gpg: Move S2K encoding function to a shared file.

* g10/passphrase.c (encode_s2k_iterations): Move function to ...
* common/openpgp-s2k.c: new file.  Remove default intialization code.
* common/openpgpdefs.h (S2K_DECODE_COUNT): New to keep only one copy.
* g10/call-agent.c (agent_get_s2k_count): Change to return the count
and print an error.
* agent/protect.c: Include openpgpdefs.h
* g10/card-util.c (gen_kdf_data): Adjust for changes
* g10/gpgcompose.c: Include call-agent.h.
(sk_esk): Adjust for changes.
* g10/passphrase (passphrase_to_dek): Adjust for changes.
* g10/main.h (S2K_DECODE_COUNT): Remove macro.

Signed-off-by: Werner Koch <wk@gnupg.org>

agent/protect.c

@@ -41,6 +41,7 @@
 
 #include "cvt-openpgp.h"
 #include "../common/sexp-parse.h"
+#include "../common/openpgpdefs.h"  /* For s2k functions.  */
 
 
 /* The protection mode for encryption.  The supported modes for
@@ -49,9 +50,6 @@
 #define PROT_CIPHER_STRING "aes"
 #define PROT_CIPHER_KEYLEN (128/8)
 
-/* Decode an rfc4880 encoded S2K count.  */
-#define S2K_DECODE_COUNT(_val) ((16ul + ((_val) & 15)) << (((_val) >> 4) + 6))
-
 
 /* A table containing the information needed to create a protected
    private key.  */

common/Makefile.am

@@ -83,7 +83,7 @@ common_sources = \
 	localename.c \
 	session-env.c session-env.h \
 	userids.c userids.h \
-	openpgp-oid.c \
+	openpgp-oid.c openpgp-s2k.c \
 	ssh-utils.c ssh-utils.h \
 	agent-opt.c \
 	helpfile.c \

common/openpgp-s2k.c

@@ -0,0 +1,67 @@
+/* openpgp-s2ks.c - OpenPGP S2K helper functions
+ * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
+ *               2005, 2006 Free Software Foundation, Inc.
+ * Copyright (C) 2010, 2019 g10 Code GmbH
+ *
+ * This file is part of GnuPG.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either
+ *
+ *   - the GNU Lesser General Public License as published by the Free
+ *     Software Foundation; either version 3 of the License, or (at
+ *     your option) any later version.
+ *
+ * or
+ *
+ *   - the GNU General Public License as published by the Free
+ *     Software Foundation; either version 2 of the License, or (at
+ *     your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * This file is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "util.h"
+#include "openpgpdefs.h"
+
+
+/* Pack an s2k iteration count into the form specified in RFC-48800.
+ * If we're in between valid values, round up.  */
+unsigned char
+encode_s2k_iterations (int iterations)
+{
+  unsigned char c=0;
+  unsigned char result;
+  unsigned int count;
+
+  if (iterations <= 1024)
+    return 0;  /* Command line arg compatibility.  */
+
+  if (iterations >= 65011712)
+    return 255;
+
+  /* Need count to be in the range 16-31 */
+  for (count=iterations>>6; count>=32; count>>=1)
+    c++;
+
+  result = (c<<4)|(count-16);
+
+  if (S2K_DECODE_COUNT(result) < iterations)
+    result++;
+
+  return result;
+}

common/openpgpdefs.h

@@ -197,4 +197,14 @@ typedef enum
 compress_algo_t;
 
 
+
+
+/* Decode an rfc4880 encoded S2K count.  */
+#define S2K_DECODE_COUNT(_val) ((16ul + ((_val) & 15)) << (((_val) >> 4) + 6))
+
+
+/*--openpgp-s2k.c --*/
+unsigned char encode_s2k_iterations (int iterations);
+
+
 #endif /*GNUPG_COMMON_OPENPGPDEFS_H*/

common/ttyio.c

@@ -564,6 +564,8 @@ do_get( const char *prompt, int hidden )
 }
 
 
+
+/* Note: This function never returns NULL. */
 char *
 tty_get( const char *prompt )
 {

g10/call-agent.c

@@ -1461,19 +1461,19 @@ gpg_agent_get_confirmation (const char *desc)
 }
 
 
-/* Return the S2K iteration count as computed by gpg-agent.  */
-gpg_error_t
-agent_get_s2k_count (unsigned long *r_count)
+/* Return the S2K iteration count as computed by gpg-agent.  On error
+ * print a warning and return a default value. */
+unsigned long
+agent_get_s2k_count (void)
 {
   gpg_error_t err;
   membuf_t data;
   char *buf;
-
-  *r_count = 0;
+  unsigned long count = 0;
 
   err = start_agent (NULL, 0);
   if (err)
-    return err;
+    goto leave;
 
   init_membuf (&data, 32);
   err = assuan_transact (agent_ctx, "GETINFO s2k_count",
@@ -1489,10 +1489,22 @@ agent_get_s2k_count (unsigned long *r_count)
         err = gpg_error_from_syserror ();
       else
         {
-          *r_count = strtoul (buf, NULL, 10);
+          count = strtoul (buf, NULL, 10);
           xfree (buf);
         }
     }
+
+ leave:
+  if (err || count < 65536)
+    {
+      /* Don't print an error if an older agent is used.  */
+      if (err && gpg_err_code (err) != GPG_ERR_ASS_PARAMETER)
+        log_error (_("problem with the agent: %s\n"), gpg_strerror (err));
+
+      /* Default to 65536 which was used up to 2.0.13.  */
+      return 65536;
+    }
+
   return err;
 }
 

g10/call-agent.h

@@ -146,7 +146,7 @@ gpg_error_t agent_clear_passphrase (const char *cache_id);
 gpg_error_t gpg_agent_get_confirmation (const char *desc);
 
 /* Return the S2K iteration count as computed by gpg-agent.  */
-gpg_error_t agent_get_s2k_count (unsigned long *r_count);
+unsigned long agent_get_s2k_count (void);
 
 /* Check whether a secret key for public key PK is available.  Returns
    0 if the secret key is available. */

g10/card-util.c

@@ -2039,7 +2039,7 @@ gen_kdf_data (unsigned char *data, int single_salt)
 
   p = data;
 
-  s2k_char = encode_s2k_iterations (0);
+  s2k_char = encode_s2k_iterations (agent_get_s2k_count ());
   iterations = S2K_DECODE_COUNT (s2k_char);
   count_4byte[0] = (iterations >> 24) & 0xff;
   count_4byte[1] = (iterations >> 16) & 0xff;

g10/gpgcompose.c

@@ -25,6 +25,7 @@
 #include "keydb.h"
 #include "main.h"
 #include "options.h"
+#include "call-agent.h"
 
 static int do_debug;
 #define debug(fmt, ...) \
@@ -2248,9 +2249,12 @@ sk_esk (const char *option, int argc, char *argv[], void *cookie)
   log_assert (sizeof (si.salt) == sizeof (ske->s2k.salt));
   memcpy (ske->s2k.salt, si.salt, sizeof (ske->s2k.salt));
   if (! si.s2k_is_session_key)
-    /* 0 means get the default.  */
-    ske->s2k.count = encode_s2k_iterations (si.iterations);
-
+    {
+      if (!si.iterations)
+        ske->s2k.count = encode_s2k_iterations (agent_get_s2k_count ());
+      else
+        ske->s2k.count = encode_s2k_iterations (si.iterations);
+    }
 
   /* Derive the symmetric key that is either the session key or the
      key used to encrypt the session key.  */

g10/keydb.h

@@ -276,7 +276,6 @@ gpg_error_t build_sk_list (ctrl_t ctrl, strlist_t locusr,
                            SK_LIST *ret_sk_list, unsigned use);
 
 /*-- passphrase.h --*/
-unsigned char encode_s2k_iterations (int iterations);
 int  have_static_passphrase(void);
 const char *get_static_passphrase (void);
 void set_passphrase_from_string(const char *pass);

g10/main.h

@@ -507,8 +507,6 @@ gpg_error_t  card_generate_subkey (ctrl_t ctrl, kbnode_t pub_keyblock);
 int  card_store_subkey (KBNODE node, int use);
 #endif
 
-#define S2K_DECODE_COUNT(_val) ((16ul + ((_val) & 15)) << (((_val) >> 4) + 6))
-
 /*-- migrate.c --*/
 void migrate_secring (ctrl_t ctrl);
 

g10/passphrase.c

@@ -48,57 +48,6 @@ static char *next_pw = NULL;
 static char *last_pw = NULL;
 
 
-
-/* Pack an s2k iteration count into the form specified in 2440.  If
-   we're in between valid values, round up.  With value 0 return the
-   old default.  */
-unsigned char
-encode_s2k_iterations (int iterations)
-{
-  gpg_error_t err;
-  unsigned char c=0;
-  unsigned char result;
-  unsigned int count;
-
-  if (!iterations)
-    {
-      unsigned long mycnt;
-
-      /* Ask the gpg-agent for a useful iteration count.  */
-      err = agent_get_s2k_count (&mycnt);
-      if (err || mycnt < 65536)
-        {
-          /* Don't print an error if an older agent is used.  */
-          if (err && gpg_err_code (err) != GPG_ERR_ASS_PARAMETER)
-            log_error (_("problem with the agent: %s\n"), gpg_strerror (err));
-          /* Default to 65536 which we used up to 2.0.13.  */
-          return 96;
-        }
-      else if (mycnt >= 65011712)
-        return 255; /* Largest possible value.  */
-      else
-        return encode_s2k_iterations ((int)mycnt);
-    }
-
-  if (iterations <= 1024)
-    return 0;  /* Command line arg compatibility.  */
-
-  if (iterations >= 65011712)
-    return 255;
-
-  /* Need count to be in the range 16-31 */
-  for (count=iterations>>6; count>=32; count>>=1)
-    c++;
-
-  result = (c<<4)|(count-16);
-
-  if (S2K_DECODE_COUNT(result) < iterations)
-    result++;
-
-  return result;
-}
-
-
 int
 have_static_passphrase()
 {
@@ -106,6 +55,7 @@ have_static_passphrase()
           && (opt.batch || opt.pinentry_mode == PINENTRY_MODE_LOOPBACK));
 }
 
+
 /* Return a static passphrase.  The returned value is only valid as
    long as no other passphrase related function is called.  NULL may
    be returned if no passphrase has been set; better use
@@ -342,7 +292,7 @@ passphrase_to_dek (int cipher_algo, STRING2KEY *s2k,
              call out to gpg-agent and that should not be done during
              option processing in main().  */
           if (!opt.s2k_count)
-            opt.s2k_count = encode_s2k_iterations (0);
+            opt.s2k_count = encode_s2k_iterations (agent_get_s2k_count ());
           s2k->count = opt.s2k_count;
         }
     }