types.h>
  29 #include <sys/stat.h>
  30
  31 #include <mach-o/loader.h>
  32
  33 #define INSTALLD "/usr/libexec/installd"
  34 #define LIBUICACHE "/usr/lib/libpatcyh.dylib"
  35
  36 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"));
  37
  38 template <typename Header>
  39 static bool PatchInstall(bool uninstall, void *data) {
  40     Header *header(reinterpret_cast<Header *>(data));
  41
  42     load_command *command(reinterpret_cast<load_command *>(header + 1));
  43     for (size_t i(0); i != header->ncmds; ++i, command = reinterpret_cast<load_command *>(reinterpret_cast<uint8_t *>(command) + command->cmdsize)) {
  44         if (command->cmdsize > sizeof(Header) + header->sizeofcmds - (reinterpret_cast<uint8_t *>(command) - reinterpret_cast<uint8_t *>(header))) {
  45             fprintf(stderr, "load command is to long to fit in header\n");
  46             return false;
  47         }
  48
  49         if (command->cmd != LC_LOAD_DYLIB)
  50             continue;
  51
  52         dylib_command *load(reinterpret_cast<dylib_command *>(command));
  53         const char *name(reinterpret_cast<char *>(command) + load->dylib.name.offset);
  54         if (strcmp(name, LIBUICACHE) != 0)
  55             continue;
  56
  57         if (!uninstall)
  58             return true;
  59
  60         if (i != header->ncmds - 1) {
  61             fprintf(stderr, "load command not in final position %zd %zd\n", i, header->ncmds);
  62             return false;
  63         }
  64
  65         if (reinterpret_cast<uint8_t *>(command) + command->cmdsize != reinterpret_cast<uint8_t *>(header + 1) + header->sizeofcmds) {
  66             fprintf(stderr, "load command header size integrity fail\n");
  67             return false;
  68         }
  69
  70         --header->ncmds;
  71         header->sizeofcmds -= command->cmdsize;
  72         memset(command, 0, command->cmdsize);
  73
  74         return true;
  75     }
  76
  77     if (reinterpret_cast<uint8_t *>(command) != reinterpret_cast<uint8_t *>(header + 1) + header->sizeofcmds) {
  78         fprintf(stderr, "load command header size integrity fail\n");
  79         return false;
  80     }
  81
  82     if (uninstall)
  83         return true;
  84
  85     dylib_command *load(reinterpret_cast<dylib_command *>(command));
  86     memset(load, 0, sizeof(*load));
  87     load->cmd = LC_LOAD_DYLIB;
  88
  89     load->cmdsize = sizeof(*load) + sizeof(LIBUICACHE);
  90     load->cmdsize = (load->cmdsize + 15) / 16 * 16;
  91     memset(load + 1, 0, load->cmdsize - sizeof(*load));
  92
  93     dylib *dylib(&load->dylib);
  94     dylib->name.offset = sizeof(*load);
  95     memcpy(load + 1, LIBUICACHE, sizeof(LIBUICACHE));
  96
  97     ++header->ncmds;
  98     header->sizeofcmds += load->cmdsize;
  99
 100     return true;
 101 }
 102
 103 static bool PatchInstall(bool uninstall, bool abort) {
 104     if (!abort && system("ldid --") != 0) {
 105         fprintf(stderr, "this package requires ldid to be installed\n");
 106         return false;
 107     }
 108
 109     int fd(open(INSTALLD, O_RDWR));
 110     if (fd == -1)
 111         return false;
 112
 113     struct stat stat;
 114     if (fstat(fd, &stat) == -1) {
 115         close(fd);
 116         return false;
 117     }
 118
 119     size_t size(stat.st_size);
 120     void *data(mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
 121     close(fd);
 122     if (data == MAP_FAILED)
 123         return false;
 124
 125     bool changed(false);
 126     uint32_t magic(*reinterpret_cast<uint32_t *>(data));
 127     switch (magic) {
 128         case MH_MAGIC:
 129             changed = PatchInstall<mach_header>(uninstall, data);
 130             break;
 131         case MH_MAGIC_64:
 132             changed = PatchInstall<mach_header_64>(uninstall, data);
 133             break;
 134         default:
 135             fprintf(stderr, "unknown header magic on installd: %08x\n", magic);
 136             return false;
 137     }
 138
 139     munmap(data, size);
 140
 141     if (changed) {
 142         system("ldid -s "INSTALLD"");
 143         system("cp -af "INSTALLD" "INSTALLD"_");
 144         system("mv -f "INSTALLD"_ "INSTALLD"");
 145     }
 146
 147     return true;
 148 }
 149
 150 #endif//PATCH_HPP