diff options
Diffstat (limited to 'drivers/char/tty_audit.c')
| -rw-r--r-- | drivers/char/tty_audit.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/drivers/char/tty_audit.c b/drivers/char/tty_audit.c new file mode 100644 index 00000000000..d222012c1b0 --- /dev/null +++ b/drivers/char/tty_audit.c @@ -0,0 +1,345 @@ +/* + * Creating audit events from TTY input. + * + * Copyright (C) 2007 Red Hat, Inc. All rights reserved. This copyrighted + * material is made available to anyone wishing to use, modify, copy, or + * redistribute it subject to the terms and conditions of the GNU General + * Public License v.2. + * + * Authors: Miloslav Trmac <mitr@redhat.com> + */ + +#include <linux/audit.h> +#include <linux/file.h> +#include <linux/tty.h> + +struct tty_audit_buf { + atomic_t count; + struct mutex mutex; /* Protects all data below */ + int major, minor; /* 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_alloc(int major, int minor, + int icanon) +{ + struct tty_audit_buf *buf; + + buf = kmalloc(sizeof (*buf), GFP_KERNEL); + if (!buf) + goto err; + if (PAGE_SIZE != N_TTY_BUF_SIZE) + buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL); + else + buf->data = (unsigned char *)__get_free_page(GFP_KERNEL); + if (!buf->data) + goto err_buf; + atomic_set(&buf->count, 1); + mutex_init(&buf->mutex); + buf->major = major; + buf->minor = minor; + buf->icanon = icanon; + 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); + if (PAGE_SIZE != N_TTY_BUF_SIZE) + kfree(buf->data); + else + free_page((unsigned long)buf->data); + kfree(buf); +} + +static void tty_audit_buf_put(struct tty_audit_buf *buf) +{ + if (atomic_dec_and_test(&buf->count)) + tty_audit_buf_free(buf); +} + +/** + * tty_audit_buf_push - Push buffered data out + * + * Generate an audit message from the contents of @buf, which is owned by + * @tsk with @loginuid. @buf->mutex must be locked. + */ +static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid, + struct tty_audit_buf *buf) +{ + struct audit_buffer *ab; + + if (buf->valid == 0) + return; + if (audit_enabled == 0) + return; + ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY); + if (ab) { + char name[sizeof(tsk->comm)]; + + audit_log_format(ab, "tty pid=%u uid=%u auid=%u major=%d " + "minor=%d comm=", tsk->pid, tsk->uid, + loginuid, buf->major, buf->minor); + get_task_comm(name, tsk); + audit_log_untrustedstring(ab, name); + audit_log_format(ab, " data="); + audit_log_n_untrustedstring(ab, buf->valid, buf->data); + audit_log_end(ab); + } + buf->valid = 0; +} + +/** + * tty_audit_buf_push_current - 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_current(struct tty_audit_buf *buf) +{ + tty_audit_buf_push(current, audit_get_loginuid(current->audit_context), + buf); +} + +/** + * 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. + */ +void tty_audit_exit(void) +{ + struct tty_audit_buf *buf; + + spin_lock_irq(¤t->sighand->siglock); + buf = current->signal->tty_audit_buf; + current->signal->tty_audit_buf = NULL; + spin_unlock_irq(¤t->sighand->siglock); + if (!buf) + return; + + mutex_lock(&buf->mutex); + tty_audit_buf_push_current(buf); + mutex_unlock(&buf->mutex); + + tty_audit_buf_put(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) +{ + spin_lock_irq(¤t->sighand->siglock); + sig->audit_tty = current->signal->audit_tty; + spin_unlock_irq(¤t->sighand->siglock); + sig->tty_audit_buf = NULL; +} + +/** + * tty_audit_push_task - Flush task's pending audit data + */ +void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid) +{ + struct tty_audit_buf *buf; + + spin_lock_irq(&tsk->sighand->siglock); + buf = tsk->signal->tty_audit_buf; + if (buf) + atomic_inc(&buf->count); + spin_unlock_irq(&tsk->sighand->siglock); + if (!buf) + return; + + mutex_lock(&buf->mutex); + tty_audit_buf_push(tsk, loginuid, buf); + mutex_unlock(&buf->mutex); + + tty_audit_buf_put(buf); +} + +/** + * tty_audit_buf_get - Get an audit buffer. + * + * Get an audit buffer for @tty, allocate it if necessary. Return %NULL + * if TTY auditing is disabled or out of memory. Otherwise, return a new + * reference to the buffer. + */ +static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty) +{ + struct tty_audit_buf *buf, *buf2; + + buf = NULL; + buf2 = NULL; + spin_lock_irq(¤t->sighand->siglock); + if (likely(!current->signal->audit_tty)) + goto out; + buf = current->signal->tty_audit_buf; + if (buf) { + atomic_inc(&buf->count); + goto out; + } + spin_unlock_irq(¤t->sighand->siglock); + + buf2 = tty_audit_buf_alloc(tty->driver->major, + tty->driver->minor_start + tty->index, + tty->icanon); + if (buf2 == NULL) { + audit_log_lost("out of memory in TTY auditing"); + return NULL; + } + + spin_lock_irq(¤t->sighand->siglock); + if (!current->signal->audit_tty) + goto out; + buf = current->signal->tty_audit_buf; + if (!buf) { + current->signal->tty_audit_buf = buf2; + buf = buf2; + buf2 = NULL; + } + atomic_inc(&buf->count); + /* Fall through */ + out: + spin_unlock_irq(¤t->sighand->siglock); + if (buf2) + tty_audit_buf_free(buf2); + return buf; +} + +/** + * 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, unsigned char *data, + size_t size) +{ + struct tty_audit_buf *buf; + int major, minor; + + if (unlikely(size == 0)) + return; + + buf = tty_audit_buf_get(tty); + if (!buf) + return; + + mutex_lock(&buf->mutex); + major = tty->driver->major; + minor = tty->driver->minor_start + tty->index; + if (buf->major != major || buf->minor != minor + || buf->icanon != tty->icanon) { + tty_audit_buf_push_current(buf); + buf->major = major; + buf->minor = minor; + buf->icanon = tty->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_current(buf); + } while (size != 0); + mutex_unlock(&buf->mutex); + tty_audit_buf_put(buf); +} + +/** + * tty_audit_push - Push buffered data out + * + * Make sure no audit data is pending for @tty on the current process. + */ +void tty_audit_push(struct tty_struct *tty) +{ + struct tty_audit_buf *buf; + + spin_lock_irq(¤t->sighand->siglock); + if (likely(!current->signal->audit_tty)) { + spin_unlock_irq(¤t->sighand->siglock); + return; + } + buf = current->signal->tty_audit_buf; + if (buf) + atomic_inc(&buf->count); + spin_unlock_irq(¤t->sighand->siglock); + + if (buf) { + int major, minor; + + major = tty->driver->major; + minor = tty->driver->minor_start + tty->index; + mutex_lock(&buf->mutex); + if (buf->major == major && buf->minor == minor) + tty_audit_buf_push_current(buf); + mutex_unlock(&buf->mutex); + tty_audit_buf_put(buf); + } +} + +/** + * tty_audit_opening - A TTY is being opened. + * + * As a special hack, tasks that close all their TTYs and open new ones + * are assumed to be system daemons (e.g. getty) and auditing is + * automatically disabled for them. + */ +void tty_audit_opening(void) +{ + int disable; + + disable = 1; + spin_lock_irq(¤t->sighand->siglock); + if (current->signal->audit_tty == 0) + disable = 0; + spin_unlock_irq(¤t->sighand->siglock); + if (!disable) + return; + + task_lock(current); + if (current->files) { + struct fdtable *fdt; + unsigned i; + + /* + * We don't take a ref to the file, so we must hold ->file_lock + * instead. + */ + spin_lock(¤t->files->file_lock); + fdt = files_fdtable(current->files); + for (i = 0; i < fdt->max_fds; i++) { + struct file *filp; + + filp = fcheck_files(current->files, i); + if (filp && is_tty(filp)) { + disable = 0; + break; + } + } + spin_unlock(¤t->files->file_lock); + } + task_unlock(current); + if (!disable) + return; + + spin_lock_irq(¤t->sighand->siglock); + current->signal->audit_tty = 0; + spin_unlock_irq(¤t->sighand->siglock); +} |