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-rw-r--r--Documentation/security/keys.txt52
1 files changed, 52 insertions, 0 deletions
diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 8c183873b2b7..20d05719bceb 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -823,6 +823,36 @@ The keyctl syscall functions are:
A process must have search permission on the key for this function to be
successful.
+ (*) Compute a Diffie-Hellman shared secret or public key
+
+ long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params,
+ char *buffer, size_t buflen);
+
+ The params struct contains serial numbers for three keys:
+
+ - The prime, p, known to both parties
+ - The local private key
+ - The base integer, which is either a shared generator or the
+ remote public key
+
+ The value computed is:
+
+ result = base ^ private (mod prime)
+
+ If the base is the shared generator, the result is the local
+ public key. If the base is the remote public key, the result is
+ the shared secret.
+
+ The buffer length must be at least the length of the prime, or zero.
+
+ If the buffer length is nonzero, the length of the result is
+ returned when it is successfully calculated and copied in to the
+ buffer. When the buffer length is zero, the minimum required
+ buffer length is returned.
+
+ This function will return error EOPNOTSUPP if the key type is not
+ supported, error ENOKEY if the key could not be found, or error
+ EACCES if the key is not readable by the caller.
===============
KERNEL SERVICES
@@ -999,6 +1029,10 @@ payload contents" for more information.
struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
const struct cred *cred,
key_perm_t perm,
+ int (*restrict_link)(struct key *,
+ const struct key_type *,
+ unsigned long,
+ const union key_payload *),
unsigned long flags,
struct key *dest);
@@ -1010,6 +1044,24 @@ payload contents" for more information.
KEY_ALLOC_NOT_IN_QUOTA in flags if the keyring shouldn't be accounted
towards the user's quota). Error ENOMEM can also be returned.
+ If restrict_link not NULL, it should point to a function that will be
+ called each time an attempt is made to link a key into the new keyring.
+ This function is called to check whether a key may be added into the keying
+ or not. Callers of key_create_or_update() within the kernel can pass
+ KEY_ALLOC_BYPASS_RESTRICTION to suppress the check. An example of using
+ this is to manage rings of cryptographic keys that are set up when the
+ kernel boots where userspace is also permitted to add keys - provided they
+ can be verified by a key the kernel already has.
+
+ When called, the restriction function will be passed the keyring being
+ added to, the key flags value and the type and payload of the key being
+ added. Note that when a new key is being created, this is called between
+ payload preparsing and actual key creation. The function should return 0
+ to allow the link or an error to reject it.
+
+ A convenience function, restrict_link_reject, exists to always return
+ -EPERM to in this case.
+
(*) To check the validity of a key, this function can be called:
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