1 // SPDX-License-Identifier: GPL-2.0 2 /* 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 14 struct tty_audit_buf { 15 struct mutex mutex; /* Protects all data below */ 16 dev_t dev; /* The TTY which the data is from */ 17 unsigned icanon:1; 18 size_t valid; 19 unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */ 20 }; 21 22 static struct tty_audit_buf *tty_audit_buf_ref(void) 23 { 24 struct tty_audit_buf *buf; 25 26 buf = current->signal->tty_audit_buf; 27 WARN_ON(buf == ERR_PTR(-ESRCH)); 28 return buf; 29 } 30 31 static struct tty_audit_buf *tty_audit_buf_alloc(void) 32 { 33 struct tty_audit_buf *buf; 34 35 buf = kmalloc(sizeof(*buf), GFP_KERNEL); 36 if (!buf) 37 goto err; 38 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL); 39 if (!buf->data) 40 goto err_buf; 41 mutex_init(&buf->mutex); 42 buf->dev = MKDEV(0, 0); 43 buf->icanon = 0; 44 buf->valid = 0; 45 return buf; 46 47 err_buf: 48 kfree(buf); 49 err: 50 return NULL; 51 } 52 53 static void tty_audit_buf_free(struct tty_audit_buf *buf) 54 { 55 WARN_ON(buf->valid != 0); 56 kfree(buf->data); 57 kfree(buf); 58 } 59 60 static void tty_audit_log(const char *description, dev_t dev, 61 unsigned char *data, size_t size) 62 { 63 struct audit_buffer *ab; 64 pid_t pid = task_pid_nr(current); 65 uid_t uid = from_kuid(&init_user_ns, task_uid(current)); 66 uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current)); 67 unsigned int sessionid = audit_get_sessionid(current); 68 69 ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY); 70 if (ab) { 71 char name[sizeof(current->comm)]; 72 73 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d" 74 " minor=%d comm=", description, pid, uid, 75 loginuid, sessionid, MAJOR(dev), MINOR(dev)); 76 get_task_comm(name, current); 77 audit_log_untrustedstring(ab, name); 78 audit_log_format(ab, " data="); 79 audit_log_n_hex(ab, data, size); 80 audit_log_end(ab); 81 } 82 } 83 84 /* 85 * tty_audit_buf_push - Push buffered data out 86 * 87 * Generate an audit message from the contents of @buf, which is owned by 88 * the current task. @buf->mutex must be locked. 89 */ 90 static void tty_audit_buf_push(struct tty_audit_buf *buf) 91 { 92 if (buf->valid == 0) 93 return; 94 if (audit_enabled == AUDIT_OFF) { 95 buf->valid = 0; 96 return; 97 } 98 tty_audit_log("tty", buf->dev, buf->data, buf->valid); 99 buf->valid = 0; 100 } 101 102 /** 103 * tty_audit_exit - Handle a task exit 104 * 105 * Make sure all buffered data is written out and deallocate the buffer. 106 * Only needs to be called if current->signal->tty_audit_buf != %NULL. 107 * 108 * The process is single-threaded at this point; no other threads share 109 * current->signal. 110 */ 111 void tty_audit_exit(void) 112 { 113 struct tty_audit_buf *buf; 114 115 buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH)); 116 if (!buf) 117 return; 118 119 tty_audit_buf_push(buf); 120 tty_audit_buf_free(buf); 121 } 122 123 /* 124 * tty_audit_fork - Copy TTY audit state for a new task 125 * 126 * Set up TTY audit state in @sig from current. @sig needs no locking. 127 */ 128 void tty_audit_fork(struct signal_struct *sig) 129 { 130 sig->audit_tty = current->signal->audit_tty; 131 } 132 133 /* 134 * tty_audit_tiocsti - Log TIOCSTI 135 */ 136 void tty_audit_tiocsti(struct tty_struct *tty, char ch) 137 { 138 dev_t dev; 139 140 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index; 141 if (tty_audit_push()) 142 return; 143 144 if (audit_enabled) 145 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1); 146 } 147 148 /* 149 * tty_audit_push - Flush current's pending audit data 150 * 151 * Returns 0 if success, -EPERM if tty audit is disabled 152 */ 153 int tty_audit_push(void) 154 { 155 struct tty_audit_buf *buf; 156 157 if (~current->signal->audit_tty & AUDIT_TTY_ENABLE) 158 return -EPERM; 159 160 buf = tty_audit_buf_ref(); 161 if (!IS_ERR_OR_NULL(buf)) { 162 mutex_lock(&buf->mutex); 163 tty_audit_buf_push(buf); 164 mutex_unlock(&buf->mutex); 165 } 166 return 0; 167 } 168 169 /* 170 * tty_audit_buf_get - Get an audit buffer. 171 * 172 * Get an audit buffer, allocate it if necessary. Return %NULL 173 * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already 174 * occurred. Otherwise, return a new reference to the buffer. 175 */ 176 static struct tty_audit_buf *tty_audit_buf_get(void) 177 { 178 struct tty_audit_buf *buf; 179 180 buf = tty_audit_buf_ref(); 181 if (buf) 182 return buf; 183 184 buf = tty_audit_buf_alloc(); 185 if (buf == NULL) { 186 audit_log_lost("out of memory in TTY auditing"); 187 return NULL; 188 } 189 190 /* Race to use this buffer, free it if another wins */ 191 if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL) 192 tty_audit_buf_free(buf); 193 return tty_audit_buf_ref(); 194 } 195 196 /* 197 * tty_audit_add_data - Add data for TTY auditing. 198 * 199 * Audit @data of @size from @tty, if necessary. 200 */ 201 void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size) 202 { 203 struct tty_audit_buf *buf; 204 unsigned int icanon = !!L_ICANON(tty); 205 unsigned int audit_tty; 206 dev_t dev; 207 208 audit_tty = READ_ONCE(current->signal->audit_tty); 209 if (~audit_tty & AUDIT_TTY_ENABLE) 210 return; 211 212 if (unlikely(size == 0)) 213 return; 214 215 if (tty->driver->type == TTY_DRIVER_TYPE_PTY 216 && tty->driver->subtype == PTY_TYPE_MASTER) 217 return; 218 219 if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty)) 220 return; 221 222 buf = tty_audit_buf_get(); 223 if (IS_ERR_OR_NULL(buf)) 224 return; 225 226 mutex_lock(&buf->mutex); 227 dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index; 228 if (buf->dev != dev || buf->icanon != icanon) { 229 tty_audit_buf_push(buf); 230 buf->dev = dev; 231 buf->icanon = icanon; 232 } 233 do { 234 size_t run; 235 236 run = N_TTY_BUF_SIZE - buf->valid; 237 if (run > size) 238 run = size; 239 memcpy(buf->data + buf->valid, data, run); 240 buf->valid += run; 241 data += run; 242 size -= run; 243 if (buf->valid == N_TTY_BUF_SIZE) 244 tty_audit_buf_push(buf); 245 } while (size != 0); 246 mutex_unlock(&buf->mutex); 247 } 248