Make gpgv error message about a missing keyring more useful. This fixes

Debian#494040.  Also implement readonly semantic for extra safety.

g10/ChangeLog

@@ -1,3 +1,16 @@
+2009-04-03  Werner Koch  <wk@g10code.com>
+
+	* gpgv.c (main): Open keyrings readonly.
+	* keydb.c (keydb_add_resource): Add readonly flag bit.
+	(keydb_rebuild_caches): Don't act on readonly resources.
+
+	* keyring.c (keyring_register_filename): Add arg READONLY. 
+	(struct keyring_name): Add field READONLY.
+	(keyring_is_writable): Implement readonly feature.
+	(keyring_update_keyblock): Return GPG_ERR_EACCES for readonly
+	keyrings.
+	(keyring_insert_keyblock, keyring_delete_keyblock): 
+
 2009-04-01  Werner Koch  <wk@g10code.com>
 
 	* gpg.c (main): Properly handle UTF8 usernames with --sign-key and

g10/gpg.h

@@ -75,7 +75,7 @@ struct server_control_s
 #define g10_errstr(a)  gpg_strerror ((a))
 
 
-/* Mapping of the old erro codes to the gpg-error ones.  Fixme: This
+/* Mapping of the old error codes to the gpg-error ones.  Fixme: This
    is just a temporary solution: We need to do all these gpg_error()
    calls in the code.  */
 #define G10ERR_BAD_KEY         GPG_ERR_BAD_KEY          

g10/gpgv.c

@@ -194,10 +194,11 @@ main( int argc, char **argv )
   if (opt.verbose > 1)
     set_packet_list_mode(1);
 
-  if (!nrings)  /* no keyring given: use default one */
+  /* Note: We open all keyrings in read-only mode (flag value: 8).  */
-    keydb_add_resource ("trustedkeys" EXTSEP_S "gpg", 0, 0);
+  if (!nrings)  /* No keyring given: use default one. */
+    keydb_add_resource ("trustedkeys" EXTSEP_S "gpg", 8, 0);
   for (sl = nrings; sl; sl = sl->next)
-    keydb_add_resource (sl->d, 0, 0 );
+    keydb_add_resource (sl->d, 8, 0 );
    
   FREE_STRLIST (nrings);
     

g10/keydb.c

@@ -1,6 +1,6 @@
 /* keydb.c - key database dispatcher
  * Copyright (C) 2001, 2002, 2003, 2004, 2005, 
- *               2008 Free Software Foundation, Inc.
+ *               2008, 2009 Free Software Foundation, Inc.
  *
  * This file is part of GnuPG.
  *
@@ -207,9 +207,10 @@ maybe_create_keyring (char *filename, int force)
  * created if it does not exist.
  * Note: this function may be called before secure memory is
  * available.
- * Flag 1 == force
+ * Flag 1   - Force.
- * Flag 2 == mark resource as primary
+ * Flag 2   - Mark resource as primary.
- * Flag 4 == This is a default resources
+ * Flag 4   - This is a default resources.
+ * Flag 8   - Open as read-only.
  */
 int
 keydb_add_resource (const char *url, int flags, int secret)
@@ -217,11 +218,15 @@ keydb_add_resource (const char *url, int flags, int secret)
     static int any_secret, any_public;
     const char *resname = url;
     char *filename = NULL;
-    int force=(flags&1);
+    int force = (flags&1);
+    int readonly = !!(flags&8);
     int rc = 0;
     KeydbResourceType rt = KEYDB_RESOURCE_TYPE_NONE;
     void *token;
 
+    if (readonly)
+      force = 0;
+
     /* Do we have an URL?
      *	gnupg-ring:filename  := this is a plain keyring
      *	filename := See what is is, but create as plain keyring.
@@ -249,10 +254,10 @@ keydb_add_resource (const char *url, int flags, int secret)
     else
 	filename = xstrdup (resname);
 
-    if (!force)
+    if (!force && !readonly)
 	force = secret? !any_secret : !any_public;
 
-    /* see whether we can determine the filetype */
+    /* See whether we can determine the filetype.  */
     if (rt == KEYDB_RESOURCE_TYPE_NONE) {
 	FILE *fp = fopen( filename, "rb" );
 
@@ -284,7 +289,7 @@ keydb_add_resource (const char *url, int flags, int secret)
         if (rc)
           goto leave;
 
-        if(keyring_register_filename (filename, secret, &token))
+        if(keyring_register_filename (filename, secret, readonly, &token))
 	  {
 	    if (used_resources >= MAX_KEYDB_RESOURCES)
 	      rc = G10ERR_RESOURCE_LIMIT;
@@ -702,6 +707,8 @@ keydb_rebuild_caches (int noisy)
     {
       if (all_resources[i].secret)
         continue;
+      if (!keyring_is_writable (all_resources[i].token))
+        continue;
       switch (all_resources[i].type)
         {
         case KEYDB_RESOURCE_TYPE_NONE: /* ignore */

g10/keyring.c

@@ -50,9 +50,11 @@ typedef struct off_item **OffsetHashTable;
 
 
 typedef struct keyring_name *KR_NAME;
-struct keyring_name {
+struct keyring_name 
+{
   struct keyring_name *next;
   int secret;
+  int readonly;
   DOTLOCK lockhd;
   int is_locked;
   int did_full_scan;
@@ -199,7 +201,8 @@ update_offset_hash_table_from_kb (OffsetHashTable tbl, KBNODE node, off_t off)
  * if a new keyring was registered.
 */
 int
-keyring_register_filename (const char *fname, int secret, void **ptr)
+keyring_register_filename (const char *fname, int secret, int readonly, 
+                           void **ptr)
 {
     KR_NAME kr;
 
@@ -210,8 +213,11 @@ keyring_register_filename (const char *fname, int secret, void **ptr)
       {
         if (same_file_p (kr->fname, fname))
 	  {
+            /* Already registered. */
+            if (readonly)
+              kr->readonly = 1;
             *ptr=kr;
-	    return 0; /* Already registered.  */
+	    return 0; 
 	  }
       }
 
@@ -221,6 +227,7 @@ keyring_register_filename (const char *fname, int secret, void **ptr)
     kr = xmalloc (sizeof *kr + strlen (fname));
     strcpy (kr->fname, fname);
     kr->secret = !!secret;
+    kr->readonly = readonly;
     kr->lockhd = NULL;
     kr->is_locked = 0;
     kr->did_full_scan = 0;
@@ -242,7 +249,7 @@ keyring_is_writable (void *token)
 {
   KR_NAME r = token;
 
-  return r? !access (r->fname, W_OK) : 0;
+  return r? (r->readonly || !access (r->fname, W_OK)) : 0;
 }
     
 
@@ -499,6 +506,9 @@ keyring_update_keyblock (KEYRING_HANDLE hd, KBNODE kb)
     if (!hd->found.kr)
         return -1; /* no successful prior search */
 
+    if (hd->found.kr->readonly)
+      return gpg_error (GPG_ERR_EACCES);
+
     if (!hd->found.n_packets) {
         /* need to know the number of packets - do a dummy get_keyblock*/
         rc = keyring_get_keyblock (hd, NULL);
@@ -540,16 +550,24 @@ keyring_insert_keyblock (KEYRING_HANDLE hd, KBNODE kb)
     if (!hd)
         fname = NULL;
     else if (hd->found.kr)
+      {
         fname = hd->found.kr->fname;
+        if (hd->found.kr->readonly)
+          return gpg_error (GPG_ERR_EACCES);
+      }
     else if (hd->current.kr)
+      {
         fname = hd->current.kr->fname;
+        if (hd->current.kr->readonly)
+          return gpg_error (GPG_ERR_EACCES);
+      }
     else 
         fname = hd->resource? hd->resource->fname:NULL;
 
     if (!fname)
         return G10ERR_GENERAL; 
 
-    /* close this one otherwise we will lose the position for
+    /* Close this one otherwise we will lose the position for
      * a next search.  Fixme: it would be better to adjust the position
      * after the write opertions.
      */
@@ -575,6 +593,9 @@ keyring_delete_keyblock (KEYRING_HANDLE hd)
     if (!hd->found.kr)
         return -1; /* no successful prior search */
 
+    if (hd->found.kr->readonly)
+      return gpg_error (GPG_ERR_EACCES);
+
     if (!hd->found.n_packets) {
         /* need to know the number of packets - do a dummy get_keyblock*/
         rc = keyring_get_keyblock (hd, NULL);

g10/keyring.h

@@ -23,7 +23,8 @@
 
 typedef struct keyring_handle *KEYRING_HANDLE;
 
-int keyring_register_filename (const char *fname, int secret, void **ptr);
+int keyring_register_filename (const char *fname, int secret, int readonly,
+                               void **ptr);
 int keyring_is_writable (void *token);
 
 KEYRING_HANDLE keyring_new (void *token, int secret);