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![David Howells](/assets/img/avatar_default.png)
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>
92 lines
2.5 KiB
C
92 lines
2.5 KiB
C
/* compat.c: 32-bit compatibility syscall for 64-bit systems
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*
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* Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/syscalls.h>
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#include <linux/keyctl.h>
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#include <linux/compat.h>
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#include "internal.h"
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/*****************************************************************************/
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/*
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* the key control system call, 32-bit compatibility version for 64-bit archs
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* - this should only be called if the 64-bit arch uses weird pointers in
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* 32-bit mode or doesn't guarantee that the top 32-bits of the argument
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* registers on taking a 32-bit syscall are zero
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* - if you can, you should call sys_keyctl directly
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*/
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asmlinkage long compat_sys_keyctl(u32 option,
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u32 arg2, u32 arg3, u32 arg4, u32 arg5)
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{
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switch (option) {
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case KEYCTL_GET_KEYRING_ID:
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return keyctl_get_keyring_ID(arg2, arg3);
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case KEYCTL_JOIN_SESSION_KEYRING:
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return keyctl_join_session_keyring(compat_ptr(arg2));
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case KEYCTL_UPDATE:
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return keyctl_update_key(arg2, compat_ptr(arg3), arg4);
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case KEYCTL_REVOKE:
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return keyctl_revoke_key(arg2);
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case KEYCTL_DESCRIBE:
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return keyctl_describe_key(arg2, compat_ptr(arg3), arg4);
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case KEYCTL_CLEAR:
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return keyctl_keyring_clear(arg2);
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case KEYCTL_LINK:
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return keyctl_keyring_link(arg2, arg3);
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case KEYCTL_UNLINK:
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return keyctl_keyring_unlink(arg2, arg3);
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case KEYCTL_SEARCH:
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return keyctl_keyring_search(arg2, compat_ptr(arg3),
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compat_ptr(arg4), arg5);
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case KEYCTL_READ:
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return keyctl_read_key(arg2, compat_ptr(arg3), arg4);
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case KEYCTL_CHOWN:
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return keyctl_chown_key(arg2, arg3, arg4);
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case KEYCTL_SETPERM:
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return keyctl_setperm_key(arg2, arg3);
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case KEYCTL_INSTANTIATE:
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return keyctl_instantiate_key(arg2, compat_ptr(arg3), arg4,
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arg5);
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case KEYCTL_NEGATE:
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return keyctl_negate_key(arg2, arg3, arg4);
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case KEYCTL_SET_REQKEY_KEYRING:
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return keyctl_set_reqkey_keyring(arg2);
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case KEYCTL_SET_TIMEOUT:
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return keyctl_set_timeout(arg2, arg3);
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case KEYCTL_ASSUME_AUTHORITY:
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return keyctl_assume_authority(arg2);
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case KEYCTL_GET_SECURITY:
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return keyctl_get_security(arg2, compat_ptr(arg3), arg4);
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case KEYCTL_SESSION_TO_PARENT:
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return keyctl_session_to_parent();
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default:
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return -EOPNOTSUPP;
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}
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} /* end compat_sys_keyctl() */
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