linux/kernel/capability.c
<<
>>
Prefs
   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#include <linux/audit.h>
  11#include <linux/capability.h>
  12#include <linux/mm.h>
  13#include <linux/export.h>
  14#include <linux/security.h>
  15#include <linux/syscalls.h>
  16#include <linux/pid_namespace.h>
  17#include <linux/user_namespace.h>
  18#include <asm/uaccess.h>
  19
  20/*
  21 * Leveraged for setting/resetting capabilities
  22 */
  23
  24const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
  25
  26EXPORT_SYMBOL(__cap_empty_set);
  27
  28int file_caps_enabled = 1;
  29
  30static int __init file_caps_disable(char *str)
  31{
  32        file_caps_enabled = 0;
  33        return 1;
  34}
  35__setup("no_file_caps", file_caps_disable);
  36
  37/*
  38 * More recent versions of libcap are available from:
  39 *
  40 *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
  41 */
  42
  43static void warn_legacy_capability_use(void)
  44{
  45        static int warned;
  46        if (!warned) {
  47                char name[sizeof(current->comm)];
  48
  49                printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
  50                       " (legacy support in use)\n",
  51                       get_task_comm(name, current));
  52                warned = 1;
  53        }
  54}
  55
  56/*
  57 * Version 2 capabilities worked fine, but the linux/capability.h file
  58 * that accompanied their introduction encouraged their use without
  59 * the necessary user-space source code changes. As such, we have
  60 * created a version 3 with equivalent functionality to version 2, but
  61 * with a header change to protect legacy source code from using
  62 * version 2 when it wanted to use version 1. If your system has code
  63 * that trips the following warning, it is using version 2 specific
  64 * capabilities and may be doing so insecurely.
  65 *
  66 * The remedy is to either upgrade your version of libcap (to 2.10+,
  67 * if the application is linked against it), or recompile your
  68 * application with modern kernel headers and this warning will go
  69 * away.
  70 */
  71
  72static void warn_deprecated_v2(void)
  73{
  74        static int warned;
  75
  76        if (!warned) {
  77                char name[sizeof(current->comm)];
  78
  79                printk(KERN_INFO "warning: `%s' uses deprecated v2"
  80                       " capabilities in a way that may be insecure.\n",
  81                       get_task_comm(name, current));
  82                warned = 1;
  83        }
  84}
  85
  86/*
  87 * Version check. Return the number of u32s in each capability flag
  88 * array, or a negative value on error.
  89 */
  90static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
  91{
  92        __u32 version;
  93
  94        if (get_user(version, &header->version))
  95                return -EFAULT;
  96
  97        switch (version) {
  98        case _LINUX_CAPABILITY_VERSION_1:
  99                warn_legacy_capability_use();
 100                *tocopy = _LINUX_CAPABILITY_U32S_1;
 101                break;
 102        case _LINUX_CAPABILITY_VERSION_2:
 103                warn_deprecated_v2();
 104                /*
 105                 * fall through - v3 is otherwise equivalent to v2.
 106                 */
 107        case _LINUX_CAPABILITY_VERSION_3:
 108                *tocopy = _LINUX_CAPABILITY_U32S_3;
 109                break;
 110        default:
 111                if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
 112                        return -EFAULT;
 113                return -EINVAL;
 114        }
 115
 116        return 0;
 117}
 118
 119/*
 120 * The only thing that can change the capabilities of the current
 121 * process is the current process. As such, we can't be in this code
 122 * at the same time as we are in the process of setting capabilities
 123 * in this process. The net result is that we can limit our use of
 124 * locks to when we are reading the caps of another process.
 125 */
 126static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
 127                                     kernel_cap_t *pIp, kernel_cap_t *pPp)
 128{
 129        int ret;
 130
 131        if (pid && (pid != task_pid_vnr(current))) {
 132                struct task_struct *target;
 133
 134                rcu_read_lock();
 135
 136                target = find_task_by_vpid(pid);
 137                if (!target)
 138                        ret = -ESRCH;
 139                else
 140                        ret = security_capget(target, pEp, pIp, pPp);
 141
 142                rcu_read_unlock();
 143        } else
 144                ret = security_capget(current, pEp, pIp, pPp);
 145
 146        return ret;
 147}
 148
 149/**
 150 * sys_capget - get the capabilities of a given process.
 151 * @header: pointer to struct that contains capability version and
 152 *      target pid data
 153 * @dataptr: pointer to struct that contains the effective, permitted,
 154 *      and inheritable capabilities that are returned
 155 *
 156 * Returns 0 on success and < 0 on error.
 157 */
 158SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
 159{
 160        int ret = 0;
 161        pid_t pid;
 162        unsigned tocopy;
 163        kernel_cap_t pE, pI, pP;
 164
 165        ret = cap_validate_magic(header, &tocopy);
 166        if ((dataptr == NULL) || (ret != 0))
 167                return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
 168
 169        if (get_user(pid, &header->pid))
 170                return -EFAULT;
 171
 172        if (pid < 0)
 173                return -EINVAL;
 174
 175        ret = cap_get_target_pid(pid, &pE, &pI, &pP);
 176        if (!ret) {
 177                struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 178                unsigned i;
 179
 180                for (i = 0; i < tocopy; i++) {
 181                        kdata[i].effective = pE.cap[i];
 182                        kdata[i].permitted = pP.cap[i];
 183                        kdata[i].inheritable = pI.cap[i];
 184                }
 185
 186                /*
 187                 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
 188                 * we silently drop the upper capabilities here. This
 189                 * has the effect of making older libcap
 190                 * implementations implicitly drop upper capability
 191                 * bits when they perform a: capget/modify/capset
 192                 * sequence.
 193                 *
 194                 * This behavior is considered fail-safe
 195                 * behavior. Upgrading the application to a newer
 196                 * version of libcap will enable access to the newer
 197                 * capabilities.
 198                 *
 199                 * An alternative would be to return an error here
 200                 * (-ERANGE), but that causes legacy applications to
 201                 * unexpectidly fail; the capget/modify/capset aborts
 202                 * before modification is attempted and the application
 203                 * fails.
 204                 */
 205                if (copy_to_user(dataptr, kdata, tocopy
 206                                 * sizeof(struct __user_cap_data_struct))) {
 207                        return -EFAULT;
 208                }
 209        }
 210
 211        return ret;
 212}
 213
 214/**
 215 * sys_capset - set capabilities for a process or (*) a group of processes
 216 * @header: pointer to struct that contains capability version and
 217 *      target pid data
 218 * @data: pointer to struct that contains the effective, permitted,
 219 *      and inheritable capabilities
 220 *
 221 * Set capabilities for the current process only.  The ability to any other
 222 * process(es) has been deprecated and removed.
 223 *
 224 * The restrictions on setting capabilities are specified as:
 225 *
 226 * I: any raised capabilities must be a subset of the old permitted
 227 * P: any raised capabilities must be a subset of the old permitted
 228 * E: must be set to a subset of new permitted
 229 *
 230 * Returns 0 on success and < 0 on error.
 231 */
 232SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
 233{
 234        struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 235        unsigned i, tocopy, copybytes;
 236        kernel_cap_t inheritable, permitted, effective;
 237        struct cred *new;
 238        int ret;
 239        pid_t pid;
 240
 241        ret = cap_validate_magic(header, &tocopy);
 242        if (ret != 0)
 243                return ret;
 244
 245        if (get_user(pid, &header->pid))
 246                return -EFAULT;
 247
 248        /* may only affect current now */
 249        if (pid != 0 && pid != task_pid_vnr(current))
 250                return -EPERM;
 251
 252        copybytes = tocopy * sizeof(struct __user_cap_data_struct);
 253        if (copybytes > sizeof(kdata))
 254                return -EFAULT;
 255
 256        if (copy_from_user(&kdata, data, copybytes))
 257                return -EFAULT;
 258
 259        for (i = 0; i < tocopy; i++) {
 260                effective.cap[i] = kdata[i].effective;
 261                permitted.cap[i] = kdata[i].permitted;
 262                inheritable.cap[i] = kdata[i].inheritable;
 263        }
 264        while (i < _KERNEL_CAPABILITY_U32S) {
 265                effective.cap[i] = 0;
 266                permitted.cap[i] = 0;
 267                inheritable.cap[i] = 0;
 268                i++;
 269        }
 270
 271        new = prepare_creds();
 272        if (!new)
 273                return -ENOMEM;
 274
 275        ret = security_capset(new, current_cred(),
 276                              &effective, &inheritable, &permitted);
 277        if (ret < 0)
 278                goto error;
 279
 280        audit_log_capset(pid, new, current_cred());
 281
 282        return commit_creds(new);
 283
 284error:
 285        abort_creds(new);
 286        return ret;
 287}
 288
 289/**
 290 * has_ns_capability - Does a task have a capability in a specific user ns
 291 * @t: The task in question
 292 * @ns: target user namespace
 293 * @cap: The capability to be tested for
 294 *
 295 * Return true if the specified task has the given superior capability
 296 * currently in effect to the specified user namespace, false if not.
 297 *
 298 * Note that this does not set PF_SUPERPRIV on the task.
 299 */
 300bool has_ns_capability(struct task_struct *t,
 301                       struct user_namespace *ns, int cap)
 302{
 303        int ret;
 304
 305        rcu_read_lock();
 306        ret = security_capable(__task_cred(t), ns, cap);
 307        rcu_read_unlock();
 308
 309        return (ret == 0);
 310}
 311
 312/**
 313 * has_capability - Does a task have a capability in init_user_ns
 314 * @t: The task in question
 315 * @cap: The capability to be tested for
 316 *
 317 * Return true if the specified task has the given superior capability
 318 * currently in effect to the initial user namespace, false if not.
 319 *
 320 * Note that this does not set PF_SUPERPRIV on the task.
 321 */
 322bool has_capability(struct task_struct *t, int cap)
 323{
 324        return has_ns_capability(t, &init_user_ns, cap);
 325}
 326
 327/**
 328 * has_ns_capability_noaudit - Does a task have a capability (unaudited)
 329 * in a specific user ns.
 330 * @t: The task in question
 331 * @ns: target user namespace
 332 * @cap: The capability to be tested for
 333 *
 334 * Return true if the specified task has the given superior capability
 335 * currently in effect to the specified user namespace, false if not.
 336 * Do not write an audit message for the check.
 337 *
 338 * Note that this does not set PF_SUPERPRIV on the task.
 339 */
 340bool has_ns_capability_noaudit(struct task_struct *t,
 341                               struct user_namespace *ns, int cap)
 342{
 343        int ret;
 344
 345        rcu_read_lock();
 346        ret = security_capable_noaudit(__task_cred(t), ns, cap);
 347        rcu_read_unlock();
 348
 349        return (ret == 0);
 350}
 351
 352/**
 353 * has_capability_noaudit - Does a task have a capability (unaudited) in the
 354 * initial user ns
 355 * @t: The task in question
 356 * @cap: The capability to be tested for
 357 *
 358 * Return true if the specified task has the given superior capability
 359 * currently in effect to init_user_ns, false if not.  Don't write an
 360 * audit message for the check.
 361 *
 362 * Note that this does not set PF_SUPERPRIV on the task.
 363 */
 364bool has_capability_noaudit(struct task_struct *t, int cap)
 365{
 366        return has_ns_capability_noaudit(t, &init_user_ns, cap);
 367}
 368
 369/**
 370 * ns_capable - Determine if the current task has a superior capability in effect
 371 * @ns:  The usernamespace we want the capability in
 372 * @cap: The capability to be tested for
 373 *
 374 * Return true if the current task has the given superior capability currently
 375 * available for use, false if not.
 376 *
 377 * This sets PF_SUPERPRIV on the task if the capability is available on the
 378 * assumption that it's about to be used.
 379 */
 380bool ns_capable(struct user_namespace *ns, int cap)
 381{
 382        if (unlikely(!cap_valid(cap))) {
 383                printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
 384                BUG();
 385        }
 386
 387        if (security_capable(current_cred(), ns, cap) == 0) {
 388                current->flags |= PF_SUPERPRIV;
 389                return true;
 390        }
 391        return false;
 392}
 393EXPORT_SYMBOL(ns_capable);
 394
 395/**
 396 * capable - Determine if the current task has a superior capability in effect
 397 * @cap: The capability to be tested for
 398 *
 399 * Return true if the current task has the given superior capability currently
 400 * available for use, false if not.
 401 *
 402 * This sets PF_SUPERPRIV on the task if the capability is available on the
 403 * assumption that it's about to be used.
 404 */
 405bool capable(int cap)
 406{
 407        return ns_capable(&init_user_ns, cap);
 408}
 409EXPORT_SYMBOL(capable);
 410
 411/**
 412 * nsown_capable - Check superior capability to one's own user_ns
 413 * @cap: The capability in question
 414 *
 415 * Return true if the current task has the given superior capability
 416 * targeted at its own user namespace.
 417 */
 418bool nsown_capable(int cap)
 419{
 420        return ns_capable(current_user_ns(), cap);
 421}
 422
 423/**
 424 * inode_capable - Check superior capability over inode
 425 * @inode: The inode in question
 426 * @cap: The capability in question
 427 *
 428 * Return true if the current task has the given superior capability
 429 * targeted at it's own user namespace and that the given inode is owned
 430 * by the current user namespace or a child namespace.
 431 *
 432 * Currently we check to see if an inode is owned by the current
 433 * user namespace by seeing if the inode's owner maps into the
 434 * current user namespace.
 435 *
 436 */
 437bool inode_capable(const struct inode *inode, int cap)
 438{
 439        struct user_namespace *ns = current_user_ns();
 440
 441        return ns_capable(ns, cap) && kuid_has_mapping(ns, inode->i_uid);
 442}
 443
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.