Hello,
I have several machines where almost all user accounts come by NIS. The NIS
server is running on a Solaris machine. As usual, the Solaris NIS server
exports the passwd data in the map "passwd" and the shadow data in the map
"passwd.adjunct.byname". These two maps are mangled together in some calls
of libc6, for example in getpwnam. This makes it possible for every user who
has an account on the NIS client machine to see the encrypted passwords of
all NIS users. This is a grave security bug.

Furthermore, getspnam returns a NULL pointer for all NIS users, even if
getspnam is called by root.

I wrote a patch nis_shadow.diff that solves these problems. It makes the 
following changes:

* In nis-pwd.c, do not mangle encrypted password from 
  passwd.adjunct.byname map  into the password field
  of passwd map, instead mangle an 'x' into the field

* In nis-spwd.c, look for key in passwd.adjunct.byname if shadow.byname
  does not exist and add the two missing fields (passwd.adjunct.byname
  has two fields less than shadow)

diff -Naurp glibc-2.7.original/nis/nss_nis/nis-pwd.c 
glibc-2.7/nis/nss_nis/nis-pwd.c
--- glibc-2.7.original/nis/nss_nis/nis-pwd.c	2006-05-02 00:31:15.000000000 
+0200
+++ glibc-2.7/nis/nss_nis/nis-pwd.c	2009-12-22 09:04:46.000000000 +0100
@@ -275,8 +275,8 @@ internal_nis_getpwent_r (struct passwd *
 	      yp_match (domain, "passwd.adjunct.byname", result, namelen,
 			&result2, &len2)) == YPERR_SUCCESS)
 	{
-	  /* We found a passwd.adjunct entry.  Merge encrypted
-	     password therein into original result.  */
+	  /* We found a passwd.adjunct entry.  Merge "x"
+	     into original result.  */
 	  char *encrypted = strchr (result2, ':');
 	  char *endp;
 	  size_t restlen;
@@ -304,7 +304,7 @@ internal_nis_getpwent_r (struct passwd *
 
 	  mempcpy (mempcpy (mempcpy (mempcpy (buffer, result, namelen),
 				     ":", 1),
-			    encrypted, endp - encrypted),
+			    "x", 1),
 		   p, restlen + 1);
 	  p = buffer;
 
@@ -408,8 +408,8 @@ _nss_nis_getpwnam_r (const char *name, s
       && yp_match (domain, "passwd.adjunct.byname", name, namelen,
 		   &result2, &len2) == YPERR_SUCCESS)
     {
-      /* We found a passwd.adjunct entry.  Merge encrypted password
-	 therein into original result.  */
+      /* We found a passwd.adjunct entry.  Merge "x"
+	 into original result.  */
       char *encrypted = strchr (result2, ':');
       char *endp;
 
@@ -436,7 +436,7 @@ _nss_nis_getpwnam_r (const char *name, s
 
       __mempcpy (__mempcpy (__mempcpy (__mempcpy (buffer, name, namelen),
 				       ":", 1),
-			    encrypted, endp - encrypted),
+			    "x", 1),
 		 p, restlen + 1);
       p = buffer;
 
@@ -509,8 +509,8 @@ _nss_nis_getpwuid_r (uid_t uid, struct p
 	  yp_match (domain, "passwd.adjunct.byname", result, namelen,
 		    &result2, &len2)) == YPERR_SUCCESS)
     {
-      /* We found a passwd.adjunct entry.  Merge encrypted password
-	 therein into original result.  */
+      /* We found a passwd.adjunct entry.  Merge "x"
+	 into original result.  */
       char *encrypted = strchr (result2, ':');
       char *endp;
       size_t restlen;
@@ -538,7 +538,7 @@ _nss_nis_getpwuid_r (uid_t uid, struct p
 
       __mempcpy (__mempcpy (__mempcpy (__mempcpy (buffer, result, namelen),
 				       ":", 1),
-			    encrypted, endp - encrypted),
+			    "x", 1),
 		 p, restlen + 1);
       p = buffer;
 
diff -Naurp glibc-2.7.original/nis/nss_nis/nis-spwd.c 
glibc-2.7/nis/nss_nis/nis-spwd.c
--- glibc-2.7.original/nis/nss_nis/nis-spwd.c	2006-04-29 03:09:49.000000000 
+0200
+++ glibc-2.7/nis/nss_nis/nis-spwd.c	2009-12-22 10:02:25.000000000 +0100
@@ -78,17 +78,42 @@ internal_nis_getspent_r (struct spwd *sp
     {
       char *result;
       char *outkey;
+      char *p;
       int len;
       int keylen;
       int yperr;
+      int adjunct_used = 0;
 
-      if (new_start)
+      if (new_start) {
         yperr = yp_first (domain, "shadow.byname", &outkey, &keylen, &result,
 			  &len);
-      else
+        
+        if (yperr == YPERR_MAP) {
+	  if (result != NULL)
+	    free result;
+
+	  yperr = yp_first (domain, "passwd.adjunct.byname", &outkey, &keylen, 
&result,
+			    &len);
+
+	  adjunct_used = 1;
+	}
+      }
+          
+      else {
         yperr = yp_next (domain, "shadow.byname", oldkey, oldkeylen, &outkey,
 			 &keylen, &result, &len);
 
+        if (yperr == YPERR_MAP) {
+	  if (result != NULL)
+	    free result;
+
+	  yperr = yp_next (domain, "passwd.adjunct.byname", oldkey, oldkeylen, 
&outkey,
+			   &keylen, &result, &len);
+	  
+	  adjunct_used = 1;
+	}
+      }
+
       if (__builtin_expect (yperr != YPERR_SUCCESS, 0))
         {
 	  enum nss_status retval = yperr2nss (yperr);
@@ -98,15 +123,32 @@ internal_nis_getspent_r (struct spwd *sp
           return retval;
         }
 
-      if (__builtin_expect ((size_t) (len + 1) > buflen, 0))
-        {
-          free (result);
-	  *errnop = ERANGE;
-          return NSS_STATUS_TRYAGAIN;
-        }
+      if (! adjunct_used)
+	{
+	  if (__builtin_expect ((size_t) (len + 1) > buflen, 0))
+	    {
+	      free (result);
+	      *errnop = ERANGE;
+	      return NSS_STATUS_TRYAGAIN;
+	    }
+
+	  p = strncpy (buffer, result, len);
+	  buffer[len] = '\0';  
+	}
+      else
+	{
+	  if (__builtin_expect ((size_t) (len + 3) > buflen, 0))
+	    {
+	      free (result);
+	      *errnop = ERANGE;
+	      return NSS_STATUS_TRYAGAIN;
+	    }
+
+	  p = strncpy (buffer, result, len);
+	  buffer[len] = '\0';  
+	  p = strcat (buffer, "::");
+	}
 
-      char *p = strncpy (buffer, result, len);
-      buffer[len] = '\0';
       while (isspace (*p))
         ++p;
       free (result);
@@ -149,6 +191,9 @@ enum nss_status
 _nss_nis_getspnam_r (const char *name, struct spwd *sp,
 		     char *buffer, size_t buflen, int *errnop)
 {
+  int adjunct_used = 0;
+  char *p;
+
   if (name == NULL)
     {
       *errnop = EINVAL;
@@ -164,6 +209,15 @@ _nss_nis_getspnam_r (const char *name, s
   int yperr = yp_match (domain, "shadow.byname", name, strlen (name), &result,
 			&len);
 
+  if (yperr == YPERR_MAP) {
+    if (result != NULL)
+      free result;
+
+    yperr = yp_match (domain, "passwd.adjunct.byname", name, strlen (name), 
&result,
+		      &len);
+    adjunct_used = 1;
+  }
+
   if (__builtin_expect (yperr != YPERR_SUCCESS, 0))
     {
       enum nss_status retval = yperr2nss (yperr);
@@ -173,15 +227,32 @@ _nss_nis_getspnam_r (const char *name, s
       return retval;
     }
 
-  if (__builtin_expect ((size_t) (len + 1) > buflen, 0))
+  if (! adjunct_used)
     {
-      free (result);
-      *errnop = ERANGE;
-      return NSS_STATUS_TRYAGAIN;
+      if (__builtin_expect ((size_t) (len + 1) > buflen, 0))
+	{
+	  free (result);
+	  *errnop = ERANGE;
+	  return NSS_STATUS_TRYAGAIN;
+	}
+
+      p = strncpy (buffer, result, len);
+      buffer[len] = '\0';  
     }
+  else
+    {
+      if (__builtin_expect ((size_t) (len + 3) > buflen, 0))
+	{
+	  free (result);
+	  *errnop = ERANGE;
+	  return NSS_STATUS_TRYAGAIN;
+	}
 
-  char *p = strncpy (buffer, result, len);
-  buffer[len] = '\0';
+      p = strncpy (buffer, result, len);
+      buffer[len] = '\0';  
+      p = strcat (buffer, "::");
+    }
+  
   while (isspace (*p))
     ++p;
   free (result);


Regards
  Christoph