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      1 /*
      2  * Copyright (C) 2008 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 <stdarg.h>
     18 #include <stdlib.h>
     19 #include <stdio.h>
     20 #include <string.h>
     21 #include <fcntl.h>
     22 #include <ctype.h>
     23 #include <errno.h>
     24 #include <time.h>
     25 #include <ftw.h>
     26 
     27 #include <selinux/label.h>
     28 #include <selinux/android.h>
     29 
     30 #include <sys/stat.h>
     31 #include <sys/types.h>
     32 #include <sys/socket.h>
     33 #include <sys/un.h>
     34 
     35 #include <android-base/file.h>
     36 #include <android-base/strings.h>
     37 
     38 /* for ANDROID_SOCKET_* */
     39 #include <cutils/sockets.h>
     40 #include <android-base/stringprintf.h>
     41 
     42 #include <private/android_filesystem_config.h>
     43 
     44 #include "init.h"
     45 #include "log.h"
     46 #include "property_service.h"
     47 #include "util.h"
     48 
     49 /*
     50  * android_name_to_id - returns the integer uid/gid associated with the given
     51  * name, or UINT_MAX on error.
     52  */
     53 static unsigned int android_name_to_id(const char *name)
     54 {
     55     const struct android_id_info *info = android_ids;
     56     unsigned int n;
     57 
     58     for (n = 0; n < android_id_count; n++) {
     59         if (!strcmp(info[n].name, name))
     60             return info[n].aid;
     61     }
     62 
     63     return UINT_MAX;
     64 }
     65 
     66 static unsigned int do_decode_uid(const char *s)
     67 {
     68     unsigned int v;
     69 
     70     if (!s || *s == '\0')
     71         return UINT_MAX;
     72     if (isalpha(s[0]))
     73         return android_name_to_id(s);
     74 
     75     errno = 0;
     76     v = (unsigned int) strtoul(s, 0, 0);
     77     if (errno)
     78         return UINT_MAX;
     79     return v;
     80 }
     81 
     82 /*
     83  * decode_uid - decodes and returns the given string, which can be either the
     84  * numeric or name representation, into the integer uid or gid. Returns
     85  * UINT_MAX on error.
     86  */
     87 unsigned int decode_uid(const char *s) {
     88     unsigned int v = do_decode_uid(s);
     89     if (v == UINT_MAX) {
     90         ERROR("decode_uid: Unable to find UID for '%s'. Returning UINT_MAX\n", s);
     91     }
     92     return v;
     93 }
     94 
     95 /*
     96  * create_socket - creates a Unix domain socket in ANDROID_SOCKET_DIR
     97  * ("/dev/socket") as dictated in init.rc. This socket is inherited by the
     98  * daemon. We communicate the file descriptor's value via the environment
     99  * variable ANDROID_SOCKET_ENV_PREFIX<name> ("ANDROID_SOCKET_foo").
    100  */
    101 int create_socket(const char *name, int type, mode_t perm, uid_t uid,
    102                   gid_t gid, const char *socketcon)
    103 {
    104     struct sockaddr_un addr;
    105     int fd, ret, savederrno;
    106     char *filecon;
    107 
    108     if (socketcon) {
    109         if (setsockcreatecon(socketcon) == -1) {
    110             ERROR("setsockcreatecon(\"%s\") failed: %s\n", socketcon, strerror(errno));
    111             return -1;
    112         }
    113     }
    114 
    115     fd = socket(PF_UNIX, type, 0);
    116     if (fd < 0) {
    117         ERROR("Failed to open socket '%s': %s\n", name, strerror(errno));
    118         return -1;
    119     }
    120 
    121     if (socketcon)
    122         setsockcreatecon(NULL);
    123 
    124     memset(&addr, 0 , sizeof(addr));
    125     addr.sun_family = AF_UNIX;
    126     snprintf(addr.sun_path, sizeof(addr.sun_path), ANDROID_SOCKET_DIR"/%s",
    127              name);
    128 
    129     ret = unlink(addr.sun_path);
    130     if (ret != 0 && errno != ENOENT) {
    131         ERROR("Failed to unlink old socket '%s': %s\n", name, strerror(errno));
    132         goto out_close;
    133     }
    134 
    135     filecon = NULL;
    136     if (sehandle) {
    137         ret = selabel_lookup(sehandle, &filecon, addr.sun_path, S_IFSOCK);
    138         if (ret == 0)
    139             setfscreatecon(filecon);
    140     }
    141 
    142     ret = bind(fd, (struct sockaddr *) &addr, sizeof (addr));
    143     savederrno = errno;
    144 
    145     setfscreatecon(NULL);
    146     freecon(filecon);
    147 
    148     if (ret) {
    149         ERROR("Failed to bind socket '%s': %s\n", name, strerror(savederrno));
    150         goto out_unlink;
    151     }
    152 
    153     ret = lchown(addr.sun_path, uid, gid);
    154     if (ret) {
    155         ERROR("Failed to lchown socket '%s': %s\n", addr.sun_path, strerror(errno));
    156         goto out_unlink;
    157     }
    158     ret = fchmodat(AT_FDCWD, addr.sun_path, perm, AT_SYMLINK_NOFOLLOW);
    159     if (ret) {
    160         ERROR("Failed to fchmodat socket '%s': %s\n", addr.sun_path, strerror(errno));
    161         goto out_unlink;
    162     }
    163 
    164     INFO("Created socket '%s' with mode '%o', user '%d', group '%d'\n",
    165          addr.sun_path, perm, uid, gid);
    166 
    167     return fd;
    168 
    169 out_unlink:
    170     unlink(addr.sun_path);
    171 out_close:
    172     close(fd);
    173     return -1;
    174 }
    175 
    176 bool read_file(const char* path, std::string* content) {
    177     content->clear();
    178 
    179     int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY|O_NOFOLLOW|O_CLOEXEC));
    180     if (fd == -1) {
    181         return false;
    182     }
    183 
    184     // For security reasons, disallow world-writable
    185     // or group-writable files.
    186     struct stat sb;
    187     if (fstat(fd, &sb) == -1) {
    188         ERROR("fstat failed for '%s': %s\n", path, strerror(errno));
    189         return false;
    190     }
    191     if ((sb.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
    192         ERROR("skipping insecure file '%s'\n", path);
    193         return false;
    194     }
    195 
    196     bool okay = android::base::ReadFdToString(fd, content);
    197     close(fd);
    198     return okay;
    199 }
    200 
    201 int write_file(const char* path, const char* content) {
    202     int fd = TEMP_FAILURE_RETRY(open(path, O_WRONLY|O_CREAT|O_NOFOLLOW|O_CLOEXEC, 0600));
    203     if (fd == -1) {
    204         NOTICE("write_file: Unable to open '%s': %s\n", path, strerror(errno));
    205         return -1;
    206     }
    207     int result = android::base::WriteStringToFd(content, fd) ? 0 : -1;
    208     if (result == -1) {
    209         NOTICE("write_file: Unable to write to '%s': %s\n", path, strerror(errno));
    210     }
    211     close(fd);
    212     return result;
    213 }
    214 
    215 #define MAX_MTD_PARTITIONS 16
    216 
    217 static struct {
    218     char name[16];
    219     int number;
    220 } mtd_part_map[MAX_MTD_PARTITIONS];
    221 
    222 static int mtd_part_count = -1;
    223 
    224 static void find_mtd_partitions(void)
    225 {
    226     int fd;
    227     char buf[1024];
    228     char *pmtdbufp;
    229     ssize_t pmtdsize;
    230     int r;
    231 
    232     fd = open("/proc/mtd", O_RDONLY|O_CLOEXEC);
    233     if (fd < 0)
    234         return;
    235 
    236     buf[sizeof(buf) - 1] = '\0';
    237     pmtdsize = read(fd, buf, sizeof(buf) - 1);
    238     pmtdbufp = buf;
    239     while (pmtdsize > 0) {
    240         int mtdnum, mtdsize, mtderasesize;
    241         char mtdname[16];
    242         mtdname[0] = '\0';
    243         mtdnum = -1;
    244         r = sscanf(pmtdbufp, "mtd%d: %x %x %15s",
    245                    &mtdnum, &mtdsize, &mtderasesize, mtdname);
    246         if ((r == 4) && (mtdname[0] == '"')) {
    247             char *x = strchr(mtdname + 1, '"');
    248             if (x) {
    249                 *x = 0;
    250             }
    251             INFO("mtd partition %d, %s\n", mtdnum, mtdname + 1);
    252             if (mtd_part_count < MAX_MTD_PARTITIONS) {
    253                 strcpy(mtd_part_map[mtd_part_count].name, mtdname + 1);
    254                 mtd_part_map[mtd_part_count].number = mtdnum;
    255                 mtd_part_count++;
    256             } else {
    257                 ERROR("too many mtd partitions\n");
    258             }
    259         }
    260         while (pmtdsize > 0 && *pmtdbufp != '\n') {
    261             pmtdbufp++;
    262             pmtdsize--;
    263         }
    264         if (pmtdsize > 0) {
    265             pmtdbufp++;
    266             pmtdsize--;
    267         }
    268     }
    269     close(fd);
    270 }
    271 
    272 int mtd_name_to_number(const char *name)
    273 {
    274     int n;
    275     if (mtd_part_count < 0) {
    276         mtd_part_count = 0;
    277         find_mtd_partitions();
    278     }
    279     for (n = 0; n < mtd_part_count; n++) {
    280         if (!strcmp(name, mtd_part_map[n].name)) {
    281             return mtd_part_map[n].number;
    282         }
    283     }
    284     return -1;
    285 }
    286 
    287 time_t gettime() {
    288     timespec now;
    289     clock_gettime(CLOCK_MONOTONIC, &now);
    290     return now.tv_sec;
    291 }
    292 
    293 uint64_t gettime_ns() {
    294     timespec now;
    295     clock_gettime(CLOCK_MONOTONIC, &now);
    296     return static_cast<uint64_t>(now.tv_sec) * UINT64_C(1000000000) + now.tv_nsec;
    297 }
    298 
    299 int mkdir_recursive(const char *pathname, mode_t mode)
    300 {
    301     char buf[128];
    302     const char *slash;
    303     const char *p = pathname;
    304     int width;
    305     int ret;
    306     struct stat info;
    307 
    308     while ((slash = strchr(p, '/')) != NULL) {
    309         width = slash - pathname;
    310         p = slash + 1;
    311         if (width < 0)
    312             break;
    313         if (width == 0)
    314             continue;
    315         if ((unsigned int)width > sizeof(buf) - 1) {
    316             ERROR("path too long for mkdir_recursive\n");
    317             return -1;
    318         }
    319         memcpy(buf, pathname, width);
    320         buf[width] = 0;
    321         if (stat(buf, &info) != 0) {
    322             ret = make_dir(buf, mode);
    323             if (ret && errno != EEXIST)
    324                 return ret;
    325         }
    326     }
    327     ret = make_dir(pathname, mode);
    328     if (ret && errno != EEXIST)
    329         return ret;
    330     return 0;
    331 }
    332 
    333 /*
    334  * replaces any unacceptable characters with '_', the
    335  * length of the resulting string is equal to the input string
    336  */
    337 void sanitize(char *s)
    338 {
    339     const char* accept =
    340             "abcdefghijklmnopqrstuvwxyz"
    341             "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    342             "0123456789"
    343             "_-.";
    344 
    345     if (!s)
    346         return;
    347 
    348     while (*s) {
    349         s += strspn(s, accept);
    350         if (*s) *s++ = '_';
    351     }
    352 }
    353 
    354 void make_link_init(const char *oldpath, const char *newpath)
    355 {
    356     int ret;
    357     char buf[256];
    358     char *slash;
    359     int width;
    360 
    361     slash = strrchr(newpath, '/');
    362     if (!slash)
    363         return;
    364     width = slash - newpath;
    365     if (width <= 0 || width > (int)sizeof(buf) - 1)
    366         return;
    367     memcpy(buf, newpath, width);
    368     buf[width] = 0;
    369     ret = mkdir_recursive(buf, 0755);
    370     if (ret)
    371         ERROR("Failed to create directory %s: %s (%d)\n", buf, strerror(errno), errno);
    372 
    373     ret = symlink(oldpath, newpath);
    374     if (ret && errno != EEXIST)
    375         ERROR("Failed to symlink %s to %s: %s (%d)\n", oldpath, newpath, strerror(errno), errno);
    376 }
    377 
    378 void remove_link(const char *oldpath, const char *newpath)
    379 {
    380     char path[256];
    381     ssize_t ret;
    382     ret = readlink(newpath, path, sizeof(path) - 1);
    383     if (ret <= 0)
    384         return;
    385     path[ret] = 0;
    386     if (!strcmp(path, oldpath))
    387         unlink(newpath);
    388 }
    389 
    390 int wait_for_file(const char *filename, int timeout)
    391 {
    392     struct stat info;
    393     uint64_t timeout_time_ns = gettime_ns() + timeout * UINT64_C(1000000000);
    394     int ret = -1;
    395 
    396     while (gettime_ns() < timeout_time_ns && ((ret = stat(filename, &info)) < 0))
    397         usleep(10000);
    398 
    399     return ret;
    400 }
    401 
    402 void open_devnull_stdio(void)
    403 {
    404     // Try to avoid the mknod() call if we can. Since SELinux makes
    405     // a /dev/null replacement available for free, let's use it.
    406     int fd = open("/sys/fs/selinux/null", O_RDWR);
    407     if (fd == -1) {
    408         // OOPS, /sys/fs/selinux/null isn't available, likely because
    409         // /sys/fs/selinux isn't mounted. Fall back to mknod.
    410         static const char *name = "/dev/__null__";
    411         if (mknod(name, S_IFCHR | 0600, (1 << 8) | 3) == 0) {
    412             fd = open(name, O_RDWR);
    413             unlink(name);
    414         }
    415         if (fd == -1) {
    416             exit(1);
    417         }
    418     }
    419 
    420     dup2(fd, 0);
    421     dup2(fd, 1);
    422     dup2(fd, 2);
    423     if (fd > 2) {
    424         close(fd);
    425     }
    426 }
    427 
    428 void import_kernel_cmdline(bool in_qemu,
    429                            std::function<void(const std::string&, const std::string&, bool)> fn) {
    430     std::string cmdline;
    431     android::base::ReadFileToString("/proc/cmdline", &cmdline);
    432 
    433     for (const auto& entry : android::base::Split(android::base::Trim(cmdline), " ")) {
    434         std::vector<std::string> pieces = android::base::Split(entry, "=");
    435         if (pieces.size() == 2) {
    436             fn(pieces[0], pieces[1], in_qemu);
    437         }
    438     }
    439 }
    440 
    441 int make_dir(const char *path, mode_t mode)
    442 {
    443     int rc;
    444 
    445     char *secontext = NULL;
    446 
    447     if (sehandle) {
    448         selabel_lookup(sehandle, &secontext, path, mode);
    449         setfscreatecon(secontext);
    450     }
    451 
    452     rc = mkdir(path, mode);
    453 
    454     if (secontext) {
    455         int save_errno = errno;
    456         freecon(secontext);
    457         setfscreatecon(NULL);
    458         errno = save_errno;
    459     }
    460 
    461     return rc;
    462 }
    463 
    464 int restorecon(const char* pathname)
    465 {
    466     return selinux_android_restorecon(pathname, 0);
    467 }
    468 
    469 int restorecon_recursive(const char* pathname)
    470 {
    471     return selinux_android_restorecon(pathname, SELINUX_ANDROID_RESTORECON_RECURSE);
    472 }
    473 
    474 /*
    475  * Writes hex_len hex characters (1/2 byte) to hex from bytes.
    476  */
    477 std::string bytes_to_hex(const uint8_t* bytes, size_t bytes_len) {
    478     std::string hex("0x");
    479     for (size_t i = 0; i < bytes_len; i++)
    480         android::base::StringAppendF(&hex, "%02x", bytes[i]);
    481     return hex;
    482 }
    483 
    484 /*
    485  * Returns true is pathname is a directory
    486  */
    487 bool is_dir(const char* pathname) {
    488     struct stat info;
    489     if (stat(pathname, &info) == -1) {
    490         return false;
    491     }
    492     return S_ISDIR(info.st_mode);
    493 }
    494 
    495 bool expand_props(const std::string& src, std::string* dst) {
    496     const char* src_ptr = src.c_str();
    497 
    498     if (!dst) {
    499         return false;
    500     }
    501 
    502     /* - variables can either be $x.y or ${x.y}, in case they are only part
    503      *   of the string.
    504      * - will accept $$ as a literal $.
    505      * - no nested property expansion, i.e. ${foo.${bar}} is not supported,
    506      *   bad things will happen
    507      */
    508     while (*src_ptr) {
    509         const char* c;
    510 
    511         c = strchr(src_ptr, '$');
    512         if (!c) {
    513             dst->append(src_ptr);
    514             return true;
    515         }
    516 
    517         dst->append(src_ptr, c);
    518         c++;
    519 
    520         if (*c == '$') {
    521             dst->push_back(*(c++));
    522             src_ptr = c;
    523             continue;
    524         } else if (*c == '\0') {
    525             return true;
    526         }
    527 
    528         std::string prop_name;
    529         if (*c == '{') {
    530             c++;
    531             const char* end = strchr(c, '}');
    532             if (!end) {
    533                 // failed to find closing brace, abort.
    534                 ERROR("unexpected end of string in '%s', looking for }\n", src.c_str());
    535                 return false;
    536             }
    537             prop_name = std::string(c, end);
    538             c = end + 1;
    539         } else {
    540             prop_name = c;
    541             ERROR("using deprecated syntax for specifying property '%s', use ${name} instead\n",
    542                   c);
    543             c += prop_name.size();
    544         }
    545 
    546         if (prop_name.empty()) {
    547             ERROR("invalid zero-length prop name in '%s'\n", src.c_str());
    548             return false;
    549         }
    550 
    551         std::string prop_val = property_get(prop_name.c_str());
    552         if (prop_val.empty()) {
    553             ERROR("property '%s' doesn't exist while expanding '%s'\n",
    554                   prop_name.c_str(), src.c_str());
    555             return false;
    556         }
    557 
    558         dst->append(prop_val);
    559         src_ptr = c;
    560     }
    561 
    562     return true;
    563 }
    564