gnupg/g10/revoke.c

/* revoke.c - Create recovation certificates.
 * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003,
 *               2004 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * GnuPG 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 <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <ctype.h>

#include "gpg.h"
#include "options.h"
#include "packet.h"
#include "status.h"
#include "keydb.h"
#include "util.h"
#include "main.h"
#include "ttyio.h"
#include "status.h"
#include "i18n.h"
#include "call-agent.h"

struct revocation_reason_info {
    int code;
    char *desc;
};


int
revocation_reason_build_cb( PKT_signature *sig, void *opaque )
{
    struct revocation_reason_info *reason = opaque;
    char *ud = NULL;
    byte *buffer;
    size_t buflen = 1;

    if(!reason)
      return 0;

    if( reason->desc ) {
	ud = native_to_utf8( reason->desc );
	buflen += strlen(ud);
    }
    buffer = xmalloc( buflen );
    *buffer = reason->code;
    if( ud ) {
	memcpy(buffer+1, ud, strlen(ud) );
	xfree( ud );
    }

    build_sig_subpkt( sig, SIGSUBPKT_REVOC_REASON, buffer, buflen );
    xfree( buffer );
    return 0;
}

/* Outputs a minimal pk (as defined by 2440) from a keyblock.  A
   minimal pk consists of the public key packet and a user ID.  We try
   and pick a user ID that has a uid signature, and include it if
   possible. */
static int
export_minimal_pk(IOBUF out,KBNODE keyblock,
		  PKT_signature *revsig,PKT_signature *revkey)
{
  KBNODE node;
  PACKET pkt;
  PKT_user_id *uid=NULL;
  PKT_signature *selfsig=NULL;
  u32 keyid[2];
  int rc;

  node=find_kbnode(keyblock,PKT_PUBLIC_KEY);
  if(!node)
    {
      log_error("key incomplete\n");
      return GPG_ERR_GENERAL;
    }

  keyid_from_pk(node->pkt->pkt.public_key,keyid);

  pkt=*node->pkt;
  rc=build_packet(out,&pkt);
  if(rc)
    {
      log_error(_("build_packet failed: %s\n"), gpg_strerror (rc) );
      return rc;
    }

  init_packet(&pkt);
  pkt.pkttype=PKT_SIGNATURE;

  /* the revocation itself, if any.  2440 likes this to come first. */
  if(revsig)
    {
      pkt.pkt.signature=revsig;
      rc=build_packet(out,&pkt);
      if(rc)
	{
	  log_error("build_packet failed: %s\n", gpg_strerror (rc) );
	  return rc;
	}
    }

  /* If a revkey in a 1F sig is present, include it too */
  if(revkey)
    {
      pkt.pkt.signature=revkey;
      rc=build_packet(out,&pkt);
      if(rc)
	{
	  log_error(_("build_packet failed: %s\n"), gpg_strerror (rc) );
	  return rc;
	}
    }

  while(!selfsig)
    {
      KBNODE signode;

      node=find_next_kbnode(node,PKT_USER_ID);
      if(!node)
	{
	  /* We're out of user IDs - none were self-signed. */
	  if(uid)
	    break;
	  else
	    {
	      log_error(_("key %s has no user IDs\n"),keystr(keyid));
	      return GPG_ERR_GENERAL;
	    }
	}

      if(node->pkt->pkt.user_id->attrib_data)
	continue;

      uid=node->pkt->pkt.user_id;
      signode=node;

      while((signode=find_next_kbnode(signode,PKT_SIGNATURE)))
	{
	  if(keyid[0]==signode->pkt->pkt.signature->keyid[0] &&
	     keyid[1]==signode->pkt->pkt.signature->keyid[1] &&
	     IS_UID_SIG(signode->pkt->pkt.signature))
	    {
	      selfsig=signode->pkt->pkt.signature;
	      break;
	    }
	}
    }

  pkt.pkttype=PKT_USER_ID;
  pkt.pkt.user_id=uid;

  rc=build_packet(out,&pkt);
  if(rc)
    {
      log_error(_("build_packet failed: %s\n"), gpg_strerror (rc) );
      return rc;
    }

  if(selfsig)
    {
      pkt.pkttype=PKT_SIGNATURE;
      pkt.pkt.signature=selfsig;

      rc=build_packet(out,&pkt);
      if(rc)
	{
	  log_error(_("build_packet failed: %s\n"), gpg_strerror (rc) );
	  return rc;
	}
    }

  return 0;
}

/****************
 * Generate a revocation certificate for UNAME via a designated revoker
 */
int
gen_desig_revoke (ctrl_t ctrl, const char *uname, strlist_t locusr)
{
    int rc = 0;
    armor_filter_context_t *afx;
    PKT_public_key *pk = NULL;
    PKT_public_key *pk2 = NULL;
    PKT_signature *sig = NULL;
    IOBUF out = NULL;
    struct revocation_reason_info *reason = NULL;
    KEYDB_HANDLE kdbhd;
    KEYDB_SEARCH_DESC desc;
    KBNODE keyblock=NULL,node;
    u32 keyid[2];
    int i,any=0;
    SK_LIST sk_list=NULL;

    if( opt.batch )
      {
	log_error(_("can't do this in batch mode\n"));
	return GPG_ERR_GENERAL;
      }

    afx = new_armor_context ();

    kdbhd = keydb_new ();
    rc = classify_user_id (uname, &desc, 1);
    if (!rc)
      rc = keydb_search (kdbhd, &desc, 1, NULL);
    if (rc) {
	log_error (_("key \"%s\" not found: %s\n"),uname, gpg_strerror (rc));
	goto leave;
    }

    rc = keydb_get_keyblock (kdbhd, &keyblock );
    if( rc ) {
	log_error (_("error reading keyblock: %s\n"), gpg_strerror (rc) );
	goto leave;
    }

    /* To parse the revkeys */
    merge_keys_and_selfsig(keyblock);

    /* get the key from the keyblock */
    node = find_kbnode( keyblock, PKT_PUBLIC_KEY );
    if( !node )
      BUG ();

    pk=node->pkt->pkt.public_key;

    keyid_from_pk(pk,keyid);

    if(locusr)
      {
	rc = build_sk_list (ctrl, locusr, &sk_list, PUBKEY_USAGE_CERT);
	if(rc)
	  goto leave;
      }

    /* Are we a designated revoker for this key? */

    if(!pk->revkey && pk->numrevkeys)
      BUG();

    for(i=0;i<pk->numrevkeys;i++)
      {
	SK_LIST list;

        free_public_key (pk2);
        pk2 = NULL;

	if(sk_list)
	  {
	    for(list=sk_list;list;list=list->next)
	      {
		byte fpr[MAX_FINGERPRINT_LEN];
		size_t fprlen;

		fingerprint_from_pk (list->pk, fpr, &fprlen);

		/* Don't get involved with keys that don't have 160
		   bit fingerprints */
		if(fprlen!=20)
		  continue;

		if(memcmp(fpr,pk->revkey[i].fpr,20)==0)
		  break;
	      }

	    if (list)
	      pk2 = copy_public_key (NULL, list->pk);
	    else
	      continue;
	  }
	else
	  {
	    pk2 = xmalloc_clear (sizeof *pk2);
	    rc = get_pubkey_byfprint (pk2, NULL,
                                      pk->revkey[i].fpr, MAX_FINGERPRINT_LEN);
	  }

	/* We have the revocation key.  */
	if(!rc)
	  {
	    PKT_signature *revkey = NULL;

	    any = 1;

            print_pubkey_info (NULL, pk);
	    tty_printf ("\n");

	    tty_printf (_("To be revoked by:\n"));
            print_seckey_info (pk2);

	    if(pk->revkey[i].class&0x40)
	      tty_printf(_("(This is a sensitive revocation key)\n"));
	    tty_printf("\n");

	    rc = agent_probe_secret_key (ctrl, pk2);
	    if (rc)
	      {
		tty_printf (_("Secret key is not available.\n"));
		continue;
	      }

	    if( !cpr_get_answer_is_yes("gen_desig_revoke.okay",
         _("Create a designated revocation certificate for this key? (y/N) ")))
	      continue;

	    /* get the reason for the revocation (this is always v4) */
	    reason = ask_revocation_reason( 1, 0, 1 );
	    if( !reason )
	      continue;

	    if( !opt.armor )
	      tty_printf(_("ASCII armored output forced.\n"));

	    if( (rc = open_outfile (-1, NULL, 0, 1, &out )) )
	      goto leave;

	    afx->what = 1;
	    afx->hdrlines = "Comment: A designated revocation certificate"
	      " should follow\n";
	    push_armor_filter (afx, out);

	    /* create it */
	    rc = make_keysig_packet( &sig, pk, NULL, NULL, pk2, 0x20, 0,
				     0, 0,
				     revocation_reason_build_cb, reason,
                                     NULL);
	    if( rc ) {
	      log_error(_("make_keysig_packet failed: %s\n"), gpg_strerror (rc));
	      goto leave;
	    }

	    /* Spit out a minimal pk as well, since otherwise there is
               no way to know which key to attach this revocation to.
               Also include the direct key signature that contains
               this revocation key.  We're allowed to include
               sensitive revocation keys along with a revocation, as
               this may be the only time the recipient has seen it.
               Note that this means that if we have multiple different
               sensitive revocation keys in a given direct key
               signature, we're going to include them all here.  This
               is annoying, but the good outweighs the bad, since
               without including this a sensitive revoker can't really
               do their job.  People should not include multiple
               sensitive revocation keys in one signature: 2440 says
               "Note that it may be appropriate to isolate this
               subpacket within a separate signature so that it is not
               combined with other subpackets that need to be
               exported." -dms */

	    while(!revkey)
	      {
		KBNODE signode;

		signode=find_next_kbnode(node,PKT_SIGNATURE);
		if(!signode)
		  break;

		node=signode;

		if(keyid[0]==signode->pkt->pkt.signature->keyid[0] &&
		   keyid[1]==signode->pkt->pkt.signature->keyid[1] &&
		   IS_KEY_SIG(signode->pkt->pkt.signature))
		  {
		    int j;

		    for(j=0;j<signode->pkt->pkt.signature->numrevkeys;j++)
		      {
			if(pk->revkey[i].class==
			   signode->pkt->pkt.signature->revkey[j].class &&
			   pk->revkey[i].algid==
			   signode->pkt->pkt.signature->revkey[j].algid &&
			   memcmp(pk->revkey[i].fpr,
				  signode->pkt->pkt.signature->revkey[j].fpr,
				  MAX_FINGERPRINT_LEN)==0)
			  {
			    revkey=signode->pkt->pkt.signature;
			    break;
			  }
		      }
		  }
	      }

	    if(!revkey)
	      BUG();

	    rc=export_minimal_pk(out,keyblock,sig,revkey);
	    if(rc)
	      goto leave;

	    /* and issue a usage notice */
	    tty_printf(_("Revocation certificate created.\n"));
	    break;
	  }
      }

    if(!any)
      log_error(_("no revocation keys found for \"%s\"\n"),uname);

  leave:
    free_public_key (pk);
    free_public_key (pk2);
    if( sig )
	free_seckey_enc( sig );

    release_sk_list(sk_list);

    if( rc )
	iobuf_cancel(out);
    else
	iobuf_close(out);
    release_revocation_reason_info( reason );
    release_armor_context (afx);
    return rc;
}


/* Common core to create the revocation. FILENAME may be NULL to write
   to stdout or the filename given by --output.  REASON describes the
   revocation reason.  PSK is the public primary key - we expect that
   a corresponding secret key is available.  KEYBLOCK is the entire
   KEYBLOCK which is used in PGP mode to write a a minimal key and not
   just the naked revocation signature; it may be NULL.  If LEADINTEXT
   is not NULL, it is written right before the (armored) output.*/
static int
create_revocation (const char *filename,
                   struct revocation_reason_info *reason,
                   PKT_public_key *psk,
                   kbnode_t keyblock,
                   const char *leadintext, int suffix,
                   const char *cache_nonce)
{
  int rc;
  iobuf_t out = NULL;
  armor_filter_context_t *afx;
  PKT_signature *sig = NULL;
  PACKET pkt;

  afx = new_armor_context ();

  if ((rc = open_outfile (-1, filename, suffix, 1, &out)))
    goto leave;

  if (leadintext )
    iobuf_writestr (out, leadintext);

  afx->what = 1;
  afx->hdrlines = "Comment: This is a revocation certificate\n";
  push_armor_filter (afx, out);

  rc = make_keysig_packet (&sig, psk, NULL, NULL, psk, 0x20, 0,
                           0, 0,
                           revocation_reason_build_cb, reason, cache_nonce);
  if (rc)
    {
      log_error (_("make_keysig_packet failed: %s\n"), gpg_strerror (rc));
      goto leave;
    }

  if (keyblock && (PGP6 || PGP7 || PGP8))
    {
      /* Use a minimal pk for PGPx mode, since PGP can't import bare
         revocation certificates. */
      rc = export_minimal_pk (out, keyblock, sig, NULL);
      if (rc)
        goto leave;
    }
  else
    {
      init_packet (&pkt);
      pkt.pkttype = PKT_SIGNATURE;
      pkt.pkt.signature = sig;

      rc = build_packet (out, &pkt);
      if (rc)
        {
          log_error (_("build_packet failed: %s\n"), gpg_strerror (rc));
          goto leave;
        }
    }

 leave:
  if (sig)
    free_seckey_enc (sig);
  if (rc)
    iobuf_cancel (out);
  else
    iobuf_close (out);
  release_armor_context (afx);
  return rc;
}


/* This function is used to generate a standard revocation certificate
   by gpg's interactive key generation function.  The certificate is
   stored at a dedicated place in a slightly modified form to avoid an
   accidental import.  PSK is the primary key; a corresponding secret
   key must be available.  CACHE_NONCE is optional but can be used to
   help gpg-agent to avoid an extra passphrase prompt. */
int
gen_standard_revoke (PKT_public_key *psk, const char *cache_nonce)
{
  int rc;
  estream_t memfp;
  struct revocation_reason_info reason;
  char *dir, *tmpstr, *fname;
  void *leadin;
  size_t len;
  u32 keyid[2];
  char pkstrbuf[PUBKEY_STRING_SIZE];
  char *orig_codeset;

  dir = get_openpgp_revocdir (opt.homedir);
  tmpstr = hexfingerprint (psk, NULL, 0);
  fname = xstrconcat (dir, DIRSEP_S, tmpstr, NULL);
  xfree (tmpstr);
  xfree (dir);

  keyid_from_pk (psk, keyid);

  memfp = es_fopenmem (0, "r+");
  if (!memfp)
    log_fatal ("error creating memory stream\n");

  orig_codeset = i18n_switchto_utf8 ();

  es_fprintf (memfp, "%s\n\n",
              _("This is a revocation certificate for the OpenPGP key:"));

  es_fprintf (memfp, "pub  %s/%s %s\n",
              pubkey_string (psk, pkstrbuf, sizeof pkstrbuf),
              keystr (keyid),
              datestr_from_pk (psk));

  print_fingerprint (memfp, psk, 3);

  tmpstr = get_user_id (keyid, &len);
  es_fprintf (memfp, "uid%*s%.*s\n\n",
              (int)keystrlen () + 10, "",
              (int)len, tmpstr);
  xfree (tmpstr);

  es_fprintf (memfp, "%s\n\n%s\n\n:",
     _("Use it to revoke this key in case of a compromise or loss of\n"
       "the secret key.  However, if the secret key is still accessible,\n"
       "it is better to generate a new revocation certificate and give\n"
       "a reason for the revocation."),
     _("To avoid an accidental use of this file, a colon has been inserted\n"
       "before the 5 dashes below.  Remove this colon with a text editor\n"
       "before making use of this revocation certificate."));

  es_putc (0, memfp);

  i18n_switchback (orig_codeset);

  if (es_fclose_snatch (memfp, &leadin, NULL))
    log_fatal ("error snatching memory stream\n");

  reason.code = 0x00; /* No particular reason.  */
  reason.desc = NULL;
  rc = create_revocation (fname, &reason, psk, NULL, leadin, 3, cache_nonce);
  xfree (leadin);
  xfree (fname);

  return rc;
}



/****************
 * Generate a revocation certificate for UNAME
 */
int
gen_revoke (const char *uname)
{
  int rc = 0;
  PKT_public_key *psk;
  u32 keyid[2];
  kbnode_t keyblock = NULL;
  kbnode_t node;
  KEYDB_HANDLE kdbhd;
  struct revocation_reason_info *reason = NULL;
  KEYDB_SEARCH_DESC desc;

  if( opt.batch )
    {
      log_error(_("can't do this in batch mode\n"));
      return GPG_ERR_GENERAL;
    }

  /* Search the userid; we don't want the whole getkey stuff here.  */
  kdbhd = keydb_new ();
  rc = classify_user_id (uname, &desc, 1);
  if (!rc)
    rc = keydb_search (kdbhd, &desc, 1, NULL);
  if (rc)
    {
      if (gpg_err_code (rc) == GPG_ERR_NOT_FOUND)
        log_error (_("no secret key matches the search term \"%s\"\n"),
                     uname);
      else
        log_error (_("error looking up secret key \"%s\": %s\n"),
                   uname, gpg_strerror (rc));
      goto leave;
    }

  rc = keydb_get_keyblock (kdbhd, &keyblock );
  if (rc)
    {
      log_error (_("error reading keyblock: %s\n"), gpg_strerror (rc) );
      goto leave;
    }

  rc = keydb_search (kdbhd, &desc, 1, NULL);
  if (gpg_err_code (rc) == GPG_ERR_NOT_FOUND)
    /* Not ambiguous.  */
    {
    }
  else if (rc == 0)
    /* Ambiguous.  */
    {
      char *info;

      log_error (_("'%s' matches multiple secret keys:\n"), uname);

      info = format_seckey_info (keyblock->pkt->pkt.public_key);
      log_error ("  %s\n", info);
      xfree (info);
      release_kbnode (keyblock);

      rc = keydb_get_keyblock (kdbhd, &keyblock);
      while (! rc)
        {
          info = format_seckey_info (keyblock->pkt->pkt.public_key);
          log_error ("  %s\n", info);
          xfree (info);
          release_kbnode (keyblock);
          keyblock = NULL;

          rc = keydb_search (kdbhd, &desc, 1, NULL);
          if (! rc)
            rc = keydb_get_keyblock (kdbhd, &keyblock);
        }

      rc = GPG_ERR_AMBIGUOUS_NAME;

      goto leave;
    }
  else
    {
      log_error (_("error searching the keyring: %s\n"), gpg_strerror (rc));
      goto leave;
    }

  /* Get the keyid from the keyblock.  */
  node = find_kbnode (keyblock, PKT_PUBLIC_KEY);
  if (!node)
    BUG ();

  psk = node->pkt->pkt.public_key;
  rc = agent_probe_secret_key (NULL, psk);
  if (rc)
    {
      log_error (_("secret key \"%s\" not found: %s\n"),
                 uname, gpg_strerror (rc));
      goto leave;
    }

  keyid_from_pk (psk, keyid );
  print_seckey_info (psk);

  tty_printf("\n");
  if (!cpr_get_answer_is_yes ("gen_revoke.okay",
                _("Create a revocation certificate for this key? (y/N) ")))
    {
      rc = 0;
      goto leave;
    }

  /* Get the reason for the revocation.  */
  reason = ask_revocation_reason (1, 0, 1);
  if (!reason)
    {
      /* User decided to cancel.  */
      rc = 0;
      goto leave;
    }

  if (!opt.armor)
    tty_printf (_("ASCII armored output forced.\n"));

  rc = create_revocation (NULL, reason, psk, keyblock, NULL, 0, NULL);
  if (rc)
    goto leave;

  /* and issue a usage notice */
  tty_printf (_(
"Revocation certificate created.\n\n"
"Please move it to a medium which you can hide away; if Mallory gets\n"
"access to this certificate he can use it to make your key unusable.\n"
"It is smart to print this certificate and store it away, just in case\n"
"your media become unreadable.  But have some caution:  The print system of\n"
"your machine might store the data and make it available to others!\n"));

 leave:
  release_kbnode (keyblock);
  keydb_release (kdbhd);
  release_revocation_reason_info( reason );
  return rc;
}



struct revocation_reason_info *
ask_revocation_reason( int key_rev, int cert_rev, int hint )
{
    int code=-1;
    char *description = NULL;
    struct revocation_reason_info *reason;
    const char *text_0 = _("No reason specified");
    const char *text_1 = _("Key has been compromised");
    const char *text_2 = _("Key is superseded");
    const char *text_3 = _("Key is no longer used");
    const char *text_4 = _("User ID is no longer valid");
    const char *code_text = NULL;

    do {
        code=-1;
	xfree(description);
	description = NULL;

	tty_printf(_("Please select the reason for the revocation:\n"));
	tty_printf(    "  0 = %s\n", text_0 );
	if( key_rev )
	    tty_printf("  1 = %s\n", text_1 );
	if( key_rev )
	    tty_printf("  2 = %s\n", text_2 );
	if( key_rev )
	    tty_printf("  3 = %s\n", text_3 );
	if( cert_rev )
	    tty_printf("  4 = %s\n", text_4 );
	tty_printf(    "  Q = %s\n", _("Cancel") );
	if( hint )
	    tty_printf(_("(Probably you want to select %d here)\n"), hint );

	while(code==-1) {
	    int n;
	    char *answer = cpr_get("ask_revocation_reason.code",
						_("Your decision? "));
	    trim_spaces( answer );
	    cpr_kill_prompt();
	    if( *answer == 'q' || *answer == 'Q')
	      return NULL; /* cancel */
	    if( hint && !*answer )
		n = hint;
	    else if(!digitp( answer ) )
 	        n = -1;
	    else
		n = atoi(answer);
	    xfree(answer);
	    if( n == 0 ) {
	        code = 0x00; /* no particular reason */
		code_text = text_0;
	    }
	    else if( key_rev && n == 1 ) {
		code = 0x02; /* key has been compromised */
		code_text = text_1;
	    }
	    else if( key_rev && n == 2 ) {
		code = 0x01; /* key is superseded */
		code_text = text_2;
	    }
	    else if( key_rev && n == 3 ) {
		code = 0x03; /* key is no longer used */
		code_text = text_3;
	    }
	    else if( cert_rev && n == 4 ) {
		code = 0x20; /* uid is no longer valid */
		code_text = text_4;
	    }
	    else
		tty_printf(_("Invalid selection.\n"));
	}

	tty_printf(_("Enter an optional description; "
		     "end it with an empty line:\n") );
	for(;;) {
	    char *answer = cpr_get("ask_revocation_reason.text", "> " );
	    trim_trailing_ws( answer, strlen(answer) );
	    cpr_kill_prompt();
	    if( !*answer ) {
		xfree(answer);
		break;
	    }

	    {
		char *p = make_printable_string( answer, strlen(answer), 0 );
		xfree(answer);
		answer = p;
	    }

	    if( !description )
		description = xstrdup(answer);
	    else {
		char *p = xmalloc( strlen(description) + strlen(answer) + 2 );
		strcpy(stpcpy(stpcpy( p, description),"\n"),answer);
		xfree(description);
		description = p;
	    }
	    xfree(answer);
	}

	tty_printf(_("Reason for revocation: %s\n"), code_text );
	if( !description )
	    tty_printf(_("(No description given)\n") );
	else
	    tty_printf("%s\n", description );

    } while( !cpr_get_answer_is_yes("ask_revocation_reason.okay",
					    _("Is this okay? (y/N) "))  );

    reason = xmalloc( sizeof *reason );
    reason->code = code;
    reason->desc = description;
    return reason;
}

void
release_revocation_reason_info( struct revocation_reason_info *reason )
{
    if( reason ) {
	xfree( reason->desc );
	xfree( reason );
    }
}