diff options
Diffstat (limited to 'drivers/tty/tty_audit.c')
| -rw-r--r-- | drivers/tty/tty_audit.c | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c new file mode 100644 index 000000000..9b30edee7 --- /dev/null +++ b/drivers/tty/tty_audit.c @@ -0,0 +1,248 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Creating audit events from TTY input. + * + * Copyright (C) 2007 Red Hat, Inc. All rights reserved. + * + * Authors: Miloslav Trmac <mitr@redhat.com> + */ + +#include <linux/audit.h> +#include <linux/slab.h> +#include <linux/tty.h> +#include "tty.h" + +struct tty_audit_buf { + struct mutex mutex; /* Protects all data below */ + dev_t dev; /* The TTY which the data is from */ + unsigned icanon:1; + size_t valid; + unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */ +}; + +static struct tty_audit_buf *tty_audit_buf_ref(void) +{ + struct tty_audit_buf *buf; + + buf = current->signal->tty_audit_buf; + WARN_ON(buf == ERR_PTR(-ESRCH)); + return buf; +} + +static struct tty_audit_buf *tty_audit_buf_alloc(void) +{ + struct tty_audit_buf *buf; + + buf = kmalloc(sizeof(*buf), GFP_KERNEL); + if (!buf) + goto err; + buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL); + if (!buf->data) + goto err_buf; + mutex_init(&buf->mutex); + buf->dev = MKDEV(0, 0); + buf->icanon = 0; + buf->valid = 0; + return buf; + +err_buf: + kfree(buf); +err: + return NULL; +} + +static void tty_audit_buf_free(struct tty_audit_buf *buf) +{ + WARN_ON(buf->valid != 0); + kfree(buf->data); + kfree(buf); +} + +static void tty_audit_log(const char *description, dev_t dev, + unsigned char *data, size_t size) +{ + struct audit_buffer *ab; + pid_t pid = task_pid_nr(current); + uid_t uid = from_kuid(&init_user_ns, task_uid(current)); + uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current)); + unsigned int sessionid = audit_get_sessionid(current); + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY); + if (ab) { + char name[sizeof(current->comm)]; + + audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d" + " minor=%d comm=", description, pid, uid, + loginuid, sessionid, MAJOR(dev), MINOR(dev)); + get_task_comm(name, current); + audit_log_untrustedstring(ab, name); + audit_log_format(ab, " data="); + audit_log_n_hex(ab, data, size); + audit_log_end(ab); + } +} + +/** + * tty_audit_buf_push - Push buffered data out + * + * Generate an audit message from the contents of @buf, which is owned by + * the current task. @buf->mutex must be locked. + */ +static void tty_audit_buf_push(struct tty_audit_buf *buf) +{ + if (buf->valid == 0) + return; + if (audit_enabled == AUDIT_OFF) { + buf->valid = 0; + return; + } + tty_audit_log("tty", buf->dev, buf->data, buf->valid); + buf->valid = 0; +} + +/** + * tty_audit_exit - Handle a task exit + * + * Make sure all buffered data is written out and deallocate the buffer. + * Only needs to be called if current->signal->tty_audit_buf != %NULL. + * + * The process is single-threaded at this point; no other threads share + * current->signal. + */ +void tty_audit_exit(void) +{ + struct tty_audit_buf *buf; + + buf = xchg(¤t->signal->tty_audit_buf, ERR_PTR(-ESRCH)); + if (!buf) + return; + + tty_audit_buf_push(buf); + tty_audit_buf_free(buf); +} + +/** + * tty_audit_fork - Copy TTY audit state for a new task + * + * Set up TTY audit state in @sig from current. @sig needs no locking. + */ +void tty_audit_fork(struct signal_struct *sig) +{ + sig->audit_tty = current->signal->audit_tty; +} + +/** + * tty_audit_tiocsti - Log TIOCSTI + */ +void tty_audit_tiocsti(struct tty_struct *tty, char ch) +{ + dev_t dev; + + dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index; + if (tty_audit_push()) + return; + + if (audit_enabled) + tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1); +} + +/** + * tty_audit_push - Flush current's pending audit data + * + * Returns 0 if success, -EPERM if tty audit is disabled + */ +int tty_audit_push(void) +{ + struct tty_audit_buf *buf; + + if (~current->signal->audit_tty & AUDIT_TTY_ENABLE) + return -EPERM; + + buf = tty_audit_buf_ref(); + if (!IS_ERR_OR_NULL(buf)) { + mutex_lock(&buf->mutex); + tty_audit_buf_push(buf); + mutex_unlock(&buf->mutex); + } + return 0; +} + +/** + * tty_audit_buf_get - Get an audit buffer. + * + * Get an audit buffer, allocate it if necessary. Return %NULL + * if out of memory or ERR_PTR(-ESRCH) if tty_audit_exit() has already + * occurred. Otherwise, return a new reference to the buffer. + */ +static struct tty_audit_buf *tty_audit_buf_get(void) +{ + struct tty_audit_buf *buf; + + buf = tty_audit_buf_ref(); + if (buf) + return buf; + + buf = tty_audit_buf_alloc(); + if (buf == NULL) { + audit_log_lost("out of memory in TTY auditing"); + return NULL; + } + + /* Race to use this buffer, free it if another wins */ + if (cmpxchg(¤t->signal->tty_audit_buf, NULL, buf) != NULL) + tty_audit_buf_free(buf); + return tty_audit_buf_ref(); +} + +/** + * tty_audit_add_data - Add data for TTY auditing. + * + * Audit @data of @size from @tty, if necessary. + */ +void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size) +{ + struct tty_audit_buf *buf; + unsigned int icanon = !!L_ICANON(tty); + unsigned int audit_tty; + dev_t dev; + + audit_tty = READ_ONCE(current->signal->audit_tty); + if (~audit_tty & AUDIT_TTY_ENABLE) + return; + + if (unlikely(size == 0)) + return; + + if (tty->driver->type == TTY_DRIVER_TYPE_PTY + && tty->driver->subtype == PTY_TYPE_MASTER) + return; + + if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty)) + return; + + buf = tty_audit_buf_get(); + if (IS_ERR_OR_NULL(buf)) + return; + + mutex_lock(&buf->mutex); + dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index; + if (buf->dev != dev || buf->icanon != icanon) { + tty_audit_buf_push(buf); + buf->dev = dev; + buf->icanon = icanon; + } + do { + size_t run; + + run = N_TTY_BUF_SIZE - buf->valid; + if (run > size) + run = size; + memcpy(buf->data + buf->valid, data, run); + buf->valid += run; + data += run; + size -= run; + if (buf->valid == N_TTY_BUF_SIZE) + tty_audit_buf_push(buf); + } while (size != 0); + mutex_unlock(&buf->mutex); +} |