pam/modules/pam_group/pam_group.c

/*
 * pam_group module
 *
 * Written by Andrew Morgan <morgan@linux.kernel.org> 1996/7/6
 * Field parsing rewritten by Tomas Mraz <tm@t8m.info>
 */

#include "config.h"

#include <sys/file.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <stdarg.h>
#include <time.h>
#include <syslog.h>
#include <string.h>
#include <errno.h>

#include <grp.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <netdb.h>

#define PAM_GROUP_CONF		SCONFIG_DIR "/group.conf"
#ifdef VENDOR_SCONFIG_DIR
# define VENDOR_PAM_GROUP_CONF	VENDOR_SCONFIG_DIR "/group.conf"
#endif
#define PAM_GROUP_BUFLEN        1000
#define FIELD_SEPARATOR         ';'   /* this is new as of .02 */

#ifndef TRUE
# define TRUE 1
#endif
#ifndef FALSE
# define FALSE 0
#endif

typedef enum { AND, OR } operator;

#include <security/pam_modules.h>
#include <security/_pam_macros.h>
#include <security/pam_modutil.h>
#include <security/pam_ext.h>
#include "pam_inline.h"

/* --- static functions for checking whether the user should be let in --- */

static char *
shift_buf(char *mem, int from)
{
    char *start = mem;
    while ((*mem = mem[from]) != '\0')
	++mem;
    pam_overwrite_n(mem, PAM_GROUP_BUFLEN - (mem - start));
    return mem;
}

static void
trim_spaces(char *buf, char *from)
{
    while (from > buf) {
	--from;
	if (*from == ' ')
	    *from = '\0';
	else
	    break;
    }
}

#define STATE_NL       0 /* new line starting */
#define STATE_COMMENT  1 /* inside comment */
#define STATE_FIELD    2 /* field following */
#define STATE_EOF      3 /* end of file or error */

static int
read_field(const pam_handle_t *pamh, int fd, char **buf, int *from, int *state,
	   const char *conf_filename)
{
    char *to;
    char *src;
    int i;
    char c;
    int onspace;

    /* is buf set ? */
    if (! *buf) {
	*buf = calloc(1, PAM_GROUP_BUFLEN+1);
	if (! *buf) {
	    pam_syslog(pamh, LOG_CRIT, "out of memory");
	    D(("no memory"));
	    *state = STATE_EOF;
	    return -1;
	}
	*from = 0;
        *state = STATE_NL;
	fd = open(conf_filename, O_RDONLY);
	if (fd < 0) {
	    pam_syslog(pamh, LOG_ERR, "error opening %s: %m", conf_filename);
	    _pam_drop(*buf);
	    *state = STATE_EOF;
	    return -1;
	}
    }

    if (*from > 0)
	to = shift_buf(*buf, *from);
    else
	to = *buf;

    while (fd != -1 && to - *buf < PAM_GROUP_BUFLEN) {
	i = pam_modutil_read(fd, to, PAM_GROUP_BUFLEN - (to - *buf));
	if (i < 0) {
	    pam_syslog(pamh, LOG_ERR, "error reading %s: %m", conf_filename);
	    close(fd);
	    pam_overwrite_n(*buf, PAM_GROUP_BUFLEN);
	    _pam_drop(*buf);
	    *state = STATE_EOF;
	    return -1;
	} else if (!i) {
	    close(fd);
	    fd = -1;          /* end of file reached */
	}

	to += i;
    }

    if (to == *buf) {
	/* nothing previously in buf, nothing read */
	_pam_drop(*buf);
	*state = STATE_EOF;
	return -1;
    }

    pam_overwrite_n(to, PAM_GROUP_BUFLEN - (to - *buf));

    to = *buf;
    onspace = 1; /* delete any leading spaces */

    for (src = to; (c=*src) != '\0'; ++src) {
	if (*state == STATE_COMMENT && c != '\n') {
		continue;
	}

	switch (c) {
	    case '\n':
		*state = STATE_NL;
                *to = '\0';
		*from = (src - *buf) + 1;
		trim_spaces(*buf, to);
		return fd;

	    case '\t':
            case ' ':
		if (!onspace) {
		    onspace = 1;
		    *to++ = ' ';
		}
		break;

            case '!':
		onspace = 1; /* ignore following spaces */
		*to++ = '!';
		break;

	    case '#':
		*state = STATE_COMMENT;
		break;

	    case FIELD_SEPARATOR:
		*state = STATE_FIELD;
                *to = '\0';
		*from = (src - *buf) + 1;
		trim_spaces(*buf, to);
		return fd;

	    case '\\':
		if (src[1] == '\n') {
		    ++src; /* skip it */
		    break;
		}
	    /* fallthrough */
	    default:
		*to++ = c;
		onspace = 0;
	}
	if (src > to)
	    *src = '\0'; /* clearing */
    }

    if (*state != STATE_COMMENT) {
	*state = STATE_COMMENT;
	pam_syslog(pamh, LOG_ERR, "field too long - ignored");
	**buf = '\0';
    } else {
	*to = '\0';
	trim_spaces(*buf, to);
    }

    *from = 0;
    return fd;
}

/* read a member from a field */

static int logic_member(const char *string, int *at)
{
     int c,to;
     int done=0;
     int token=0;

     to=*at;
     do {
	  c = string[to++];

	  switch (c) {

	  case '\0':
	       --to;
	       done = 1;
	       break;

	  case '&':
	  case '|':
	  case '!':
	       if (token) {
		    --to;
	       }
	       done = 1;
	       break;

	  default:
	       if (isalpha((unsigned char)c) || c == '*' || isdigit((unsigned char)c) || c == '_'
		    || c == '-' || c == '.' || c == '/' || c == ':') {
		    token = 1;
	       } else if (token) {
		    --to;
		    done = 1;
	       } else {
		    ++*at;
	       }
	  }
     } while (!done);

     return to - *at;
}

typedef enum { VAL, OP } expect;

static int
logic_field (const pam_handle_t *pamh, const void *me,
             const char *x, int rule,
             int (*agrees)(const pam_handle_t *pamh, const void *,
                               const char *, int, int))
{
     int left=FALSE, right, not=FALSE;
     operator oper=OR;
     int at=0, l;
     expect next=VAL;

     while ((l = logic_member(x,&at))) {
	  int c = x[at];

	  if (next == VAL) {
	       if (c == '!')
		    not = !not;
	       else if (isalpha((unsigned char)c) || c == '*' || isdigit((unsigned char)c) || c == '_'
                    || c == '-' || c == '.' || c == '/' || c == ':') {
		    right = not ^ agrees(pamh, me, x+at, l, rule);
		    if (oper == AND)
			 left &= right;
		    else
			 left |= right;
		    next = OP;
	       } else {
		    pam_syslog(pamh, LOG_ERR,
			       "garbled syntax; expected name (rule #%d)",
			       rule);
		    return FALSE;
	       }
	  } else {   /* OP */
	       switch (c) {
	       case '&':
		    oper = AND;
		    break;
	       case '|':
		    oper = OR;
		    break;
	       default:
		    pam_syslog(pamh, LOG_ERR,
			       "garbled syntax; expected & or | (rule #%d)",
			       rule);
		    D(("%c at %d",c,at));
		    return FALSE;
	       }
	       next = VAL;
	       not = FALSE;
	  }
	  at += l;
     }

     return left;
}

static int
is_same (const pam_handle_t *pamh UNUSED,
         const void *A, const char *b, int len, int rule UNUSED)
{
     int i;
     const char *a;

     a = A;
     for (i=0; len > 0; ++i, --len) {
	  if (b[i] != a[i]) {
	       if (b[i++] == '*') {
		    return (!--len || !strncmp(b+i,a+strlen(a)-len,len));
	       } else
		    return FALSE;
	  }
     }

     /* Ok, we know that b is a substring from A and does not contain
        wildcards, but now the length of both strings must be the same,
        too. In this case it means, a[i] has to be the end of the string. */
     if (a[i] != '\0')
          return FALSE;

     return ( !len );
}

typedef struct {
     int day;             /* array of 7 bits, one set for today */
     int minute;            /* integer, hour*100+minute for now */
} TIME;

static struct day {
     const char *d;
     int bit;
} const days[11] = {
     { "su", 01 },
     { "mo", 02 },
     { "tu", 04 },
     { "we", 010 },
     { "th", 020 },
     { "fr", 040 },
     { "sa", 0100 },
     { "wk", 076 },
     { "wd", 0101 },
     { "al", 0177 },
     { NULL, 0 }
};

static TIME time_now(void)
{
     struct tm *local;
     time_t the_time;
     TIME this;

     the_time = time((time_t *)0);                /* get the current time */
     local = localtime(&the_time);
     this.day = days[local->tm_wday].bit;
     this.minute = local->tm_hour*100 + local->tm_min;

     D(("day: 0%o, time: %.4d", this.day, this.minute));
     return this;
}

/* take the current date and see if the range "date" passes it */
static int
check_time (const pam_handle_t *pamh, const void *AT,
            const char *times, int len, int rule)
{
     int not,pass;
     int marked_day, time_start, time_end;
     const TIME *at;
     int i,j=0;

     at = AT;
     D(("checking: 0%o/%.4d vs. %s", at->day, at->minute, times));

     if (times == NULL) {
	  /* this should not happen */
	  pam_syslog(pamh, LOG_CRIT, "internal error in file %s at line %d",
		     __FILE__, __LINE__);
	  return FALSE;
     }

     if (times[j] == '!') {
	  ++j;
	  not = TRUE;
     } else {
	  not = FALSE;
     }

     for (marked_day = 0; len > 0 && isalpha((unsigned char)times[j]); --len) {
	  int this_day=-1;

	  D(("%c%c ?", times[j], times[j+1]));
	  for (i=0; days[i].d != NULL; ++i) {
	       if (tolower((unsigned char)times[j]) == days[i].d[0]
		   && tolower((unsigned char)times[j+1]) == days[i].d[1] ) {
		    this_day = days[i].bit;
		    break;
	       }
	  }
	  j += 2;
	  if (this_day == -1) {
	       pam_syslog(pamh, LOG_ERR, "bad day specified (rule #%d)", rule);
	       return FALSE;
	  }
	  marked_day ^= this_day;
     }
     if (marked_day == 0) {
	  pam_syslog(pamh, LOG_ERR, "no day specified");
	  return FALSE;
     }
     D(("day range = 0%o", marked_day));

     time_start = 0;
     for (i=0; len > 0 && i < 4 && isdigit((unsigned char)times[i+j]); ++i, --len) {
	  time_start *= 10;
	  time_start += times[i+j]-'0';       /* is this portable? */
     }
     j += i;

     if (times[j] == '-') {
	  time_end = 0;
	  for (i=1; len > 0 && i < 5 && isdigit((unsigned char)times[i+j]); ++i, --len) {
	       time_end *= 10;
	       time_end += times[i+j]-'0';    /* is this portable? */
	  }
	  j += i;
     } else
	  time_end = -1;

     D(("i=%d, time_end=%d, times[j]='%c'", i, time_end, times[j]));
     if (i != 5 || time_end == -1) {
	  pam_syslog(pamh, LOG_ERR, "no/bad times specified (rule #%d)", rule);
	  return TRUE;
     }
     D(("times(%d to %d)", time_start,time_end));
     D(("marked_day = 0%o", marked_day));

     /* compare with the actual time now */

     pass = FALSE;
     if (time_start < time_end) {    /* start < end ? --> same day */
	  if ((at->day & marked_day) && (at->minute >= time_start)
	      && (at->minute < time_end)) {
	       D(("time is listed"));
	       pass = TRUE;
	  }
     } else {                                    /* spans two days */
	  if ((at->day & marked_day) && (at->minute >= time_start)) {
	       D(("caught on first day"));
	       pass = TRUE;
	  } else {
	       marked_day <<= 1;
	       marked_day |= (marked_day & 0200) ? 1:0;
	       D(("next day = 0%o", marked_day));
	       if ((at->day & marked_day) && (at->minute <= time_end)) {
		    D(("caught on second day"));
		    pass = TRUE;
	       }
	  }
     }

     return (not ^ pass);
}

static int find_member(const char *string, int *at)
{
     int c,to;
     int done=0;
     int token=0;

     to=*at;
     do {
          c = string[to++];

          switch (c) {

          case '\0':
               --to;
               done = 1;
               break;

          case '&':
          case '|':
	  case '!':
               if (token) {
                    --to;
               }
               done = 1;
               break;

          default:
               if (isalpha((unsigned char)c) || isdigit((unsigned char)c) || c == '_' || c == '*'
                    || c == '-') {
                    token = 1;
               } else if (token) {
                    --to;
                    done = 1;
               } else {
                    ++*at;
               }
          }
     } while (!done);

     return to - *at;
}

#define GROUP_BLK 10
#define blk_size(len) ((((len)-1 + GROUP_BLK)/GROUP_BLK)*GROUP_BLK)

static int mkgrplist(pam_handle_t *pamh, char *buf, gid_t **list, int len)
{
     int l,at=0;
     int blks;

     blks = blk_size(len);
     D(("cf. blks=%d and len=%d", blks,len));

     while ((l = find_member(buf,&at))) {
	  int edge;

	  if (len >= blks) {
	       gid_t *tmp;

	       D(("allocating new block"));
	       tmp = realloc((*list), sizeof(gid_t) * (blks += GROUP_BLK));
	       if (tmp != NULL) {
		    (*list) = tmp;
	       } else {
		    pam_syslog(pamh, LOG_ERR, "out of memory for group list");
		    free(*list);
		    (*list) = NULL;
		    return -1;
	       }
	  }

	  /* '\0' terminate the entry */

	  edge = (buf[at+l]) ? 1:0;
	  buf[at+l] = '\0';
	  D(("found group: %s",buf+at));

	  /* this is where we convert a group name to a gid_t */
	  {
	      const struct group *grp;

	      grp = pam_modutil_getgrnam(pamh, buf+at);
	      if (grp == NULL) {
		  pam_syslog(pamh, LOG_ERR, "bad group: %s", buf+at);
	      } else {
		  D(("group %s exists", buf+at));
		  (*list)[len++] = grp->gr_gid;
	      }
	  }

	  /* next entry along */

	  at += l + edge;
     }
     D(("returning with [%p/len=%d]->%p",list,len,*list));
     return len;
}


static int check_account(pam_handle_t *pamh, const char *service,
			 const char *tty, const char *user)
{
    int from=0, state=STATE_NL, fd=-1;
    char *buffer=NULL;
    int count=0;
    TIME here_and_now;
    int retval=PAM_SUCCESS;
    gid_t *grps;
    int no_grps;
    const char *conf_filename = PAM_GROUP_CONF;

#ifdef VENDOR_PAM_GROUP_CONF
    /*
     * Check whether PAM_GROUP_CONF file is available.
     * If it does not exist, fall back to VENDOR_PAM_GROUP_CONF file.
     */
    struct stat stat_buffer;
    if (stat(conf_filename, &stat_buffer) != 0 && errno == ENOENT) {
	conf_filename = VENDOR_PAM_GROUP_CONF;
    }
#endif

    /*
     * first we get the current list of groups - the application
     * will have previously done an initgroups(), or equivalent.
     */

    D(("counting supplementary groups"));
    no_grps = getgroups(0, NULL);      /* find the current number of groups */
    if (no_grps > 0) {
	grps = calloc( blk_size(no_grps) , sizeof(gid_t) );
	D(("copying current list into grps [%d big]",blk_size(no_grps)));
	if (getgroups(no_grps, grps) < 0) {
	    D(("getgroups call failed"));
	    no_grps = 0;
	    _pam_drop(grps);
	}
#ifdef PAM_DEBUG
	{
	    int z;
	    for (z=0; z<no_grps; ++z) {
		D(("gid[%d]=%d", z, grps[z]));
	    }
	}
#endif
    } else {
	D(("no supplementary groups known"));
	no_grps = 0;
	grps = NULL;
    }

    here_and_now = time_now();                         /* find current time */

    /* parse the rules in the configuration file */
    do {
	int good=TRUE;

	/* here we get the service name field */

	fd = read_field(pamh, fd, &buffer, &from, &state, conf_filename);
	if (!buffer || !buffer[0]) {
	    /* empty line .. ? */
	    continue;
	}
	++count;
	D(("working on rule #%d",count));

	if (state != STATE_FIELD) {
	    pam_syslog(pamh, LOG_ERR,
		       "%s: malformed rule #%d", conf_filename, count);
	    continue;
	}

	good = logic_field(pamh,service, buffer, count, is_same);
	D(("with service: %s", good ? "passes":"fails" ));

	/* here we get the terminal name field */

	fd = read_field(pamh, fd, &buffer, &from, &state, conf_filename);
	if (state != STATE_FIELD) {
	    pam_syslog(pamh, LOG_ERR,
		       "%s: malformed rule #%d", conf_filename, count);
	    continue;
	}
	good &= logic_field(pamh,tty, buffer, count, is_same);
	D(("with tty: %s", good ? "passes":"fails" ));

	/* here we get the username field */

	fd = read_field(pamh, fd, &buffer, &from, &state, conf_filename);
	if (state != STATE_FIELD) {
	    pam_syslog(pamh, LOG_ERR,
		       "%s: malformed rule #%d", conf_filename, count);
	    continue;
	}
	/* If buffer starts with @, we are using netgroups */
	if (buffer[0] == '@')
#ifdef HAVE_INNETGR
	  good &= innetgr (&buffer[1], NULL, user, NULL);
#else
	  pam_syslog (pamh, LOG_ERR, "pam_group does not have netgroup support");
#endif
	/* otherwise, if the buffer starts with %, it's a UNIX group */
	else if (buffer[0] == '%')
          good &= pam_modutil_user_in_group_nam_nam(pamh, user, &buffer[1]);
	else
	  good &= logic_field(pamh,user, buffer, count, is_same);
	D(("with user: %s", good ? "passes":"fails" ));

	/* here we get the time field */

	fd = read_field(pamh, fd, &buffer, &from, &state, conf_filename);
	if (state != STATE_FIELD) {
	    pam_syslog(pamh, LOG_ERR,
		       "%s: malformed rule #%d", conf_filename, count);
	    continue;
	}

	good &= logic_field(pamh,&here_and_now, buffer, count, check_time);
	D(("with time: %s", good ? "passes":"fails" ));

	fd = read_field(pamh, fd, &buffer, &from, &state, conf_filename);
	if (state == STATE_FIELD) {
	    pam_syslog(pamh, LOG_ERR,
		       "%s: poorly terminated rule #%d", conf_filename, count);
	    continue;
	}

	/*
	 * so we have a list of groups, we need to turn it into
	 * something to send to setgroups(2)
	 */

	if (good) {
	    D(("adding %s to gid list", buffer));
	    good = mkgrplist(pamh, buffer, &grps, no_grps);
	    if (good < 0) {
		no_grps = 0;
	    } else {
		no_grps = good;
	    }
	}

	if (good > 0) {
	    D(("rule #%d passed, added %d groups", count, good));
	} else if (good < 0) {
	    retval = PAM_BUF_ERR;
	} else {
	    D(("rule #%d failed", count));
	}

    } while (state != STATE_EOF);

    /* now set the groups for the user */

    if (no_grps > 0) {
#ifdef PAM_DEBUG
	int err;
#endif
	D(("trying to set %d groups", no_grps));
#ifdef PAM_DEBUG
	for (err=0; err<no_grps; ++err) {
	    D(("gid[%d]=%d", err, grps[err]));
	}
#endif
	if (setgroups(no_grps, grps) != 0) {
	    D(("but couldn't set groups %m"));
	    pam_syslog(pamh, LOG_ERR,
		       "unable to set the group membership for user: %m");
	    retval = PAM_CRED_ERR;
	}
    }

    if (grps) {                                          /* tidy up */
	pam_overwrite_n(grps, sizeof(gid_t) * blk_size(no_grps));
	_pam_drop(grps);
	no_grps = 0;
    }

    return retval;
}

/* --- public authentication management functions --- */

int
pam_sm_authenticate (pam_handle_t *pamh UNUSED, int flags UNUSED,
		     int argc UNUSED, const char **argv UNUSED)
{
    return PAM_IGNORE;
}

int
pam_sm_setcred (pam_handle_t *pamh, int flags,
		int argc UNUSED, const char **argv UNUSED)
{
    const void *service=NULL, *void_tty=NULL;
    const char *user=NULL;
    const char *tty;
    int retval;
    unsigned setting;

    /* only interested in establishing credentials */

    setting = flags;
    if (!(setting & (PAM_ESTABLISH_CRED | PAM_REINITIALIZE_CRED))) {
	D(("ignoring call - not for establishing credentials"));
	return PAM_SUCCESS;            /* don't fail because of this */
    }

    /* set service name */

    if (pam_get_item(pamh, PAM_SERVICE, &service)
	!= PAM_SUCCESS || service == NULL) {
	pam_syslog(pamh, LOG_ERR, "cannot find the current service name");
	return PAM_ABORT;
    }

    /* set username */

    if (pam_get_user(pamh, &user, NULL) != PAM_SUCCESS || *user == '\0') {
	pam_syslog(pamh, LOG_NOTICE, "cannot determine user name");
	return PAM_USER_UNKNOWN;
    }

    /* set tty name */

    if (pam_get_item(pamh, PAM_TTY, &void_tty) != PAM_SUCCESS
	|| void_tty == NULL) {
	D(("PAM_TTY not set, probing stdin"));
	tty = ttyname(STDIN_FILENO);
	if (tty == NULL) {
	    tty = "";
	}
	if (pam_set_item(pamh, PAM_TTY, tty) != PAM_SUCCESS) {
	    pam_syslog(pamh, LOG_ERR, "couldn't set tty name");
	    return PAM_ABORT;
	}
    }
    else
      tty = (const char *) void_tty;

    if (tty[0] == '/') {   /* full path */
	const char *t;
        tty++;
        if ((t = strchr(tty, '/')) != NULL) {
	    tty = t + 1;
	}
    }

    /* good, now we have the service name, the user and the terminal name */

    D(("service=%s", (const char *) service));
    D(("user=%s", user));
    D(("tty=%s", tty));

    retval = check_account(pamh,service,tty,user);          /* get groups */

    return retval;
}

/* end of module definition */