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authorYael Tzur <yaelt@google.com>2022-02-15 17:19:53 +0300
committerMimi Zohar <zohar@linux.ibm.com>2022-02-22 03:47:45 +0300
commitcd3bc044af483422cc81a93f23c78c20c978b17c (patch)
tree62b081ee07f758e6395d04416c874cd4c5fd9fab /security/keys
parent8c54135e2e6da677291012813a26a5f1b2c8a90a (diff)
downloadlinux-cd3bc044af483422cc81a93f23c78c20c978b17c.tar.xz
KEYS: encrypted: Instantiate key with user-provided decrypted data
For availability and performance reasons master keys often need to be released outside of a Key Management Service (KMS) to clients. It would be beneficial to provide a mechanism where the wrapping/unwrapping of data encryption keys (DEKs) is not dependent on a remote call at runtime yet security is not (or only minimally) compromised. Master keys could be securely stored in the Kernel and be used to wrap/unwrap keys from Userspace. The encrypted.c class supports instantiation of encrypted keys with either an already-encrypted key material, or by generating new key material based on random numbers. This patch defines a new datablob format: [<format>] <master-key name> <decrypted data length> <decrypted data> that allows to inject and encrypt user-provided decrypted data. The decrypted data must be hex-ascii encoded. Signed-off-by: Yael Tzur <yaelt@google.com> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Reviewed-by: Sumit Garg <sumit.garg@linaro.org> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/Kconfig19
-rw-r--r--security/keys/encrypted-keys/encrypted.c71
2 files changed, 67 insertions, 23 deletions
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 969122c7b92f..0e30b361e1c1 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -98,10 +98,21 @@ config ENCRYPTED_KEYS
select CRYPTO_RNG
help
This option provides support for create/encrypting/decrypting keys
- in the kernel. Encrypted keys are kernel generated random numbers,
- which are encrypted/decrypted with a 'master' symmetric key. The
- 'master' key can be either a trusted-key or user-key type.
- Userspace only ever sees/stores encrypted blobs.
+ in the kernel. Encrypted keys are instantiated using kernel
+ generated random numbers or provided decrypted data, and are
+ encrypted/decrypted with a 'master' symmetric key. The 'master'
+ key can be either a trusted-key or user-key type. Only encrypted
+ blobs are ever output to Userspace.
+
+ If you are unsure as to whether this is required, answer N.
+
+config USER_DECRYPTED_DATA
+ bool "Allow encrypted keys with user decrypted data"
+ depends on ENCRYPTED_KEYS
+ help
+ This option provides support for instantiating encrypted keys using
+ user-provided decrypted data. The decrypted data must be hex-ascii
+ encoded.
If you are unsure as to whether this is required, answer N.
diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 87432b35d771..e05cfc2e49ae 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -78,6 +78,11 @@ static const match_table_t key_tokens = {
{Opt_err, NULL}
};
+static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA);
+module_param(user_decrypted_data, bool, 0);
+MODULE_PARM_DESC(user_decrypted_data,
+ "Allow instantiation of encrypted keys using provided decrypted data");
+
static int aes_get_sizes(void)
{
struct crypto_skcipher *tfm;
@@ -158,7 +163,7 @@ static int valid_master_desc(const char *new_desc, const char *orig_desc)
* datablob_parse - parse the keyctl data
*
* datablob format:
- * new [<format>] <master-key name> <decrypted data length>
+ * new [<format>] <master-key name> <decrypted data length> [<decrypted data>]
* load [<format>] <master-key name> <decrypted data length>
* <encrypted iv + data>
* update <new-master-key name>
@@ -170,7 +175,7 @@ static int valid_master_desc(const char *new_desc, const char *orig_desc)
*/
static int datablob_parse(char *datablob, const char **format,
char **master_desc, char **decrypted_datalen,
- char **hex_encoded_iv)
+ char **hex_encoded_iv, char **decrypted_data)
{
substring_t args[MAX_OPT_ARGS];
int ret = -EINVAL;
@@ -231,6 +236,7 @@ static int datablob_parse(char *datablob, const char **format,
"when called from .update method\n", keyword);
break;
}
+ *decrypted_data = strsep(&datablob, " \t");
ret = 0;
break;
case Opt_load:
@@ -595,7 +601,8 @@ out:
static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
const char *format,
const char *master_desc,
- const char *datalen)
+ const char *datalen,
+ const char *decrypted_data)
{
struct encrypted_key_payload *epayload = NULL;
unsigned short datablob_len;
@@ -604,6 +611,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
unsigned int encrypted_datalen;
unsigned int format_len;
long dlen;
+ int i;
int ret;
ret = kstrtol(datalen, 10, &dlen);
@@ -613,6 +621,24 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
format_len = (!format) ? strlen(key_format_default) : strlen(format);
decrypted_datalen = dlen;
payload_datalen = decrypted_datalen;
+
+ if (decrypted_data) {
+ if (!user_decrypted_data) {
+ pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n");
+ return ERR_PTR(-EINVAL);
+ }
+ if (strlen(decrypted_data) != decrypted_datalen) {
+ pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n");
+ return ERR_PTR(-EINVAL);
+ }
+ for (i = 0; i < strlen(decrypted_data); i++) {
+ if (!isxdigit(decrypted_data[i])) {
+ pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n");
+ return ERR_PTR(-EINVAL);
+ }
+ }
+ }
+
if (format) {
if (!strcmp(format, key_format_ecryptfs)) {
if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
@@ -740,13 +766,14 @@ static void __ekey_init(struct encrypted_key_payload *epayload,
/*
* encrypted_init - initialize an encrypted key
*
- * For a new key, use a random number for both the iv and data
- * itself. For an old key, decrypt the hex encoded data.
+ * For a new key, use either a random number or user-provided decrypted data in
+ * case it is provided. A random number is used for the iv in both cases. For
+ * an old key, decrypt the hex encoded data.
*/
static int encrypted_init(struct encrypted_key_payload *epayload,
const char *key_desc, const char *format,
const char *master_desc, const char *datalen,
- const char *hex_encoded_iv)
+ const char *hex_encoded_iv, const char *decrypted_data)
{
int ret = 0;
@@ -760,21 +787,26 @@ static int encrypted_init(struct encrypted_key_payload *epayload,
}
__ekey_init(epayload, format, master_desc, datalen);
- if (!hex_encoded_iv) {
- get_random_bytes(epayload->iv, ivsize);
-
- get_random_bytes(epayload->decrypted_data,
- epayload->decrypted_datalen);
- } else
+ if (hex_encoded_iv) {
ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
+ } else if (decrypted_data) {
+ get_random_bytes(epayload->iv, ivsize);
+ memcpy(epayload->decrypted_data, decrypted_data,
+ epayload->decrypted_datalen);
+ } else {
+ get_random_bytes(epayload->iv, ivsize);
+ get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen);
+ }
return ret;
}
/*
* encrypted_instantiate - instantiate an encrypted key
*
- * Decrypt an existing encrypted datablob or create a new encrypted key
- * based on a kernel random number.
+ * Instantiates the key:
+ * - by decrypting an existing encrypted datablob, or
+ * - by creating a new encrypted key based on a kernel random number, or
+ * - using provided decrypted data.
*
* On success, return 0. Otherwise return errno.
*/
@@ -787,6 +819,7 @@ static int encrypted_instantiate(struct key *key,
char *master_desc = NULL;
char *decrypted_datalen = NULL;
char *hex_encoded_iv = NULL;
+ char *decrypted_data = NULL;
size_t datalen = prep->datalen;
int ret;
@@ -799,18 +832,18 @@ static int encrypted_instantiate(struct key *key,
datablob[datalen] = 0;
memcpy(datablob, prep->data, datalen);
ret = datablob_parse(datablob, &format, &master_desc,
- &decrypted_datalen, &hex_encoded_iv);
+ &decrypted_datalen, &hex_encoded_iv, &decrypted_data);
if (ret < 0)
goto out;
epayload = encrypted_key_alloc(key, format, master_desc,
- decrypted_datalen);
+ decrypted_datalen, decrypted_data);
if (IS_ERR(epayload)) {
ret = PTR_ERR(epayload);
goto out;
}
ret = encrypted_init(epayload, key->description, format, master_desc,
- decrypted_datalen, hex_encoded_iv);
+ decrypted_datalen, hex_encoded_iv, decrypted_data);
if (ret < 0) {
kfree_sensitive(epayload);
goto out;
@@ -860,7 +893,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
buf[datalen] = 0;
memcpy(buf, prep->data, datalen);
- ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
+ ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL);
if (ret < 0)
goto out;
@@ -869,7 +902,7 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
goto out;
new_epayload = encrypted_key_alloc(key, epayload->format,
- new_master_desc, epayload->datalen);
+ new_master_desc, epayload->datalen, NULL);
if (IS_ERR(new_epayload)) {
ret = PTR_ERR(new_epayload);
goto out;