From 3ef1fec92e9e8a76bb3ed531b6d9a961ea1e40dd Mon Sep 17 00:00:00 2001
From: mdw <mdw>
Date: Fri, 6 May 2005 20:31:51 +0000
Subject: [PATCH] Check the proposed socket directory before trusting its
 contents.

---
 noip.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 58 insertions(+), 17 deletions(-)

diff --git a/noip.c b/noip.c
index 61d4a62..e674bed 100644
--- a/noip.c
+++ b/noip.c
@@ -105,7 +105,7 @@ static void *xmalloc(size_t n)
 {
   void *p;
   if (!n) return (0);
-  if ((p = malloc(n)) == 0) { perror("malloc"); exit(1); }
+  if ((p = malloc(n)) == 0) { perror("malloc"); exit(127); }
   return (p);
 }
 
@@ -117,7 +117,7 @@ static char *xstrdup(const char *p)
   return (q);
 }
 
-static int unix_socket_status(struct sockaddr_un *sun, int quick_p)
+static int unix_socket_status(struct sockaddr_un *sun, int quickp)
 {
   struct stat st;
   FILE *fp = 0;
@@ -125,13 +125,11 @@ static int unix_socket_status(struct sockaddr_un *sun, int quick_p)
   int rc;
   char buf[256];
 
-  rc = UNUSED;
-  if (stat(sun->sun_path, &st) && errno == ENOENT)
-    goto done;
+  if (stat(sun->sun_path, &st))
+    return (errno == ENOENT ? UNUSED : USED);
+  if (!S_ISSOCK(st.st_mode) || !quickp)
+    return (USED);
   rc = USED;
-  if (quick_p)
-    goto done;
-
   if ((fp = fopen("/proc/net/unix", "r")) == 0)
     goto done;
   fgets(buf, sizeof(buf), fp); /* skip header */
@@ -237,7 +235,7 @@ static int encode_inet_addr(struct sockaddr_un *sun,
 			    int want)
 {
   int i;
-  int desperate_p = 0;
+  int desperatep = 0;
   char buf[INET_ADDRSTRLEN];
   int rc;
 
@@ -264,12 +262,12 @@ static int encode_inet_addr(struct sockaddr_un *sun,
 	       randrange(minautoport, maxautoport));
       if (unix_socket_status(sun, 1) == UNUSED) goto found;
     }
-    for (desperate_p = 0; desperate_p < 2; desperate_p++) {
+    for (desperatep = 0; desperatep < 2; desperatep++) {
       for (i = minautoport; i <= maxautoport; i++) {
 	snprintf(sun->sun_path, sizeof(sun->sun_path), "%s/%s:%u", sockdir,
 		 inet_ntop(AF_INET, &sin->sin_addr, buf, sizeof(buf)),
 		 (unsigned)i);
-	rc = unix_socket_status(sun, !desperate_p);
+	rc = unix_socket_status(sun, !desperatep);
 	switch (rc) {
 	  case STALE: unlink(sun->sun_path);
 	  case UNUSED: goto found;
@@ -452,9 +450,13 @@ static char *home(void)
   char *p;
   struct passwd *pw;
 
-  if ((p = getenv("HOME")) != 0) return (p);
-  else if ((pw = getpwuid(uid)) != 0) return (pw->pw_dir);
-  else return "/notexist";
+  if (getuid() == uid &&
+      (p = getenv("HOME")) != 0)
+    return (p);
+  else if ((pw = getpwuid(uid)) != 0)
+    return (pw->pw_dir);
+  else
+    return "/notexist";
 }
 
 static char *tmpdir(void)
@@ -703,7 +705,7 @@ done:
     snprintf(buf, sizeof(buf), "%s/noip-%s", tmpdir(), user());
     sockdir = xstrdup(buf);
   }
-  D( fprintf(stderr, "noip: sockdir: %s\n", sockdir);
+  D( fprintf(stderr, "noip: socketdir: %s\n", sockdir);
      fprintf(stderr, "noip: autoports: %u-%u\n",
 	     minautoport, maxautoport);
      fprintf(stderr, "noip: realbind acl:\n");
@@ -908,7 +910,9 @@ static void cleanup_sockdir(void)
 {
   DIR *dir;
   struct dirent *d;
+  struct sockaddr_in sin;
   struct sockaddr_un sun;
+  struct stat st;
 
   if ((dir = opendir(sockdir)) == 0)
     return;
@@ -916,6 +920,10 @@ static void cleanup_sockdir(void)
     if (d->d_name[0] == '.') continue;
     snprintf(sun.sun_path, sizeof(sun.sun_path),
 	     "%s/%s", sockdir, d->d_name);
+    if (decode_inet_addr(&sin, &sun, SUN_LEN(&sun)) ||
+	stat(sun.sun_path, &st) ||
+	!S_ISSOCK(st.st_mode))
+      continue;
     if (unix_socket_status(&sun, 0) == STALE) {
       D( fprintf(stderr, "noip: clearing away stale socket %s\n",
 		 d->d_name); )
@@ -950,18 +958,51 @@ static void get_local_ipaddrs(void)
   close(sk);
 }
 
+static void printerr(const char *p) { write(STDERR_FILENO, p, strlen(p)); }
+
+static void create_sockdir(void)
+{
+  struct stat st;
+
+  if (stat(sockdir, &st)) {
+    if (errno == ENOENT) {
+      if (mkdir(sockdir, 0700)) {
+	perror("noip: creating socketdir");
+	exit(127);
+      }
+      if (!stat(sockdir, &st))
+	goto check;
+    }
+    perror("noip: checking socketdir");
+    exit(127);
+  }
+check:
+  if (!S_ISDIR(st.st_mode)) {
+    printerr("noip: bad socketdir: not a directory\n");
+    exit(127);
+  }
+  if (st.st_uid != uid) {
+    printerr("noip: bad socketdir: not owner\n");
+    exit(127);
+  }
+  if (st.st_mode & 077) {
+    printerr("noip: bad socketdir: not private\n");
+    exit(127);
+  }
+}
+
 static void setup(void)
 {
   PRESERVING_ERRNO({
     char *p;
 
     import();
-    uid = getuid();
+    uid = geteuid();
     if ((p = getenv("NOIP_DEBUG")) && atoi(p))
       debug = 1;
     get_local_ipaddrs();
     readconfig();
-    mkdir(sockdir, 0700);
+    create_sockdir();
     cleanup_sockdir();
   });
 }
-- 
2.11.0