diff options
95 files changed, 3240 insertions, 1120 deletions
diff --git a/Documentation/crypto/asymmetric-keys.txt b/Documentation/crypto/asymmetric-keys.txt index 2b7816dea370..5ad6480e3fb9 100644 --- a/Documentation/crypto/asymmetric-keys.txt +++ b/Documentation/crypto/asymmetric-keys.txt @@ -311,3 +311,54 @@ Functions are provided to register and unregister parsers: Parsers may not have the same name. The names are otherwise only used for displaying in debugging messages. + + +========================= +KEYRING LINK RESTRICTIONS +========================= + +Keyrings created from userspace using add_key can be configured to check the +signature of the key being linked. + +Several restriction methods are available: + + (1) Restrict using the kernel builtin trusted keyring + + - Option string used with KEYCTL_RESTRICT_KEYRING: + - "builtin_trusted" + + The kernel builtin trusted keyring will be searched for the signing + key. The ca_keys kernel parameter also affects which keys are used for + signature verification. + + (2) Restrict using the kernel builtin and secondary trusted keyrings + + - Option string used with KEYCTL_RESTRICT_KEYRING: + - "builtin_and_secondary_trusted" + + The kernel builtin and secondary trusted keyrings will be searched for the + signing key. The ca_keys kernel parameter also affects which keys are used + for signature verification. + + (3) Restrict using a separate key or keyring + + - Option string used with KEYCTL_RESTRICT_KEYRING: + - "key_or_keyring:<key or keyring serial number>[:chain]" + + Whenever a key link is requested, the link will only succeed if the key + being linked is signed by one of the designated keys. This key may be + specified directly by providing a serial number for one asymmetric key, or + a group of keys may be searched for the signing key by providing the + serial number for a keyring. + + When the "chain" option is provided at the end of the string, the keys + within the destination keyring will also be searched for signing keys. + This allows for verification of certificate chains by adding each + cert in order (starting closest to the root) to one keyring. + +In all of these cases, if the signing key is found the signature of the key to +be linked will be verified using the signing key. The requested key is added +to the keyring only if the signature is successfully verified. -ENOKEY is +returned if the parent certificate could not be found, or -EKEYREJECTED is +returned if the signature check fails or the key is blacklisted. Other errors +may be returned if the signature check could not be performed. diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt index 0e03baf271bd..cd5019934d7f 100644 --- a/Documentation/security/keys.txt +++ b/Documentation/security/keys.txt @@ -827,7 +827,7 @@ The keyctl syscall functions are: long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params, char *buffer, size_t buflen, - void *reserved); + struct keyctl_kdf_params *kdf); The params struct contains serial numbers for three keys: @@ -844,18 +844,61 @@ The keyctl syscall functions are: public key. If the base is the remote public key, the result is the shared secret. - The reserved argument must be set to NULL. + If the parameter kdf is NULL, the following applies: - The buffer length must be at least the length of the prime, or zero. + - 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. + - 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. + + The kdf parameter allows the caller to apply a key derivation function + (KDF) on the Diffie-Hellman computation where only the result + of the KDF is returned to the caller. The KDF is characterized with + struct keyctl_kdf_params as follows: + + - char *hashname specifies the NUL terminated string identifying + the hash used from the kernel crypto API and applied for the KDF + operation. The KDF implemenation complies with SP800-56A as well + as with SP800-108 (the counter KDF). + + - char *otherinfo specifies the OtherInfo data as documented in + SP800-56A section 5.8.1.2. The length of the buffer is given with + otherinfolen. The format of OtherInfo is defined by the caller. + The otherinfo pointer may be NULL if no OtherInfo shall be used. 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. + EACCES if the key is not readable by the caller. In addition, the + function will return EMSGSIZE when the parameter kdf is non-NULL + and either the buffer length or the OtherInfo length exceeds the + allowed length. + + (*) Restrict keyring linkage + + long keyctl(KEYCTL_RESTRICT_KEYRING, key_serial_t keyring, + const char *type, const char *restriction); + + An existing keyring can restrict linkage of additional keys by evaluating + the contents of the key according to a restriction scheme. + + "keyring" is the key ID for an existing keyring to apply a restriction + to. It may be empty or may already have keys linked. Existing linked keys + will remain in the keyring even if the new restriction would reject them. + + "type" is a registered key type. + + "restriction" is a string describing how key linkage is to be restricted. + The format varies depending on the key type, and the string is passed to + the lookup_restriction() function for the requested type. It may specify + a method and relevant data for the restriction such as signature + verification or constraints on key payload. If the requested key type is + later unregistered, no keys may be added to the keyring after the key type + is removed. + + To apply a keyring restriction the process must have Set Attribute + permission and the keyring must not be previously restricted. =============== KERNEL SERVICES @@ -1032,10 +1075,7 @@ 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 *), + struct key_restriction *restrict_link, unsigned long flags, struct key *dest); @@ -1047,20 +1087,23 @@ 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. + If restrict_link is not NULL, it should point to a structure that contains + the function that will be called each time an attempt is made to link a + key into the new keyring. The structure may also contain a key pointer + and an associated key type. The function is called to check whether a key + may be added into the keyring or not. The key type is used by the garbage + collector to clean up function or data pointers in this structure if the + given key type is unregistered. 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. + added to, the key type, the payload of the key being added, and data to be + used in the restriction check. 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. @@ -1445,6 +1488,15 @@ The structure has a number of fields, some of which are mandatory: The authorisation key. + (*) struct key_restriction *(*lookup_restriction)(const char *params); + + This optional method is used to enable userspace configuration of keyring + restrictions. The restriction parameter string (not including the key type + name) is passed in, and this method returns a pointer to a key_restriction + structure containing the relevant functions and data to evaluate each + attempted key link operation. If there is no match, -EINVAL is returned. + + ============================ REQUEST-KEY CALLBACK SERVICE ============================ diff --git a/certs/Kconfig b/certs/Kconfig index fc5955f5fc8a..6ce51ede9e9b 100644 --- a/certs/Kconfig +++ b/certs/Kconfig @@ -64,4 +64,22 @@ config SECONDARY_TRUSTED_KEYRING those keys are not blacklisted and are vouched for by a key built into the kernel or already in the secondary trusted keyring. +config SYSTEM_BLACKLIST_KEYRING + bool "Provide system-wide ring of blacklisted keys" + depends on KEYS + help + Provide a system keyring to which blacklisted keys can be added. + Keys in the keyring are considered entirely untrusted. Keys in this + keyring are used by the module signature checking to reject loading + of modules signed with a blacklisted key. + +config SYSTEM_BLACKLIST_HASH_LIST + string "Hashes to be preloaded into the system blacklist keyring" + depends on SYSTEM_BLACKLIST_KEYRING + help + If set, this option should be the filename of a list of hashes in the + form "<hash>", "<hash>", ... . This will be included into a C + wrapper to incorporate the list into the kernel. Each <hash> should + be a string of hex digits. + endmenu diff --git a/certs/Makefile b/certs/Makefile index 2773c4afa24c..4119bb376ea1 100644 --- a/certs/Makefile +++ b/certs/Makefile @@ -3,6 +3,12 @@ # obj-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += system_keyring.o system_certificates.o +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist.o +ifneq ($(CONFIG_SYSTEM_BLACKLIST_HASH_LIST),"") +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_hashes.o +else +obj-$(CONFIG_SYSTEM_BLACKLIST_KEYRING) += blacklist_nohashes.o +endif ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYRING),y) diff --git a/certs/blacklist.c b/certs/blacklist.c new file mode 100644 index 000000000000..3eddce0e307a --- /dev/null +++ b/certs/blacklist.c @@ -0,0 +1,174 @@ +/* System hash blacklist. + * + * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#define pr_fmt(fmt) "blacklist: "fmt +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/key.h> +#include <linux/key-type.h> +#include <linux/sched.h> +#include <linux/ctype.h> +#include <linux/err.h> +#include <linux/seq_file.h> +#include <keys/system_keyring.h> +#include "blacklist.h" + +static struct key *blacklist_keyring; + +/* + * The description must be a type prefix, a colon and then an even number of + * hex digits. The hash is kept in the description. + */ +static int blacklist_vet_description(const char *desc) +{ + |