174 lines
4.2 KiB
C
174 lines
4.2 KiB
C
/* getusershell.c -- Return names of valid user shells.
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Copyright (C) 1991, 1997, 2000-2001, 2003-2006, 2008-2020 Free Software
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Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by David MacKenzie <djm@gnu.ai.mit.edu> */
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#include <config.h>
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/* Specification. */
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#include <unistd.h>
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#ifndef SHELLS_FILE
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# ifndef __DJGPP__
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/* File containing a list of nonrestricted shells, one per line. */
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# define SHELLS_FILE "/etc/shells"
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# else
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/* This is a horrible kludge. Isn't there a better way? */
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# define SHELLS_FILE "/dev/env/DJDIR/etc/shells"
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# endif
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#endif
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#include <stdlib.h>
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#include <ctype.h>
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#include "stdio--.h"
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#include "xalloc.h"
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#if USE_UNLOCKED_IO
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# include "unlocked-io.h"
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#endif
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static size_t readname (char **, size_t *, FILE *);
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#if ! defined ADDITIONAL_DEFAULT_SHELLS && defined __MSDOS__
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# define ADDITIONAL_DEFAULT_SHELLS \
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"c:/dos/command.com", "c:/windows/command.com", "c:/command.com",
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#else
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# define ADDITIONAL_DEFAULT_SHELLS /* empty */
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#endif
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/* List of shells to use if the shells file is missing. */
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static char const* const default_shells[] =
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{
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ADDITIONAL_DEFAULT_SHELLS
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"/bin/sh", "/bin/csh", "/usr/bin/sh", "/usr/bin/csh", NULL
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};
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/* Index of the next shell in 'default_shells' to return.
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0 means we are not using 'default_shells'. */
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static size_t default_index = 0;
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/* Input stream from the shells file. */
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static FILE *shellstream = NULL;
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/* Line of input from the shells file. */
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static char *line = NULL;
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/* Number of bytes allocated for 'line'. */
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static size_t line_size = 0;
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/* Return an entry from the shells file, ignoring comment lines.
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If the file doesn't exist, use the list in DEFAULT_SHELLS (above).
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In any case, the returned string is in memory allocated through malloc.
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Return NULL if there are no more entries. */
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char *
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getusershell (void)
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{
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if (default_index > 0)
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{
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if (default_shells[default_index])
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/* Not at the end of the list yet. */
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return xstrdup (default_shells[default_index++]);
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return NULL;
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}
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if (shellstream == NULL)
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{
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shellstream = fopen (SHELLS_FILE, "r");
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if (shellstream == NULL)
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{
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/* No shells file. Use the default list. */
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default_index = 1;
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return xstrdup (default_shells[0]);
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}
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}
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while (readname (&line, &line_size, shellstream))
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{
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if (*line != '#')
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return line;
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}
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return NULL; /* End of file. */
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}
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/* Rewind the shells file. */
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void
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setusershell (void)
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{
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default_index = 0;
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if (shellstream)
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rewind (shellstream);
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}
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/* Close the shells file. */
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void
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endusershell (void)
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{
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if (shellstream)
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{
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fclose (shellstream);
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shellstream = NULL;
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}
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}
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/* Read a line from STREAM, removing any newline at the end.
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Place the result in *NAME, which is malloc'd
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and/or realloc'd as necessary and can start out NULL,
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and whose size is passed and returned in *SIZE.
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Return the number of bytes placed in *NAME
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if some nonempty sequence was found, otherwise 0. */
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static size_t
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readname (char **name, size_t *size, FILE *stream)
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{
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int c;
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size_t name_index = 0;
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/* Skip blank space. */
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while ((c = getc (stream)) != EOF && isspace (c))
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/* Do nothing. */ ;
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for (;;)
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{
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if (*size <= name_index)
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*name = x2nrealloc (*name, size, sizeof **name);
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if (c == EOF || isspace (c))
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break;
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(*name)[name_index++] = c;
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c = getc (stream);
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}
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(*name)[name_index] = '\0';
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return name_index;
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}
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#ifdef TEST
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int
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main (void)
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{
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char *s;
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while (s = getusershell ())
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puts (s);
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exit (0);
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}
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#endif
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