diff options
Diffstat (limited to 'src/runas.c')
-rw-r--r-- | src/runas.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/src/runas.c b/src/runas.c new file mode 100644 index 0000000..9d2a6c1 --- /dev/null +++ b/src/runas.c @@ -0,0 +1,191 @@ +/* This file is part of genrc +Copyryght (C) 2018 Sergey Poznyakoff +License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> +This is free software: you are free to change and redistribute it. +There is NO WARRANTY, to the extent permitted by law. +*/ +#include "genrc.h" +#include <pwd.h> +#include <grp.h> + +static void +addgid(gid_t **pgv, size_t *pgc, size_t *pgi, gid_t gid) +{ + gid_t *gv = *pgv; + size_t gc = *pgc; + size_t gi = *pgi; + + if (gi == gc) + gv = x2nrealloc(gv, &gc, sizeof(gv[0])); + + gv[gi++] = gid; + *pgv = gv; + *pgc = gc; + *pgi = gi; +} + +static int +member(gid_t *gv, size_t gc, gid_t gid) +{ + size_t i; + + for (i = 0; i < gc; i++) + if (gv[i] == gid) + return 1; + return 0; +} + +static size_t +get_user_groups(const char *user, gid_t **pgv, size_t *pgc) +{ + struct group *gr; + size_t gi = 0; + + setgrent(); + while ((gr = getgrent())) { + char **p; + for (p = gr->gr_mem; *p; p++) + if (strcmp(*p, user) == 0) + addgid(pgv, pgc, &gi, gr->gr_gid); + } + endgrent(); + return gi; +} + +static gid_t +strtogid(char const *str) +{ + struct group *gr; + + if (str[0] == '+') { + char *end; + unsigned long n; + + errno = 0; + n = strtoul(str, &end, 10); + if (errno || *end) { + genrc_error("invalid group name %s", str); + exit(1); + } + + gr = getgrgid(n); + } else + gr = getgrnam(str); + + if (!gr) { + genrc_error("%s: no such group", str); + exit(1); + } + + return gr->gr_gid; +} + +void +runas(void) +{ + struct passwd *pw; + uid_t uid; + gid_t gid; + gid_t *gv; + size_t gc, gn; + char const *runas_user; + char const *runas_groups; + + runas_user = getenv("GENRC_USER"); + runas_groups = getenv("GENRC_GROUP"); + + if (!(runas_user || runas_groups)) + return; + if (getuid() != 0) { + genrc_error("not root: can't switch to user privileges"); + exit(1); + } + + if (!runas_user) { + pw = getpwuid(0); + runas_user = "root"; + } else if (runas_user[0] == '+') { + char *end; + unsigned long n; + + errno = 0; + n = strtoul(runas_user + 1, &end, 10); + if (errno || *end) { + genrc_error("invalid user name %s", runas_user); + exit(1); + } + + pw = getpwuid(n); + } else + pw = getpwnam(runas_user); + + if (!pw) { + genrc_error("%s: no such user", runas_user); + exit(1); + } + runas_user = pw->pw_name; + + uid = pw->pw_uid; + gid = pw->pw_gid; + + gv = NULL; + gc = 0; + + if (runas_groups && runas_groups[0]) { + struct wordsplit ws; + size_t i; + + ws.ws_delim = ","; + ws.ws_error = genrc_error; + if (wordsplit(runas_groups, &ws, + WRDSF_NOCMD + | WRDSF_NOVAR + | WRDSF_DELIM + | WRDSF_ENOMEMABRT + | WRDSF_SHOWERR + | WRDSF_ERROR)) + exit(1); + + if (ws.ws_wordc == 0) { + genrc_error("bad group list: '%s'", runas_groups); + exit(1); + } + + gid = strtogid(ws.ws_wordv[0]); + for (i = 1; i < ws.ws_wordc; i++) + addgid(&gv, &gc, &gn, strtogid(ws.ws_wordv[i])); + + wordsplit_free(&ws); + } + + if (gc == 0) { + gn = get_user_groups(runas_user, &gv, &gc); + if (!member(gv, gn, gid)) + addgid(&gv, &gc, &gn, gid); + } + + /* Reset group permissions */ + if (setgroups(gn, gv)) { + system_error(errno, "setgroups"); + exit(1); + } + free(gv); + + if (gid) { + /* Switch to the user's gid. */ + if (setgid(gid)) { + system_error(errno, "setgid(%lu) failed", + (unsigned long) gid); + exit(1); + } + } + + /* Now reset uid */ + if (uid) { + if (setuid(uid)) { + system_error(errno, "setuid(%lu) failed: %s", + (unsigned long) uid); + exit(1); + } + } +} |