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