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1// SPDX-License-Identifier: GPL-2.02/*3 * Creating audit events from TTY input.4 *5 * Copyright (C) 2007 Red Hat, Inc. All rights reserved.6 *7 * Authors: Miloslav Trmac <mitr@redhat.com>8 */9 10#include <linux/audit.h>11#include <linux/slab.h>12#include <linux/tty.h>13#include "tty.h"14 15struct tty_audit_buf {16 struct mutex mutex; /* Protects all data below */17 dev_t dev; /* The TTY which the data is from */18 bool icanon;19 size_t valid;20 u8 *data; /* Allocated size N_TTY_BUF_SIZE */21};22 23static struct tty_audit_buf *tty_audit_buf_ref(void)24{25 struct tty_audit_buf *buf;26 27 buf = current->signal->tty_audit_buf;28 WARN_ON(buf == ERR_PTR(-ESRCH));29 return buf;30}31 32static struct tty_audit_buf *tty_audit_buf_alloc(void)33{34 struct tty_audit_buf *buf;35 36 buf = kzalloc(sizeof(*buf), GFP_KERNEL);37 if (!buf)38 goto err;39 40 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);41 if (!buf->data)42 goto err_buf;43 44 mutex_init(&buf->mutex);45 46 return buf;47 48err_buf:49 kfree(buf);50err:51 return NULL;52}53 54static void tty_audit_buf_free(struct tty_audit_buf *buf)55{56 WARN_ON(buf->valid != 0);57 kfree(buf->data);58 kfree(buf);59}60 61static void tty_audit_log(const char *description, dev_t dev,62 const u8 *data, size_t size)63{64 struct audit_buffer *ab;65 pid_t pid = task_pid_nr(current);66 uid_t uid = from_kuid(&init_user_ns, task_uid(current));67 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));68 unsigned int sessionid = audit_get_sessionid(current);69 char name[TASK_COMM_LEN];70 71 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);72 if (!ab)73 return;74 75 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d minor=%d comm=",76 description, pid, uid, loginuid, sessionid,77 MAJOR(dev), MINOR(dev));78 get_task_comm(name, current);79 audit_log_untrustedstring(ab, name);80 audit_log_format(ab, " data=");81 audit_log_n_hex(ab, data, size);82 audit_log_end(ab);83}84 85/*86 * tty_audit_buf_push - Push buffered data out87 *88 * Generate an audit message from the contents of @buf, which is owned by89 * the current task. @buf->mutex must be locked.90 */91static void tty_audit_buf_push(struct tty_audit_buf *buf)92{93 if (buf->valid == 0)94 return;95 if (audit_enabled == AUDIT_OFF) {96 buf->valid = 0;97 return;98 }99 tty_audit_log("tty", buf->dev, buf->data, buf->valid);100 buf->valid = 0;101}102 103/**104 * tty_audit_exit - Handle a task exit105 *106 * Make sure all buffered data is written out and deallocate the buffer.107 * Only needs to be called if current->signal->tty_audit_buf != %NULL.108 *109 * The process is single-threaded at this point; no other threads share110 * current->signal.111 */112void tty_audit_exit(void)113{114 struct tty_audit_buf *buf;115 116 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH));117 if (!buf)118 return;119 120 tty_audit_buf_push(buf);121 tty_audit_buf_free(buf);122}123 124/*125 * tty_audit_fork - Copy TTY audit state for a new task126 *127 * Set up TTY audit state in @sig from current. @sig needs no locking.128 */129void tty_audit_fork(struct signal_struct *sig)130{131 sig->audit_tty = current->signal->audit_tty;132}133 134/*135 * tty_audit_tiocsti - Log TIOCSTI136 */137void tty_audit_tiocsti(const struct tty_struct *tty, u8 ch)138{139 dev_t dev;140 141 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;142 if (tty_audit_push())143 return;144 145 if (audit_enabled)146 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);147}148 149/*150 * tty_audit_push - Flush current's pending audit data151 *152 * Returns 0 if success, -EPERM if tty audit is disabled153 */154int tty_audit_push(void)155{156 struct tty_audit_buf *buf;157 158 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)159 return -EPERM;160 161 buf = tty_audit_buf_ref();162 if (!IS_ERR_OR_NULL(buf)) {163 mutex_lock(&buf->mutex);164 tty_audit_buf_push(buf);165 mutex_unlock(&buf->mutex);166 }167 return 0;168}169 170/*171 * tty_audit_buf_get - Get an audit buffer.172 *173 * Get an audit buffer, allocate it if necessary. Return %NULL174 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already175 * occurred. Otherwise, return a new reference to the buffer.176 */177static struct tty_audit_buf *tty_audit_buf_get(void)178{179 struct tty_audit_buf *buf;180 181 buf = tty_audit_buf_ref();182 if (buf)183 return buf;184 185 buf = tty_audit_buf_alloc();186 if (buf == NULL) {187 audit_log_lost("out of memory in TTY auditing");188 return NULL;189 }190 191 /* Race to use this buffer, free it if another wins */192 if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL)193 tty_audit_buf_free(buf);194 return tty_audit_buf_ref();195}196 197/*198 * tty_audit_add_data - Add data for TTY auditing.199 *200 * Audit @data of @size from @tty, if necessary.201 */202void tty_audit_add_data(const struct tty_struct *tty, const void *data,203 size_t size)204{205 struct tty_audit_buf *buf;206 unsigned int audit_tty;207 bool icanon = L_ICANON(tty);208 dev_t dev;209 210 audit_tty = READ_ONCE(current->signal->audit_tty);211 if (~audit_tty & AUDIT_TTY_ENABLE)212 return;213 214 if (unlikely(size == 0))215 return;216 217 if (tty->driver->type == TTY_DRIVER_TYPE_PTY218 && tty->driver->subtype == PTY_TYPE_MASTER)219 return;220 221 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))222 return;223 224 buf = tty_audit_buf_get();225 if (IS_ERR_OR_NULL(buf))226 return;227 228 mutex_lock(&buf->mutex);229 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;230 if (buf->dev != dev || buf->icanon != icanon) {231 tty_audit_buf_push(buf);232 buf->dev = dev;233 buf->icanon = icanon;234 }235 do {236 size_t run;237 238 run = N_TTY_BUF_SIZE - buf->valid;239 if (run > size)240 run = size;241 memcpy(buf->data + buf->valid, data, run);242 buf->valid += run;243 data += run;244 size -= run;245 if (buf->valid == N_TTY_BUF_SIZE)246 tty_audit_buf_push(buf);247 } while (size != 0);248 mutex_unlock(&buf->mutex);249}250