src/lxc/file_utils.c

   1 /* liblxcapi
   2  *
   3  * Copyright © 2019 Christian Brauner <christian.brauner@ubuntu.com>.
   4  * Copyright © 2019 Canonical Ltd.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this library; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  19  */
  20
  21 #ifndef _GNU_SOURCE
  22 #define _GNU_SOURCE 1
  23 #endif
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <linux/magic.h>
  27 #include <stdlib.h>
  28 #include <sys/stat.h>
  29 #include <sys/sendfile.h>
  30 #include <sys/types.h>
  31
  32 #include "config.h"
  33 #include "file_utils.h"
  34 #include "macro.h"
  35 #include "memory_utils.h"
  36 #include "string_utils.h"
  37 #include "utils.h"
  38
  39 int lxc_write_to_file(const char *filename, const void *buf, size_t count,
  40                       bool add_newline, mode_t mode)
  41 {
  42         int fd, saved_errno;
  43         ssize_t ret;
  44
  45         fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
  46         if (fd < 0)
  47                 return -1;
  48
  49         ret = lxc_write_nointr(fd, buf, count);
  50         if (ret < 0)
  51                 goto out_error;
  52
  53         if ((size_t)ret != count)
  54                 goto out_error;
  55
  56         if (add_newline) {
  57                 ret = lxc_write_nointr(fd, "\n", 1);
  58                 if (ret != 1)
  59                         goto out_error;
  60         }
  61
  62         close(fd);
  63         return 0;
  64
  65 out_error:
  66         saved_errno = errno;
  67         close(fd);
  68         errno = saved_errno;
  69         return -1;
  70 }
  71
  72 int lxc_read_from_file(const char *filename, void *buf, size_t count)
  73 {
  74         int fd = -1, saved_errno;
  75         ssize_t ret;
  76
  77         fd = open(filename, O_RDONLY | O_CLOEXEC);
  78         if (fd < 0)
  79                 return -1;
  80
  81         if (!buf || !count) {
  82                 char buf2[100];
  83                 size_t count2 = 0;
  84
  85                 while ((ret = lxc_read_nointr(fd, buf2, 100)) > 0)
  86                         count2 += ret;
  87
  88                 if (ret >= 0)
  89                         ret = count2;
  90         } else {
  91                 memset(buf, 0, count);
  92                 ret = lxc_read_nointr(fd, buf, count);
  93         }
  94
  95         saved_errno = errno;
  96         close(fd);
  97         errno = saved_errno;
  98         return ret;
  99 }
 100
 101 ssize_t lxc_write_nointr(int fd, const void *buf, size_t count)
 102 {
 103         ssize_t ret;
 104 again:
 105         ret = write(fd, buf, count);
 106         if (ret < 0 && errno == EINTR)
 107                 goto again;
 108
 109         return ret;
 110 }
 111
 112 ssize_t lxc_send_nointr(int sockfd, void *buf, size_t len, int flags)
 113 {
 114         ssize_t ret;
 115 again:
 116         ret = send(sockfd, buf, len, flags);
 117         if (ret < 0 && errno == EINTR)
 118                 goto again;
 119
 120         return ret;
 121 }
 122
 123 ssize_t lxc_read_nointr(int fd, void *buf, size_t count)
 124 {
 125         ssize_t ret;
 126 again:
 127         ret = read(fd, buf, count);
 128         if (ret < 0 && errno == EINTR)
 129                 goto again;
 130
 131         return ret;
 132 }
 133
 134 ssize_t lxc_recv_nointr(int sockfd, void *buf, size_t len, int flags)
 135 {
 136         ssize_t ret;
 137 again:
 138         ret = recv(sockfd, buf, len, flags);
 139         if (ret < 0 && errno == EINTR)
 140                 goto again;
 141
 142         return ret;
 143 }
 144
 145 ssize_t lxc_recvmsg_nointr_iov(int sockfd, struct iovec *iov, size_t iovlen,
 146                                int flags)
 147 {
 148         ssize_t ret;
 149         struct msghdr msg;
 150
 151         memset(&msg, 0, sizeof(msg));
 152         msg.msg_iov = iov;
 153         msg.msg_iovlen = iovlen;
 154
 155 again:
 156         ret = recvmsg(sockfd, &msg, flags);
 157         if (ret < 0 && errno == EINTR)
 158                 goto again;
 159
 160         return ret;
 161 }
 162
 163 ssize_t lxc_read_nointr_expect(int fd, void *buf, size_t count, const void *expected_buf)
 164 {
 165         ssize_t ret;
 166
 167         ret = lxc_read_nointr(fd, buf, count);
 168         if (ret < 0)
 169                 return ret;
 170
 171         if ((size_t)ret != count)
 172                 return -1;
 173
 174         if (expected_buf && memcmp(buf, expected_buf, count) != 0) {
 175                 errno = EINVAL;
 176                 return -1;
 177         }
 178
 179         return 0;
 180 }
 181
 182 ssize_t lxc_read_file_expect(const char *path, void *buf, size_t count, const void *expected_buf)
 183 {
 184         __do_close_prot_errno int fd = -EBADF;
 185
 186         fd = open(path, O_RDONLY | O_CLOEXEC);
 187         if (fd < 0)
 188                 return -1;
 189
 190         return lxc_read_nointr_expect(fd, buf, count, expected_buf);
 191 }
 192
 193 bool file_exists(const char *f)
 194 {
 195         struct stat statbuf;
 196
 197         return stat(f, &statbuf) == 0;
 198 }
 199
 200 int print_to_file(const char *file, const char *content)
 201 {
 202         FILE *f;
 203         int ret = 0;
 204
 205         f = fopen(file, "w");
 206         if (!f)
 207                 return -1;
 208
 209         if (fprintf(f, "%s", content) != strlen(content))
 210                 ret = -1;
 211
 212         fclose(f);
 213         return ret;
 214 }
 215
 216 int is_dir(const char *path)
 217 {
 218         struct stat statbuf;
 219         int ret;
 220
 221         ret = stat(path, &statbuf);
 222         if (ret == 0 && S_ISDIR(statbuf.st_mode))
 223                 return 1;
 224
 225         return 0;
 226 }
 227
 228 /*
 229  * Return the number of lines in file @fn, or -1 on error
 230  */
 231 int lxc_count_file_lines(const char *fn)
 232 {
 233         FILE *f;
 234         char *line = NULL;
 235         size_t sz = 0;
 236         int n = 0;
 237
 238         f = fopen_cloexec(fn, "r");
 239         if (!f)
 240                 return -1;
 241
 242         while (getline(&line, &sz, f) != -1) {
 243                 n++;
 244         }
 245
 246         free(line);
 247         fclose(f);
 248         return n;
 249 }
 250
 251 int lxc_make_tmpfile(char *template, bool rm)
 252 {
 253         __do_close_prot_errno int fd = -EBADF;
 254         int ret;
 255         mode_t msk;
 256
 257         msk = umask(0022);
 258         fd = mkstemp(template);
 259         umask(msk);
 260         if (fd < 0)
 261                 return -1;
 262
 263         if (lxc_set_cloexec(fd))
 264                 return -1;
 265
 266         if (!rm)
 267                 return move_fd(fd);
 268
 269         ret = unlink(template);
 270         if (ret < 0)
 271                 return -1;
 272
 273         return move_fd(fd);
 274 }
 275
 276 bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val)
 277 {
 278         return (fs->f_type == (fs_type_magic)magic_val);
 279 }
 280
 281 bool has_fs_type(const char *path, fs_type_magic magic_val)
 282 {
 283         int ret;
 284         struct statfs sb;
 285
 286         ret = statfs(path, &sb);
 287         if (ret < 0)
 288                 return false;
 289
 290         return is_fs_type(&sb, magic_val);
 291 }
 292
 293 bool fhas_fs_type(int fd, fs_type_magic magic_val)
 294 {
 295         int ret;
 296         struct statfs sb;
 297
 298         ret = fstatfs(fd, &sb);
 299         if (ret < 0)
 300                 return false;
 301
 302         return is_fs_type(&sb, magic_val);
 303 }
 304
 305 FILE *fopen_cloexec(const char *path, const char *mode)
 306 {
 307         int open_mode = 0;
 308         int step = 0;
 309         int fd;
 310         int saved_errno = 0;
 311         FILE *ret;
 312
 313         if (!strncmp(mode, "r+", 2)) {
 314                 open_mode = O_RDWR;
 315                 step = 2;
 316         } else if (!strncmp(mode, "r", 1)) {
 317                 open_mode = O_RDONLY;
 318                 step = 1;
 319         } else if (!strncmp(mode, "w+", 2)) {
 320                 open_mode = O_RDWR | O_TRUNC | O_CREAT;
 321                 step = 2;
 322         } else if (!strncmp(mode, "w", 1)) {
 323                 open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 324                 step = 1;
 325         } else if (!strncmp(mode, "a+", 2)) {
 326                 open_mode = O_RDWR | O_CREAT | O_APPEND;
 327                 step = 2;
 328         } else if (!strncmp(mode, "a", 1)) {
 329                 open_mode = O_WRONLY | O_CREAT | O_APPEND;
 330                 step = 1;
 331         }
 332         for (; mode[step]; step++)
 333                 if (mode[step] == 'x')
 334                         open_mode |= O_EXCL;
 335         open_mode |= O_CLOEXEC;
 336
 337         fd = open(path, open_mode, 0660);
 338         if (fd < 0)
 339                 return NULL;
 340
 341         ret = fdopen(fd, mode);
 342         saved_errno = errno;
 343         if (!ret)
 344                 close(fd);
 345         errno = saved_errno;
 346         return ret;
 347 }
 348
 349 ssize_t lxc_sendfile_nointr(int out_fd, int in_fd, off_t *offset, size_t count)
 350 {
 351         ssize_t ret;
 352
 353 again:
 354         ret = sendfile(out_fd, in_fd, offset, count);
 355         if (ret < 0) {
 356                 if (errno == EINTR)
 357                         goto again;
 358
 359                 return -1;
 360         }
 361
 362         return ret;
 363 }
 364
 365 char *file_to_buf(char *path, size_t *length)
 366 {
 367         int fd;
 368         char buf[PATH_MAX];
 369         char *copy = NULL;
 370
 371         if (!length)
 372                 return NULL;
 373
 374         fd = open(path, O_RDONLY | O_CLOEXEC);
 375         if (fd < 0)
 376                 return NULL;
 377
 378         *length = 0;
 379         for (;;) {
 380                 int n;
 381                 char *old = copy;
 382
 383                 n = lxc_read_nointr(fd, buf, sizeof(buf));
 384                 if (n < 0)
 385                         goto on_error;
 386                 if (!n)
 387                         break;
 388
 389                 copy = must_realloc(old, (*length + n) * sizeof(*old));
 390                 memcpy(copy + *length, buf, n);
 391                 *length += n;
 392         }
 393
 394         close(fd);
 395         return copy;
 396
 397 on_error:
 398         close(fd);
 399         free(copy);
 400
 401         return NULL;
 402 }
 403
 404 int fd_to_fd(int from, int to)
 405 {
 406         for (;;) {
 407                 uint8_t buf[PATH_MAX];
 408                 uint8_t *p = buf;
 409                 ssize_t bytes_to_write;
 410                 ssize_t bytes_read;
 411
 412                 bytes_read = lxc_read_nointr(from, buf, sizeof buf);
 413                 if (bytes_read < 0)
 414                         return -1;
 415                 if (bytes_read == 0)
 416                         break;
 417
 418                 bytes_to_write = (size_t)bytes_read;
 419                 do {
 420                         ssize_t bytes_written;
 421
 422                         bytes_written = lxc_write_nointr(to, p, bytes_to_write);
 423                         if (bytes_written < 0)
 424                                 return -1;
 425
 426                         bytes_to_write -= bytes_written;
 427                         p += bytes_written;
 428                 } while (bytes_to_write > 0);
 429         }
 430
 431         return 0;
 432 }