diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 8c183873b2b77f771deb13dd74c21c49e19ec5ed..a2f70cf6763a39f43e7fc9eb0fb89a7fb2183d80 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
diff --git a/include/uapi/linux/keyctl.h b/include/uapi/linux/keyctl.h
index 840cb990abe2e7147ec89c92ef143e86a35ce0f8..86eddd6241f36eb21897d65c6bb51f15bbb4ec58 100644
--- a/include/uapi/linux/keyctl.h
+++ b/include/uapi/linux/keyctl.h
@@ -12,6 +12,8 @@
#ifndef _LINUX_KEYCTL_H
#define _LINUX_KEYCTL_H
+#include <linux/types.h>
+
/* special process keyring shortcut IDs */
#define KEY_SPEC_THREAD_KEYRING -1 /* - key ID for thread-specific keyring */
#define KEY_SPEC_PROCESS_KEYRING -2 /* - key ID for process-specific keyring */
@@ -57,5 +59,13 @@
#define KEYCTL_INSTANTIATE_IOV 20 /* instantiate a partially constructed key */
#define KEYCTL_INVALIDATE 21 /* invalidate a key */
#define KEYCTL_GET_PERSISTENT 22 /* get a user's persistent keyring */
+#define KEYCTL_DH_COMPUTE 23 /* Compute Diffie-Hellman values */
+
+/* keyctl structures */
+struct keyctl_dh_params {
+ __s32 private;
+ __s32 prime;
+ __s32 base;
+};
#endif /* _LINUX_KEYCTL_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index 45828095080d660bf3b23a257e0e288126261bd8..f826e87390233c1cfddb87e969642ab44219d84f 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -85,3 +85,14 @@ config ENCRYPTED_KEYS
Userspace only ever sees/stores encrypted blobs.
If you are unsure as to whether this is required, answer N.
+
+config KEY_DH_OPERATIONS
+ bool "Diffie-Hellman operations on retained keys"
+ depends on KEYS
+ select MPILIB
+ help
+ This option provides support for calculating Diffie-Hellman
+ public keys and shared secrets using values stored as keys
+ in the kernel.
+
+ If you are unsure as to whether this is required, answer N.
diff --git a/security/keys/Makefile b/security/keys/Makefile
index dfb3a7bededf548ac1eed24b094de858e7a07df6..1fd4a16e6dafb6779f770690319918ad4341b9c7 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_KEYS_COMPAT) += compat.o
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SYSCTL) += sysctl.o
obj-$(CONFIG_PERSISTENT_KEYRINGS) += persistent.o
+obj-$(CONFIG_KEY_DH_OPERATIONS) += dh.o
#
# Key types
diff --git a/security/keys/compat.c b/security/keys/compat.c
index 25430a3aa7f7b9d6e6b4d10ae9bc72c8669c00fe..c8783b3b628ca6282bd59597eb1a7f685f1e48cc 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -132,6 +132,10 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
case KEYCTL_GET_PERSISTENT:
return keyctl_get_persistent(arg2, arg3);
+ case KEYCTL_DH_COMPUTE:
+ return keyctl_dh_compute(compat_ptr(arg2), compat_ptr(arg3),
+ arg4);
+
default:
return -EOPNOTSUPP;
}
diff --git a/security/keys/dh.c b/security/keys/dh.c
new file mode 100644
index 0000000000000000000000000000000000000000..880505a4b9f1e273429783aa5ebe1eee2579674c
--- /dev/null
+++ b/security/keys/dh.c
@@ -0,0 +1,160 @@
+/* Crypto operations using stored keys
+ *
+ * Copyright (c) 2016, Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/mpi.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+/*
+ * Public key or shared secret generation function [RFC2631 sec 2.1.1]
+ *
+ * ya = g^xa mod p;
+ * or
+ * ZZ = yb^xa mod p;
+ *
+ * where xa is the local private key, ya is the local public key, g is
+ * the generator, p is the prime, yb is the remote public key, and ZZ
+ * is the shared secret.
+ *
+ * Both are the same calculation, so g or yb are the "base" and ya or
+ * ZZ are the "result".
+ */
+static int do_dh(MPI result, MPI base, MPI xa, MPI p)
+{
+ return mpi_powm(result, base, xa, p);
+}
+
+static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
+{
+ struct key *key;
+ key_ref_t key_ref;
+ long status;
+ ssize_t ret;
+
+ key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
+ if (IS_ERR(key_ref)) {
+ ret = -ENOKEY;
+ goto error;
+ }
+
+ key = key_ref_to_ptr(key_ref);
+
+ ret = -EOPNOTSUPP;
+ if (key->type == &key_type_user) {
+ down_read(&key->sem);
+ status = key_validate(key);
+ if (status == 0) {
+ const struct user_key_payload *payload;
+
+ payload = user_key_payload(key);
+
+ if (maxlen == 0) {
+ *mpi = NULL;
+ ret = payload->datalen;
+ } else if (payload->datalen <= maxlen) {
+ *mpi = mpi_read_raw_data(payload->data,
+ payload->datalen);
+ if (*mpi)
+ ret = payload->datalen;
+ } else {
+ ret = -EINVAL;
+ }
+ }
+ up_read(&key->sem);
+ }
+
+ key_put(key);
+error:
+ return ret;
+}
+
+long keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen)
+{
+ long ret;
+ MPI base, private, prime, result;
+ unsigned nbytes;
+ struct keyctl_dh_params pcopy;
+ uint8_t *kbuf;
+ ssize_t keylen;
+ size_t resultlen;
+
+ if (!params || (!buffer && buflen)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ keylen = mpi_from_key(pcopy.prime, buflen, &prime);
+ if (keylen < 0 || !prime) {
+ /* buflen == 0 may be used to query the required buffer size,
+ * which is the prime key length.
+ */
+ ret = keylen;
+ goto out;
+ }
+
+ /* The result is never longer than the prime */
+ resultlen = keylen;
+
+ keylen = mpi_from_key(pcopy.base, SIZE_MAX, &base);
+ if (keylen < 0 || !base) {
+ ret = keylen;
+ goto error1;
+ }
+
+ keylen = mpi_from_key(pcopy.private, SIZE_MAX, &private);
+ if (keylen < 0 || !private) {
+ ret = keylen;
+ goto error2;
+ }
+
+ result = mpi_alloc(0);
+ if (!result) {
+ ret = -ENOMEM;
+ goto error3;
+ }
+
+ kbuf = kmalloc(resultlen, GFP_KERNEL);
+ if (!kbuf) {
+ ret = -ENOMEM;
+ goto error4;
+ }
+
+ ret = do_dh(result, base, private, prime);
+ if (ret)
+ goto error5;
+
+ ret = mpi_read_buffer(result, kbuf, resultlen, &nbytes, NULL);
+ if (ret != 0)
+ goto error5;
+
+ ret = nbytes;
+ if (copy_to_user(buffer, kbuf, nbytes) != 0)
+ ret = -EFAULT;
+
+error5:
+ kfree(kbuf);
+error4:
+ mpi_free(result);
+error3:
+ mpi_free(private);
+error2:
+ mpi_free(base);
+error1:
+ mpi_free(prime);
+out:
+ return ret;
+}
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 5105c2c2da75b0e13dec1196be67c88f4d789e72..8ec7a528365d967b8c82a97ded54c20df2459ce6 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -15,6 +15,7 @@
#include <linux/sched.h>
#include <linux/key-type.h>
#include <linux/task_work.h>
+#include <linux/keyctl.h>
struct iovec;
@@ -257,6 +258,17 @@ static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring)
}
#endif
+#ifdef CONFIG_KEY_DH_OPERATIONS
+extern long keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
+ size_t);
+#else
+static inline long keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen)
+{
+ return -EOPNOTSUPP;
+}
+#endif
+
/*
* Debugging key validation
*/
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index ed73c6c1c326c02bf0f4f80923e4792f292ec2fd..3b135a0af34406a52dc8019f664fd855c5ad0068 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1686,6 +1686,11 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
case KEYCTL_GET_PERSISTENT:
return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);
+ case KEYCTL_DH_COMPUTE:
+ return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
+ (char __user *) arg3,
+ (size_t) arg4);
+
default:
return -EOPNOTSUPP;
}