From 5d767065171e8d73f0e812ba894b979bbea8ef73 Mon Sep 17 00:00:00 2001
From: deva <deva>
Date: Tue, 18 Mar 2008 08:35:47 +0000
Subject: Applied Bertho Stultiens' daemon patch for user/group switch and
 filedescriptor leak fix.

---
 miavd/daemon.cc | 96 +++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 66 insertions(+), 30 deletions(-)

diff --git a/miavd/daemon.cc b/miavd/daemon.cc
index 6e46bd5..a687d38 100644
--- a/miavd/daemon.cc
+++ b/miavd/daemon.cc
@@ -30,6 +30,8 @@
 #include <fcntl.h>
 #include <signal.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
 
 // For getgrent and getgrent
 #include <sys/types.h>
@@ -39,6 +41,38 @@
 // For strcmp
 #include <string.h>
 
+/* Resolve a group's name or id into a numeric gid */
+static gid_t get_gid(const char *grp)
+{
+  char *eptr;
+  gid_t xid = strtoul(grp, &eptr, 10);
+  struct group *gr;
+  errno = 0;      /* Per getgrnam(3) and getgrgid(3) manual page */
+  if(!*eptr)
+    gr = getgrgid(xid);
+  else
+    gr = getgrnam(grp);
+  return !gr ? 0 : gr->gr_gid;
+}
+
+/* Resolve a user's name or id into a numeric uid with associated gid */
+static uid_t get_uid(const char *usr, gid_t *gid)
+{
+  char *eptr;
+  uid_t xid = strtoul(usr, &eptr, 10);
+  struct passwd *pw;
+  errno = 0;      /* Per getpwnam(3) and getpwuid(3) manual page */
+  if(!*eptr)
+    pw = getpwuid(xid);
+  else
+    pw = getpwnam(usr);
+  if(!pw)
+    return 0;
+  if(!gid)
+    *gid = pw->pw_gid;
+  return pw->pw_uid;
+}
+
 Daemon::Daemon()
 {}
 
@@ -50,50 +84,50 @@ int Daemon::run(const char *user, const char* group)
   int f;
   int fd;
 
-  // Fetch user id
-  int uid = -1;
-  struct passwd *p = getpwent();
-  while(p) {
-    if(strcmp(p->pw_name, user) == 0) uid = p->pw_uid;
-    p = getpwent();
-  }
-  if(uid == -1) {
-    fprintf(stderr, "Could not find user \"%s\" in /etc/passwd file.\n", user);
+  // Fetch user and group IDs
+  gid_t gid = 0;
+  uid_t uid = 0;
+  if(user && *user) {
+    uid = get_uid(user, &gid);
+    if(errno) {
+      fprintf(stderr, "Could resolve user \"%s\"", user);
+      perror("");
+    }
   }
 
-  // Fetch group id
-  int gid = -1;
-  struct group *g = getgrent();
-  while(g) {
-    if(strcmp(g->gr_name, group) == 0) gid = g->gr_gid;
-    g = getgrent();
-  }
-  if(gid == -1) {
-    fprintf(stderr, "Could not find group \"%s\" in /etc/group file.\n", group);
+  if(group && *group) {
+    gid = get_gid(group);
+    if(errno) {
+      fprintf(stderr, "Could not resolve group \"%s\"", group);
+      perror("");
+    }
   }
 
   chdir("/");
   umask(0);
 
-  f = fork();
-  switch(f) {
+  switch(fork()) {
   case -1: // Fork error
     perror("Fork in daemon.cc");
     return 1;
 
   case 0:  // Forked child
-    // Switch to given group
-    if(setgid(gid) != 0) {
-      fprintf(stderr, "Failed to change to group \"%s\" (gid: %d), quitting.\n", group, gid);
-      perror("");
-      fprintf(stderr, "Runnning daemon as current group\n");
+    if(gid) {
+      // Switch to given group
+      if(setgid(gid) != 0) {
+        fprintf(stderr, "Failed to change to group \"%s\" (gid: %d), quitting.\n", group, gid);
+        perror("");
+        fprintf(stderr, "Runnning daemon as current group\n");
+      }
     }
     
-    // Switch to given user
-    if(setuid(uid) != 0) {
-      fprintf(stderr, "Failed to change to user \"%s\" (uid: %d), quitting.\n", user, uid);
-      perror("");
-      fprintf(stderr, "Runnning daemon as current user\n");
+    if(uid) {
+      // Switch to given user
+      if(setuid(uid) != 0) {
+        fprintf(stderr, "Failed to change to user \"%s\" (uid: %d), quitting.\n", user, uid);
+        perror("");
+        fprintf(stderr, "Runnning daemon as current user\n");
+      }
     }
     
     // Redirect stdin, stdout and stderr to /dev/null
@@ -103,6 +137,8 @@ int Daemon::run(const char *user, const char* group)
     dup2(1, fd);
     dup2(2, fd);
     
+    close(fd);
+
     setsid();
 
     signal (SIGTERM, SIG_IGN);
-- 
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