/* 
   Unix SMB/CIFS implementation.
   Username handling
   Copyright (C) Andrew Tridgell 1992-1998
   Copyright (C) Jeremy Allison 1997-2001.
   Copyright (C) Andrew Bartlett 2002

   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 "system/passwd.h"
#include "../lib/util/memcache.h"
#include "../lib/util/util_pw.h"

/* internal functions */
static struct passwd *uname_string_combinations(char *s, TALLOC_CTX *mem_ctx,
						struct passwd * (*fn) (TALLOC_CTX *mem_ctx, const char *),
						int N);
static struct passwd *uname_string_combinations2(char *s, TALLOC_CTX *mem_ctx, int offset,
						 struct passwd * (*fn) (TALLOC_CTX *mem_ctx, const char *),
						 int N);

static struct passwd *getpwnam_alloc_cached(TALLOC_CTX *mem_ctx, const char *name)
{
	struct passwd *pw, *for_cache;

	pw = (struct passwd *)memcache_lookup_talloc(
		NULL, GETPWNAM_CACHE, data_blob_string_const_null(name));
	if (pw != NULL) {
		return tcopy_passwd(mem_ctx, pw);
	}

	pw = getpwnam(name);
	if (pw == NULL) {
		return NULL;
	}

	for_cache = tcopy_passwd(talloc_tos(), pw);
	if (for_cache == NULL) {
		return NULL;
	}

	memcache_add_talloc(NULL, GETPWNAM_CACHE,
			data_blob_string_const_null(name), &for_cache);

	return tcopy_passwd(mem_ctx, pw);
}

/****************************************************************************
 Flush all cached passwd structs.
****************************************************************************/

void flush_pwnam_cache(void)
{
        memcache_flush(NULL, GETPWNAM_CACHE);
}

/****************************************************************************
 Get a users home directory.
****************************************************************************/

char *get_user_home_dir(TALLOC_CTX *mem_ctx, const char *user)
{
	struct passwd *pass;
	char *result;

	/* Ensure the user exists. */

	pass = Get_Pwnam_alloc(mem_ctx, user);

	if (!pass)
		return(NULL);

	/* Return home directory from struct passwd. */

	result = talloc_move(mem_ctx, &pass->pw_dir);

	TALLOC_FREE(pass);
	return result;
}

/****************************************************************************
 * A wrapper for getpwnam().  The following variations are tried:
 *   - as transmitted
 *   - in all lower case if this differs from transmitted
 *   - in all upper case if this differs from transmitted
 *   - using lp_usernamelevel() for permutations.
****************************************************************************/

static struct passwd *Get_Pwnam_internals(TALLOC_CTX *mem_ctx,
					  const char *user, char *user2)
{
	struct passwd *ret = NULL;

	if (!user2 || !(*user2))
		return(NULL);

	if (!user || !(*user))
		return(NULL);

	/* Try in all lower case first as this is the most 
	   common case on UNIX systems */
	if (!strlower_m(user2)) {
		DEBUG(5,("strlower_m %s failed\n", user2));
		goto done;
	}

	DEBUG(5,("Trying _Get_Pwnam(), username as lowercase is %s\n",user2));
	ret = getpwnam_alloc_cached(mem_ctx, user2);
	if(ret)
		goto done;

	/* Try as given, if username wasn't originally lowercase */
	if(strcmp(user, user2) != 0) {
		DEBUG(5,("Trying _Get_Pwnam(), username as given is %s\n",
			 user));
		ret = getpwnam_alloc_cached(mem_ctx, user);
		if(ret)
			goto done;
	}

	/* Try as uppercase, if username wasn't originally uppercase */
	if (!strupper_m(user2)) {
		goto done;
	}

	if(strcmp(user, user2) != 0) {
		DEBUG(5,("Trying _Get_Pwnam(), username as uppercase is %s\n",
			 user2));
		ret = getpwnam_alloc_cached(mem_ctx, user2);
		if(ret)
			goto done;
	}

	/* Try all combinations up to usernamelevel */
	if (!strlower_m(user2)) {
		DEBUG(5,("strlower_m %s failed\n", user2));
		goto done;
	}
	DEBUG(5,("Checking combinations of %d uppercase letters in %s\n",
		 lp_usernamelevel(), user2));
	ret = uname_string_combinations(user2, mem_ctx, getpwnam_alloc_cached,
					lp_usernamelevel());

done:
	DEBUG(5,("Get_Pwnam_internals %s find user [%s]!\n",ret ?
		 "did":"didn't", user));

	return ret;
}

/****************************************************************************
 Get_Pwnam wrapper without modification.
  NOTE: This with NOT modify 'user'! 
  This will return an allocated structure
****************************************************************************/

struct passwd *Get_Pwnam_alloc(TALLOC_CTX *mem_ctx, const char *user)
{
	fstring user2;

	if ( *user == '\0' ) {
		DEBUG(10,("Get_Pwnam: empty username!\n"));
		return NULL;
	}

	fstrcpy(user2, user);

	DEBUG(5,("Finding user %s\n", user));

	return Get_Pwnam_internals(mem_ctx, user, user2);
}

/* The functions below have been taken from password.c and slightly modified */
/****************************************************************************
 Apply a function to upper/lower case combinations
 of a string and return true if one of them returns true.
 Try all combinations with N uppercase letters.
 offset is the first char to try and change (start with 0)
 it assumes the string starts lowercased
****************************************************************************/

static struct passwd *uname_string_combinations2(char *s, TALLOC_CTX *mem_ctx,
						 int offset,
						 struct passwd *(*fn)(TALLOC_CTX *mem_ctx, const char *),
						 int N)
{
	ssize_t len = (ssize_t)strlen(s);
	int i;
	struct passwd *ret;

	if (N <= 0 || offset >= len)
		return(fn(mem_ctx, s));

	for (i=offset;i<(len-(N-1));i++) {
		char c = s[i];
		if (!islower_m((int)c))
			continue;
		s[i] = toupper_m(c);
		ret = uname_string_combinations2(s, mem_ctx, i+1, fn, N-1);
		if(ret)
			return(ret);
		s[i] = c;
	}
	return(NULL);
}

/****************************************************************************
 Apply a function to upper/lower case combinations
 of a string and return true if one of them returns true.
 Try all combinations with up to N uppercase letters.
 offset is the first char to try and change (start with 0)
 it assumes the string starts lowercased
****************************************************************************/

static struct passwd * uname_string_combinations(char *s, TALLOC_CTX *mem_ctx,
						 struct passwd * (*fn)(TALLOC_CTX *mem_ctx, const char *),
						 int N)
{
	int n;
	struct passwd *ret;

	for (n=1;n<=N;n++) {
		ret = uname_string_combinations2(s,mem_ctx,0,fn,n);
		if(ret)
			return(ret);
	}  
	return(NULL);
}