src/basic/smack-util.c

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