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authorStephan Mueller <smueller@chronox.de>2016-08-19 20:39:09 +0200
committerDavid Howells <dhowells@redhat.com>2017-04-04 22:33:38 +0100
commitf1c316a3ab9d24df6022682422fe897492f2c0c8 (patch)
tree369b53c45d1f0c2bbd4c6f745cb9a694e1b28cbe /security/keys
parentf0df90cd7cf2f4a8195c3fff0d2f4c85088fd39c (diff)
KEYS: add SP800-56A KDF support for DH
SP800-56A defines the use of DH with key derivation function based on a counter. The input to the KDF is defined as (DH shared secret || other information). The value for the "other information" is to be provided by the caller. The KDF is implemented using the hash support from the kernel crypto API. The implementation uses the symmetric hash support as the input to the hash operation is usually very small. The caller is allowed to specify the hash name that he wants to use to derive the key material allowing the use of all supported hashes provided with the kernel crypto API. As the KDF implements the proper truncation of the DH shared secret to the requested size, this patch fills the caller buffer up to its size. The patch is tested with a new test added to the keyutils user space code which uses a CAVS test vector testing the compliance with SP800-56A. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/Kconfig1
-rw-r--r--security/keys/Makefile3
-rw-r--r--security/keys/compat.c5
-rw-r--r--security/keys/compat_dh.c38
-rw-r--r--security/keys/dh.c220
-rw-r--r--security/keys/internal.h24
-rw-r--r--security/keys/keyctl.c2
7 files changed, 275 insertions, 18 deletions
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index d942c7c2bc0a..4ac1b83a23f8 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -90,6 +90,7 @@ config KEY_DH_OPERATIONS
bool "Diffie-Hellman operations on retained keys"
depends on KEYS
select MPILIB
+ select CRYPTO_HASH
help
This option provides support for calculating Diffie-Hellman
public keys and shared secrets using values stored as keys
diff --git a/security/keys/Makefile b/security/keys/Makefile
index 1fd4a16e6daf..57dff0c15809 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -15,7 +15,8 @@ obj-y := \
request_key.o \
request_key_auth.o \
user_defined.o
-obj-$(CONFIG_KEYS_COMPAT) += compat.o
+compat-obj-$(CONFIG_KEY_DH_OPERATIONS) += compat_dh.o
+obj-$(CONFIG_KEYS_COMPAT) += compat.o $(compat-obj-y)
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SYSCTL) += sysctl.o
obj-$(CONFIG_PERSISTENT_KEYRINGS) += persistent.o
diff --git a/security/keys/compat.c b/security/keys/compat.c
index bb98f2b8dd7d..e87c89c0177c 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -133,8 +133,9 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
return keyctl_get_persistent(arg2, arg3);
case KEYCTL_DH_COMPUTE:
- return keyctl_dh_compute(compat_ptr(arg2), compat_ptr(arg3),
- arg4, compat_ptr(arg5));
+ return compat_keyctl_dh_compute(compat_ptr(arg2),
+ compat_ptr(arg3),
+ arg4, compat_ptr(arg5));
case KEYCTL_RESTRICT_KEYRING:
return keyctl_restrict_keyring(arg2, compat_ptr(arg3),
diff --git a/security/keys/compat_dh.c b/security/keys/compat_dh.c
new file mode 100644
index 000000000000..a6a659b6bcb6
--- /dev/null
+++ b/security/keys/compat_dh.c
@@ -0,0 +1,38 @@
+/* 32-bit compatibility syscall for 64-bit systems for DH operations
+ *
+ * Copyright (C) 2016 Stephan Mueller <smueller@chronox.de>
+ *
+ * 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/uaccess.h>
+
+#include "internal.h"
+
+/*
+ * Perform the DH computation or DH based key derivation.
+ *
+ * If successful, 0 will be returned.
+ */
+long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen,
+ struct compat_keyctl_kdf_params __user *kdf)
+{
+ struct keyctl_kdf_params kdfcopy;
+ struct compat_keyctl_kdf_params compat_kdfcopy;
+
+ if (!kdf)
+ return __keyctl_dh_compute(params, buffer, buflen, NULL);
+
+ if (copy_from_user(&compat_kdfcopy, kdf, sizeof(compat_kdfcopy)) != 0)
+ return -EFAULT;
+
+ kdfcopy.hashname = compat_ptr(compat_kdfcopy.hashname);
+ kdfcopy.otherinfo = compat_ptr(compat_kdfcopy.otherinfo);
+ kdfcopy.otherinfolen = compat_kdfcopy.otherinfolen;
+
+ return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
+}
diff --git a/security/keys/dh.c b/security/keys/dh.c
index 893af4c45038..e603bd912e4c 100644
--- a/security/keys/dh.c
+++ b/security/keys/dh.c
@@ -11,6 +11,8 @@
#include <linux/mpi.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
+#include <linux/crypto.h>
+#include <crypto/hash.h>
#include <keys/user-type.h>
#include "internal.h"
@@ -77,9 +79,146 @@ error:
return ret;
}
-long keyctl_dh_compute(struct keyctl_dh_params __user *params,
- char __user *buffer, size_t buflen,
- void __user *reserved)
+struct kdf_sdesc {
+ struct shash_desc shash;
+ char ctx[];
+};
+
+static int kdf_alloc(struct kdf_sdesc **sdesc_ret, char *hashname)
+{
+ struct crypto_shash *tfm;
+ struct kdf_sdesc *sdesc;
+ int size;
+
+ /* allocate synchronous hash */
+ tfm = crypto_alloc_shash(hashname, 0, 0);
+ if (IS_ERR(tfm)) {
+ pr_info("could not allocate digest TFM handle %s\n", hashname);
+ return PTR_ERR(tfm);
+ }
+
+ size = sizeof(struct shash_desc) + crypto_shash_descsize(tfm);
+ sdesc = kmalloc(size, GFP_KERNEL);
+ if (!sdesc)
+ return -ENOMEM;
+ sdesc->shash.tfm = tfm;
+ sdesc->shash.flags = 0x0;
+
+ *sdesc_ret = sdesc;
+
+ return 0;
+}
+
+static void kdf_dealloc(struct kdf_sdesc *sdesc)
+{
+ if (!sdesc)
+ return;
+
+ if (sdesc->shash.tfm)
+ crypto_free_shash(sdesc->shash.tfm);
+
+ kzfree(sdesc);
+}
+
+/* convert 32 bit integer into its string representation */
+static inline void crypto_kw_cpu_to_be32(u32 val, u8 *buf)
+{
+ __be32 *a = (__be32 *)buf;
+
+ *a = cpu_to_be32(val);
+}
+
+/*
+ * Implementation of the KDF in counter mode according to SP800-108 section 5.1
+ * as well as SP800-56A section 5.8.1 (Single-step KDF).
+ *
+ * SP800-56A:
+ * The src pointer is defined as Z || other info where Z is the shared secret
+ * from DH and other info is an arbitrary string (see SP800-56A section
+ * 5.8.1.2).
+ */
+static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
+ u8 *dst, unsigned int dlen)
+{
+ struct shash_desc *desc = &sdesc->shash;
+ unsigned int h = crypto_shash_digestsize(desc->tfm);
+ int err = 0;
+ u8 *dst_orig = dst;
+ u32 i = 1;
+ u8 iteration[sizeof(u32)];
+
+ while (dlen) {
+ err = crypto_shash_init(desc);
+ if (err)
+ goto err;
+
+ crypto_kw_cpu_to_be32(i, iteration);
+ err = crypto_shash_update(desc, iteration, sizeof(u32));
+ if (err)
+ goto err;
+
+ if (src && slen) {
+ err = crypto_shash_update(desc, src, slen);
+ if (err)
+ goto err;
+ }
+
+ if (dlen < h) {
+ u8 tmpbuffer[h];
+
+ err = crypto_shash_final(desc, tmpbuffer);
+ if (err)
+ goto err;
+ memcpy(dst, tmpbuffer, dlen);
+ memzero_explicit(tmpbuffer, h);
+ return 0;
+ } else {
+ err = crypto_shash_final(desc, dst);
+ if (err)
+ goto err;
+
+ dlen -= h;
+ dst += h;
+ i++;
+ }
+ }
+
+ return 0;
+
+err:
+ memzero_explicit(dst_orig, dlen);
+ return err;
+}
+
+static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
+ char __user *buffer, size_t buflen,
+ uint8_t *kbuf, size_t kbuflen)
+{
+ uint8_t *outbuf = NULL;
+ int ret;
+
+ outbuf = kmalloc(buflen, GFP_KERNEL);
+ if (!outbuf) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen);
+ if (ret)
+ goto err;
+
+ ret = buflen;
+ if (copy_to_user(buffer, outbuf, buflen) != 0)
+ ret = -EFAULT;
+
+err:
+ kzfree(outbuf);
+ return ret;
+}
+
+long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen,
+ struct keyctl_kdf_params *kdfcopy)
{
long ret;
MPI base, private, prime, result;
@@ -88,6 +227,7 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
uint8_t *kbuf;
ssize_t keylen;
size_t resultlen;
+ struct kdf_sdesc *sdesc = NULL;
if (!params || (!buffer && buflen)) {
ret = -EINVAL;
@@ -98,12 +238,34 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
goto out;
}
- if (reserved) {
- ret = -EINVAL;
- goto out;
+ if (kdfcopy) {
+ char *hashname;
+
+ if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
+ kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
+ ret = -EMSGSIZE;
+ goto out;
+ }
+
+ /* get KDF name string */
+ hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
+ if (IS_ERR(hashname)) {
+ ret = PTR_ERR(hashname);
+ goto out;
+ }
+
+ /* allocate KDF from the kernel crypto API */
+ ret = kdf_alloc(&sdesc, hashname);
+ kfree(hashname);
+ if (ret)
+ goto out;
}
- keylen = mpi_from_key(pcopy.prime, buflen, &prime);
+ /*
+ * If the caller requests postprocessing with a KDF, allow an
+ * arbitrary output buffer size since the KDF ensures proper truncation.
+ */
+ keylen = mpi_from_key(pcopy.prime, kdfcopy ? SIZE_MAX : buflen, &prime);
if (keylen < 0 || !prime) {
/* buflen == 0 may be used to query the required buffer size,
* which is the prime key length.
@@ -133,12 +295,25 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
goto error3;
}
- kbuf = kmalloc(resultlen, GFP_KERNEL);
+ /* allocate space for DH shared secret and SP800-56A otherinfo */
+ kbuf = kmalloc(kdfcopy ? (resultlen + kdfcopy->otherinfolen) : resultlen,
+ GFP_KERNEL);
if (!kbuf) {
ret = -ENOMEM;
goto error4;
}
+ /*
+ * Concatenate SP800-56A otherinfo past DH shared secret -- the
+ * input to the KDF is (DH shared secret || otherinfo)
+ */
+ if (kdfcopy && kdfcopy->otherinfo &&
+ copy_from_user(kbuf + resultlen, kdfcopy->otherinfo,
+ kdfcopy->otherinfolen) != 0) {
+ ret = -EFAULT;
+ goto error5;
+ }
+
ret = do_dh(result, base, private, prime);
if (ret)
goto error5;
@@ -147,12 +322,17 @@ long keyctl_dh_compute(struct keyctl_dh_params __user *params,
if (ret != 0)
goto error5;
- ret = nbytes;
- if (copy_to_user(buffer, kbuf, nbytes) != 0)
- ret = -EFAULT;
+ if (kdfcopy) {
+ ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, kbuf,
+ resultlen + kdfcopy->otherinfolen);
+ } else {
+ ret = nbytes;
+ if (copy_to_user(buffer, kbuf, nbytes) != 0)
+ ret = -EFAULT;
+ }
error5:
- kfree(kbuf);
+ kzfree(kbuf);
error4:
mpi_free(result);
error3:
@@ -162,5 +342,21 @@ error2:
error1:
mpi_free(prime);
out:
+ kdf_dealloc(sdesc);
return ret;
}
+
+long keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen,
+ struct keyctl_kdf_params __user *kdf)
+{
+ struct keyctl_kdf_params kdfcopy;
+
+ if (!kdf)
+ return __keyctl_dh_compute(params, buffer, buflen, NULL);
+
+ if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
+ return -EFAULT;
+
+ return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
+}
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 6ce016314897..c0f8682eba69 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -18,6 +18,7 @@
#include <linux/task_work.h>
#include <linux/keyctl.h>
#include <linux/refcount.h>
+#include <linux/compat.h>
struct iovec;
@@ -267,15 +268,34 @@ static inline long keyctl_get_persistent(uid_t uid, key_serial_t destring)
#ifdef CONFIG_KEY_DH_OPERATIONS
extern long keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
- size_t, void __user *);
+ size_t, struct keyctl_kdf_params __user *);
+extern long __keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
+ size_t, struct keyctl_kdf_params *);
+#ifdef CONFIG_KEYS_COMPAT
+extern long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen,
+ struct compat_keyctl_kdf_params __user *kdf);
+#endif
+#define KEYCTL_KDF_MAX_OUTPUT_LEN 1024 /* max length of KDF output */
+#define KEYCTL_KDF_MAX_OI_LEN 64 /* max length of otherinfo */
#else
static inline long keyctl_dh_compute(struct keyctl_dh_params __user *params,
char __user *buffer, size_t buflen,
- void __user *reserved)
+ struct keyctl_kdf_params __user *kdf)
+{
+ return -EOPNOTSUPP;
+}
+
+#ifdef CONFIG_KEYS_COMPAT
+static inline long compat_keyctl_dh_compute(
+ struct keyctl_dh_params __user *params,
+ char __user *buffer, size_t buflen,
+ struct keyctl_kdf_params __user *kdf)
{
return -EOPNOTSUPP;
}
#endif
+#endif
/*
* Debugging key validation
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 6ee2826a2d06..10fcea154c0f 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1744,7 +1744,7 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
case KEYCTL_DH_COMPUTE:
return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
(char __user *) arg3, (size_t) arg4,
- (void __user *) arg5);
+ (struct keyctl_kdf_params __user *) arg5);
case KEYCTL_RESTRICT_KEYRING:
return keyctl_restrict_keyring((key_serial_t) arg2,