source: branches/samba-3.5.x/libcli/auth/session.c

/* 
   Unix SMB/CIFS implementation.

   code to encrypt/decrypt data using the user session key

   Copyright (C) Andrew Tridgell 2004
   
   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 "libcli/auth/libcli_auth.h"

/*
  encrypt or decrypt a blob of data using the user session key
  as used in lsa_SetSecret

  before calling, the out blob must be initialised to be the same size
  as the in blob
*/
void sess_crypt_blob(DATA_BLOB *out, const DATA_BLOB *in, const DATA_BLOB *session_key,
                     bool forward)
{
        int i, k;

        for (i=0,k=0;
             i<in->length;
             i += 8, k += 7) {
                uint8_t bin[8], bout[8], key[7];

                memset(bin, 0, 8);
                memcpy(bin,  &in->data[i], MIN(8, in->length-i));

                if (k + 7 > session_key->length) {
                        k = (session_key->length - k);
                }
                memcpy(key, &session_key->data[k], 7);

                des_crypt56(bout, bin, key, forward?1:0);

                memcpy(&out->data[i], bout, MIN(8, in->length-i));
        }
}


/*
  a convenient wrapper around sess_crypt_blob() for strings, using the LSA convention

  note that we round the length to a multiple of 8. This seems to be needed for 
  compatibility with windows

  caller should free using data_blob_free()
*/
DATA_BLOB sess_encrypt_string(const char *str, const DATA_BLOB *session_key)
{
        DATA_BLOB ret, src;
        int slen = strlen(str);
        int dlen = (slen+7) & ~7;

        src = data_blob(NULL, 8+dlen);
        if (!src.data) {
                return data_blob(NULL, 0);
        }

        ret = data_blob(NULL, 8+dlen);
        if (!ret.data) {
                data_blob_free(&src);
                return data_blob(NULL, 0);
        }

        SIVAL(src.data, 0, slen);
        SIVAL(src.data, 4, 1);
        memset(src.data+8, 0,   dlen);
        memcpy(src.data+8, str, slen);

        sess_crypt_blob(&ret, &src, session_key, true);
        
        data_blob_free(&src);

        return ret;
}

/*
  a convenient wrapper around sess_crypt_blob() for strings, using the LSA convention

  caller should free the returned string
*/
char *sess_decrypt_string(TALLOC_CTX *mem_ctx, 
                          DATA_BLOB *blob, const DATA_BLOB *session_key)
{
        DATA_BLOB out;
        int slen;
        char *ret;

        if (blob->length < 8) {
                return NULL;
        }
        
        out = data_blob_talloc(mem_ctx, NULL, blob->length);
        if (!out.data) {
                return NULL;
        }

        sess_crypt_blob(&out, blob, session_key, false);

        if (IVAL(out.data, 4) != 1) {
                DEBUG(0,("Unexpected revision number %d in session crypted string\n",
                         IVAL(out.data, 4)));
                data_blob_free(&out);
                return NULL;
        }

        slen = IVAL(out.data, 0);
        if (slen > blob->length - 8) {
                DEBUG(0,("Invalid crypt length %d\n", slen));
                data_blob_free(&out);
                return NULL;
        }

        ret = talloc_strndup(mem_ctx, (const char *)(out.data+8), slen);

        data_blob_free(&out);

        DEBUG(0,("decrypted string '%s' of length %d\n", ret, slen));

        return ret;
}

/*
  a convenient wrapper around sess_crypt_blob() for DATA_BLOBs, using the LSA convention

  note that we round the length to a multiple of 8. This seems to be needed for 
  compatibility with windows

  caller should free using data_blob_free()
*/
DATA_BLOB sess_encrypt_blob(TALLOC_CTX *mem_ctx, DATA_BLOB *blob_in, const DATA_BLOB *session_key)
{
        DATA_BLOB ret, src;
        int dlen = (blob_in->length+7) & ~7;

        src = data_blob_talloc(mem_ctx, NULL, 8+dlen);
        if (!src.data) {
                return data_blob(NULL, 0);
        }

        ret = data_blob_talloc(mem_ctx, NULL, 8+dlen);
        if (!ret.data) {
                data_blob_free(&src);
                return data_blob(NULL, 0);
        }

        SIVAL(src.data, 0, blob_in->length);
        SIVAL(src.data, 4, 1);
        memset(src.data+8, 0, dlen);
        memcpy(src.data+8, blob_in->data, blob_in->length);

        sess_crypt_blob(&ret, &src, session_key, true);
        
        data_blob_free(&src);

        return ret;
}

/*
  Decrypt a DATA_BLOB using the LSA convention
*/
NTSTATUS sess_decrypt_blob(TALLOC_CTX *mem_ctx, const DATA_BLOB *blob, const DATA_BLOB *session_key, 
                           DATA_BLOB *ret)
{
        DATA_BLOB out;
        int slen;

        if (blob->length < 8) {
                DEBUG(0, ("Unexpected length %d in session crypted secret (BLOB)\n",
                          (int)blob->length));
                return NT_STATUS_INVALID_PARAMETER;
        }
        
        out = data_blob_talloc(mem_ctx, NULL, blob->length);
        if (!out.data) {
                return NT_STATUS_NO_MEMORY;
        }

        sess_crypt_blob(&out, blob, session_key, false);

        if (IVAL(out.data, 4) != 1) {
                DEBUG(2,("Unexpected revision number %d in session crypted secret (BLOB)\n",
                         IVAL(out.data, 4)));
                return NT_STATUS_UNKNOWN_REVISION;
        }
                
        slen = IVAL(out.data, 0);
        if (slen > blob->length - 8) {
                DEBUG(0,("Invalid crypt length %d in session crypted secret (BLOB)\n", slen));
                return NT_STATUS_WRONG_PASSWORD;
        }

        *ret = data_blob_talloc(mem_ctx, out.data+8, slen);
        if (slen && !ret->data) {
                return NT_STATUS_NO_MEMORY;
        }

        data_blob_free(&out);

        return NT_STATUS_OK;
}