1/* 2 Unix SMB/CIFS implementation. 3 4 SMB2 Signing Code 5 6 Copyright (C) Andrew Tridgell <tridge@samba.org> 2008 7 8 This program is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or 11 (at your option) any later version. 12 13 This program is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with this program. If not, see <http://www.gnu.org/licenses/>. 20*/ 21 22#include "includes.h" 23#include "libcli/raw/libcliraw.h" 24#include "libcli/smb2/smb2.h" 25#include "libcli/smb2/smb2_calls.h" 26#include "../lib/crypto/crypto.h" 27 28/* 29 sign an outgoing message 30 */ 31NTSTATUS smb2_sign_message(struct smb2_request_buffer *buf, DATA_BLOB session_key) 32{ 33 struct HMACSHA256Context m; 34 uint8_t res[32]; 35 uint64_t session_id; 36 size_t hdr_offset; 37 38 if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) { 39 /* can't sign non-SMB2 messages */ 40 return NT_STATUS_OK; 41 } 42 43 hdr_offset = buf->hdr - buf->buffer; 44 45 session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID); 46 if (session_id == 0) { 47 /* we don't sign messages with a zero session_id. See 48 MS-SMB2 3.2.4.1.1 */ 49 return NT_STATUS_OK; 50 } 51 52 if (session_key.length == 0) { 53 DEBUG(2,("Wrong session key length %u for SMB2 signing\n", 54 (unsigned)session_key.length)); 55 return NT_STATUS_ACCESS_DENIED; 56 } 57 58 memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16); 59 60 SIVAL(buf->hdr, SMB2_HDR_FLAGS, IVAL(buf->hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED); 61 62 ZERO_STRUCT(m); 63 hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m); 64 hmac_sha256_update(buf->hdr, buf->size-hdr_offset, &m); 65 hmac_sha256_final(res, &m); 66 DEBUG(5,("signed SMB2 message of size %u\n", (unsigned)buf->size - NBT_HDR_SIZE)); 67 68 memcpy(buf->hdr + SMB2_HDR_SIGNATURE, res, 16); 69 70 return NT_STATUS_OK; 71} 72 73/* 74 check an incoming signature 75 */ 76NTSTATUS smb2_check_signature(struct smb2_request_buffer *buf, DATA_BLOB session_key) 77{ 78 uint64_t session_id; 79 struct HMACSHA256Context m; 80 uint8_t res[SHA256_DIGEST_LENGTH]; 81 uint8_t sig[16]; 82 size_t hdr_offset; 83 84 if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) { 85 /* can't check non-SMB2 messages */ 86 return NT_STATUS_OK; 87 } 88 89 hdr_offset = buf->hdr - buf->buffer; 90 91 session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID); 92 if (session_id == 0) { 93 /* don't sign messages with a zero session_id. See 94 MS-SMB2 3.2.4.1.1 */ 95 return NT_STATUS_OK; 96 } 97 98 if (session_key.length == 0) { 99 /* we don't have the session key yet */ 100 return NT_STATUS_OK; 101 } 102 103 memcpy(sig, buf->hdr+SMB2_HDR_SIGNATURE, 16); 104 105 memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16); 106 107 ZERO_STRUCT(m); 108 hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m); 109 hmac_sha256_update(buf->hdr, buf->size-hdr_offset, &m); 110 hmac_sha256_final(res, &m); 111 112 memcpy(buf->hdr+SMB2_HDR_SIGNATURE, sig, 16); 113 114 if (memcmp(res, sig, 16) != 0) { 115 DEBUG(0,("Bad SMB2 signature for message of size %u\n", 116 (unsigned)buf->size-NBT_HDR_SIZE)); 117 dump_data(0, sig, 16); 118 dump_data(0, res, 16); 119 return NT_STATUS_ACCESS_DENIED; 120 } 121 122 return NT_STATUS_OK; 123} 124