linux/security/tomoyo/tomoyo.c
David Howells ee18d64c1f KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]
Add a keyctl to install a process's session keyring onto its parent.  This
replaces the parent's session keyring.  Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again.  Normally this
will be after a wait*() syscall.

To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.

The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.

Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME.  This allows the
replacement to be performed at the point the parent process resumes userspace
execution.

This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership.  However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.

This can be tested with the following program:

	#include <stdio.h>
	#include <stdlib.h>
	#include <keyutils.h>

	#define KEYCTL_SESSION_TO_PARENT	18

	#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)

	int main(int argc, char **argv)
	{
		key_serial_t keyring, key;
		long ret;

		keyring = keyctl_join_session_keyring(argv[1]);
		OSERROR(keyring, "keyctl_join_session_keyring");

		key = add_key("user", "a", "b", 1, keyring);
		OSERROR(key, "add_key");

		ret = keyctl(KEYCTL_SESSION_TO_PARENT);
		OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");

		return 0;
	}

Compiled and linked with -lkeyutils, you should see something like:

	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	355907932 --alswrv   4043    -1   \_ keyring: _uid.4043
	[dhowells@andromeda ~]$ /tmp/newpag
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: _ses
	1055658746 --alswrv   4043  4043   \_ user: a
	[dhowells@andromeda ~]$ /tmp/newpag hello
	[dhowells@andromeda ~]$ keyctl show
	Session Keyring
	       -3 --alswrv   4043  4043  keyring: hello
	340417692 --alswrv   4043  4043   \_ user: a

Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 21:29:22 +10:00

316 lines
7.7 KiB
C

/*
* security/tomoyo/tomoyo.c
*
* LSM hooks for TOMOYO Linux.
*
* Copyright (C) 2005-2009 NTT DATA CORPORATION
*
* Version: 2.2.0 2009/04/01
*
*/
#include <linux/security.h>
#include "common.h"
#include "tomoyo.h"
#include "realpath.h"
static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp)
{
new->security = NULL;
return 0;
}
static int tomoyo_cred_prepare(struct cred *new, const struct cred *old,
gfp_t gfp)
{
/*
* Since "struct tomoyo_domain_info *" is a sharable pointer,
* we don't need to duplicate.
*/
new->security = old->security;
return 0;
}
static void tomoyo_cred_transfer(struct cred *new, const struct cred *old)
{
/*
* Since "struct tomoyo_domain_info *" is a sharable pointer,
* we don't need to duplicate.
*/
new->security = old->security;
}
static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
{
int rc;
rc = cap_bprm_set_creds(bprm);
if (rc)
return rc;
/*
* Do only if this function is called for the first time of an execve
* operation.
*/
if (bprm->cred_prepared)
return 0;
/*
* Load policy if /sbin/tomoyo-init exists and /sbin/init is requested
* for the first time.
*/
if (!tomoyo_policy_loaded)
tomoyo_load_policy(bprm->filename);
/*
* Tell tomoyo_bprm_check_security() is called for the first time of an
* execve operation.
*/
bprm->cred->security = NULL;
return 0;
}
static int tomoyo_bprm_check_security(struct linux_binprm *bprm)
{
struct tomoyo_domain_info *domain = bprm->cred->security;
/*
* Execute permission is checked against pathname passed to do_execve()
* using current domain.
*/
if (!domain)
return tomoyo_find_next_domain(bprm);
/*
* Read permission is checked against interpreters using next domain.
* '1' is the result of open_to_namei_flags(O_RDONLY).
*/
return tomoyo_check_open_permission(domain, &bprm->file->f_path, 1);
}
#ifdef CONFIG_SYSCTL
static int tomoyo_prepend(char **buffer, int *buflen, const char *str)
{
int namelen = strlen(str);
if (*buflen < namelen)
return -ENOMEM;
*buflen -= namelen;
*buffer -= namelen;
memcpy(*buffer, str, namelen);
return 0;
}
/**
* tomoyo_sysctl_path - return the realpath of a ctl_table.
* @table: pointer to "struct ctl_table".
*
* Returns realpath(3) of the @table on success.
* Returns NULL on failure.
*
* This function uses tomoyo_alloc(), so the caller must call tomoyo_free()
* if this function didn't return NULL.
*/
static char *tomoyo_sysctl_path(struct ctl_table *table)
{
int buflen = TOMOYO_MAX_PATHNAME_LEN;
char *buf = tomoyo_alloc(buflen);
char *end = buf + buflen;
int error = -ENOMEM;
if (!buf)
return NULL;
*--end = '\0';
buflen--;
while (table) {
char num[32];
const char *sp = table->procname;
if (!sp) {
memset(num, 0, sizeof(num));
snprintf(num, sizeof(num) - 1, "=%d=", table->ctl_name);
sp = num;
}
if (tomoyo_prepend(&end, &buflen, sp) ||
tomoyo_prepend(&end, &buflen, "/"))
goto out;
table = table->parent;
}
if (tomoyo_prepend(&end, &buflen, "/proc/sys"))
goto out;
error = tomoyo_encode(buf, end - buf, end);
out:
if (!error)
return buf;
tomoyo_free(buf);
return NULL;
}
static int tomoyo_sysctl(struct ctl_table *table, int op)
{
int error;
char *name;
op &= MAY_READ | MAY_WRITE;
if (!op)
return 0;
name = tomoyo_sysctl_path(table);
if (!name)
return -ENOMEM;
error = tomoyo_check_file_perm(tomoyo_domain(), name, op);
tomoyo_free(name);
return error;
}
#endif
static int tomoyo_path_truncate(struct path *path, loff_t length,
unsigned int time_attrs)
{
return tomoyo_check_1path_perm(tomoyo_domain(),
TOMOYO_TYPE_TRUNCATE_ACL,
path);
}
static int tomoyo_path_unlink(struct path *parent, struct dentry *dentry)
{
struct path path = { parent->mnt, dentry };
return tomoyo_check_1path_perm(tomoyo_domain(),
TOMOYO_TYPE_UNLINK_ACL,
&path);
}
static int tomoyo_path_mkdir(struct path *parent, struct dentry *dentry,
int mode)
{
struct path path = { parent->mnt, dentry };
return tomoyo_check_1path_perm(tomoyo_domain(),
TOMOYO_TYPE_MKDIR_ACL,
&path);
}
static int tomoyo_path_rmdir(struct path *parent, struct dentry *dentry)
{
struct path path = { parent->mnt, dentry };
return tomoyo_check_1path_perm(tomoyo_domain(),
TOMOYO_TYPE_RMDIR_ACL,
&path);
}
static int tomoyo_path_symlink(struct path *parent, struct dentry *dentry,
const char *old_name)
{
struct path path = { parent->mnt, dentry };
return tomoyo_check_1path_perm(tomoyo_domain(),
TOMOYO_TYPE_SYMLINK_ACL,
&path);
}
static int tomoyo_path_mknod(struct path *parent, struct dentry *dentry,
int mode, unsigned int dev)
{
struct path path = { parent->mnt, dentry };
int type = TOMOYO_TYPE_CREATE_ACL;
switch (mode & S_IFMT) {
case S_IFCHR:
type = TOMOYO_TYPE_MKCHAR_ACL;
break;
case S_IFBLK:
type = TOMOYO_TYPE_MKBLOCK_ACL;
break;
case S_IFIFO:
type = TOMOYO_TYPE_MKFIFO_ACL;
break;
case S_IFSOCK:
type = TOMOYO_TYPE_MKSOCK_ACL;
break;
}
return tomoyo_check_1path_perm(tomoyo_domain(),
type, &path);
}
static int tomoyo_path_link(struct dentry *old_dentry, struct path *new_dir,
struct dentry *new_dentry)
{
struct path path1 = { new_dir->mnt, old_dentry };
struct path path2 = { new_dir->mnt, new_dentry };
return tomoyo_check_2path_perm(tomoyo_domain(),
TOMOYO_TYPE_LINK_ACL,
&path1, &path2);
}
static int tomoyo_path_rename(struct path *old_parent,
struct dentry *old_dentry,
struct path *new_parent,
struct dentry *new_dentry)
{
struct path path1 = { old_parent->mnt, old_dentry };
struct path path2 = { new_parent->mnt, new_dentry };
return tomoyo_check_2path_perm(tomoyo_domain(),
TOMOYO_TYPE_RENAME_ACL,
&path1, &path2);
}
static int tomoyo_file_fcntl(struct file *file, unsigned int cmd,
unsigned long arg)
{
if (cmd == F_SETFL && ((arg ^ file->f_flags) & O_APPEND))
return tomoyo_check_rewrite_permission(tomoyo_domain(), file);
return 0;
}
static int tomoyo_dentry_open(struct file *f, const struct cred *cred)
{
int flags = f->f_flags;
if ((flags + 1) & O_ACCMODE)
flags++;
flags |= f->f_flags & (O_APPEND | O_TRUNC);
/* Don't check read permission here if called from do_execve(). */
if (current->in_execve)
return 0;
return tomoyo_check_open_permission(tomoyo_domain(), &f->f_path, flags);
}
/*
* tomoyo_security_ops is a "struct security_operations" which is used for
* registering TOMOYO.
*/
static struct security_operations tomoyo_security_ops = {
.name = "tomoyo",
.cred_alloc_blank = tomoyo_cred_alloc_blank,
.cred_prepare = tomoyo_cred_prepare,
.cred_transfer = tomoyo_cred_transfer,
.bprm_set_creds = tomoyo_bprm_set_creds,
.bprm_check_security = tomoyo_bprm_check_security,
#ifdef CONFIG_SYSCTL
.sysctl = tomoyo_sysctl,
#endif
.file_fcntl = tomoyo_file_fcntl,
.dentry_open = tomoyo_dentry_open,
.path_truncate = tomoyo_path_truncate,
.path_unlink = tomoyo_path_unlink,
.path_mkdir = tomoyo_path_mkdir,
.path_rmdir = tomoyo_path_rmdir,
.path_symlink = tomoyo_path_symlink,
.path_mknod = tomoyo_path_mknod,
.path_link = tomoyo_path_link,
.path_rename = tomoyo_path_rename,
};
static int __init tomoyo_init(void)
{
struct cred *cred = (struct cred *) current_cred();
if (!security_module_enable(&tomoyo_security_ops))
return 0;
/* register ourselves with the security framework */
if (register_security(&tomoyo_security_ops))
panic("Failure registering TOMOYO Linux");
printk(KERN_INFO "TOMOYO Linux initialized\n");
cred->security = &tomoyo_kernel_domain;
tomoyo_realpath_init();
return 0;
}
security_initcall(tomoyo_init);