lib/sharesec.c

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/* 
 *  Unix SMB/Netbios implementation.
 *  SEC_DESC handling functions
 *  Copyright (C) Jeremy R. Allison            1995-2003.
 *  
 *  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 2 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, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "includes.h"

/*******************************************************************
 Create the share security tdb.
 ********************************************************************/

static TDB_CONTEXT *share_tdb; /* used for share security descriptors */
#define SHARE_DATABASE_VERSION_V1 1
#define SHARE_DATABASE_VERSION_V2 2 /* version id in little endian. */

/* Map generic permissions to file object specific permissions */

static struct generic_mapping file_generic_mapping = {
        FILE_GENERIC_READ,
        FILE_GENERIC_WRITE,
        FILE_GENERIC_EXECUTE,
        FILE_GENERIC_ALL
};


BOOL share_info_db_init(void)
{
        const char *vstring = "INFO/version";
        int32 vers_id;
 
        if (share_tdb) {
                return True;
        }

        share_tdb = tdb_open_log(lock_path("share_info.tdb"), 0, TDB_DEFAULT, O_RDWR|O_CREAT, 0600);
        if (!share_tdb) {
                DEBUG(0,("Failed to open share info database %s (%s)\n",
                        lock_path("share_info.tdb"), strerror(errno) ));
                return False;
        }
 
        /* handle a Samba upgrade */
        tdb_lock_bystring(share_tdb, vstring);

        /* Cope with byte-reversed older versions of the db. */
        vers_id = tdb_fetch_int32(share_tdb, vstring);
        if ((vers_id == SHARE_DATABASE_VERSION_V1) || (IREV(vers_id) == SHARE_DATABASE_VERSION_V1)) {
                /* Written on a bigendian machine with old fetch_int code. Save as le. */
                tdb_store_int32(share_tdb, vstring, SHARE_DATABASE_VERSION_V2);
                vers_id = SHARE_DATABASE_VERSION_V2;
        }

        if (vers_id != SHARE_DATABASE_VERSION_V2) {
                tdb_traverse(share_tdb, tdb_traverse_delete_fn, NULL);
                tdb_store_int32(share_tdb, vstring, SHARE_DATABASE_VERSION_V2);
        }
        tdb_unlock_bystring(share_tdb, vstring);

        return True;
}

/*******************************************************************
 Fake up a Everyone, default access as a default.
 def_access is a GENERIC_XXX access mode.
 ********************************************************************/

SEC_DESC *get_share_security_default( TALLOC_CTX *ctx, size_t *psize, uint32 def_access)
{
        SEC_ACCESS sa;
        SEC_ACE ace;
        SEC_ACL *psa = NULL;
        SEC_DESC *psd = NULL;
        uint32 spec_access = def_access;

        se_map_generic(&spec_access, &file_generic_mapping);

        init_sec_access(&sa, def_access | spec_access );
        init_sec_ace(&ace, &global_sid_World, SEC_ACE_TYPE_ACCESS_ALLOWED, sa, 0);

        if ((psa = make_sec_acl(ctx, NT4_ACL_REVISION, 1, &ace)) != NULL) {
                psd = make_sec_desc(ctx, SEC_DESC_REVISION, SEC_DESC_SELF_RELATIVE, NULL, NULL, NULL, psa, psize);
        }

        if (!psd) {
                DEBUG(0,("get_share_security: Failed to make SEC_DESC.\n"));
                return NULL;
        }

        return psd;
}

/*******************************************************************
 Pull a security descriptor from the share tdb.
 ********************************************************************/

SEC_DESC *get_share_security( TALLOC_CTX *ctx, const char *servicename,
                              size_t *psize)
{
        prs_struct ps;
        fstring key;
        SEC_DESC *psd = NULL;

        if (!share_info_db_init()) {
                return NULL;
        }

        *psize = 0;

        /* Fetch security descriptor from tdb */
 
        slprintf(key, sizeof(key)-1, "SECDESC/%s", servicename);
 
        if (tdb_prs_fetch(share_tdb, key, &ps, ctx)!=0 ||
                !sec_io_desc("get_share_security", &psd, &ps, 1)) {
 
                DEBUG(4, ("get_share_security: using default secdesc for %s\n",
                          servicename));
 
                return get_share_security_default(ctx, psize, GENERIC_ALL_ACCESS);
        }

        if (psd)
                *psize = sec_desc_size(psd);

        prs_mem_free(&ps);
        return psd;
}

/*******************************************************************
 Store a security descriptor in the share db.
 ********************************************************************/

BOOL set_share_security(const char *share_name, SEC_DESC *psd)
{
        prs_struct ps;
        TALLOC_CTX *mem_ctx = NULL;
        fstring key;
        BOOL ret = False;

        if (!share_info_db_init()) {
                return False;
        }

        mem_ctx = talloc_init("set_share_security");
        if (mem_ctx == NULL)
                return False;

        prs_init(&ps, (uint32)sec_desc_size(psd), mem_ctx, MARSHALL);
 
        if (!sec_io_desc("share_security", &psd, &ps, 1))
                goto out;
 
        slprintf(key, sizeof(key)-1, "SECDESC/%s", share_name);
 
        if (tdb_prs_store(share_tdb, key, &ps)==0) {
                ret = True;
                DEBUG(5,("set_share_security: stored secdesc for %s\n", share_name ));
        } else {
                DEBUG(1,("set_share_security: Failed to store secdesc for %s\n", share_name ));
        } 

        /* Free malloc'ed memory */
 
out:
 
        prs_mem_free(&ps);
        if (mem_ctx)
                talloc_destroy(mem_ctx);
        return ret;
}

/*******************************************************************
 Delete a security descriptor.
********************************************************************/

BOOL delete_share_security(const struct share_params *params)
{
        TDB_DATA kbuf;
        fstring key;

        slprintf(key, sizeof(key)-1, "SECDESC/%s",
                 lp_servicename(params->service));
        kbuf.dptr = key;
        kbuf.dsize = strlen(key)+1;

        if (tdb_trans_delete(share_tdb, kbuf) != 0) {
                DEBUG(0,("delete_share_security: Failed to delete entry for share %s\n",
                         lp_servicename(params->service) ));
                return False;
        }

        return True;
}

/*******************************************************************
 Can this user access with share with the required permissions ?
********************************************************************/

BOOL share_access_check(const NT_USER_TOKEN *token, const char *sharename,
                        uint32 desired_access)
{
        uint32 granted;
        NTSTATUS status;
        TALLOC_CTX *mem_ctx = NULL;
        SEC_DESC *psd = NULL;
        size_t sd_size;
        BOOL ret = True;

        if (!(mem_ctx = talloc_init("share_access_check"))) {
                return False;
        }

        psd = get_share_security(mem_ctx, sharename, &sd_size);

        if (!psd) {
                TALLOC_FREE(mem_ctx);
                return True;
        }

        ret = se_access_check(psd, token, desired_access, &granted, &status);

        talloc_destroy(mem_ctx);
        return ret;
}

/***************************************************************************
 Parse the contents of an acl string from a usershare file.
***************************************************************************/

BOOL parse_usershare_acl(TALLOC_CTX *ctx, const char *acl_str, SEC_DESC **ppsd)
{
        size_t s_size = 0;
        const char *pacl = acl_str;
        int num_aces = 0;
        SEC_ACE *ace_list = NULL;
        SEC_ACL *psa = NULL;
        SEC_DESC *psd = NULL;
        size_t sd_size = 0;
        int i;

        *ppsd = NULL;

        /* If the acl string is blank return "Everyone:R" */
        if (!*acl_str) {
                SEC_DESC *default_psd = get_share_security_default(ctx, &s_size, GENERIC_READ_ACCESS);
                if (!default_psd) {
                        return False;
                }
                *ppsd = default_psd;
                return True;
        }

        num_aces = 1;

        /* Add the number of ',' characters to get the number of aces. */
        num_aces += count_chars(pacl,',');

        ace_list = TALLOC_ARRAY(ctx, SEC_ACE, num_aces);
        if (!ace_list) {
                return False;
        }

        for (i = 0; i < num_aces; i++) {
                SEC_ACCESS sa;
                uint32 g_access;
                uint32 s_access;
                DOM_SID sid;
                fstring sidstr;
                uint8 type = SEC_ACE_TYPE_ACCESS_ALLOWED;

                if (!next_token(&pacl, sidstr, ":", sizeof(sidstr))) {
                        DEBUG(0,("parse_usershare_acl: malformed usershare acl looking "
                                "for ':' in string '%s'\n", pacl));
                        return False;
                }

                if (!string_to_sid(&sid, sidstr)) {
                        DEBUG(0,("parse_usershare_acl: failed to convert %s to sid.\n",
                                sidstr ));
                        return False;
                }

                switch (*pacl) {
                        case 'F': /* Full Control, ie. R+W */
                        case 'f': /* Full Control, ie. R+W */
                                s_access = g_access = GENERIC_ALL_ACCESS;
                                break;
                        case 'R': /* Read only. */
                        case 'r': /* Read only. */
                                s_access = g_access = GENERIC_READ_ACCESS;
                                break;
                        case 'D': /* Deny all to this SID. */
                        case 'd': /* Deny all to this SID. */
                                type = SEC_ACE_TYPE_ACCESS_DENIED;
                                s_access = g_access = GENERIC_ALL_ACCESS;
                                break;
                        default:
                                DEBUG(0,("parse_usershare_acl: unknown acl type at %s.\n",
                                        pacl ));
                                return False;
                }

                pacl++;
                if (*pacl && *pacl != ',') {
                        DEBUG(0,("parse_usershare_acl: bad acl string at %s.\n",
                                pacl ));
                        return False;
                }
                pacl++; /* Go past any ',' */

                se_map_generic(&s_access, &file_generic_mapping);
                init_sec_access(&sa, g_access | s_access );
                init_sec_ace(&ace_list[i], &sid, type, sa, 0);
        }

        if ((psa = make_sec_acl(ctx, NT4_ACL_REVISION, num_aces, ace_list)) != NULL) {
                psd = make_sec_desc(ctx, SEC_DESC_REVISION, SEC_DESC_SELF_RELATIVE, NULL, NULL, NULL, psa, &sd_size);
        }

        if (!psd) {
                DEBUG(0,("parse_usershare_acl: Failed to make SEC_DESC.\n"));
                return False;
        }

        *ppsd = psd;
        return True;
}

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