src/lxc/utils.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef __LXC_UTILS_H
   4 #define __LXC_UTILS_H
   5
   6 /* Properly support loop devices on 32bit systems. */
   7 #define _FILE_OFFSET_BITS 64
   8
   9 #ifndef MAX_GRBUF_SIZE
  10 #define MAX_GRBUF_SIZE 65536
  11 #endif
  12
  13 #include <errno.h>
  14 #include <linux/loop.h>
  15 #include <linux/types.h>
  16 #include <stdarg.h>
  17 #include <stdbool.h>
  18 #include <stdio.h>
  19 #include <sys/syscall.h>
  20 #include <sys/types.h>
  21 #include <sys/vfs.h>
  22 #include <unistd.h>
  23
  24 #include "compiler.h"
  25 #include "file_utils.h"
  26 #include "initutils.h"
  27 #include "macro.h"
  28 #include "memory_utils.h"
  29 #include "process_utils.h"
  30 #include "string_utils.h"
  31
  32 /* returns 1 on success, 0 if there were any failures */
  33 __hidden extern int lxc_rmdir_onedev(const char *path, const char *exclude);
  34 __hidden extern int get_u16(unsigned short *val, const char *arg, int base);
  35 __hidden extern int mkdir_p(const char *dir, mode_t mode);
  36 __hidden extern char *get_rundir(void);
  37
  38 /* Define getline() if missing from the C library */
  39 #ifndef HAVE_GETLINE
  40 #ifdef HAVE_FGETLN
  41 #include <../include/getline.h>
  42 #endif
  43 #endif
  44
  45 static inline int lxc_set_cloexec(int fd)
  46 {
  47         return fcntl(fd, F_SETFD, FD_CLOEXEC);
  48 }
  49
  50 /*
  51  * Struct to carry child pid from lxc_popen() to lxc_pclose(). Not an opaque
  52  * struct to allow direct access to the underlying FILE without additional
  53  * wrappers.
  54  */
  55 struct lxc_popen_FILE {
  56         int pipe;
  57         FILE *f;
  58         pid_t child_pid;
  59 };
  60
  61 /* popen(command, "re") replacement that restores default signal mask
  62  * via sigprocmask(2) (unblocks all signals) after fork(2) but prior to calling exec(3).
  63  * In short, popen(command, "re") does pipe() + fork()                 + exec()
  64  * while lxc_popen(command)       does pipe() + fork() + sigprocmask() + exec().
  65  * Returns pointer to struct lxc_popen_FILE, that should be freed with lxc_pclose().
  66  * On error returns NULL.
  67  */
  68 __hidden extern struct lxc_popen_FILE *lxc_popen(const char *command);
  69
  70 /* pclose() replacement to be used on struct lxc_popen_FILE *,
  71  * returned by lxc_popen().
  72  * Waits for associated process to terminate, returns its exit status and
  73  * frees resources, pointed to by struct lxc_popen_FILE *.
  74  */
  75 __hidden extern int lxc_pclose(struct lxc_popen_FILE *fp);
  76
  77 static inline void __auto_lxc_pclose__(struct lxc_popen_FILE **f)
  78 {
  79         if (*f)
  80                 lxc_pclose(*f);
  81 }
  82 #define __do_lxc_pclose __attribute__((__cleanup__(__auto_lxc_pclose__)))
  83
  84 /*
  85  * wait on a child we forked
  86  */
  87 __hidden extern int wait_for_pid(pid_t pid);
  88 __hidden extern int lxc_wait_for_pid_status(pid_t pid);
  89 __hidden extern int wait_for_pidfd(int pidfd);
  90
  91 #if HAVE_OPENSSL
  92 __hidden extern int sha1sum_file(char *fnam, unsigned char *md_value, unsigned int *md_len);
  93 #endif
  94
  95 /* initialize rand with urandom */
  96 __hidden extern int randseed(bool);
  97
  98 /* are we unprivileged with respect to our namespaces */
  99 inline static bool am_guest_unpriv(void) {
 100         return geteuid() != 0;
 101 }
 102
 103 /* are we unprivileged with respect to init_user_ns */
 104 inline static bool am_host_unpriv(void)
 105 {
 106         __do_fclose FILE *f = NULL;
 107         uid_t user, host, count;
 108         int ret;
 109
 110         if (geteuid() != 0)
 111                 return true;
 112
 113         /* Now: are we in a user namespace? Because then we're also
 114          * unprivileged.
 115          */
 116         f = fopen("/proc/self/uid_map", "re");
 117         if (!f)
 118                 return false;
 119
 120         ret = fscanf(f, "%u %u %u", &user, &host, &count);
 121         if (ret != 3)
 122                 return false;
 123
 124         return user != 0 || host != 0 || count != UINT32_MAX;
 125 }
 126
 127 /*
 128  * parse /proc/self/uid_map to find what @orig maps to
 129  */
 130 __hidden extern uid_t get_ns_uid(uid_t orig);
 131 /*
 132  * parse /proc/self/gid_map to find what @orig maps to
 133  */
 134 __hidden extern gid_t get_ns_gid(gid_t orig);
 135
 136 __hidden extern bool dir_exists(const char *path);
 137
 138 #define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
 139 __hidden extern uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval);
 140
 141 __hidden extern bool is_shared_mountpoint(const char *path);
 142 __hidden extern int detect_shared_rootfs(void);
 143 __hidden extern bool detect_ramfs_rootfs(void);
 144 __hidden extern char *on_path(const char *cmd, const char *rootfs);
 145 __hidden extern bool cgns_supported(void);
 146 __hidden extern char *choose_init(const char *rootfs);
 147 __hidden extern bool switch_to_ns(pid_t pid, const char *ns);
 148 __hidden extern char *get_template_path(const char *t);
 149 __hidden extern int safe_mount(const char *src, const char *dest, const char *fstype,
 150                                unsigned long flags, const void *data, const char *rootfs);
 151 __hidden extern int lxc_mount_proc_if_needed(const char *rootfs);
 152 __hidden extern int open_devnull(void);
 153 __hidden extern int set_stdfds(int fd);
 154 __hidden extern int null_stdfds(void);
 155 __hidden extern int lxc_preserve_ns(const int pid, const char *ns);
 156
 157 /* Check whether a signal is blocked by a process. */
 158 __hidden extern bool task_blocks_signal(pid_t pid, int signal);
 159
 160 /* Switch to a new uid and gid.
 161  * If LXC_INVALID_{G,U}ID is passed then the set{g,u}id() will not be called.
 162  */
 163 __hidden extern bool lxc_switch_uid_gid(uid_t uid, gid_t gid);
 164 __hidden extern bool lxc_setgroups(int size, gid_t list[]);
 165
 166 /* Find an unused loop device and associate it with source. */
 167 __hidden extern int lxc_prepare_loop_dev(const char *source, char *loop_dev, int flags);
 168
 169 /* Clear all mounts on a given node.
 170  * >= 0 successfully cleared. The number returned is the number of umounts
 171  *      performed.
 172  * < 0  error umounting. Return -errno.
 173  */
 174 __hidden extern int lxc_unstack_mountpoint(const char *path, bool lazy);
 175
 176 /*
 177  * run_command runs a command and collect it's std{err,out} output in buf.
 178  *
 179  * @param[out] buf     The buffer where the commands std{err,out] output will be
 180  *                     read into. If no output was produced, buf will be memset
 181  *                     to 0.
 182  * @param[in] buf_size The size of buf. This function will reserve one byte for
 183  *                     \0-termination.
 184  * @param[in] child_fn The function to be run in the child process. This
 185  *                     function must exec.
 186  * @param[in] args     Arguments to be passed to child_fn.
 187  */
 188 __hidden extern int run_command(char *buf, size_t buf_size, int (*child_fn)(void *), void *args);
 189
 190 /*
 191  * run_command runs a command and collect it's std{err,out} output in buf, returns exit status.
 192  *
 193  * @param[out] buf     The buffer where the commands std{err,out] output will be
 194  *                     read into. If no output was produced, buf will be memset
 195  *                     to 0.
 196  * @param[in] buf_size The size of buf. This function will reserve one byte for
 197  *                     \0-termination.
 198  * @param[in] child_fn The function to be run in the child process. This
 199  *                     function must exec.
 200  * @param[in] args     Arguments to be passed to child_fn.
 201  */
 202 __hidden extern int run_command_status(char *buf, size_t buf_size, int (*child_fn)(void *),
 203                                        void *args);
 204
 205 __hidden extern bool lxc_nic_exists(char *nic);
 206
 207 static inline uint64_t lxc_getpagesize(void)
 208 {
 209         int64_t pgsz;
 210
 211         pgsz = sysconf(_SC_PAGESIZE);
 212         if (pgsz <= 0)
 213                 pgsz = 1 << 12;
 214
 215         return pgsz;
 216 }
 217
 218 /* If n is not a power of 2 this function will return the next power of 2
 219  * greater than that number. Note that this function always returns the *next*
 220  * power of 2 *greater* that number not the *nearest*. For example, passing 1025
 221  * as argument this function will return 2048 although the closest power of 2
 222  * would be 1024.
 223  * If the caller passes in 0 they will receive 0 in return since this is invalid
 224  * input and 0 is not a power of 2.
 225  */
 226 __hidden extern uint64_t lxc_find_next_power2(uint64_t n);
 227
 228 /* Set a signal the child process will receive after the parent has died. */
 229 __hidden extern int lxc_set_death_signal(int signal, pid_t parent, int parent_status_fd);
 230 __hidden extern int fd_cloexec(int fd, bool cloexec);
 231 __hidden extern int lxc_rm_rf(const char *dirname);
 232 __hidden extern bool lxc_can_use_pidfd(int pidfd);
 233
 234 __hidden extern int fix_stdio_permissions(uid_t uid);
 235
 236 static inline bool uid_valid(uid_t uid)
 237 {
 238         return uid != LXC_INVALID_UID;
 239 }
 240
 241 static inline bool gid_valid(gid_t gid)
 242 {
 243         return gid != LXC_INVALID_GID;
 244 }
 245
 246 __hidden extern bool multiply_overflow(int64_t base, uint64_t mult, int64_t *res);
 247
 248 __hidden extern int safe_mount_beneath(const char *beneath, const char *src, const char *dst,
 249                                        const char *fstype, unsigned int flags, const void *data);
 250 __hidden extern int safe_mount_beneath_at(int beneat_fd, const char *src, const char *dst,
 251                                           const char *fstype, unsigned int flags, const void *data);
 252
 253 #endif /* __LXC_UTILS_H */