source: vendor/current/libcli/smb/smb_seal.c

/*
   Unix SMB/CIFS implementation.
   SMB Transport encryption (sealing) code.
   Copyright (C) Jeremy Allison 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 "smb_common.h"
#if HAVE_KRB5
#include "lib/krb5_wrap/krb5_samba.h"
#endif
#include "auth/gensec/gensec.h"
#include "libcli/smb/smb_seal.h"

#undef malloc

/******************************************************************************
 Pull out the encryption context for this packet. 0 means global context.
******************************************************************************/

NTSTATUS get_enc_ctx_num(const uint8_t *buf, uint16_t *p_enc_ctx_num)
{
        if (smb_len_nbt(buf) < 8) {
                return NT_STATUS_INVALID_BUFFER_SIZE;
        }

        if (buf[4] == 0xFF) {
                if (buf[5] == 'S' && buf [6] == 'M' && buf[7] == 'B') {
                        /* Not an encrypted buffer. */
                        return NT_STATUS_NOT_FOUND;
                }
                if (buf[5] == 'E') {
                        *p_enc_ctx_num = SVAL(buf,6);
                        return NT_STATUS_OK;
                }
        }
        return NT_STATUS_INVALID_NETWORK_RESPONSE;
}

/*******************************************************************
 Set the length and marker of an encrypted smb packet.
********************************************************************/

static void smb_set_enclen(char *buf,int len,uint16_t enc_ctx_num)
{
        _smb_setlen_tcp(buf,len);

        SCVAL(buf,4,0xFF);
        SCVAL(buf,5,'E');
        SSVAL(buf,6,enc_ctx_num);
}

/******************************************************************************
 Generic code for client and server.
 Is encryption turned on ?
******************************************************************************/

bool common_encryption_on(struct smb_trans_enc_state *es)
{
        return ((es != NULL) && es->enc_on);
}

/******************************************************************************
 Generic code for client and server.
 GENSEC decrypt an incoming buffer.
******************************************************************************/

static NTSTATUS common_gensec_decrypt_buffer(struct gensec_security *gensec,
                                             char *buf)
{
        NTSTATUS status;
        size_t buf_len = smb_len_nbt(buf) + 4; /* Don't forget the 4 length bytes. */
        DATA_BLOB in_buf, out_buf;
        TALLOC_CTX *frame;

        if (buf_len < 8) {
                return NT_STATUS_BUFFER_TOO_SMALL;
        }

        frame = talloc_stackframe();

        in_buf = data_blob_const(buf + 8, buf_len - 8);

        status = gensec_unwrap(gensec, frame, &in_buf, &out_buf);

        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0,("common_gensec_decrypt_buffer: gensec_unwrap failed. Error %s\n",
                         nt_errstr(status)));
                TALLOC_FREE(frame);
                return status;
        }

        if (out_buf.length > in_buf.length) {
                DEBUG(0,("common_gensec_decrypt_buffer: gensec_unwrap size (%u) too large (%u) !\n",
                        (unsigned int)out_buf.length,
                        (unsigned int)in_buf.length ));
                TALLOC_FREE(frame);
                return NT_STATUS_INVALID_PARAMETER;
        }

        memcpy(buf + 8, out_buf.data, out_buf.length);

        /* Reset the length and overwrite the header. */
        smb_setlen_nbt(buf, out_buf.length + 4);

        TALLOC_FREE(frame);

        return NT_STATUS_OK;
}

/******************************************************************************
 Generic code for client and server.
 NTLM encrypt an outgoing buffer. Return the encrypted pointer in ppbuf_out.
******************************************************************************/

static NTSTATUS common_gensec_encrypt_buffer(struct gensec_security *gensec,
                                      uint16_t enc_ctx_num,
                                      char *buf,
                                      char **ppbuf_out)
{
        NTSTATUS status;
        DATA_BLOB in_buf, out_buf;
        size_t buf_len = smb_len_nbt(buf) + 4; /* Don't forget the 4 length bytes. */
        TALLOC_CTX *frame;

        *ppbuf_out = NULL;

        if (buf_len < 8) {
                return NT_STATUS_BUFFER_TOO_SMALL;
        }
        in_buf = data_blob_const(buf + 8, buf_len - 8);

        frame = talloc_stackframe();

        status = gensec_wrap(gensec, frame, &in_buf, &out_buf);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0,("common_gensec_encrypt_buffer: gensec_wrap failed. Error %s\n",
                         nt_errstr(status)));
                TALLOC_FREE(frame);
                return status;
        }

        *ppbuf_out = (char *)malloc(out_buf.length + 8); /* We know this can't wrap. */
        if (!*ppbuf_out) {
                TALLOC_FREE(frame);
                return NT_STATUS_NO_MEMORY;
        }

        memcpy(*ppbuf_out+8, out_buf.data, out_buf.length);
        smb_set_enclen(*ppbuf_out, out_buf.length + 4, enc_ctx_num);

        TALLOC_FREE(frame);

        return NT_STATUS_OK;
}

/******************************************************************************
 Generic code for client and server.
 Encrypt an outgoing buffer. Return the alloced encrypted pointer in buf_out.
******************************************************************************/

NTSTATUS common_encrypt_buffer(struct smb_trans_enc_state *es, char *buffer, char **buf_out)
{
        if (!common_encryption_on(es)) {
                /* Not encrypting. */
                *buf_out = buffer;
                return NT_STATUS_OK;
        }

        return common_gensec_encrypt_buffer(es->gensec_security, es->enc_ctx_num, buffer, buf_out);
}

/******************************************************************************
 Generic code for client and server.
 Decrypt an incoming SMB buffer. Replaces the data within it.
 New data must be less than or equal to the current length.
******************************************************************************/

NTSTATUS common_decrypt_buffer(struct smb_trans_enc_state *es, char *buf)
{
        if (!common_encryption_on(es)) {
                /* Not decrypting. */
                return NT_STATUS_OK;
        }

        return common_gensec_decrypt_buffer(es->gensec_security, buf);
}

/******************************************************************************
 Free an encryption-allocated buffer.
******************************************************************************/

void common_free_enc_buffer(struct smb_trans_enc_state *es, char *buf)
{
        uint16_t enc_ctx_num;

        if (!common_encryption_on(es)) {
                return;
        }

        if (!NT_STATUS_IS_OK(get_enc_ctx_num((const uint8_t *)buf,
                        &enc_ctx_num))) {
                return;
        }

        SAFE_FREE(buf);
}