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-rw-r--r--lib/crypto/gkdi.c396
1 files changed, 396 insertions, 0 deletions
diff --git a/lib/crypto/gkdi.c b/lib/crypto/gkdi.c
new file mode 100644
index 0000000..6799dcf
--- /dev/null
+++ b/lib/crypto/gkdi.c
@@ -0,0 +1,396 @@
+/*
+ Unix SMB/CIFS implementation.
+ Group Key Distribution Protocol functions
+
+ Copyright (C) Catalyst.Net Ltd 2023
+
+ 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 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include <gnutls/gnutls.h>
+#include <gnutls/crypto.h>
+
+#include "lib/crypto/gnutls_helpers.h"
+
+#include "lib/util/bytearray.h"
+
+#include "librpc/gen_ndr/ndr_security.h"
+#include "librpc/gen_ndr/gkdi.h"
+#include "librpc/gen_ndr/ndr_gkdi.h"
+
+#include "lib/crypto/gkdi.h"
+
+static const uint8_t kds_service[] = {
+ /* “KDS service” as a NULL‐terminated UTF‐16LE string. */
+ 'K', 0, 'D', 0, 'S', 0, ' ', 0, 's', 0, 'e', 0,
+ 'r', 0, 'v', 0, 'i', 0, 'c', 0, 'e', 0, 0, 0,
+};
+
+struct GkdiContextShort {
+ uint8_t buf[sizeof((struct GUID_ndr_buf){}.buf) + sizeof(int32_t) +
+ sizeof(int32_t) + sizeof(int32_t)];
+};
+
+static NTSTATUS make_gkdi_context(const struct GkdiDerivationCtx *ctx,
+ struct GkdiContextShort *out_ctx)
+{
+ enum ndr_err_code ndr_err;
+ DATA_BLOB b = {.data = out_ctx->buf, .length = sizeof out_ctx->buf};
+
+ if (ctx->target_security_descriptor.length) {
+ return NT_STATUS_INVALID_PARAMETER;
+ }
+
+ ndr_err = ndr_push_struct_into_fixed_blob(
+ &b, ctx, (ndr_push_flags_fn_t)ndr_push_GkdiDerivationCtx);
+ if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+ return ndr_map_error2ntstatus(ndr_err);
+ }
+
+ return NT_STATUS_OK;
+}
+
+static NTSTATUS make_gkdi_context_security_descriptor(
+ TALLOC_CTX *mem_ctx,
+ const struct GkdiDerivationCtx *ctx,
+ const DATA_BLOB security_descriptor,
+ DATA_BLOB *out_ctx)
+{
+ enum ndr_err_code ndr_err;
+ struct GkdiDerivationCtx ctx_with_sd = *ctx;
+
+ if (ctx_with_sd.target_security_descriptor.length) {
+ return NT_STATUS_INVALID_PARAMETER;
+ }
+
+ ctx_with_sd.target_security_descriptor = security_descriptor;
+
+ ndr_err = ndr_push_struct_blob(out_ctx,
+ mem_ctx,
+ &ctx_with_sd,
+ (ndr_push_flags_fn_t)
+ ndr_push_GkdiDerivationCtx);
+ if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+ return ndr_map_error2ntstatus(ndr_err);
+ }
+
+ return NT_STATUS_OK;
+}
+
+struct GkdiContext {
+ struct GkdiDerivationCtx ctx;
+ gnutls_mac_algorithm_t algorithm;
+};
+
+gnutls_mac_algorithm_t get_sp800_108_mac_algorithm(
+ const struct KdfAlgorithm kdf_algorithm)
+{
+ switch (kdf_algorithm.id) {
+ case KDF_ALGORITHM_SP800_108_CTR_HMAC:
+ switch (kdf_algorithm.param.sp800_108) {
+ case KDF_PARAM_SHA1:
+ return GNUTLS_MAC_SHA1;
+ case KDF_PARAM_SHA256:
+ return GNUTLS_MAC_SHA256;
+ case KDF_PARAM_SHA384:
+ return GNUTLS_MAC_SHA384;
+ case KDF_PARAM_SHA512:
+ return GNUTLS_MAC_SHA512;
+ }
+ break;
+ }
+
+ return GNUTLS_MAC_UNKNOWN;
+}
+
+static NTSTATUS GkdiContext(const struct ProvRootKey *const root_key,
+ struct GkdiContext *const ctx)
+{
+ NTSTATUS status = NT_STATUS_OK;
+ gnutls_mac_algorithm_t algorithm = GNUTLS_MAC_UNKNOWN;
+
+ if (ctx == NULL) {
+ status = NT_STATUS_INVALID_PARAMETER;
+ goto out;
+ }
+
+ if (root_key == NULL) {
+ status = NT_STATUS_INVALID_PARAMETER;
+ goto out;
+ }
+
+ if (root_key->version != root_key_version_1) {
+ status = NT_STATUS_NOT_SUPPORTED;
+ goto out;
+ }
+
+ if (root_key->data.length != GKDI_KEY_LEN) {
+ status = NT_STATUS_NOT_SUPPORTED;
+ goto out;
+ }
+
+ algorithm = get_sp800_108_mac_algorithm(root_key->kdf_algorithm);
+ if (algorithm == GNUTLS_MAC_UNKNOWN) {
+ status = NT_STATUS_NOT_SUPPORTED;
+ goto out;
+ }
+
+ /*
+ * The context comprises the GUID corresponding to the root key, the
+ * GKID (which we shall initialize to zero), and the encoded target
+ * security descriptor (which will initially be empty).
+ */
+ *ctx = (struct GkdiContext){
+ .ctx = {.guid = root_key->id,
+ .l0_idx = 0,
+ .l1_idx = 0,
+ .l2_idx = 0,
+ .target_security_descriptor = {}},
+ .algorithm = algorithm,
+ };
+out:
+ return status;
+}
+
+static NTSTATUS compute_l1_seed_key(
+ TALLOC_CTX *mem_ctx,
+ struct GkdiContext *ctx,
+ const DATA_BLOB security_descriptor,
+ const struct ProvRootKey *const root_key,
+ const struct Gkid gkid,
+ uint8_t key[static const GKDI_KEY_LEN])
+{
+ NTSTATUS status = NT_STATUS_OK;
+ struct GkdiContextShort short_ctx;
+ int8_t n;
+
+ ctx->ctx.l0_idx = gkid.l0_idx;
+ ctx->ctx.l1_idx = -1;
+ ctx->ctx.l2_idx = -1;
+
+ status = make_gkdi_context(&ctx->ctx, &short_ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ /* Derive an L0 seed key with GKID = (L0, −1, −1). */
+
+ status = samba_gnutls_sp800_108_derive_key(root_key->data.data,
+ root_key->data.length,
+ NULL,
+ 0,
+ kds_service,
+ sizeof kds_service,
+ short_ctx.buf,
+ sizeof short_ctx.buf,
+ ctx->algorithm,
+ key,
+ GKDI_KEY_LEN);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ /* Derive an L1 seed key with GKID = (L0, 31, −1). */
+
+ ctx->ctx.l1_idx = 31;
+
+ {
+ DATA_BLOB security_descriptor_ctx;
+
+ status = make_gkdi_context_security_descriptor(
+ mem_ctx,
+ &ctx->ctx,
+ security_descriptor,
+ &security_descriptor_ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ status = samba_gnutls_sp800_108_derive_key(
+ key,
+ GKDI_KEY_LEN,
+ NULL,
+ 0,
+ kds_service,
+ sizeof kds_service,
+ security_descriptor_ctx.data,
+ security_descriptor_ctx.length,
+ ctx->algorithm,
+ key,
+ GKDI_KEY_LEN);
+ data_blob_free(&security_descriptor_ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+ }
+
+ for (n = 30; n >= gkid.l1_idx; --n) {
+ /* Derive an L1 seed key with GKID = (L0, n, −1). */
+
+ ctx->ctx.l1_idx = n;
+
+ status = make_gkdi_context(&ctx->ctx, &short_ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ status = samba_gnutls_sp800_108_derive_key(key,
+ GKDI_KEY_LEN,
+ NULL,
+ 0,
+ kds_service,
+ sizeof kds_service,
+ short_ctx.buf,
+ sizeof short_ctx.buf,
+ ctx->algorithm,
+ key,
+ GKDI_KEY_LEN);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+ }
+
+out:
+ return status;
+}
+
+static NTSTATUS derive_l2_seed_key(struct GkdiContext *ctx,
+ const struct Gkid gkid,
+ uint8_t key[static const GKDI_KEY_LEN])
+{
+ NTSTATUS status = NT_STATUS_OK;
+ int8_t n;
+
+ ctx->ctx.l0_idx = gkid.l0_idx;
+ ctx->ctx.l1_idx = gkid.l1_idx;
+
+ for (n = 31; n >= gkid.l2_idx; --n) {
+ struct GkdiContextShort short_ctx;
+
+ /* Derive an L2 seed key with GKID = (L0, L1, n). */
+
+ ctx->ctx.l2_idx = n;
+
+ status = make_gkdi_context(&ctx->ctx, &short_ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ status = samba_gnutls_sp800_108_derive_key(key,
+ GKDI_KEY_LEN,
+ NULL,
+ 0,
+ kds_service,
+ sizeof kds_service,
+ short_ctx.buf,
+ sizeof short_ctx.buf,
+ ctx->algorithm,
+ key,
+ GKDI_KEY_LEN);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+ }
+
+out:
+ return status;
+}
+
+static enum GkidType gkid_key_type(const struct Gkid gkid)
+{
+ if (gkid.l0_idx == -1) {
+ return GKID_DEFAULT;
+ }
+
+ if (gkid.l1_idx == -1) {
+ return GKID_L0_SEED_KEY;
+ }
+
+ if (gkid.l2_idx == -1) {
+ return GKID_L1_SEED_KEY;
+ }
+
+ return GKID_L2_SEED_KEY;
+}
+
+static bool gkid_is_valid(const struct Gkid gkid)
+{
+ if (gkid.l0_idx < -1) {
+ return false;
+ }
+
+ if (gkid.l1_idx < -1 || gkid.l1_idx >= gkdi_l1_key_iteration) {
+ return false;
+ }
+
+ if (gkid.l2_idx < -1 || gkid.l2_idx >= gkdi_l2_key_iteration) {
+ return false;
+ }
+
+ if (gkid.l0_idx == -1 && gkid.l1_idx != -1) {
+ return false;
+ }
+
+ if (gkid.l1_idx == -1 && gkid.l2_idx != -1) {
+ return false;
+ }
+
+ return true;
+}
+
+NTSTATUS compute_seed_key(
+ TALLOC_CTX *mem_ctx,
+ const DATA_BLOB target_security_descriptor,
+ const struct ProvRootKey *const root_key,
+ const struct Gkid gkid,
+ uint8_t key[static const GKDI_KEY_LEN])
+{
+ NTSTATUS status = NT_STATUS_OK;
+ enum GkidType gkid_type;
+ struct GkdiContext ctx;
+
+ if (!gkid_is_valid(gkid)) {
+ status = NT_STATUS_INVALID_PARAMETER;
+ goto out;
+ }
+
+ gkid_type = gkid_key_type(gkid);
+ if (gkid_type < GKID_L1_SEED_KEY) {
+ /* Don’t allow derivation of L0 seed keys. */
+ status = NT_STATUS_INVALID_PARAMETER;
+ goto out;
+ }
+
+ status = GkdiContext(root_key, &ctx);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ status = compute_l1_seed_key(
+ mem_ctx, &ctx, target_security_descriptor, root_key, gkid, key);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+
+ if (gkid_type == GKID_L2_SEED_KEY) {
+ status = derive_l2_seed_key(&ctx, gkid, key);
+ if (!NT_STATUS_IS_OK(status)) {
+ goto out;
+ }
+ }
+
+out:
+ return status;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-09 10:08:09 +0000