Adding upstream version 1:4.13+dfsg1.upstream/1%4.13+dfsg1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 483 insertions, 0 deletions

diff --git a/libmisc/find_new_gid.c b/libmisc/find_new_gid.c
new file mode 100644
index 0000000..65ab5d0
--- /dev/null
+++ b/libmisc/find_new_gid.c
@@ -0,0 +1,483 @@
+/*
+ * SPDX-FileCopyrightText: 1991 - 1994, Julianne Frances Haugh
+ * SPDX-FileCopyrightText: 2008 - 2011, Nicolas François
+ * SPDX-FileCopyrightText: 2014, Red Hat, Inc.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <config.h>
+
+#include <assert.h>
+#include <stdio.h>
+#include <errno.h>
+
+#include "prototypes.h"
+#include "groupio.h"
+#include "getdef.h"
+#include "shadowlog.h"
+
+/*
+ * get_ranges - Get the minimum and maximum ID ranges for the search
+ *
+ * This function will return the minimum and maximum ranges for IDs
+ *
+ * 0: The function completed successfully
+ * EINVAL: The provided ranges are impossible (such as maximum < minimum)
+ *
+ * preferred_min: The special-case minimum value for a specifically-
+ * requested ID, which may be lower than the standard min_id
+ */
+static int get_ranges (bool sys_group, gid_t *min_id, gid_t *max_id,
+		       gid_t *preferred_min)
+{
+	gid_t gid_def_max = 0;
+
+	if (sys_group) {
+		/* System groups */
+
+		/* A requested ID is allowed to be below the autoselect range */
+		*preferred_min = (gid_t) 1;
+
+		/* Get the minimum ID range from login.defs or default to 101 */
+		*min_id = (gid_t) getdef_ulong ("SYS_GID_MIN", 101UL);
+
+		/*
+		 * If SYS_GID_MAX is unspecified, we should assume it to be one
+		 * less than the GID_MIN (which is reserved for non-system accounts)
+		 */
+		gid_def_max = (gid_t) getdef_ulong ("GID_MIN", 1000UL) - 1;
+		*max_id = (gid_t) getdef_ulong ("SYS_GID_MAX",
+				(unsigned long) gid_def_max);
+
+		/* Check that the ranges make sense */
+		if (*max_id < *min_id) {
+			(void) fprintf (log_get_logfd(),
+                            _("%s: Invalid configuration: SYS_GID_MIN (%lu), "
+                              "GID_MIN (%lu), SYS_GID_MAX (%lu)\n"),
+                            log_get_progname(), (unsigned long) *min_id,
+                            getdef_ulong ("GID_MIN", 1000UL),
+                            (unsigned long) *max_id);
+			return EINVAL;
+		}
+		/*
+		 * Zero is reserved for root and the allocation algorithm does not
+		 * work right with it.
+		 */
+		if (*min_id == 0) {
+			*min_id = (gid_t) 1;
+		}
+	} else {
+		/* Non-system groups */
+
+		/* Get the values from login.defs or use reasonable defaults */
+		*min_id = (gid_t) getdef_ulong ("GID_MIN", 1000UL);
+		*max_id = (gid_t) getdef_ulong ("GID_MAX", 60000UL);
+
+		/*
+		 * The preferred minimum should match the standard ID minimum
+		 * for non-system groups.
+		 */
+		*preferred_min = *min_id;
+
+		/* Check that the ranges make sense */
+		if (*max_id < *min_id) {
+			(void) fprintf (log_get_logfd(),
+					_("%s: Invalid configuration: GID_MIN (%lu), "
+					  "GID_MAX (%lu)\n"),
+					log_get_progname(), (unsigned long) *min_id,
+					(unsigned long) *max_id);
+			return EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * check_gid - See if the requested GID is available
+ *
+ * On success, return 0
+ * If the ID is in use, return EEXIST
+ * If the ID is outside the range, return ERANGE
+ * In other cases, return errno from getgrgid()
+ */
+static int check_gid (const gid_t gid,
+		      const gid_t gid_min,
+		      const gid_t gid_max,
+		      const bool *used_gids)
+{
+	/* First test that the preferred ID is in the range */
+	if (gid < gid_min || gid > gid_max) {
+		return ERANGE;
+	}
+
+	/*
+	 * Check whether we already detected this GID
+	 * using the gr_next() loop
+	 */
+	if (used_gids != NULL && used_gids[gid]) {
+		return EEXIST;
+	}
+	/* Check if the GID exists according to NSS */
+	errno = 0;
+	if (prefix_getgrgid (gid) != NULL) {
+		return EEXIST;
+	} else {
+		/* getgrgid() was NULL
+		 * we have to ignore errors as temporary
+		 * failures of remote user identity services
+		 * would completely block user/group creation
+		 */
+	}
+
+	/* If we've made it here, the GID must be available */
+	return 0;
+}
+
+/*
+ * find_new_gid - Find a new unused GID.
+ *
+ * If successful, find_new_gid provides an unused group ID in the
+ * [GID_MIN:GID_MAX] range.
+ * This ID should be higher than all the used GID, but if not possible,
+ * the lowest unused ID in the range will be returned.
+ *
+ * Return 0 on success, -1 if no unused GIDs are available.
+ */
+int find_new_gid (bool sys_group,
+                 gid_t *gid,
+                 /*@null@*/gid_t const *preferred_gid)
+{
+	bool *used_gids;
+	const struct group *grp;
+	gid_t gid_min, gid_max, preferred_min;
+	gid_t id;
+	gid_t lowest_found, highest_found;
+	int result;
+	int nospam = 0;
+
+	assert(gid != NULL);
+
+	/*
+	 * First, figure out what ID range is appropriate for
+	 * automatic assignment
+	 */
+	result = get_ranges (sys_group, &gid_min, &gid_max, &preferred_min);
+	if (result == EINVAL) {
+		return -1;
+	}
+
+	/* Check if the preferred GID is available */
+	if (preferred_gid) {
+		result = check_gid (*preferred_gid, preferred_min, gid_max, NULL);
+		if (result == 0) {
+			/*
+			 * Make sure the GID isn't queued for use already
+			 */
+			if (gr_locate_gid (*preferred_gid) == NULL) {
+				*gid = *preferred_gid;
+				return 0;
+			}
+			/*
+			 * gr_locate_gid() found the GID in an as-yet uncommitted
+			 * entry. We'll proceed below and auto-set a GID.
+			 */
+		} else if (result == EEXIST || result == ERANGE) {
+			/*
+			 * Continue on below. At this time, we won't
+			 * treat these two cases differently.
+			 */
+		} else {
+			/*
+			 * An unexpected error occurred. We should report
+			 * this and fail the group creation.
+			 * This differs from the automatic creation
+			 * behavior below, since if a specific GID was
+			 * requested and generated an error, the user is
+			 * more likely to want to stop and address the
+			 * issue.
+			 */
+			fprintf (log_get_logfd(),
+				_("%s: Encountered error attempting to use "
+				  "preferred GID: %s\n"),
+				log_get_progname(), strerror (result));
+			return -1;
+		}
+	}
+
+	/*
+	 * Search the entire group file,
+	 * looking for the next unused value.
+	 *
+	 * We first check the local database with gr_rewind/gr_next to find
+	 * all local values that are in use.
+	 *
+	 * We then compare the next free value to all databases (local and
+	 * remote) and iterate until we find a free one. If there are free
+	 * values beyond the lowest (system groups) or highest (non-system
+	 * groups), we will prefer those and avoid potentially reclaiming a
+	 * deleted group (which can be a security issue, since it may grant
+	 * access to files belonging to that former group).
+	 *
+	 * If there are no GIDs available at the end of the search, we will
+	 * have no choice but to iterate through the range looking for gaps.
+	 *
+	 */
+
+	/* Create an array to hold all of the discovered GIDs */
+	used_gids = malloc (sizeof (bool) * (gid_max +1));
+	if (NULL == used_gids) {
+		fprintf (log_get_logfd(),
+			 _("%s: failed to allocate memory: %s\n"),
+			 log_get_progname(), strerror (errno));
+		return -1;
+	}
+	memset (used_gids, false, sizeof (bool) * (gid_max + 1));
+
+	/* First look for the lowest and highest value in the local database */
+	(void) gr_rewind ();
+	highest_found = gid_min;
+	lowest_found = gid_max;
+	while ((grp = gr_next ()) != NULL) {
+		/*
+		 * Does this entry have a lower GID than the lowest we've found
+		 * so far?
+		 */
+		if ((grp->gr_gid <= lowest_found) && (grp->gr_gid >= gid_min)) {
+			lowest_found = grp->gr_gid - 1;
+		}
+
+		/*
+		 * Does this entry have a higher GID than the highest we've found
+		 * so far?
+		 */
+		if ((grp->gr_gid >= highest_found) && (grp->gr_gid <= gid_max)) {
+			highest_found = grp->gr_gid + 1;
+		}
+
+		/* create index of used GIDs */
+		if (grp->gr_gid >= gid_min
+			&& grp->gr_gid <= gid_max) {
+
+			used_gids[grp->gr_gid] = true;
+		}
+	}
+
+	if (sys_group) {
+		/*
+		 * For system groups, we want to start from the
+		 * top of the range and work downwards.
+		 */
+
+		/*
+		 * At the conclusion of the gr_next() search, we will either
+		 * have a presumed-free GID or we will be at GID_MIN - 1.
+		 */
+		if (lowest_found < gid_min) {
+			/*
+			 * In this case, a GID is in use at GID_MIN.
+			 *
+			 * We will reset the search to GID_MAX and proceed down
+			 * through all the GIDs (skipping those we detected with
+			 * used_gids) for a free one. It is a known issue that
+			 * this may result in reusing a previously-deleted GID,
+			 * so administrators should be instructed to use this
+			 * auto-detection with care (and prefer to assign GIDs
+			 * explicitly).
+			 */
+			lowest_found = gid_max;
+		}
+
+		/* Search through all of the IDs in the range */
+		for (id = lowest_found; id >= gid_min; id--) {
+			result = check_gid (id, gid_min, gid_max, used_gids);
+			if (result == 0) {
+				/* This GID is available. Return it. */
+				*gid = id;
+				free (used_gids);
+				return 0;
+			} else if (result == EEXIST) {
+				/* This GID is in use, we'll continue to the next */
+			} else {
+				/*
+				 * An unexpected error occurred.
+				 *
+				 * Only report it the first time to avoid spamming
+				 * the logs
+				 *
+				 */
+				if (!nospam) {
+					fprintf (log_get_logfd(),
+						_("%s: Can't get unique system GID (%s). "
+						  "Suppressing additional messages.\n"),
+						log_get_progname(), strerror (result));
+					SYSLOG ((LOG_ERR,
+						"Error checking available GIDs: %s",
+						strerror (result)));
+					nospam = 1;
+				}
+				/*
+				 * We will continue anyway. Hopefully a later GID
+				 * will work properly.
+				 */
+			}
+		}
+
+		/*
+		 * If we get all the way through the loop, try again from GID_MAX,
+		 * unless that was where we previously started. (NOTE: the worst-case
+		 * scenario here is that we will run through (GID_MAX - GID_MIN - 1)
+		 * cycles *again* if we fall into this case with lowest_found as
+		 * GID_MAX - 1, all groups in the range in use and maintained by
+		 * network services such as LDAP.)
+		 */
+		if (lowest_found != gid_max) {
+			for (id = gid_max; id >= gid_min; id--) {
+				result = check_gid (id, gid_min, gid_max, used_gids);
+				if (result == 0) {
+					/* This GID is available. Return it. */
+					*gid = id;
+					free (used_gids);
+					return 0;
+				} else if (result == EEXIST) {
+					/* This GID is in use, we'll continue to the next */
+				} else {
+					/*
+					 * An unexpected error occurred.
+					 *
+					 * Only report it the first time to avoid spamming
+					 * the logs
+					 *
+					 */
+					if (!nospam) {
+						fprintf (log_get_logfd(),
+							_("%s: Can't get unique system GID (%s). "
+							  "Suppressing additional messages.\n"),
+							log_get_progname(), strerror (result));
+						SYSLOG ((LOG_ERR,
+							"Error checking available GIDs: %s",
+							strerror (result)));
+						nospam = 1;
+					}
+					/*
+					 * We will continue anyway. Hopefully a later GID
+					 * will work properly.
+					 */
+				}
+			}
+		}
+	} else { /* !sys_group */
+		/*
+		 * For non-system groups, we want to start from the
+		 * bottom of the range and work upwards.
+		 */
+
+		/*
+		 * At the conclusion of the gr_next() search, we will either
+		 * have a presumed-free GID or we will be at GID_MAX + 1.
+		 */
+		if (highest_found > gid_max) {
+			/*
+			 * In this case, a GID is in use at GID_MAX.
+			 *
+			 * We will reset the search to GID_MIN and proceed up
+			 * through all the GIDs (skipping those we detected with
+			 * used_gids) for a free one. It is a known issue that
+			 * this may result in reusing a previously-deleted GID,
+			 * so administrators should be instructed to use this
+			 * auto-detection with care (and prefer to assign GIDs
+			 * explicitly).
+			 */
+			highest_found = gid_min;
+		}
+
+		/* Search through all of the IDs in the range */
+		for (id = highest_found; id <= gid_max; id++) {
+			result = check_gid (id, gid_min, gid_max, used_gids);
+			if (result == 0) {
+				/* This GID is available. Return it. */
+				*gid = id;
+				free (used_gids);
+				return 0;
+			} else if (result == EEXIST) {
+				/* This GID is in use, we'll continue to the next */
+			} else {
+				/*
+				 * An unexpected error occurred.
+				 *
+				 * Only report it the first time to avoid spamming
+				 * the logs
+				 *
+				 */
+				if (!nospam) {
+					fprintf (log_get_logfd(),
+						_("%s: Can't get unique GID (%s). "
+						  "Suppressing additional messages.\n"),
+						log_get_progname(), strerror (result));
+					SYSLOG ((LOG_ERR,
+						"Error checking available GIDs: %s",
+						strerror (result)));
+					nospam = 1;
+				}
+				/*
+				 * We will continue anyway. Hopefully a later GID
+				 * will work properly.
+				 */
+			}
+		}
+
+		/*
+		 * If we get all the way through the loop, try again from GID_MIN,
+		 * unless that was where we previously started. (NOTE: the worst-case
+		 * scenario here is that we will run through (GID_MAX - GID_MIN - 1)
+		 * cycles *again* if we fall into this case with highest_found as
+		 * GID_MIN + 1, all groups in the range in use and maintained by
+		 * network services such as LDAP.)
+		 */
+		if (highest_found != gid_min) {
+			for (id = gid_min; id <= gid_max; id++) {
+				result = check_gid (id, gid_min, gid_max, used_gids);
+				if (result == 0) {
+					/* This GID is available. Return it. */
+					*gid = id;
+					free (used_gids);
+					return 0;
+				} else if (result == EEXIST) {
+					/* This GID is in use, we'll continue to the next */
+				} else {
+					/*
+					 * An unexpected error occurred.
+					 *
+					 * Only report it the first time to avoid spamming
+					 * the logs
+					 *
+					 */
+					if (!nospam) {
+						fprintf (log_get_logfd(),
+							_("%s: Can't get unique GID (%s). "
+							  "Suppressing additional messages.\n"),
+							log_get_progname(), strerror (result));
+						SYSLOG ((LOG_ERR,
+							"Error checking available GIDs: %s",
+							strerror (result)));
+						nospam = 1;
+					}
+					/*
+					 * We will continue anyway. Hopefully a later GID
+					 * will work properly.
+					 */
+				}
+			}
+		}
+	}
+
+	/* The code reached here and found no available IDs in the range */
+	fprintf (log_get_logfd(),
+		_("%s: Can't get unique GID (no more available GIDs)\n"),
+		log_get_progname());
+	SYSLOG ((LOG_WARN, "no more available GIDs on the system"));
+	free (used_gids);
+	return -1;
+}
+