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, 0);
 119         if (r < 0)
 120                 return r;
 121
 122         return r;
 123 }
 124
 125 int mac_smack_fix(const char *path, LabelFixFlags flags) {
 126         char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
 127         _cleanup_close_ int fd = -1;
 128         const char *label;
 129         struct stat st;
 130         int r;
 131
 132         assert(path);
 133
 134         if (!mac_smack_use())
 135                 return 0;
 136
 137         /* Path must be in /dev. Note that this check is pretty sloppy, as we might be called with non-normalized paths
 138          * and hence not detect all cases of /dev. */
 139
 140         if (path_is_absolute(path)) {
 141                 if (!path_startswith(path, "/dev"))
 142                         return 0;
 143         } else {
 144                 _cleanup_free_ char *cwd = NULL;
 145
 146                 r = safe_getcwd(&cwd);
 147                 if (r < 0)
 148                         return r;
 149
 150                 if (!path_startswith(cwd, "/dev"))
 151                         return 0;
 152         }
 153
 154         fd = open(path, O_NOFOLLOW|O_CLOEXEC|O_PATH);
 155         if (fd < 0) {
 156                 if ((flags & LABEL_IGNORE_ENOENT) && errno == ENOENT)
 157                         return 0;
 158
 159                 return -errno;
 160         }
 161
 162         if (fstat(fd, &st) < 0)
 163                 return -errno;
 164
 165         /*
 166          * Label directories and character devices "*".
 167          * Label symlinks "_".
 168          * Don't change anything else.
 169          */
 170
 171         if (S_ISDIR(st.st_mode))
 172                 label = SMACK_STAR_LABEL;
 173         else if (S_ISLNK(st.st_mode))
 174                 label = SMACK_FLOOR_LABEL;
 175         else if (S_ISCHR(st.st_mode))
 176                 label = SMACK_STAR_LABEL;
 177         else
 178                 return 0;
 179
 180         xsprintf(procfs_path, "/proc/self/fd/%i", fd);
 181         if (setxattr(procfs_path, "security.SMACK64", label, strlen(label), 0) < 0) {
 182                 _cleanup_free_ char *old_label = NULL;
 183
 184                 r = -errno;
 185
 186                 /* If the FS doesn't support labels, then exit without warning */
 187                 if (r == -EOPNOTSUPP)
 188                         return 0;
 189
 190                 /* It the FS is read-only and we were told to ignore failures caused by that, suppress error */
 191                 if (r == -EROFS && (flags & LABEL_IGNORE_EROFS))
 192                         return 0;
 193
 194                 /* If the old label is identical to the new one, suppress any kind of error */
 195                 if (getxattr_malloc(procfs_path, "security.SMACK64", &old_label, false) >= 0 &&
 196                     streq(old_label, label))
 197                         return 0;
 198
 199                 return log_debug_errno(r, "Unable to fix SMACK label of %s: %m", path);
 200         }
 201
 202         return 0;
 203 }
 204
 205 int mac_smack_copy(const char *dest, const char *src) {
 206         int r = 0;
 207         _cleanup_free_ char *label = NULL;
 208
 209         assert(dest);
 210         assert(src);
 211
 212         r = mac_smack_read(src, SMACK_ATTR_ACCESS, &label);
 213         if (r < 0)
 214                 return r;
 215
 216         r = mac_smack_apply(dest, SMACK_ATTR_ACCESS, label);
 217         if (r < 0)
 218                 return r;
 219
 220         return r;
 221 }
 222
 223 #else
 224 bool mac_smack_use(void) {
 225         return false;
 226 }
 227
 228 int mac_smack_read(const char *path, SmackAttr attr, char **label) {
 229         return -EOPNOTSUPP;
 230 }
 231
 232 int mac_smack_read_fd(int fd, SmackAttr attr, char **label) {
 233         return -EOPNOTSUPP;
 234 }
 235
 236 int mac_smack_apply(const char *path, SmackAttr attr, const char *label) {
 237         return 0;
 238 }
 239
 240 int mac_smack_apply_fd(int fd, SmackAttr attr, const char *label) {
 241         return 0;
 242 }
 243
 244 int mac_smack_apply_pid(pid_t pid, const char *label) {
 245         return 0;
 246 }
 247
 248 int mac_smack_fix(const char *path, LabelFixFlags flags) {
 249         return 0;
 250 }
 251
 252 int mac_smack_copy(const char *dest, const char *src) {
 253         return 0;
 254 }
 255 #endif