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Diffstat (limited to '')
| -rw-r--r-- | lib/subordinateio.c | 701 |
1 files changed, 701 insertions, 0 deletions
diff --git a/lib/subordinateio.c b/lib/subordinateio.c new file mode 100644 index 0000000..0d64a91 --- /dev/null +++ b/lib/subordinateio.c @@ -0,0 +1,701 @@ +/* + * Copyright (c) 2012 - Eric Biederman + */ + +#include <config.h> + +#ifdef ENABLE_SUBIDS + +#include "prototypes.h" +#include "defines.h" +#include <stdio.h> +#include "commonio.h" +#include "subordinateio.h" +#include <sys/types.h> +#include <pwd.h> + +struct subordinate_range { + const char *owner; + unsigned long start; + unsigned long count; +}; + +#define NFIELDS 3 + +/* + * subordinate_dup: create a duplicate range + * + * @ent: a pointer to a subordinate_range struct + * + * Returns a pointer to a newly allocated duplicate subordinate_range struct + * or NULL on failure + */ +static /*@null@*/ /*@only@*/void *subordinate_dup (const void *ent) +{ + const struct subordinate_range *rangeent = ent; + struct subordinate_range *range; + + range = (struct subordinate_range *) malloc (sizeof *range); + if (NULL == range) { + return NULL; + } + range->owner = strdup (rangeent->owner); + if (NULL == range->owner) { + free(range); + return NULL; + } + range->start = rangeent->start; + range->count = rangeent->count; + + return range; +} + +/* + * subordinate_free: free a subordinate_range struct + * + * @ent: pointer to a subordinate_range struct to free. + */ +static void subordinate_free (/*@out@*/ /*@only@*/void *ent) +{ + struct subordinate_range *rangeent = ent; + + free ((void *)(rangeent->owner)); + free (rangeent); +} + +/* + * subordinate_parse: + * + * @line: a line to parse + * + * Returns a pointer to a subordinate_range struct representing the values + * in @line, or NULL on failure. Note that the returned value should not + * be freed by the caller. + */ +static void *subordinate_parse (const char *line) +{ + static struct subordinate_range range; + static char rangebuf[1024]; + int i; + char *cp; + char *fields[NFIELDS]; + + /* + * Copy the string to a temporary buffer so the substrings can + * be modified to be NULL terminated. + */ + if (strlen (line) >= sizeof rangebuf) + return NULL; /* fail if too long */ + strcpy (rangebuf, line); + + /* + * Save a pointer to the start of each colon separated + * field. The fields are converted into NUL terminated strings. + */ + + for (cp = rangebuf, i = 0; (i < NFIELDS) && (NULL != cp); i++) { + fields[i] = cp; + while (('\0' != *cp) && (':' != *cp)) { + cp++; + } + + if ('\0' != *cp) { + *cp = '\0'; + cp++; + } else { + cp = NULL; + } + } + + /* + * There must be exactly NFIELDS colon separated fields or + * the entry is invalid. Also, fields must be non-blank. + */ + if (i != NFIELDS || *fields[0] == '\0' || *fields[1] == '\0' || *fields[2] == '\0') + return NULL; + range.owner = fields[0]; + if (getulong (fields[1], &range.start) == 0) + return NULL; + if (getulong (fields[2], &range.count) == 0) + return NULL; + + return ⦥ +} + +/* + * subordinate_put: print a subordinate_range value to a file + * + * @ent: a pointer to a subordinate_range struct to print out. + * @file: file to which to print. + * + * Returns 0 on success, -1 on error. + */ +static int subordinate_put (const void *ent, FILE * file) +{ + const struct subordinate_range *range = ent; + + return fprintf(file, "%s:%lu:%lu\n", + range->owner, + range->start, + range->count) < 0 ? -1 : 0; +} + +static struct commonio_ops subordinate_ops = { + subordinate_dup, /* dup */ + subordinate_free, /* free */ + NULL, /* getname */ + subordinate_parse, /* parse */ + subordinate_put, /* put */ + fgets, /* fgets */ + fputs, /* fputs */ + NULL, /* open_hook */ + NULL, /* close_hook */ +}; + +static /*@observer@*/ /*@null*/const struct subordinate_range *subordinate_next(struct commonio_db *db) +{ + return (const struct subordinate_range *)commonio_next (db); +} + +/* + * range_exists: Check whether @owner owns any ranges + * + * @db: database to query + * @owner: owner being queried + * + * Returns true if @owner owns any subuid ranges, false otherwise. + */ +static const bool range_exists(struct commonio_db *db, const char *owner) +{ + const struct subordinate_range *range; + commonio_rewind(db); + while ((range = commonio_next(db)) != NULL) { + if (0 == strcmp(range->owner, owner)) + return true; + } + return false; +} + +/* + * find_range: find a range which @owner is authorized to use which includes + * subuid @val. + * + * @db: database to query + * @owner: owning uid being queuried + * @val: subuid being searched for. + * + * Returns a range of subuids belonging to @owner and including the subuid + * @val, or NULL if no such range exists. + */ +static const struct subordinate_range *find_range(struct commonio_db *db, + const char *owner, unsigned long val) +{ + const struct subordinate_range *range; + + /* + * Search for exact username/group specification + * + * This is the original method - go fast through the db, doing only + * exact username/group string comparison. Therefore we leave it as-is + * for the time being, in order to keep it equally fast as it was + * before. + */ + commonio_rewind(db); + while ((range = commonio_next(db)) != NULL) { + unsigned long first = range->start; + unsigned long last = first + range->count - 1; + + if (0 != strcmp(range->owner, owner)) + continue; + + if ((val >= first) && (val <= last)) + return range; + } + + + /* + * We only do special handling for these two files + */ + if ((0 != strcmp(db->filename, "/etc/subuid")) && (0 != strcmp(db->filename, "/etc/subgid"))) + return NULL; + + /* + * Search loop above did not produce any result. Let's rerun it, + * but this time try to matcha actual UIDs. The first entry that + * matches is considered a success. + * (It may be specified as literal UID or as another username which + * has the same UID as the username we are looking for.) + */ + struct passwd *pwd; + uid_t owner_uid; + char owner_uid_string[33] = ""; + + + /* Get UID of the username we are looking for */ + pwd = getpwnam(owner); + if (NULL == pwd) { + /* Username not defined in /etc/passwd, or error occured during lookup */ + return NULL; + } + owner_uid = pwd->pw_uid; + sprintf(owner_uid_string, "%lu", (unsigned long int)owner_uid); + + commonio_rewind(db); + while ((range = commonio_next(db)) != NULL) { + unsigned long first = range->start; + unsigned long last = first + range->count - 1; + + /* For performance reasons check range before using getpwnam() */ + if ((val < first) || (val > last)) { + continue; + } + + /* + * Range matches. Check if range owner is specified + * as numeric UID and if it matches. + */ + if (0 == strcmp(range->owner, owner_uid_string)) { + return range; + } + + /* + * Ok, this range owner is not specified as numeric UID + * we are looking for. It may be specified as another + * UID or as a literal username. + * + * If specified as another UID, the call to getpwnam() + * will return NULL. + * + * If specified as literal username, we will get its + * UID and compare that to UID we are looking for. + */ + const struct passwd *range_owner_pwd; + + range_owner_pwd = getpwnam(range->owner); + if (NULL == range_owner_pwd) { + continue; + } + + if (owner_uid == range_owner_pwd->pw_uid) { + return range; + } + } + + return NULL; +} + +/* + * have_range: check whether @owner is authorized to use the range + * (@start .. @start+@count-1). + * @db: database to check + * @owner: owning uid being queried + * @start: start of range + * @count: number of uids in range + * + * Returns true if @owner is authorized to use the range, false otherwise. + */ +static bool have_range(struct commonio_db *db, + const char *owner, unsigned long start, unsigned long count) +{ + const struct subordinate_range *range; + unsigned long end; + + if (count == 0) + return false; + + end = start + count - 1; + range = find_range (db, owner, start); + while (range) { + unsigned long last; + + last = range->start + range->count - 1; + if (last >= (start + count - 1)) + return true; + + count = end - last; + start = last + 1; + range = find_range(db, owner, start); + } + return false; +} + +/* + * subordinate_range_cmp: compare uid ranges + * + * @p1: pointer to a commonio_entry struct to compare + * @p2: pointer to second commonio_entry struct to compare + * + * Returns 0 if the entries are the same. Otherwise return -1 + * if the range in p1 is lower than that in p2, or (if the ranges are + * equal) if the owning uid in p1 is lower than p2's. Return 1 if p1's + * range or owning uid is great than p2's. + */ +static int subordinate_range_cmp (const void *p1, const void *p2) +{ + struct subordinate_range *range1, *range2; + + if ((*(struct commonio_entry **) p1)->eptr == NULL) + return 1; + if ((*(struct commonio_entry **) p2)->eptr == NULL) + return -1; + + range1 = ((struct subordinate_range *) (*(struct commonio_entry **) p1)->eptr); + range2 = ((struct subordinate_range *) (*(struct commonio_entry **) p2)->eptr); + + if (range1->start < range2->start) + return -1; + else if (range1->start > range2->start) + return 1; + else if (range1->count < range2->count) + return -1; + else if (range1->count > range2->count) + return 1; + else + return strcmp(range1->owner, range2->owner); +} + +/* + * find_free_range: find an unused consecutive sequence of ids to allocate + * to a user. + * @db: database to search + * @min: the first uid in the range to find + * @max: the highest uid to find + * @count: the number of uids needed + * + * Return the lowest new uid, or ULONG_MAX on failure. + */ +static unsigned long find_free_range(struct commonio_db *db, + unsigned long min, unsigned long max, + unsigned long count) +{ + const struct subordinate_range *range; + unsigned long low, high; + + /* When given invalid parameters fail */ + if ((count == 0) || (max < min)) + goto fail; + + /* Sort by range then by owner */ + commonio_sort (db, subordinate_range_cmp); + commonio_rewind(db); + + low = min; + while ((range = commonio_next(db)) != NULL) { + unsigned long first = range->start; + unsigned long last = first + range->count - 1; + + /* Find the top end of the hole before this range */ + high = first; + + /* Don't allocate IDs after max (included) */ + if (high > max + 1) { + high = max + 1; + } + + /* Is the hole before this range large enough? */ + if ((high > low) && ((high - low) >= count)) + return low; + + /* Compute the low end of the next hole */ + if (low < (last + 1)) + low = last + 1; + if (low > max) + goto fail; + } + + /* Is the remaining unclaimed area large enough? */ + if (((max - low) + 1) >= count) + return low; +fail: + return ULONG_MAX; +} + +/* + * add_range: add a subuid range to an owning uid's list of authorized + * subuids. + * @db: database to which to add + * @owner: uid which owns the subuid + * @start: the first uid in the owned range + * @count: the number of uids in the range + * + * Return 1 if the range is already present or on succcess. On error + * return 0 and set errno appropriately. + */ +static int add_range(struct commonio_db *db, + const char *owner, unsigned long start, unsigned long count) +{ + struct subordinate_range range; + range.owner = owner; + range.start = start; + range.count = count; + + /* See if the range is already present */ + if (have_range(db, owner, start, count)) + return 1; + + /* Otherwise append the range */ + return commonio_append(db, &range); +} + +/* + * remove_range: remove a range of subuids from an owning uid's list + * of authorized subuids. + * @db: database to work on + * @owner: owning uid whose range is being removed + * @start: start of the range to be removed + * @count: number of uids in the range. + * + * Returns 0 on failure, 1 on success. Failure means that we needed to + * create a new range to represent the new limits, and failed doing so. + */ +static int remove_range (struct commonio_db *db, + const char *owner, + unsigned long start, unsigned long count) +{ + struct commonio_entry *ent; + unsigned long end; + + if (count == 0) { + return 1; + } + + end = start + count - 1; + for (ent = db->head; NULL != ent; ent = ent->next) { + struct subordinate_range *range = ent->eptr; + unsigned long first; + unsigned long last; + + /* Skip unparsed entries */ + if (NULL == range) { + continue; + } + + first = range->start; + last = first + range->count - 1; + + /* Skip entries with a different owner */ + if (0 != strcmp (range->owner, owner)) { + continue; + } + + /* Skip entries outside of the range to remove */ + if ((end < first) || (start > last)) { + continue; + } + + if (start <= first) { + if (end >= last) { + /* to be removed: [start, end] + * range: [first, last] */ + /* entry completely contained in the + * range to remove */ + commonio_del_entry (db, ent); + } else { + /* to be removed: [start, end] + * range: [first, last] */ + /* Remove only the start of the entry */ + range->start = end + 1; + range->count = (last - range->start) + 1; + + ent->changed = true; + db->changed = true; + } + } else { + if (end >= last) { + /* to be removed: [start, end] + * range: [first, last] */ + /* Remove only the end of the entry */ + range->count = start - range->start; + + ent->changed = true; + db->changed = true; + } else { + /* to be removed: [start, end] + * range: [first, last] */ + /* Remove the middle of the range + * This requires to create a new range */ + struct subordinate_range tail; + tail.owner = range->owner; + tail.start = end + 1; + tail.count = (last - tail.start) + 1; + + if (commonio_append (db, &tail) == 0) { + return 0; + } + + range->count = start - range->start; + + ent->changed = true; + db->changed = true; + } + } + } + + return 1; +} + +static struct commonio_db subordinate_uid_db = { + "/etc/subuid", /* filename */ + &subordinate_ops, /* ops */ + NULL, /* fp */ +#ifdef WITH_SELINUX + NULL, /* scontext */ +#endif + 0644, /* st_mode */ + 0, /* st_uid */ + 0, /* st_gid */ + NULL, /* head */ + NULL, /* tail */ + NULL, /* cursor */ + false, /* changed */ + false, /* isopen */ + false, /* locked */ + false /* readonly */ +}; + +int sub_uid_setdbname (const char *filename) +{ + return commonio_setname (&subordinate_uid_db, filename); +} + +/*@observer@*/const char *sub_uid_dbname (void) +{ + return subordinate_uid_db.filename; +} + +bool sub_uid_file_present (void) +{ + return commonio_present (&subordinate_uid_db); +} + +int sub_uid_lock (void) +{ + return commonio_lock (&subordinate_uid_db); +} + +int sub_uid_open (int mode) +{ + return commonio_open (&subordinate_uid_db, mode); +} + +bool sub_uid_assigned(const char *owner) +{ + return range_exists (&subordinate_uid_db, owner); +} + +bool have_sub_uids(const char *owner, uid_t start, unsigned long count) +{ + return have_range (&subordinate_uid_db, owner, start, count); +} + +int sub_uid_add (const char *owner, uid_t start, unsigned long count) +{ + return add_range (&subordinate_uid_db, owner, start, count); +} + +int sub_uid_remove (const char *owner, uid_t start, unsigned long count) +{ + return remove_range (&subordinate_uid_db, owner, start, count); +} + +int sub_uid_close (void) +{ + return commonio_close (&subordinate_uid_db); +} + +int sub_uid_unlock (void) +{ + return commonio_unlock (&subordinate_uid_db); +} + +uid_t sub_uid_find_free_range(uid_t min, uid_t max, unsigned long count) +{ + unsigned long start; + start = find_free_range (&subordinate_uid_db, min, max, count); + return start == ULONG_MAX ? (uid_t) -1 : start; +} + +static struct commonio_db subordinate_gid_db = { + "/etc/subgid", /* filename */ + &subordinate_ops, /* ops */ + NULL, /* fp */ +#ifdef WITH_SELINUX + NULL, /* scontext */ +#endif + 0644, /* st_mode */ + 0, /* st_uid */ + 0, /* st_gid */ + NULL, /* head */ + NULL, /* tail */ + NULL, /* cursor */ + false, /* changed */ + false, /* isopen */ + false, /* locked */ + false /* readonly */ +}; + +int sub_gid_setdbname (const char *filename) +{ + return commonio_setname (&subordinate_gid_db, filename); +} + +/*@observer@*/const char *sub_gid_dbname (void) +{ + return subordinate_gid_db.filename; +} + +bool sub_gid_file_present (void) +{ + return commonio_present (&subordinate_gid_db); +} + +int sub_gid_lock (void) +{ + return commonio_lock (&subordinate_gid_db); +} + +int sub_gid_open (int mode) +{ + return commonio_open (&subordinate_gid_db, mode); +} + +bool have_sub_gids(const char *owner, gid_t start, unsigned long count) +{ + return have_range(&subordinate_gid_db, owner, start, count); +} + +bool sub_gid_assigned(const char *owner) +{ + return range_exists (&subordinate_gid_db, owner); +} + +int sub_gid_add (const char *owner, gid_t start, unsigned long count) +{ + return add_range (&subordinate_gid_db, owner, start, count); +} + +int sub_gid_remove (const char *owner, gid_t start, unsigned long count) +{ + return remove_range (&subordinate_gid_db, owner, start, count); +} + +int sub_gid_close (void) +{ + return commonio_close (&subordinate_gid_db); +} + +int sub_gid_unlock (void) +{ + return commonio_unlock (&subordinate_gid_db); +} + +gid_t sub_gid_find_free_range(gid_t min, gid_t max, unsigned long count) +{ + unsigned long start; + start = find_free_range (&subordinate_gid_db, min, max, count); + return start == ULONG_MAX ? (gid_t) -1 : start; +} +#else /* !ENABLE_SUBIDS */ +extern int errno; /* warning: ANSI C forbids an empty source file */ +#endif /* !ENABLE_SUBIDS */ + |