src/basic/smack-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2013 Intel Corporation
   6
   7   Author: Auke Kok <auke-jan.h.kok@intel.com>
   8 ***/
   9
  10 #include <errno.h>
  11 #include <fcntl.h>
  12 #include <string.h>
  13 #include <sys/stat.h>
  14 #include <sys/xattr.h>
  15 #include <unistd.h>
  16
  17 #include "alloc-util.h"
  18 #include "fd-util.h"
  19 #include "fileio.h"
  20 #include "log.h"
  21 #include "macro.h"
  22 #include "path-util.h"
  23 #include "process-util.h"
  24 #include "smack-util.h"
  25 #include "stdio-util.h"
  26 #include "string-table.h"
  27 #include "xattr-util.h"
  28
  29 #if ENABLE_SMACK
  30 bool mac_smack_use(void) {
  31         static int cached_use = -1;
  32
  33         if (cached_use < 0)
  34                 cached_use = access("/sys/fs/smackfs/", F_OK) >= 0;
  35
  36         return cached_use;
  37 }
  38
  39 static const char* const smack_attr_table[_SMACK_ATTR_MAX] = {
  40         [SMACK_ATTR_ACCESS]     = "security.SMACK64",
  41         [SMACK_ATTR_EXEC]       = "security.SMACK64EXEC",
  42         [SMACK_ATTR_MMAP]       = "security.SMACK64MMAP",
  43         [SMACK_ATTR_TRANSMUTE]  = "security.SMACK64TRANSMUTE",
  44         [SMACK_ATTR_IPIN]       = "security.SMACK64IPIN",
  45         [SMACK_ATTR_IPOUT]      = "security.SMACK64IPOUT",
  46 };
  47
  48 DEFINE_STRING_TABLE_LOOKUP(smack_attr, SmackAttr);
  49
  50 int mac_smack_read(const char *path, SmackAttr attr, char **label) {
  51         assert(path);
  52         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  53         assert(label);
  54
  55         if (!mac_smack_use())
  56                 return 0;
  57
  58         return getxattr_malloc(path, smack_attr_to_string(attr), label, true);
  59 }
  60
  61 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
  62         assert(fd >= 0);
  63         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  64         assert(label);
  65
  66         if (!mac_smack_use())
  67                 return 0;
  68
  69         return fgetxattr_malloc(fd, smack_attr_to_string(attr), label);
  70 }
  71
  72 int mac_smack_apply(const char *path, SmackAttr attr, const char *label) {
  73         int r;
  74
  75         assert(path);
  76         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  77
  78         if (!mac_smack_use())
  79                 return 0;
  80
  81         if (label)
  82                 r = lsetxattr(path, smack_attr_to_string(attr), label, strlen(label), 0);
  83         else
  84                 r = lremovexattr(path, smack_attr_to_string(attr));
  85         if (r < 0)
  86                 return -errno;
  87
  88         return 0;
  89 }
  90
  91 int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
  92         int r;
  93
  94         assert(fd >= 0);
  95         assert(attr >= 0 && attr < _SMACK_ATTR_MAX);
  96
  97         if (!mac_smack_use())
  98                 return 0;
  99
 100         if (label)
 101                 r = fsetxattr(fd, smack_attr_to_string(attr), label, strlen(label), 0);
 102         else
 103                 r = fremovexattr(fd, smack_attr_to_string(attr));
 104         if (r < 0)
 105                 return -errno;
 106
 107         return 0;
 108 }
 109
 110 int mac_smack_apply_pid(pid_t pid, const char *label) {
 111         const char *p;
 112         int r = 0;
 113
 114         assert(label);
 115
 116         if (!mac_smack_use())
 117                 return 0;
 118
 119         p = procfs_file_alloca(pid, "attr/current");
 120         r = write_string_file(p, label, 0);
 121         if (r < 0)
 122                 return r;
 123
 124         return r;
 125 }
 126
 127 int mac_smack_fix(const char *path, LabelFixFlags flags) {
 128         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 129         _cleanup_close_ int fd = -1;
 130         const char *label;
 131         struct stat st;
 132         int r;
 133
 134         assert(path);
 135
 136         if (!mac_smack_use())
 137                 return 0;
 138
 139         /* Path must be in /dev. Note that this check is pretty sloppy, as we might be called with non-normalized paths
 140          * and hence not detect all cases of /dev. */
 141
 142         if (path_is_absolute(path)) {
 143                 if (!path_startswith(path, "/dev"))
 144                         return 0;
 145         } else {
 146                 _cleanup_free_ char *cwd = NULL;
 147
 148                 r = safe_getcwd(&cwd);
 149                 if (r < 0)
 150                         return r;
 151
 152                 if (!path_startswith(cwd, "/dev"))
 153                         return 0;
 154         }
 155
 156         fd = open(path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 157         if (fd < 0) {
 158                 if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 159                         return 0;
 160
 161                 return -errno;
 162         }
 163
 164         if (fstat(fd, &st) < 0)
 165                 return -errno;
 166
 167         /*
 168          * Label directories and character devices "*".
 169          * Label symlinks "_".
 170          * Don't change anything else.
 171          */
 172
 173         if (S_ISDIR(st.st_mode))
 174                 label = SMACK_STAR_LABEL;
 175         else if (S_ISLNK(st.st_mode))
 176                 label = SMACK_FLOOR_LABEL;
 177         else if (S_ISCHR(st.st_mode))
 178                 label = SMACK_STAR_LABEL;
 179         else
 180                 return 0;
 181
 182         xsprintf(procfs_path, "/proc/self/fd/%i", fd);
 183         if (setxattr(procfs_path, "security.SMACK64", label, strlen(label), 0) < 0) {
 184                 _cleanup_free_ char *old_label = NULL;
 185
 186                 r = -errno;
 187
 188                 /* If the FS doesn't support labels, then exit without warning */
 189                 if (r == -EOPNOTSUPP)
 190                         return 0;
 191
 192                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 193                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 194                         return 0;
 195
 196                 /* If the old label is identical to the new one, suppress any kind of error */
 197                 if (getxattr_malloc(procfs_path, "security.SMACK64", &old_label, false) >= 0 &&
 198                     streq(old_label, label))
 199                         return 0;
 200
 201                 return log_debug_errno(r, "Unable to fix SMACK label of %s: %m", path);
 202         }
 203
 204         return 0;
 205 }
 206
 207 int mac_smack_copy(const char *dest, const char *src) {
 208         int r = 0;
 209         _cleanup_free_ char *label = NULL;
 210
 211         assert(dest);
 212         assert(src);
 213
 214         r = mac_smack_read(src, SMACK_ATTR_ACCESS, &label);
 215         if (r < 0)
 216                 return r;
 217
 218         r = mac_smack_apply(dest, SMACK_ATTR_ACCESS, label);
 219         if (r < 0)
 220                 return r;
 221
 222         return r;
 223 }
 224
 225 #else
 226 bool mac_smack_use(void) {
 227         return false;
 228 }
 229
 230 int mac_smack_read(const char *path, SmackAttr attr, char **label) {
 231         return -EOPNOTSUPP;
 232 }
 233
 234 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
 235         return -EOPNOTSUPP;
 236 }
 237
 238 int mac_smack_apply(const char *path, SmackAttr attr, const char *label) {
 239         return 0;
 240 }
 241
 242 int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
 243         return 0;
 244 }
 245
 246 int mac_smack_apply_pid(pid_t pid, const char *label) {
 247         return 0;
 248 }
 249
 250 int mac_smack_fix(const char *path, LabelFixFlags flags) {
 251         return 0;
 252 }
 253
 254 int mac_smack_copy(const char *dest, const char *src) {
 255         return 0;
 256 }
 257 #endif