xref: /openbmc/linux/security/keys/Kconfig (revision aec499c7)
1# SPDX-License-Identifier: GPL-2.0-only
2#
3# Key management configuration
4#
5
6config KEYS
7	bool "Enable access key retention support"
8	select ASSOCIATIVE_ARRAY
9	help
10	  This option provides support for retaining authentication tokens and
11	  access keys in the kernel.
12
13	  It also includes provision of methods by which such keys might be
14	  associated with a process so that network filesystems, encryption
15	  support and the like can find them.
16
17	  Furthermore, a special type of key is available that acts as keyring:
18	  a searchable sequence of keys. Each process is equipped with access
19	  to five standard keyrings: UID-specific, GID-specific, session,
20	  process and thread.
21
22	  If you are unsure as to whether this is required, answer N.
23
24config KEYS_REQUEST_CACHE
25	bool "Enable temporary caching of the last request_key() result"
26	depends on KEYS
27	help
28	  This option causes the result of the last successful request_key()
29	  call that didn't upcall to the kernel to be cached temporarily in the
30	  task_struct.  The cache is cleared by exit and just prior to the
31	  resumption of userspace.
32
33	  This allows the key used for multiple step processes where each step
34	  wants to request a key that is likely the same as the one requested
35	  by the last step to save on the searching.
36
37	  An example of such a process is a pathwalk through a network
38	  filesystem in which each method needs to request an authentication
39	  key.  Pathwalk will call multiple methods for each dentry traversed
40	  (permission, d_revalidate, lookup, getxattr, getacl, ...).
41
42config PERSISTENT_KEYRINGS
43	bool "Enable register of persistent per-UID keyrings"
44	depends on KEYS
45	help
46	  This option provides a register of persistent per-UID keyrings,
47	  primarily aimed at Kerberos key storage.  The keyrings are persistent
48	  in the sense that they stay around after all processes of that UID
49	  have exited, not that they survive the machine being rebooted.
50
51	  A particular keyring may be accessed by either the user whose keyring
52	  it is or by a process with administrative privileges.  The active
53	  LSMs gets to rule on which admin-level processes get to access the
54	  cache.
55
56	  Keyrings are created and added into the register upon demand and get
57	  removed if they expire (a default timeout is set upon creation).
58
59config BIG_KEYS
60	bool "Large payload keys"
61	depends on KEYS
62	depends on TMPFS
63	depends on CRYPTO_LIB_CHACHA20POLY1305 = y
64	help
65	  This option provides support for holding large keys within the kernel
66	  (for example Kerberos ticket caches).  The data may be stored out to
67	  swapspace by tmpfs.
68
69	  If you are unsure as to whether this is required, answer N.
70
71config TRUSTED_KEYS
72	tristate "TRUSTED KEYS"
73	depends on KEYS && TCG_TPM
74	select CRYPTO
75	select CRYPTO_HMAC
76	select CRYPTO_SHA1
77	select CRYPTO_HASH_INFO
78	select ASN1_ENCODER
79	select OID_REGISTRY
80	select ASN1
81	help
82	  This option provides support for creating, sealing, and unsealing
83	  keys in the kernel. Trusted keys are random number symmetric keys,
84	  generated and RSA-sealed by the TPM. The TPM only unseals the keys,
85	  if the boot PCRs and other criteria match.  Userspace will only ever
86	  see encrypted blobs.
87
88	  If you are unsure as to whether this is required, answer N.
89
90config ENCRYPTED_KEYS
91	tristate "ENCRYPTED KEYS"
92	depends on KEYS
93	select CRYPTO
94	select CRYPTO_HMAC
95	select CRYPTO_AES
96	select CRYPTO_CBC
97	select CRYPTO_SHA256
98	select CRYPTO_RNG
99	help
100	  This option provides support for create/encrypting/decrypting keys
101	  in the kernel.  Encrypted keys are kernel generated random numbers,
102	  which are encrypted/decrypted with a 'master' symmetric key. The
103	  'master' key can be either a trusted-key or user-key type.
104	  Userspace only ever sees/stores encrypted blobs.
105
106	  If you are unsure as to whether this is required, answer N.
107
108config KEY_DH_OPERATIONS
109       bool "Diffie-Hellman operations on retained keys"
110       depends on KEYS
111       select CRYPTO
112       select CRYPTO_KDF800108_CTR
113       select CRYPTO_DH
114       help
115	 This option provides support for calculating Diffie-Hellman
116	 public keys and shared secrets using values stored as keys
117	 in the kernel.
118
119	 If you are unsure as to whether this is required, answer N.
120
121config KEY_NOTIFICATIONS
122	bool "Provide key/keyring change notifications"
123	depends on KEYS && WATCH_QUEUE
124	help
125	  This option provides support for getting change notifications
126	  on keys and keyrings on which the caller has View permission.
127	  This makes use of pipes to handle the notification buffer and
128	  provides KEYCTL_WATCH_KEY to enable/disable watches.
129