Provide key derivation interface functions and a helper to implement the
PRF+ function from rfc4402.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
crypto/krb5/Makefile | 1
crypto/krb5/kdf.c | 223 +++++++++++++++++++++++++++++++++++++++++++++++++
include/crypto/krb5.h | 29 ++++++
3 files changed, 253 insertions(+)
create mode 100644 crypto/krb5/kdf.c
diff --git a/crypto/krb5/Makefile b/crypto/krb5/Makefile
index 071ce2ff82e5..b764c4d09bf2 100644
--- a/crypto/krb5/Makefile
+++ b/crypto/krb5/Makefile
@@ -4,6 +4,7 @@
#
krb5-y += \
+ kdf.o \
main.o
obj-$(CONFIG_CRYPTO_KRB5) += krb5.o
diff --git a/crypto/krb5/kdf.c b/crypto/krb5/kdf.c
new file mode 100644
index 000000000000..8ef7ea31ee8a
--- /dev/null
+++ b/crypto/krb5/kdf.c
@@ -0,0 +1,223 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Kerberos key derivation.
+ *
+ * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <crypto/skcipher.h>
+#include <crypto/hash.h>
+#include "internal.h"
+
+/**
+ * crypto_krb5_free_enc_keys - Free an encryption keypair
+ * @e: The key pair to free.
+ */
+void crypto_krb5_free_enc_keys(struct krb5_enc_keys *e)
+{
+ if (e->Ke)
+ crypto_free_sync_skcipher(e->Ke);
+ if (e->Ki)
+ crypto_free_shash(e->Ki);
+ e->Ke = NULL;
+ e->Ki = NULL;
+}
+EXPORT_SYMBOL(crypto_krb5_free_enc_keys);
+
+/**
+ * crypto_krb5_calc_PRFplus - Calculate PRF+ [RFC4402]
+ * @krb5: The encryption type to use
+ * @K: The protocol key for the pseudo-random function
+ * @L: The length of the output
+ * @S: The input octet string
+ * @result: Result buffer, sized to krb5->prf_len
+ * @gfp: Allocation restrictions
+ *
+ * Calculate the kerberos pseudo-random function, PRF+() by the following
+ * method:
+ *
+ * PRF+(K, L, S) = truncate(L, T1 || T2 || .. || Tn)
+ * Tn = PRF(K, n || S)
+ * [rfc4402 sec 2]
+ */
+int crypto_krb5_calc_PRFplus(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *K,
+ unsigned int L,
+ const struct krb5_buffer *S,
+ struct krb5_buffer *result,
+ gfp_t gfp)
+{
+ struct krb5_buffer T_series, Tn, n_S;
+ void *buffer;
+ int ret, n = 1;
+
+ Tn.len = krb5->prf_len;
+ T_series.len = 0;
+ n_S.len = 4 + S->len;
+
+ buffer = kzalloc(round16(L + Tn.len) + round16(n_S.len), gfp);
+ if (!buffer)
+ return -ENOMEM;
+
+ T_series.data = buffer;
+ n_S.data = buffer + round16(L + Tn.len);
+ memcpy(n_S.data + 4, S->data, S->len);
+
+ while (T_series.len < L) {
+ *(__be32 *)(n_S.data) = htonl(n);
+ Tn.data = T_series.data + Tn.len * (n - 1);
+ ret = krb5->profile->calc_PRF(krb5, K, &n_S, &Tn, gfp);
+ if (ret < 0)
+ goto err;
+ T_series.len += Tn.len;
+ n++;
+ }
+
+ /* Truncate to L */
+ memcpy(result->data, T_series.data, L);
+ ret = 0;
+
+err:
+ kfree_sensitive(buffer);
+ return ret;
+}
+EXPORT_SYMBOL(crypto_krb5_calc_PRFplus);
+
+/**
+ * crypto_krb5_get_Kc - Derive key Kc and install into a hash
+ * @krb5: The encryption type to use
+ * @TK: The base key
+ * @usage: The key usage number
+ * @key: Prepped buffer to store the key into
+ * @_shash: Where to put the hash (or NULL if not wanted)
+ * @gfp: Allocation restrictions
+ *
+ * Derive the Kerberos Kc checksumming key and, optionally, allocate a hash and
+ * install the key into it, returning the hash. The key is stored into the
+ * prepared buffer.
+ */
+int crypto_krb5_get_Kc(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_shash **_shash,
+ gfp_t gfp)
+{
+ struct crypto_shash *shash;
+ int ret;
+ u8 buf[CRYPTO_MINALIGN] __aligned(CRYPTO_MINALIGN);
+ struct krb5_buffer usage_constant = { .len = 5, .data = buf };
+
+ *(__be32 *)buf = cpu_to_be32(usage);
+ buf[4] = KEY_USAGE_SEED_CHECKSUM;
+
+ key->len = krb5->Kc_len;
+ ret = krb5->profile->calc_Kc(krb5, TK, &usage_constant, key, gfp);
+ if (ret < 0)
+ return ret;
+
+ if (_shash) {
+ shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+ if (IS_ERR(shash))
+ return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
+ *_shash = shash;
+ ret = crypto_shash_setkey(shash, key->data, key->len);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(crypto_krb5_get_Kc);
+
+/**
+ * crypto_krb5_get_Ke - Derive key Ke and install into an skcipher
+ * @krb5: The encryption type to use
+ * @TK: The base key
+ * @usage: The key usage number
+ * @key: Prepped buffer to store the key into
+ * @_ci: Where to put the cipher (or NULL if not wanted)
+ * @gfp: Allocation restrictions
+ *
+ * Derive the Kerberos Ke encryption key and, optionally, allocate an skcipher
+ * and install the key into it, returning the cipher. The key is stored into
+ * the prepared buffer.
+ */
+int crypto_krb5_get_Ke(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_sync_skcipher **_ci,
+ gfp_t gfp)
+{
+ struct crypto_sync_skcipher *ci;
+ int ret;
+ u8 buf[CRYPTO_MINALIGN] __aligned(CRYPTO_MINALIGN);
+ struct krb5_buffer usage_constant = { .len = 5, .data = buf };
+
+ *(__be32 *)buf = cpu_to_be32(usage);
+ buf[4] = KEY_USAGE_SEED_ENCRYPTION;
+
+ key->len = krb5->Ke_len;
+ ret = krb5->profile->calc_Ke(krb5, TK, &usage_constant, key, gfp);
+ if (ret < 0)
+ return ret;
+
+ if (_ci) {
+ ci = crypto_alloc_sync_skcipher(krb5->encrypt_name, 0, 0);
+ if (IS_ERR(ci))
+ return (PTR_ERR(ci) == -ENOENT) ? -ENOPKG : PTR_ERR(ci);
+ *_ci = ci;
+ ret = crypto_sync_skcipher_setkey(ci, key->data, key->len);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(crypto_krb5_get_Ke);
+
+/**
+ * crypto_krb5_get_Ki - Derive key Ki and install into a hash
+ * @krb5: The encryption type to use
+ * @TK: The base key
+ * @usage: The key usage number
+ * @key: Prepped buffer to store the key into
+ * @_shash: Where to put the hash (or NULL if not wanted)
+ * @gfp: Allocation restrictions
+ *
+ * Derive the Kerberos Ki integrity checksum key and, optionally, allocate a
+ * hash and install the key into it, returning the hash. The key is stored
+ * into the prepared buffer.
+ */
+int crypto_krb5_get_Ki(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_shash **_shash,
+ gfp_t gfp)
+{
+ struct crypto_shash *shash;
+ int ret;
+ u8 buf[CRYPTO_MINALIGN] __aligned(CRYPTO_MINALIGN);
+ struct krb5_buffer usage_constant = { .len = 5, .data = buf };
+
+ *(__be32 *)buf = cpu_to_be32(usage);
+ buf[4] = KEY_USAGE_SEED_INTEGRITY;
+
+ key->len = krb5->Ki_len;
+ ret = krb5->profile->calc_Kc(krb5, TK, &usage_constant, key, gfp);
+ if (ret < 0)
+ return ret;
+
+ if (_shash) {
+ shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+ if (IS_ERR(shash))
+ return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
+ *_shash = shash;
+ ret = crypto_shash_setkey(shash, key->data, key->len);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(crypto_krb5_get_Ki);
diff --git a/include/crypto/krb5.h b/include/crypto/krb5.h
index a7e4ab4e1348..04286bacaf06 100644
--- a/include/crypto/krb5.h
+++ b/include/crypto/krb5.h
@@ -103,4 +103,33 @@ struct krb5_enctype {
*/
extern const struct krb5_enctype *crypto_krb5_find_enctype(u32 enctype);
+/*
+ * kdf.c
+ */
+extern void crypto_krb5_free_enc_keys(struct krb5_enc_keys *e);
+extern int crypto_krb5_calc_PRFplus(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *K,
+ unsigned int L,
+ const struct krb5_buffer *S,
+ struct krb5_buffer *result,
+ gfp_t gfp);
+extern int crypto_krb5_get_Kc(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_shash **_shash,
+ gfp_t gfp);
+extern int crypto_krb5_get_Ke(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_sync_skcipher **_ci,
+ gfp_t gfp);
+extern int crypto_krb5_get_Ki(const struct krb5_enctype *krb5,
+ const struct krb5_buffer *TK,
+ u32 usage,
+ struct krb5_buffer *key,
+ struct crypto_shash **_shash,
+ gfp_t gfp);
+
#endif /* _CRYPTO_KRB5_H */
