diff options
| -rw-r--r-- | doc/doc-txt/ChangeLog | 3 | ||||
| -rw-r--r-- | src/src/dbfn.c | 116 |
2 files changed, 68 insertions, 51 deletions
diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog index 313dcbf7e..4debef807 100644 --- a/doc/doc-txt/ChangeLog +++ b/doc/doc-txt/ChangeLog @@ -296,6 +296,9 @@ PP/11 Fix security issue in BDAT state confusion. HS/03 Die on "/../" in msglog file names +QS/01 Creation of (database) files in $spool_dir: only uid=0 or the euid of + the Exim runtime user are allowed to create files. + Exim version 4.94 ----------------- diff --git a/src/src/dbfn.c b/src/src/dbfn.c index 0f56ad5a6..b66d4603f 100644 --- a/src/src/dbfn.c +++ b/src/src/dbfn.c @@ -65,6 +65,66 @@ log_write(0, LOG_MAIN, "Berkeley DB error: %s", msg); +static enum { + PRIV_DROPPING, PRIV_DROPPED, + PRIV_RESTORING, PRIV_RESTORED +} priv_state = PRIV_RESTORED; + +static uid_t priv_euid; +static gid_t priv_egid; +static gid_t priv_groups[EXIM_GROUPLIST_SIZE + 1]; +static int priv_ngroups; + +/* Inspired by OpenSSH's temporarily_use_uid(). Thanks! */ + +static void +priv_drop_temp(const uid_t temp_uid, const gid_t temp_gid) +{ +if (priv_state != PRIV_RESTORED) _exit(EXIT_FAILURE); +priv_state = PRIV_DROPPING; + +priv_euid = geteuid(); +if (priv_euid == root_uid) + { + priv_egid = getegid(); + priv_ngroups = getgroups(nelem(priv_groups), priv_groups); + if (priv_ngroups < 0) _exit(EXIT_FAILURE); + + if (priv_ngroups > 0 && setgroups(1, &temp_gid) != 0) _exit(EXIT_FAILURE); + if (setegid(temp_gid) != 0) _exit(EXIT_FAILURE); + if (seteuid(temp_uid) != 0) _exit(EXIT_FAILURE); + + if (geteuid() != temp_uid) _exit(EXIT_FAILURE); + if (getegid() != temp_gid) _exit(EXIT_FAILURE); + } + +priv_state = PRIV_DROPPED; +} + +/* Inspired by OpenSSH's restore_uid(). Thanks! */ + +static void +priv_restore(void) +{ +if (priv_state != PRIV_DROPPED) _exit(EXIT_FAILURE); +priv_state = PRIV_RESTORING; + +if (priv_euid == root_uid) + { + if (seteuid(priv_euid) != 0) _exit(EXIT_FAILURE); + if (setegid(priv_egid) != 0) _exit(EXIT_FAILURE); + if (priv_ngroups > 0 && setgroups(priv_ngroups, priv_groups) != 0) _exit(EXIT_FAILURE); + + if (geteuid() != priv_euid) _exit(EXIT_FAILURE); + if (getegid() != priv_egid) _exit(EXIT_FAILURE); + } + +priv_state = PRIV_RESTORED; +} + + + + /************************************************* * Open and lock a database file * *************************************************/ @@ -96,7 +156,6 @@ dbfn_open(uschar *name, int flags, open_db *dbblock, BOOL lof, BOOL panic) { int rc, save_errno; BOOL read_only = flags == O_RDONLY; -BOOL created = FALSE; flock_t lock_data; uschar dirname[PATHLEN], filename[PATHLEN]; @@ -118,12 +177,13 @@ exists, there is no error. */ snprintf(CS dirname, sizeof(dirname), "%s/db", spool_directory); snprintf(CS filename, sizeof(filename), "%s/%s.lockfile", dirname, name); +priv_drop_temp(exim_uid, exim_gid); if ((dbblock->lockfd = Uopen(filename, O_RDWR, EXIMDB_LOCKFILE_MODE)) < 0) { - created = TRUE; (void)directory_make(spool_directory, US"db", EXIMDB_DIRECTORY_MODE, panic); dbblock->lockfd = Uopen(filename, O_RDWR|O_CREAT, EXIMDB_LOCKFILE_MODE); } +priv_restore(); if (dbblock->lockfd < 0) { @@ -172,63 +232,17 @@ it easy to pin this down, there are now debug statements on either side of the open call. */ snprintf(CS filename, sizeof(filename), "%s/%s", dirname, name); -EXIM_DBOPEN(filename, dirname, flags, EXIMDB_MODE, &(dbblock->dbptr)); +priv_drop_temp(exim_uid, exim_gid); +EXIM_DBOPEN(filename, dirname, flags, EXIMDB_MODE, &(dbblock->dbptr)); if (!dbblock->dbptr && errno == ENOENT && flags == O_RDWR) { DEBUG(D_hints_lookup) debug_printf_indent("%s appears not to exist: trying to create\n", filename); - created = TRUE; EXIM_DBOPEN(filename, dirname, flags|O_CREAT, EXIMDB_MODE, &(dbblock->dbptr)); } - save_errno = errno; - -/* If we are running as root and this is the first access to the database, its -files will be owned by root. We want them to be owned by exim. We detect this -situation by noting above when we had to create the lock file or the database -itself. Because the different dbm libraries use different extensions for their -files, I don't know of any easier way of arranging this than scanning the -directory for files with the appropriate base name. At least this deals with -the lock file at the same time. Also, the directory will typically have only -half a dozen files, so the scan will be quick. - -This code is placed here, before the test for successful opening, because there -was a case when a file was created, but the DBM library still returned NULL -because of some problem. It also sorts out the lock file if that was created -but creation of the database file failed. */ - -if (created && geteuid() == root_uid) - { - DIR * dd; - uschar path[PATHLEN]; - uschar *lastname; - int namelen = Ustrlen(name); - - Ustrcpy(path, filename); - lastname = Ustrrchr(path, '/') + 1; - *lastname = 0; - - if ((dd = exim_opendir(path))) - for (struct dirent *ent; ent = readdir(dd); ) - if (Ustrncmp(ent->d_name, name, namelen) == 0) - { - struct stat statbuf; - /* Filenames from readdir() are trusted, - so use a taint-nonchecking copy */ - strcpy(CS lastname, CCS ent->d_name); - if (Ustat(path, &statbuf) >= 0 && statbuf.st_uid != exim_uid) - { - DEBUG(D_hints_lookup) - debug_printf_indent("ensuring %s is owned by exim\n", path); - if (exim_chown(path, exim_uid, exim_gid)) - DEBUG(D_hints_lookup) - debug_printf_indent("failed setting %s to owned by exim\n", path); - } - } - - closedir(dd); - } +priv_restore(); /* If the open has failed, return NULL, leaving errno set. If lof is TRUE, log the event - also for debugging - but debug only if the file just doesn't |