kernel/capability.c

   1 /*
   2  * linux/kernel/capability.c
   3  *
   4  * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
   5  *
   6  * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@kernel.org>
   7  * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/audit.h>
  13 #include <linux/capability.h>
  14 #include <linux/mm.h>
  15 #include <linux/export.h>
  16 #include <linux/security.h>
  17 #include <linux/syscalls.h>
  18 #include <linux/pid_namespace.h>
  19 #include <linux/user_namespace.h>
  20 #include <asm/uaccess.h>
  21
  22 #ifdef CONFIG_LOD_SEC
  23 #include <linux/linux_on_dex.h>
  24 #endif
  25
  26 /*
  27  * Leveraged for setting/resetting capabilities
  28  */
  29
  30 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
  31 EXPORT_SYMBOL(__cap_empty_set);
  32
  33 int file_caps_enabled = 1;
  34
  35 static int __init file_caps_disable(char *str)
  36 {
  37         file_caps_enabled = 0;
  38         return 1;
  39 }
  40 __setup("no_file_caps", file_caps_disable);
  41
  42 #ifdef CONFIG_MULTIUSER
  43 /*
  44  * More recent versions of libcap are available from:
  45  *
  46  *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
  47  */
  48
  49 static void warn_legacy_capability_use(void)
  50 {
  51         char name[sizeof(current->comm)];
  52
  53         pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
  54                      get_task_comm(name, current));
  55 }
  56
  57 /*
  58  * Version 2 capabilities worked fine, but the linux/capability.h file
  59  * that accompanied their introduction encouraged their use without
  60  * the necessary user-space source code changes. As such, we have
  61  * created a version 3 with equivalent functionality to version 2, but
  62  * with a header change to protect legacy source code from using
  63  * version 2 when it wanted to use version 1. If your system has code
  64  * that trips the following warning, it is using version 2 specific
  65  * capabilities and may be doing so insecurely.
  66  *
  67  * The remedy is to either upgrade your version of libcap (to 2.10+,
  68  * if the application is linked against it), or recompile your
  69  * application with modern kernel headers and this warning will go
  70  * away.
  71  */
  72
  73 static void warn_deprecated_v2(void)
  74 {
  75         char name[sizeof(current->comm)];
  76
  77         pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
  78                      get_task_comm(name, current));
  79 }
  80
  81 /*
  82  * Version check. Return the number of u32s in each capability flag
  83  * array, or a negative value on error.
  84  */
  85 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
  86 {
  87         __u32 version;
  88
  89         if (get_user(version, &header->version))
  90                 return -EFAULT;
  91
  92         switch (version) {
  93         case _LINUX_CAPABILITY_VERSION_1:
  94                 warn_legacy_capability_use();
  95                 *tocopy = _LINUX_CAPABILITY_U32S_1;
  96                 break;
  97         case _LINUX_CAPABILITY_VERSION_2:
  98                 warn_deprecated_v2();
  99                 /*
 100                  * fall through - v3 is otherwise equivalent to v2.
 101                  */
 102         case _LINUX_CAPABILITY_VERSION_3:
 103                 *tocopy = _LINUX_CAPABILITY_U32S_3;
 104                 break;
 105         default:
 106                 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
 107                         return -EFAULT;
 108                 return -EINVAL;
 109         }
 110
 111         return 0;
 112 }
 113
 114 /*
 115  * The only thing that can change the capabilities of the current
 116  * process is the current process. As such, we can't be in this code
 117  * at the same time as we are in the process of setting capabilities
 118  * in this process. The net result is that we can limit our use of
 119  * locks to when we are reading the caps of another process.
 120  */
 121 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
 122                                      kernel_cap_t *pIp, kernel_cap_t *pPp)
 123 {
 124         int ret;
 125
 126         if (pid && (pid != task_pid_vnr(current))) {
 127                 struct task_struct *target;
 128
 129                 rcu_read_lock();
 130
 131                 target = find_task_by_vpid(pid);
 132                 if (!target)
 133                         ret = -ESRCH;
 134                 else
 135                         ret = security_capget(target, pEp, pIp, pPp);
 136
 137                 rcu_read_unlock();
 138         } else
 139                 ret = security_capget(current, pEp, pIp, pPp);
 140
 141         return ret;
 142 }
 143
 144 /**
 145  * sys_capget - get the capabilities of a given process.
 146  * @header: pointer to struct that contains capability version and
 147  *      target pid data
 148  * @dataptr: pointer to struct that contains the effective, permitted,
 149  *      and inheritable capabilities that are returned
 150  *
 151  * Returns 0 on success and < 0 on error.
 152  */
 153 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
 154 {
 155         int ret = 0;
 156         pid_t pid;
 157         unsigned tocopy;
 158         kernel_cap_t pE, pI, pP;
 159
 160         ret = cap_validate_magic(header, &tocopy);
 161         if ((dataptr == NULL) || (ret != 0))
 162                 return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
 163
 164         if (get_user(pid, &header->pid))
 165                 return -EFAULT;
 166
 167         if (pid < 0)
 168                 return -EINVAL;
 169
 170         ret = cap_get_target_pid(pid, &pE, &pI, &pP);
 171         if (!ret) {
 172                 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 173                 unsigned i;
 174
 175                 for (i = 0; i < tocopy; i++) {
 176                         kdata[i].effective = pE.cap[i];
 177                         kdata[i].permitted = pP.cap[i];
 178                         kdata[i].inheritable = pI.cap[i];
 179                 }
 180
 181                 /*
 182                  * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
 183                  * we silently drop the upper capabilities here. This
 184                  * has the effect of making older libcap
 185                  * implementations implicitly drop upper capability
 186                  * bits when they perform a: capget/modify/capset
 187                  * sequence.
 188                  *
 189                  * This behavior is considered fail-safe
 190                  * behavior. Upgrading the application to a newer
 191                  * version of libcap will enable access to the newer
 192                  * capabilities.
 193                  *
 194                  * An alternative would be to return an error here
 195                  * (-ERANGE), but that causes legacy applications to
 196                  * unexpectedly fail; the capget/modify/capset aborts
 197                  * before modification is attempted and the application
 198                  * fails.
 199                  */
 200                 if (copy_to_user(dataptr, kdata, tocopy
 201                                  * sizeof(struct __user_cap_data_struct))) {
 202                         return -EFAULT;
 203                 }
 204         }
 205
 206         return ret;
 207 }
 208
 209 /**
 210  * sys_capset - set capabilities for a process or (*) a group of processes
 211  * @header: pointer to struct that contains capability version and
 212  *      target pid data
 213  * @data: pointer to struct that contains the effective, permitted,
 214  *      and inheritable capabilities
 215  *
 216  * Set capabilities for the current process only.  The ability to any other
 217  * process(es) has been deprecated and removed.
 218  *
 219  * The restrictions on setting capabilities are specified as:
 220  *
 221  * I: any raised capabilities must be a subset of the old permitted
 222  * P: any raised capabilities must be a subset of the old permitted
 223  * E: must be set to a subset of new permitted
 224  *
 225  * Returns 0 on success and < 0 on error.
 226  */
 227 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
 228 {
 229         struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 230         unsigned i, tocopy, copybytes;
 231         kernel_cap_t inheritable, permitted, effective;
 232         struct cred *new;
 233         int ret;
 234         pid_t pid;
 235
 236         ret = cap_validate_magic(header, &tocopy);
 237         if (ret != 0)
 238                 return ret;
 239
 240         if (get_user(pid, &header->pid))
 241                 return -EFAULT;
 242
 243         /* may only affect current now */
 244         if (pid != 0 && pid != task_pid_vnr(current))
 245                 return -EPERM;
 246
 247         copybytes = tocopy * sizeof(struct __user_cap_data_struct);
 248         if (copybytes > sizeof(kdata))
 249                 return -EFAULT;
 250
 251         if (copy_from_user(&kdata, data, copybytes))
 252                 return -EFAULT;
 253
 254         for (i = 0; i < tocopy; i++) {
 255                 effective.cap[i] = kdata[i].effective;
 256                 permitted.cap[i] = kdata[i].permitted;
 257                 inheritable.cap[i] = kdata[i].inheritable;
 258         }
 259         while (i < _KERNEL_CAPABILITY_U32S) {
 260                 effective.cap[i] = 0;
 261                 permitted.cap[i] = 0;
 262                 inheritable.cap[i] = 0;
 263                 i++;
 264         }
 265
 266         effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 267         permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 268         inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
 269
 270         new = prepare_creds();
 271         if (!new)
 272                 return -ENOMEM;
 273
 274         ret = security_capset(new, current_cred(),
 275                               &effective, &inheritable, &permitted);
 276         if (ret < 0)
 277                 goto error;
 278
 279         audit_log_capset(new, current_cred());
 280
 281         return commit_creds(new);
 282
 283 error:
 284         abort_creds(new);
 285         return ret;
 286 }
 287
 288 /**
 289  * has_ns_capability - Does a task have a capability in a specific user ns
 290  * @t: The task in question
 291  * @ns: target user namespace
 292  * @cap: The capability to be tested for
 293  *
 294  * Return true if the specified task has the given superior capability
 295  * currently in effect to the specified user namespace, false if not.
 296  *
 297  * Note that this does not set PF_SUPERPRIV on the task.
 298  */
 299 bool has_ns_capability(struct task_struct *t,
 300                        struct user_namespace *ns, int cap)
 301 {
 302         int ret;
 303
 304         rcu_read_lock();
 305         ret = security_capable(__task_cred(t), ns, cap);
 306         rcu_read_unlock();
 307
 308         return (ret == 0);
 309 }
 310
 311 /**
 312  * has_capability - Does a task have a capability in init_user_ns
 313  * @t: The task in question
 314  * @cap: The capability to be tested for
 315  *
 316  * Return true if the specified task has the given superior capability
 317  * currently in effect to the initial user namespace, false if not.
 318  *
 319  * Note that this does not set PF_SUPERPRIV on the task.
 320  */
 321 bool has_capability(struct task_struct *t, int cap)
 322 {
 323         return has_ns_capability(t, &init_user_ns, cap);
 324 }
 325
 326 /**
 327  * has_ns_capability_noaudit - Does a task have a capability (unaudited)
 328  * in a specific user ns.
 329  * @t: The task in question
 330  * @ns: target user namespace
 331  * @cap: The capability to be tested for
 332  *
 333  * Return true if the specified task has the given superior capability
 334  * currently in effect to the specified user namespace, false if not.
 335  * Do not write an audit message for the check.
 336  *
 337  * Note that this does not set PF_SUPERPRIV on the task.
 338  */
 339 bool has_ns_capability_noaudit(struct task_struct *t,
 340                                struct user_namespace *ns, int cap)
 341 {
 342         int ret;
 343
 344         rcu_read_lock();
 345         ret = security_capable_noaudit(__task_cred(t), ns, cap);
 346         rcu_read_unlock();
 347
 348         return (ret == 0);
 349 }
 350
 351 /**
 352  * has_capability_noaudit - Does a task have a capability (unaudited) in the
 353  * initial user ns
 354  * @t: The task in question
 355  * @cap: The capability to be tested for
 356  *
 357  * Return true if the specified task has the given superior capability
 358  * currently in effect to init_user_ns, false if not.  Don't write an
 359  * audit message for the check.
 360  *
 361  * Note that this does not set PF_SUPERPRIV on the task.
 362  */
 363 bool has_capability_noaudit(struct task_struct *t, int cap)
 364 {
 365         return has_ns_capability_noaudit(t, &init_user_ns, cap);
 366 }
 367
 368 static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
 369 {
 370         int capable;
 371
 372         if (unlikely(!cap_valid(cap))) {
 373                 pr_crit("capable() called with invalid cap=%u\n", cap);
 374                 BUG();
 375         }
 376
 377         capable = audit ? security_capable(current_cred(), ns, cap) :
 378                           security_capable_noaudit(current_cred(), ns, cap);
 379         if (capable == 0) {
 380                 current->flags |= PF_SUPERPRIV;
 381                 return true;
 382         }
 383         return false;
 384 }
 385
 386 /**
 387  * ns_capable - Determine if the current task has a superior capability in effect
 388  * @ns:  The usernamespace we want the capability in
 389  * @cap: The capability to be tested for
 390  *
 391  * Return true if the current task has the given superior capability currently
 392  * available for use, false if not.
 393  *
 394  * This sets PF_SUPERPRIV on the task if the capability is available on the
 395  * assumption that it's about to be used.
 396  */
 397 bool ns_capable(struct user_namespace *ns, int cap)
 398 {
 399         return ns_capable_common(ns, cap, true);
 400 }
 401 EXPORT_SYMBOL(ns_capable);
 402
 403 /**
 404  * ns_capable_noaudit - Determine if the current task has a superior capability
 405  * (unaudited) in effect
 406  * @ns:  The usernamespace we want the capability in
 407  * @cap: The capability to be tested for
 408  *
 409  * Return true if the current task has the given superior capability currently
 410  * available for use, false if not.
 411  *
 412  * This sets PF_SUPERPRIV on the task if the capability is available on the
 413  * assumption that it's about to be used.
 414  */
 415 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
 416 {
 417         return ns_capable_common(ns, cap, false);
 418 }
 419 EXPORT_SYMBOL(ns_capable_noaudit);
 420
 421 /**
 422  * capable - Determine if the current task has a superior capability in effect
 423  * @cap: The capability to be tested for
 424  *
 425  * Return true if the current task has the given superior capability currently
 426  * available for use, false if not.
 427  *
 428  * This sets PF_SUPERPRIV on the task if the capability is available on the
 429  * assumption that it's about to be used.
 430  */
 431 bool capable(int cap)
 432 {
 433         return ns_capable(&init_user_ns, cap);
 434 }
 435 EXPORT_SYMBOL(capable);
 436 #endif /* CONFIG_MULTIUSER */
 437
 438 /**
 439  * file_ns_capable - Determine if the file's opener had a capability in effect
 440  * @file:  The file we want to check
 441  * @ns:  The usernamespace we want the capability in
 442  * @cap: The capability to be tested for
 443  *
 444  * Return true if task that opened the file had a capability in effect
 445  * when the file was opened.
 446  *
 447  * This does not set PF_SUPERPRIV because the caller may not
 448  * actually be privileged.
 449  */
 450 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
 451                      int cap)
 452 {
 453         if (WARN_ON_ONCE(!cap_valid(cap)))
 454                 return false;
 455
 456         if (security_capable(file->f_cred, ns, cap) == 0)
 457                 return true;
 458
 459         return false;
 460 }
 461 EXPORT_SYMBOL(file_ns_capable);
 462
 463 /**
 464  * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode?
 465  * @ns: The user namespace in question
 466  * @inode: The inode in question
 467  *
 468  * Return true if the inode uid and gid are within the namespace.
 469  */
 470 bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode)
 471 {
 472         return kuid_has_mapping(ns, inode->i_uid) &&
 473                 kgid_has_mapping(ns, inode->i_gid);
 474 }
 475
 476 /**
 477  * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped
 478  * @inode: The inode in question
 479  * @cap: The capability in question
 480  *
 481  * Return true if the current task has the given capability targeted at
 482  * its own user namespace and that the given inode's uid and gid are
 483  * mapped into the current user namespace.
 484  */
 485 bool capable_wrt_inode_uidgid(const struct inode *inode, int cap)
 486 {
 487         struct user_namespace *ns = current_user_ns();
 488
 489         //Never allow LOD container process access outside inodes
 490 #ifdef CONFIG_LOD_SEC
 491         if (current_is_LOD() && (!inode_is_LOD(inode))){
 492 #ifndef CONFIG_SAMSUNG_PRODUCT_SHIP
 493                 printk(KERN_ERR "LOD capable_wrt_inode_uidgid: blocking CAP %d of PROC %s "
 494                         "PID %d PROC_UID %d INODE_UID %d\n", cap, current->comm, current->pid,
 495                         current_cred()->uid.val, inode->i_uid.val);
 496 #endif
 497                 return false;
 498         }
 499 #endif
 500
 501         return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode);
 502 }
 503 EXPORT_SYMBOL(capable_wrt_inode_uidgid);
 504
 505 /**
 506  * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace
 507  * @tsk: The task that may be ptraced
 508  * @ns: The user namespace to search for CAP_SYS_PTRACE in
 509  *
 510  * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE
 511  * in the specified user namespace.
 512  */
 513 bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
 514 {
 515         int ret = 0;  /* An absent tracer adds no restrictions */
 516         const struct cred *cred;
 517         rcu_read_lock();
 518         cred = rcu_dereference(tsk->ptracer_cred);
 519         if (cred)
 520                 ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
 521         rcu_read_unlock();
 522         return (ret == 0);
 523 }