1 files changed, 68 insertions, 0 deletions
diff --git a/src/daemontools-extras/s6-applyuidgid.c b/src/daemontools-extras/s6-applyuidgid.c
new file mode 100644
index 0000000..77beef2
--- /dev/null
+++ b/src/daemontools-extras/s6-applyuidgid.c
@@ -0,0 +1,68 @@
+/* ISC license. */
+
+#include <skalibs/nonposix.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <grp.h>
+#include <limits.h>
+#include <skalibs/uint.h>
+#include <skalibs/gidstuff.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/sgetopt.h>
+#include <skalibs/env.h>
+#include <skalibs/djbunix.h>
+
+#define USAGE "s6-applyuidgid [ -z ] [ -u uid ] [ -g gid ] [ -G gidlist ] [ -U ] prog..."
+#define dieusage() strerr_dieusage(100, USAGE)
+
+int main (int argc, char const *const *argv, char const *const *envp)
+{
+  unsigned int uid = 0, gid = 0 ;
+  gid_t gids[NGROUPS_MAX] ;
+  unsigned int gidn = (unsigned int)-1 ;
+  int unexport = 0 ;
+  PROG = "s6-applyuidgid" ;
+  {
+    subgetopt_t l = SUBGETOPT_ZERO ;
+    for (;;)
+    {
+      register int opt = subgetopt_r(argc, argv, "zUu:g:G:", &l) ;
+      if (opt == -1) break ;
+      switch (opt)
+      {
+        case 'z' : unexport = 1 ; break ;
+        case 'u' : if (!uint0_scan(l.arg, &uid)) dieusage() ; break ;
+        case 'g' : if (!uint0_scan(l.arg, &gid)) dieusage() ; break ;
+        case 'G' : if (!gid_scanlist(gids, NGROUPS_MAX, l.arg, &gidn)) dieusage() ; break ;
+        case 'U' :
+        {
+          char const *x = env_get2(envp, "UID") ;
+          if (!x) strerr_dienotset(100, "UID") ;
+          if (!uint0_scan(x, &uid)) strerr_dieinvalid(100, "UID") ;
+          x = env_get2(envp, "GID") ;
+          if (!x) strerr_dienotset(100, "GID") ;
+          if (!uint0_scan(x, &gid)) strerr_dieinvalid(100, "GID") ;
+          x = env_get2(envp, "GIDLIST") ;
+          if (!x) strerr_dienotset(100, "GIDLIST") ;
+          if (!gid_scanlist(gids, NGROUPS_MAX, x, &gidn) && *x)
+            strerr_dieinvalid(100, "GIDLIST") ;
+          break ;
+        }
+        default : dieusage() ;
+      }
+    }
+    argc -= l.ind ; argv += l.ind ;
+  }
+  if (!argc) dieusage() ;
+
+  if (gidn != (unsigned int)-1 && setgroups(gidn, gids) < 0)
+    strerr_diefu1sys(111, "set supplementary group list") ;
+  if (gid && setgid(gid) < 0)
+    strerr_diefu1sys(111, "setgid") ;
+  if (uid && setuid(uid) < 0)
+    strerr_diefu1sys(111, "setuid") ;
+
+  if (unexport) pathexec_r(argv, envp, env_len(envp), "UID\0GID\0GIDLIST", 16) ;
+  else pathexec_run(argv[0], argv, envp) ;
+  strerr_dieexec(111, argv[0]) ;
+}