src/shared/smack-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 /***
   3   Copyright © 2013 Intel Corporation
   4
   5   Author: Auke Kok <auke-jan.h.kok@intel.com>
   6 ***/
   7
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <sys/stat.h>
  11 #include <sys/xattr.h>
  12 #include <unistd.h>
  13
  14 #include "alloc-util.h"
  15 #include "errno-util.h"
  16 #include "fd-util.h"
  17 #include "fileio.h"
  18 #include "label.h"
  19 #include "log.h"
  20 #include "macro.h"
  21 #include "path-util.h"
  22 #include "process-util.h"
  23 #include "smack-util.h"
  24 #include "stdio-util.h"
  25 #include "string-table.h"
  26 #include "xattr-util.h"
  27
  28 #if ENABLE_SMACK
  29 bool mac_smack_use(void) {
  30         static int cached_use = -1;
  31
  32         if (cached_use < 0)
  33                 cached_use = access("/sys/fs/smackfs/", F_OK) >= 0;
  34
  35         return cached_use;
  36 }
  37
  38 static const char* const smack_attr_table[_SMACK_ATTR_MAX] = {
  39         [SMACK_ATTR_ACCESS]     = "security.SMACK64",
  40         [SMACK_ATTR_EXEC]       = "security.SMACK64EXEC",
  41         [SMACK_ATTR_MMAP]       = "security.SMACK64MMAP",
  42         [SMACK_ATTR_TRANSMUTE]  = "security.SMACK64TRANSMUTE",
  43         [SMACK_ATTR_IPIN]       = "security.SMACK64IPIN",
  44         [SMACK_ATTR_IPOUT]      = "security.SMACK64IPOUT",
  45 };
  46
  47 DEFINE_STRING_TABLE_LOOKUP(smack_attr, SmackAttr);
  48
  49 int mac_smack_read(const char *path, SmackAttr attr, char **label) {
  50         assert(path);
  51         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  52         assert(label);
  53
  54         if (!mac_smack_use())
  55                 return 0;
  56
  57         return getxattr_malloc(path, smack_attr_to_string(attr), label);
  58 }
  59
  60 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
  61         assert(fd >= 0);
  62         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  63         assert(label);
  64
  65         if (!mac_smack_use())
  66                 return 0;
  67
  68         return fgetxattr_malloc(fd, smack_attr_to_string(attr), label);
  69 }
  70
  71 int mac_smack_apply_at(int dir_fd, const char *path, SmackAttr attr, const char *label) {
  72         _cleanup_close_ int fd = -EBADF;
  73
  74         assert(path);
  75         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  76
  77         if (!mac_smack_use())
  78                 return 0;
  79
  80         fd = openat(dir_fd, path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
  81         if (fd < 0)
  82                 return -errno;
  83
  84         return mac_smack_apply_fd(fd, attr, label);
  85 }
  86
  87 int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
  88         int r;
  89
  90         assert(fd >= 0);
  91         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  92
  93         if (!mac_smack_use())
  94                 return 0;
  95
  96         if (label)
  97                 r = setxattr(FORMAT_PROC_FD_PATH(fd), smack_attr_to_string(attr), label, strlen(label), 0);
  98         else
  99                 r = removexattr(FORMAT_PROC_FD_PATH(fd), smack_attr_to_string(attr));
 100         if (r < 0)
 101                 return -errno;
 102
 103         return 0;
 104 }
 105
 106 int mac_smack_apply_pid(pid_t pid, const char *label) {
 107         const char *p;
 108         int r;
 109
 110         assert(label);
 111
 112         if (!mac_smack_use())
 113                 return 0;
 114
 115         p = procfs_file_alloca(pid, "attr/current");
 116         r = write_string_file(p, label, WRITE_STRING_FILE_DISABLE_BUFFER);
 117         if (r < 0)
 118                 return r;
 119
 120         return r;
 121 }
 122
 123 static int smack_fix_fd(
 124                 int fd,
 125                 const char *label_path,
 126                 LabelFixFlags flags) {
 127
 128         const char *label;
 129         struct stat st;
 130         int r;
 131
 132         /* The caller should have done the sanity checks. */
 133         assert(fd >= 0);
 134         assert(label_path);
 135         assert(path_is_absolute(label_path));
 136
 137         /* Path must be in /dev. */
 138         if (!path_startswith(label_path, "/dev"))
 139                 return 0;
 140
 141         if (fstat(fd, &st) < 0)
 142                 return -errno;
 143
 144         /*
 145          * Label directories and character devices "*".
 146          * Label symlinks "_".
 147          * Don't change anything else.
 148          */
 149
 150         if (S_ISDIR(st.st_mode))
 151                 label = SMACK_STAR_LABEL;
 152         else if (S_ISLNK(st.st_mode))
 153                 label = SMACK_FLOOR_LABEL;
 154         else if (S_ISCHR(st.st_mode))
 155                 label = SMACK_STAR_LABEL;
 156         else
 157                 return 0;
 158
 159         if (setxattr(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", label, strlen(label), 0) < 0) {
 160                 _cleanup_free_ char *old_label = NULL;
 161
 162                 r = -errno;
 163
 164                 /* If the FS doesn't support labels, then exit without warning */
 165                 if (ERRNO_IS_NOT_SUPPORTED(r))
 166                         return 0;
 167
 168                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 169                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 170                         return 0;
 171
 172                 /* If the old label is identical to the new one, suppress any kind of error */
 173                 if (lgetxattr_malloc(FORMAT_PROC_FD_PATH(fd), "security.SMACK64", &old_label) >= 0 &&
 174                     streq(old_label, label))
 175                         return 0;
 176
 177                 return log_debug_errno(r, "Unable to fix SMACK label of %s: %m", label_path);
 178         }
 179
 180         return 0;
 181 }
 182
 183 int mac_smack_fix_full(
 184                 int atfd,
 185                 const char *inode_path,
 186                 const char *label_path,
 187                 LabelFixFlags flags) {
 188
 189         _cleanup_close_ int opened_fd = -EBADF;
 190         _cleanup_free_ char *p = NULL;
 191         int r, inode_fd;
 192
 193         assert(atfd >= 0 || atfd == AT_FDCWD);
 194         assert(atfd >= 0 || inode_path);
 195
 196         if (!mac_smack_use())
 197                 return 0;
 198
 199         if (inode_path) {
 200                 opened_fd = openat(atfd, inode_path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 201                 if (opened_fd < 0) {
 202                         if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 203                                 return 0;
 204
 205                         return -errno;
 206                 }
 207                 inode_fd = opened_fd;
 208         } else
 209                 inode_fd = atfd;
 210
 211         if (!label_path) {
 212                 if (path_is_absolute(inode_path))
 213                         label_path = inode_path;
 214                 else {
 215                         r = fd_get_path(inode_fd, &p);
 216                         if (r < 0)
 217                                 return r;
 218
 219                         label_path = p;
 220                 }
 221         }
 222
 223         return smack_fix_fd(inode_fd, label_path, flags);
 224 }
 225
 226 int mac_smack_copy(const char *dest, const char *src) {
 227         int r;
 228         _cleanup_free_ char *label = NULL;
 229
 230         assert(dest);
 231         assert(src);
 232
 233         r = mac_smack_read(src, SMACK_ATTR_ACCESS, &label);
 234         if (r < 0)
 235                 return r;
 236
 237         r = mac_smack_apply(dest, SMACK_ATTR_ACCESS, label);
 238         if (r < 0)
 239                 return r;
 240
 241         return r;
 242 }
 243
 244 #else
 245 bool mac_smack_use(void) {
 246         return false;
 247 }
 248
 249 int mac_smack_read(const char *path, SmackAttr attr, char **label) {
 250         return -EOPNOTSUPP;
 251 }
 252
 253 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
 254         return -EOPNOTSUPP;
 255 }
 256
 257 int mac_smack_apply_at(int dir_fd, const char *path, SmackAttr attr, const char *label) {
 258         return 0;
 259 }
 260
 261 int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
 262         return 0;
 263 }
 264
 265 int mac_smack_apply_pid(pid_t pid, const char *label) {
 266         return 0;
 267 }
 268
 269 int mac_smack_fix_full(int atfd, const char *inode_path, const char *label_path, LabelFixFlags flags) {
 270         return 0;
 271 }
 272
 273 int mac_smack_copy(const char *dest, const char *src) {
 274         return 0;
 275 }
 276 #endif
 277
 278 int renameat_and_apply_smack_floor_label(int fdf, const char *from, int fdt, const char *to) {
 279
 280         assert(fdf >= 0 || fdf == AT_FDCWD);
 281         assert(fdt >= 0 || fdt == AT_FDCWD);
 282
 283         if (renameat(fdf, from, fdt, to) < 0)
 284                 return -errno;
 285
 286 #if HAVE_SMACK_RUN_LABEL
 287         return mac_smack_apply_at(fdt, to, SMACK_ATTR_ACCESS, SMACK_FLOOR_LABEL);
 288 #else
 289         return 0;
 290 #endif
 291 }
 292
 293 static int mac_smack_label_pre(int dir_fd, const char *path, mode_t mode) {
 294         return 0;
 295 }
 296
 297 static int mac_smack_label_post(int dir_fd, const char *path) {
 298         return mac_smack_fix_full(dir_fd, path, NULL, 0);
 299 }
 300
 301 int mac_smack_init(void) {
 302         static const LabelOps label_ops = {
 303                 .pre = mac_smack_label_pre,
 304                 .post = mac_smack_label_post,
 305         };
 306
 307         if (!mac_smack_use())
 308                 return 0;
 309
 310         return label_ops_set(&label_ops);
 311 }