Move DRSUAPI per-attribute decryption into a common file

This file (contining metze's decryption routines) is now also be used by
Samba3's DRSUAPI implementation

Andrew Bartlett

3 files changed, 229 insertions, 0 deletions

diff --git a/libcli/drsuapi/config.mk b/libcli/drsuapi/config.mk
new file mode 100644
index 0000000000..cb002ca3dc
--- /dev/null
+++ b/libcli/drsuapi/config.mk
@@ -0,0 +1,8 @@
+[SUBSYSTEM::LIBCLI_DRSUAPI]
+PUBLIC_DEPENDENCIES = \
+		LIBCLI_AUTH
+
+LIBCLI_DRSUAPI_OBJ_FILES = $(addprefix $(libclicommonsrcdir)/drsuapi/, \
+		repl_decrypt.o)
+
+PUBLIC_HEADERS += ../libcli/drsuapi/drsuapi.h
diff --git a/libcli/drsuapi/drsuapi.h b/libcli/drsuapi/drsuapi.h
new file mode 100644
index 0000000000..b95350779a
--- /dev/null
+++ b/libcli/drsuapi/drsuapi.h
@@ -0,0 +1,33 @@
+/* 
+   Unix SMB/CIFS mplementation.
+   Helper functions for applying replicated objects
+   
+   Copyright (C) Stefan Metzmacher <metze@samba.org> 2007
+    
+   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 <http://www.gnu.org/licenses/>.
+   
+*/
+
+WERROR drsuapi_decrypt_attribute_value(TALLOC_CTX *mem_ctx,
+				       const DATA_BLOB *gensec_skey,
+				       bool rid_crypt,
+				       uint32_t rid,
+				       DATA_BLOB *in,
+				       DATA_BLOB *out);
+
+WERROR drsuapi_decrypt_attribute(TALLOC_CTX *mem_ctx, 
+				 const DATA_BLOB *gensec_skey,
+				 uint32_t rid,
+				 struct drsuapi_DsReplicaAttribute *attr);
+
diff --git a/libcli/drsuapi/repl_decrypt.c b/libcli/drsuapi/repl_decrypt.c
new file mode 100644
index 0000000000..9d7c1b6acf
--- /dev/null
+++ b/libcli/drsuapi/repl_decrypt.c
@@ -0,0 +1,188 @@
+/* 
+   Unix SMB/CIFS mplementation.
+   Helper functions for applying replicated objects
+   
+   Copyright (C) Stefan Metzmacher <metze@samba.org> 2007
+    
+   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 <http://www.gnu.org/licenses/>.
+   
+*/
+
+#include "includes.h"
+#include "../lib/util/dlinklist.h"
+#include "librpc/gen_ndr/ndr_misc.h"
+#include "librpc/gen_ndr/ndr_drsuapi.h"
+#include "librpc/gen_ndr/ndr_drsblobs.h"
+#include "../lib/crypto/crypto.h"
+#include "../libcli/drsuapi/drsuapi.h"
+#include "libcli/auth/libcli_auth.h"
+
+WERROR drsuapi_decrypt_attribute_value(TALLOC_CTX *mem_ctx,
+				       const DATA_BLOB *gensec_skey,
+				       bool rid_crypt,
+				       uint32_t rid,
+				       DATA_BLOB *in,
+				       DATA_BLOB *out)
+{
+	DATA_BLOB confounder;
+	DATA_BLOB enc_buffer;
+
+	struct MD5Context md5;
+	uint8_t _enc_key[16];
+	DATA_BLOB enc_key;
+
+	DATA_BLOB dec_buffer;
+
+	uint32_t crc32_given;
+	uint32_t crc32_calc;
+	DATA_BLOB checked_buffer;
+
+	DATA_BLOB plain_buffer;
+
+	/*
+	 * users with rid == 0 should not exist
+	 */
+	if (rid_crypt && rid == 0) {
+		return WERR_DS_DRA_INVALID_PARAMETER;
+	}
+
+	/* 
+	 * the first 16 bytes at the beginning are the confounder
+	 * followed by the 4 byte crc32 checksum
+	 */
+	if (in->length < 20) {
+		return WERR_DS_DRA_INVALID_PARAMETER;
+	}
+	confounder = data_blob_const(in->data, 16);
+	enc_buffer = data_blob_const(in->data + 16, in->length - 16);
+
+	/* 
+	 * build the encryption key md5 over the session key followed
+	 * by the confounder
+	 * 
+	 * here the gensec session key is used and
+	 * not the dcerpc ncacn_ip_tcp "SystemLibraryDTC" key!
+	 */
+	enc_key = data_blob_const(_enc_key, sizeof(_enc_key));
+	MD5Init(&md5);
+	MD5Update(&md5, gensec_skey->data, gensec_skey->length);
+	MD5Update(&md5, confounder.data, confounder.length);
+	MD5Final(enc_key.data, &md5);
+
+	/*
+	 * copy the encrypted buffer part and 
+	 * decrypt it using the created encryption key using arcfour
+	 */
+	dec_buffer = data_blob_const(enc_buffer.data, enc_buffer.length);
+	arcfour_crypt_blob(dec_buffer.data, dec_buffer.length, &enc_key);
+
+	/* 
+	 * the first 4 byte are the crc32 checksum
+	 * of the remaining bytes
+	 */
+	crc32_given = IVAL(dec_buffer.data, 0);
+	crc32_calc = crc32_calc_buffer(dec_buffer.data + 4 , dec_buffer.length - 4);
+	if (crc32_given != crc32_calc) {
+		return WERR_SEC_E_DECRYPT_FAILURE;
+	}
+	checked_buffer = data_blob_const(dec_buffer.data + 4, dec_buffer.length - 4);
+
+	plain_buffer = data_blob_talloc(mem_ctx, checked_buffer.data, checked_buffer.length);
+	W_ERROR_HAVE_NO_MEMORY(plain_buffer.data);
+
+	/*
+	 * The following rid_crypt obfuscation isn't session specific
+	 * and not really needed here, because we allways know the rid of the
+	 * user account.
+	 *
+	 * some attributes with this 'additional encryption' include
+	 * dBCSPwd, unicodePwd, ntPwdHistory, lmPwdHistory
+	 *
+	 * But for the rest of samba it's easier when we remove this static
+	 * obfuscation here
+	 */
+	if (rid_crypt) {
+		uint32_t i, num_hashes;
+
+		if ((checked_buffer.length % 16) != 0) {
+			return WERR_DS_DRA_INVALID_PARAMETER;
+		}
+
+		num_hashes = plain_buffer.length / 16;
+		for (i = 0; i < num_hashes; i++) {
+			uint32_t offset = i * 16;
+			sam_rid_crypt(rid, checked_buffer.data + offset, plain_buffer.data + offset, 0);
+		}
+	}
+
+	*out = plain_buffer;
+	return WERR_OK;
+}
+
+WERROR drsuapi_decrypt_attribute(TALLOC_CTX *mem_ctx, 
+				 const DATA_BLOB *gensec_skey,
+				 uint32_t rid,
+				 struct drsuapi_DsReplicaAttribute *attr)
+{
+	WERROR status;
+	DATA_BLOB *enc_data;
+	DATA_BLOB plain_data;
+	bool rid_crypt = false;
+
+	if (attr->value_ctr.num_values == 0) {
+		return WERR_OK;
+	}
+
+	switch (attr->attid) {
+	case DRSUAPI_ATTRIBUTE_dBCSPwd:
+	case DRSUAPI_ATTRIBUTE_unicodePwd:
+	case DRSUAPI_ATTRIBUTE_ntPwdHistory:
+	case DRSUAPI_ATTRIBUTE_lmPwdHistory:
+		rid_crypt = true;
+		break;
+	case DRSUAPI_ATTRIBUTE_supplementalCredentials:
+	case DRSUAPI_ATTRIBUTE_priorValue:
+	case DRSUAPI_ATTRIBUTE_currentValue:
+	case DRSUAPI_ATTRIBUTE_trustAuthOutgoing:
+	case DRSUAPI_ATTRIBUTE_trustAuthIncoming:
+	case DRSUAPI_ATTRIBUTE_initialAuthOutgoing:
+	case DRSUAPI_ATTRIBUTE_initialAuthIncoming:
+		break;
+	default:
+		return WERR_OK;
+	}
+
+	if (attr->value_ctr.num_values > 1) {
+		return WERR_DS_DRA_INVALID_PARAMETER;
+	}
+
+	if (!attr->value_ctr.values[0].blob) {
+		return WERR_DS_DRA_INVALID_PARAMETER;
+	}
+
+	enc_data	= attr->value_ctr.values[0].blob;
+
+	status = drsuapi_decrypt_attribute_value(mem_ctx,
+						 gensec_skey,
+						 rid_crypt,
+						 rid,
+						 enc_data,
+						 &plain_data);
+	W_ERROR_NOT_OK_RETURN(status);
+
+	talloc_free(attr->value_ctr.values[0].blob->data);
+	*attr->value_ctr.values[0].blob = plain_data;
+
+	return WERR_OK;
+}