gpg-wks-client.c
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gpg-wks-client.c
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	/* gpg-wks-client.c - A client for the Web Key Service protocols.
	* Copyright (C) 2016 Werner Koch
	* Copyright (C) 2016 Bundesamt für Sicherheit in der Informationstechnik
	*
	* This file is part of GnuPG.
	*
	* This file is free software; you can redistribute it and/or modify
	* it under the terms of the GNU Lesser General Public License as
	* published by the Free Software Foundation; either version 2.1 of
	* the License, or (at your option) any later version.
	*
	* 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 Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public License
	* along with this program; if not, see <https://www.gnu.org/licenses/>.
	*/

	#include <config.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	#include "../common/util.h"
	#include "../common/status.h"
	#include "../common/i18n.h"
	#include "../common/sysutils.h"
	#include "../common/init.h"
	#include "../common/asshelp.h"
	#include "../common/userids.h"
	#include "../common/ccparray.h"
	#include "../common/exectool.h"
	#include "../common/mbox-util.h"
	#include "../common/name-value.h"
	#include "call-dirmngr.h"
	#include "mime-maker.h"
	#include "send-mail.h"
	#include "gpg-wks.h"


	/* Constants to identify the commands and options. */
	enum cmd_and_opt_values
	{
	aNull = 0,

	oQuiet = 'q',
	oVerbose = 'v',
	oOutput = 'o',

	oDebug = 500,

	aSupported,
	aCheck,
	aCreate,
	aReceive,
	aRead,

	oGpgProgram,
	oSend,
	oFakeSubmissionAddr,
	oStatusFD,

	oDummy
	};


	/* The list of commands and options. */
	static ARGPARSE_OPTS opts[] = {
	ARGPARSE_group (300, ("@Commands:\n ")),

	ARGPARSE_c (aSupported, "supported",
	("check whether provider supports WKS")),
	ARGPARSE_c (aCheck, "check",
	("check whether a key is available")),
	ARGPARSE_c (aCreate, "create",
	("create a publication request")),
	ARGPARSE_c (aReceive, "receive",
	("receive a MIME confirmation request")),
	ARGPARSE_c (aRead, "read",
	("receive a plain text confirmation request")),

	ARGPARSE_group (301, ("@\nOptions:\n ")),

	ARGPARSE_s_n (oVerbose, "verbose", ("verbose")),
	ARGPARSE_s_n (oQuiet, "quiet", ("be somewhat more quiet")),
	ARGPARSE_s_s (oDebug, "debug", "@"),
	ARGPARSE_s_s (oGpgProgram, "gpg", "@"),
	ARGPARSE_s_n (oSend, "send", "send the mail using sendmail"),
	ARGPARSE_s_s (oOutput, "output", "\|FILE\|write the mail to FILE"),
	ARGPARSE_s_i (oStatusFD, "status-fd", N_("\|FD\|write status info to this FD")),

	ARGPARSE_s_s (oFakeSubmissionAddr, "fake-submission-addr", "@"),

	ARGPARSE_end ()
	};


	/* The list of supported debug flags. */
	static struct debug_flags_s debug_flags [] =
	{
	{ DBG_MIME_VALUE , "mime" },
	{ DBG_PARSER_VALUE , "parser" },
	{ DBG_CRYPTO_VALUE , "crypto" },
	{ DBG_MEMORY_VALUE , "memory" },
	{ DBG_MEMSTAT_VALUE, "memstat" },
	{ DBG_IPC_VALUE , "ipc" },
	{ DBG_EXTPROG_VALUE, "extprog" },
	{ 0, NULL }
	};



	/* Value of the option --fake-submission-addr. */
	const char *fake_submission_addr;


	static void wrong_args (const char *text) GPGRT_ATTR_NORETURN;
	static gpg_error_t command_supported (char *userid);
	static gpg_error_t command_check (char *userid);
	static gpg_error_t command_send (const char fingerprint, const char userid);
	static gpg_error_t encrypt_response (estream_t *r_output, estream_t input,
	const char *addrspec,
	const char *fingerprint);
	static gpg_error_t read_confirmation_request (estream_t msg);
	static gpg_error_t command_receive_cb (void *opaque,
	const char *mediatype, estream_t fp,
	unsigned int flags);



	/* Print usage information and provide strings for help. */
	static const char *
	my_strusage( int level )
	{
	const char *p;

	switch (level)
	{
	case 11: p = "gpg-wks-client"; break;
	case 12: p = "@GNUPG@"; break;
	case 13: p = VERSION; break;
	case 17: p = PRINTABLE_OS_NAME; break;
	case 19: p = ("Please report bugs to <@EMAIL@>.\n"); break;

	case 1:
	case 40:
	p = ("Usage: gpg-wks-client [command] [options] [args] (-h for help)");
	break;
	case 41:
	p = ("Syntax: gpg-wks-client [command] [options] [args]\n"
	"Client for the Web Key Service\n");
	break;

	default: p = NULL; break;
	}
	return p;
	}


	static void
	wrong_args (const char *text)
	{
	es_fprintf (es_stderr, _("usage: %s [options] %s\n"), strusage (11), text);
	exit (2);
	}



	/* Command line parsing. */
	static enum cmd_and_opt_values
	parse_arguments (ARGPARSE_ARGS pargs, ARGPARSE_OPTS popts)
	{
	enum cmd_and_opt_values cmd = 0;
	int no_more_options = 0;

	while (!no_more_options && optfile_parse (NULL, NULL, NULL, pargs, popts))
	{
	switch (pargs->r_opt)
	{
	case oQuiet: opt.quiet = 1; break;
	case oVerbose: opt.verbose++; break;
	case oDebug:
	if (parse_debug_flag (pargs->r.ret_str, &opt.debug, debug_flags))
	{
	pargs->r_opt = ARGPARSE_INVALID_ARG;
	pargs->err = ARGPARSE_PRINT_ERROR;
	}
	break;

	case oGpgProgram:
	opt.gpg_program = pargs->r.ret_str;
	break;
	case oSend:
	opt.use_sendmail = 1;
	break;
	case oOutput:
	opt.output = pargs->r.ret_str;
	break;
	case oFakeSubmissionAddr:
	fake_submission_addr = pargs->r.ret_str;
	break;
	case oStatusFD:
	wks_set_status_fd (translate_sys2libc_fd_int (pargs->r.ret_int, 1));
	break;

	case aSupported:
	case aCreate:
	case aReceive:
	case aRead:
	case aCheck:
	cmd = pargs->r_opt;
	break;

	default: pargs->err = 2; break;
	}
	}

	return cmd;
	}



	/* gpg-wks-client main. */
	int
	main (int argc, char **argv)
	{
	gpg_error_t err;
	ARGPARSE_ARGS pargs;
	enum cmd_and_opt_values cmd;

	gnupg_reopen_std ("gpg-wks-client");
	set_strusage (my_strusage);
	log_set_prefix ("gpg-wks-client", GPGRT_LOG_WITH_PREFIX);

	/* Make sure that our subsystems are ready. */
	i18n_init();
	init_common_subsystems (&argc, &argv);

	assuan_set_gpg_err_source (GPG_ERR_SOURCE_DEFAULT);
	setup_libassuan_logging (&opt.debug, NULL);

	/* Parse the command line. */
	pargs.argc = &argc;
	pargs.argv = &argv;
	pargs.flags = ARGPARSE_FLAG_KEEP;
	cmd = parse_arguments (&pargs, opts);

	if (log_get_errorcount (0))
	exit (2);

	/* Print a warning if an argument looks like an option. */
	if (!opt.quiet && !(pargs.flags & ARGPARSE_FLAG_STOP_SEEN))
	{
	int i;

	for (i=0; i < argc; i++)
	if (argv[i][0] == '-' && argv[i][1] == '-')
	log_info (("NOTE: '%s' is not considered an option\n"), argv[i]);
	}

	/* Set defaults for non given options. */
	if (!opt.gpg_program)
	opt.gpg_program = gnupg_module_name (GNUPG_MODULE_NAME_GPG);

	/* Tell call-dirmngr what options we want. */
	set_dirmngr_options (opt.verbose, (opt.debug & DBG_IPC_VALUE), 1);

	/* Run the selected command. */
	switch (cmd)
	{
	case aSupported:
	if (argc != 1)
	wrong_args ("--supported USER-ID");
	err = command_supported (argv[0]);
	if (err && gpg_err_code (err) != GPG_ERR_FALSE)
	log_error ("checking support failed: %s\n", gpg_strerror (err));
	break;

	case aCreate:
	if (argc != 2)
	wrong_args ("--create FINGERPRINT USER-ID");
	err = command_send (argv[0], argv[1]);
	if (err)
	log_error ("creating request failed: %s\n", gpg_strerror (err));
	break;

	case aReceive:
	if (argc)
	wrong_args ("--receive < MIME-DATA");
	err = wks_receive (es_stdin, command_receive_cb, NULL);
	if (err)
	log_error ("processing mail failed: %s\n", gpg_strerror (err));
	break;

	case aRead:
	if (argc)
	wrong_args ("--read < WKS-DATA");
	err = read_confirmation_request (es_stdin);
	if (err)
	log_error ("processing mail failed: %s\n", gpg_strerror (err));
	break;

	case aCheck:
	if (argc != 1)
	wrong_args ("--check USER-ID");
	err = command_check (argv[0]);
	break;

	default:
	usage (1);
	err = 0;
	break;
	}

	if (err)
	wks_write_status (STATUS_FAILURE, "- %u", err);
	else if (log_get_errorcount (0))
	wks_write_status (STATUS_FAILURE, "- %u", GPG_ERR_GENERAL);
	else
	wks_write_status (STATUS_SUCCESS, NULL);
	return log_get_errorcount (0)? 1:0;
	}



	/* Add the user id UID to the key identified by FINGERPRINT. */
	static gpg_error_t
	add_user_id (const char fingerprint, const char uid)
	{
	gpg_error_t err;
	ccparray_t ccp;
	const char **argv = NULL;

	ccparray_init (&ccp, 0);

	ccparray_put (&ccp, "--no-options");
	if (!opt.verbose)
	ccparray_put (&ccp, "--quiet");
	else if (opt.verbose > 1)
	ccparray_put (&ccp, "--verbose");
	ccparray_put (&ccp, "--batch");
	ccparray_put (&ccp, "--always-trust");
	ccparray_put (&ccp, "--quick-add-uid");
	ccparray_put (&ccp, fingerprint);
	ccparray_put (&ccp, uid);

	ccparray_put (&ccp, NULL);
	argv = ccparray_get (&ccp, NULL);
	if (!argv)
	{
	err = gpg_error_from_syserror ();
	goto leave;
	}
	err = gnupg_exec_tool_stream (opt.gpg_program, argv, NULL,
	NULL, NULL,
	NULL, NULL);
	if (err)
	{
	log_error ("adding user id failed: %s\n", gpg_strerror (err));
	goto leave;
	}

	leave:
	xfree (argv);
	return err;
	}



	struct decrypt_stream_parm_s
	{
	char *fpr;
	char *mainfpr;
	int otrust;
	};

	static void
	decrypt_stream_status_cb (void opaque, const char keyword, char *args)
	{
	struct decrypt_stream_parm_s *decinfo = opaque;

	if (DBG_CRYPTO)
	log_debug ("gpg status: %s %s\n", keyword, args);
	if (!strcmp (keyword, "DECRYPTION_KEY") && !decinfo->fpr)
	{
	char *fields[3];

	if (split_fields (args, fields, DIM (fields)) >= 3)
	{
	decinfo->fpr = xstrdup (fields[0]);
	decinfo->mainfpr = xstrdup (fields[1]);
	decinfo->otrust = *fields[2];
	}
	}
	}

	/* Decrypt the INPUT stream to a new stream which is stored at success
	* at R_OUTPUT. */
	static gpg_error_t
	decrypt_stream (estream_t r_output, struct decrypt_stream_parm_s decinfo,
	estream_t input)
	{
	gpg_error_t err;
	ccparray_t ccp;
	const char **argv;
	estream_t output;

	*r_output = NULL;
	memset (decinfo, 0, sizeof *decinfo);

	output = es_fopenmem (0, "w+b");
	if (!output)
	{
	err = gpg_error_from_syserror ();
	log_error ("error allocating memory buffer: %s\n", gpg_strerror (err));
	return err;
	}

	ccparray_init (&ccp, 0);

	ccparray_put (&ccp, "--no-options");
	/* We limit the output to 64 KiB to avoid DoS using compression
	* tricks. A regular client will anyway only send a minimal key;
	* that is one w/o key signatures and attribute packets. */
	ccparray_put (&ccp, "--max-output=0x10000");
	if (!opt.verbose)
	ccparray_put (&ccp, "--quiet");
	else if (opt.verbose > 1)
	ccparray_put (&ccp, "--verbose");
	ccparray_put (&ccp, "--batch");
	ccparray_put (&ccp, "--status-fd=2");
	ccparray_put (&ccp, "--decrypt");
	ccparray_put (&ccp, "--");

	ccparray_put (&ccp, NULL);
	argv = ccparray_get (&ccp, NULL);
	if (!argv)
	{
	err = gpg_error_from_syserror ();
	goto leave;
	}
	err = gnupg_exec_tool_stream (opt.gpg_program, argv, input,
	NULL, output,
	decrypt_stream_status_cb, decinfo);
	if (!err && (!decinfo->fpr \|\| !decinfo->mainfpr \|\| !decinfo->otrust))
	err = gpg_error (GPG_ERR_INV_ENGINE);
	if (err)
	{
	log_error ("decryption failed: %s\n", gpg_strerror (err));
	goto leave;
	}
	else if (opt.verbose)
	log_info ("decryption succeeded\n");

	es_rewind (output);
	*r_output = output;
	output = NULL;

	leave:
	if (err)
	{
	xfree (decinfo->fpr);
	xfree (decinfo->mainfpr);
	memset (decinfo, 0, sizeof *decinfo);
	}
	es_fclose (output);
	xfree (argv);
	return err;
	}




	/* Check whether the provider supports the WKS protocol. */
	static gpg_error_t
	command_supported (char *userid)
	{
	gpg_error_t err;
	char *addrspec = NULL;
	char *submission_to = NULL;

	if (!strchr (userid, '@'))
	{
	char *tmp = xstrconcat ("foo@", userid, NULL);
	addrspec = mailbox_from_userid (tmp);
	xfree (tmp);
	}
	else
	addrspec = mailbox_from_userid (userid);
	if (!addrspec)
	{
	log_error (_("\"%s\" is not a proper mail address\n"), userid);
	err = gpg_error (GPG_ERR_INV_USER_ID);
	goto leave;
	}

	/* Get the submission address. */
	err = wkd_get_submission_address (addrspec, &submission_to);
	if (err)
	{
	if (gpg_err_code (err) == GPG_ERR_NO_DATA
	\|\| gpg_err_code (err) == GPG_ERR_UNKNOWN_HOST)
	{
	if (opt.verbose)
	log_info ("provider for '%s' does NOT support WKS (%s)\n",
	addrspec, gpg_strerror (err));
	err = gpg_error (GPG_ERR_FALSE);
	log_inc_errorcount ();
	}
	goto leave;
	}
	if (opt.verbose)
	log_info ("provider for '%s' supports WKS\n", addrspec);

	leave:
	xfree (submission_to);
	xfree (addrspec);
	return err;
	}



	/* Check whether the key for USERID is available in the WKD. */
	static gpg_error_t
	command_check (char *userid)
	{
	gpg_error_t err;
	char *addrspec = NULL;
	estream_t key = NULL;
	char *fpr = NULL;
	uidinfo_list_t mboxes = NULL;
	uidinfo_list_t sl;
	int found = 0;

	addrspec = mailbox_from_userid (userid);
	if (!addrspec)
	{
	log_error (_("\"%s\" is not a proper mail address\n"), userid);
	err = gpg_error (GPG_ERR_INV_USER_ID);
	goto leave;
	}

	/* Get the submission address. */
	err = wkd_get_key (addrspec, &key);
	switch (gpg_err_code (err))
	{
	case 0:
	if (opt.verbose)
	log_info ("public key for '%s' found via WKD\n", addrspec);
	/* Fixme: Check that the key contains the user id. */
	break;

	case GPG_ERR_NO_DATA: /* No such key. */
	if (opt.verbose)
	log_info ("public key for '%s' NOT found via WKD\n", addrspec);
	err = gpg_error (GPG_ERR_NO_PUBKEY);
	log_inc_errorcount ();
	break;

	case GPG_ERR_UNKNOWN_HOST:
	if (opt.verbose)
	log_info ("error looking up '%s' via WKD: %s\n",
	addrspec, gpg_strerror (err));
	err = gpg_error (GPG_ERR_NOT_SUPPORTED);
	break;

	default:
	log_error ("error looking up '%s' via WKD: %s\n",
	addrspec, gpg_strerror (err));
	break;
	}

	if (err)
	goto leave;

	/* Look closer at the key. */
	err = wks_list_key (key, &fpr, &mboxes);
	if (err)
	{
	log_error ("error parsing key: %s\n", gpg_strerror (err));
	err = gpg_error (GPG_ERR_NO_PUBKEY);
	goto leave;
	}

	if (opt.verbose)
	log_info ("fingerprint: %s\n", fpr);

	for (sl = mboxes; sl; sl = sl->next)
	{
	if (sl->mbox && !strcmp (sl->mbox, addrspec))
	found = 1;
	if (opt.verbose)
	{
	log_info (" user-id: %s\n", sl->uid);
	log_info (" created: %s\n", asctimestamp (sl->created));
	if (sl->mbox)
	log_info (" addr-spec: %s\n", sl->mbox);
	}
	}
	if (!found)
	{
	log_error ("public key for '%s' has no user id with the mail address\n",
	addrspec);
	err = gpg_error (GPG_ERR_CERT_REVOKED);
	}

	leave:
	xfree (fpr);
	free_uidinfo_list (mboxes);
	es_fclose (key);
	xfree (addrspec);
	return err;
	}



	/* Locate the key by fingerprint and userid and send a publication
	* request. */
	static gpg_error_t
	command_send (const char fingerprint, const char userid)
	{
	gpg_error_t err;
	KEYDB_SEARCH_DESC desc;
	char *addrspec = NULL;
	estream_t key = NULL;
	estream_t keyenc = NULL;
	char *submission_to = NULL;
	mime_maker_t mime = NULL;
	struct policy_flags_s policy;
	int no_encrypt = 0;
	int posteo_hack = 0;
	const char *domain;
	uidinfo_list_t uidlist = NULL;
	uidinfo_list_t uid, thisuid;
	time_t thistime;

	memset (&policy, 0, sizeof policy);

	if (classify_user_id (fingerprint, &desc, 1)
	\|\| !(desc.mode == KEYDB_SEARCH_MODE_FPR
	\|\| desc.mode == KEYDB_SEARCH_MODE_FPR20))
	{
	log_error (_("\"%s\" is not a fingerprint\n"), fingerprint);
	err = gpg_error (GPG_ERR_INV_NAME);
	goto leave;
	}

	addrspec = mailbox_from_userid (userid);
	if (!addrspec)
	{
	log_error (_("\"%s\" is not a proper mail address\n"), userid);
	err = gpg_error (GPG_ERR_INV_USER_ID);
	goto leave;
	}
	err = wks_get_key (&key, fingerprint, addrspec, 0);
	if (err)
	goto leave;

	domain = strchr (addrspec, '@');
	log_assert (domain);
	domain++;

	/* Get the submission address. */
	if (fake_submission_addr)
	{
	submission_to = xstrdup (fake_submission_addr);
	err = 0;
	}
	else
	{
	/* We first try to get the submission address from the policy
	* file (this is the new method). If both are available we
	* check that they match and print a warning if not. In the
	* latter case we keep on using the one from the
	* submission-address file. */
	estream_t mbuf;

	err = wkd_get_policy_flags (addrspec, &mbuf);
	if (err && gpg_err_code (err) != GPG_ERR_NO_DATA)
	{
	log_error ("error reading policy flags for '%s': %s\n",
	domain, gpg_strerror (err));
	goto leave;
	}
	if (mbuf)
	{
	err = wks_parse_policy (&policy, mbuf, 1);
	es_fclose (mbuf);
	if (err)
	goto leave;
	}

	err = wkd_get_submission_address (addrspec, &submission_to);
	if (err && !policy.submission_address)
	{
	log_error (_("error looking up submission address for domain '%s'"
	": %s\n"), domain, gpg_strerror (err));
	if (gpg_err_code (err) == GPG_ERR_NO_DATA)
	log_error (_("this domain probably doesn't support WKS.\n"));
	goto leave;
	}

	if (submission_to && policy.submission_address
	&& ascii_strcasecmp (submission_to, policy.submission_address))
	log_info ("Warning: different submission addresses (sa=%s, po=%s)\n",
	submission_to, policy.submission_address);

	if (!submission_to)
	{
	submission_to = xtrystrdup (policy.submission_address);
	if (!submission_to)
	{
	err = gpg_error_from_syserror ();
	goto leave;
	}
	}
	}

	log_info ("submitting request to '%s'\n", submission_to);

	if (policy.auth_submit)
	log_info ("no confirmation required for '%s'\n", addrspec);

	/* In case the key has several uids with the same addr-spec we will
	* use the newest one. */
	err = wks_list_key (key, NULL, &uidlist);
	if (err)
	{
	log_error ("error parsing key: %s\n",gpg_strerror (err));
	err = gpg_error (GPG_ERR_NO_PUBKEY);
	goto leave;
	}
	thistime = 0;
	thisuid = NULL;
	for (uid = uidlist; uid; uid = uid->next)
	{
	if (!uid->mbox)
	continue; /* Should not happen anyway. */
	if (policy.mailbox_only
	&& ascii_strcasecmp (uid->uid, uid->mbox))
	continue; /* UID has more than just the mailbox. */
	if (uid->created > thistime)
	{
	thistime = uid->created;
	thisuid = uid;
	}
	}
	if (!thisuid)
	thisuid = uidlist; /* This is the case for a missing timestamp. */
	if (opt.verbose)
	log_info ("submitting key with user id '%s'\n", thisuid->uid);

	/* If we have more than one user id we need to filter the key to
	* include only THISUID. */
	if (uidlist->next)
	{
	estream_t newkey;

	es_rewind (key);
	err = wks_filter_uid (&newkey, key, thisuid->uid, 0);
	if (err)
	{
	log_error ("error filtering key: %s\n", gpg_strerror (err));
	err = gpg_error (GPG_ERR_NO_PUBKEY);
	goto leave;
	}
	es_fclose (key);
	key = newkey;
	}

	if (policy.mailbox_only
	&& (!thisuid->mbox \|\| ascii_strcasecmp (thisuid->uid, thisuid->mbox)))
	{
	log_info ("Warning: policy requires 'mailbox-only'"
	" - adding user id '%s'\n", addrspec);
	err = add_user_id (fingerprint, addrspec);
	if (err)
	goto leave;

	/* Need to get the key again. This time we request filtering
	* for the full user id, so that we do not need check and filter
	* the key again. */
	es_fclose (key);
	key = NULL;
	err = wks_get_key (&key, fingerprint, addrspec, 1);
	if (err)
	goto leave;
	}

	/* Hack to support posteo but let them disable this by setting the
	* new policy-version flag. */
	if (policy.protocol_version < 3
	&& !ascii_strcasecmp (domain, "posteo.de"))
	{
	log_info ("Warning: Using draft-1 method for domain '%s'\n", domain);
	no_encrypt = 1;
	posteo_hack = 1;
	}

	/* Encrypt the key part. */
	if (!no_encrypt)
	{
	es_rewind (key);
	err = encrypt_response (&keyenc, key, submission_to, fingerprint);
	if (err)
	goto leave;
	es_fclose (key);
	key = NULL;
	}

	/* Send the key. */
	err = mime_maker_new (&mime, NULL);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "From", addrspec);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "To", submission_to);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "Subject", "Key publishing request");
	if (err)
	goto leave;

	/* Tell server which draft we support. */
	err = mime_maker_add_header (mime, "Wks-Draft-Version",
	STR2(WKS_DRAFT_VERSION));
	if (err)
	goto leave;

	if (no_encrypt)
	{
	void *data;
	size_t datalen, n;

	if (posteo_hack)
	{
	/* Needs a multipart/mixed with one(!) attachment. It does
	* not grok a non-multipart mail. */
	err = mime_maker_add_header (mime, "Content-Type", "multipart/mixed");
	if (err)
	goto leave;
	err = mime_maker_add_container (mime);
	if (err)
	goto leave;
	}

	err = mime_maker_add_header (mime, "Content-type",
	"application/pgp-keys");
	if (err)
	goto leave;

	if (es_fclose_snatch (key, &data, &datalen))
	{
	err = gpg_error_from_syserror ();
	goto leave;
	}
	key = NULL;
	/* We need to skip over the first line which has a content-type
	* header not needed here. */
	for (n=0; n < datalen ; n++)
	if (((const char *)data)[n] == '\n')
	{
	n++;
	break;
	}

	err = mime_maker_add_body_data (mime, (char*)data + n, datalen - n);
	xfree (data);
	if (err)
	goto leave;
	}
	else
	{
	err = mime_maker_add_header (mime, "Content-Type",
	"multipart/encrypted; "
	"protocol=\"application/pgp-encrypted\"");
	if (err)
	goto leave;
	err = mime_maker_add_container (mime);
	if (err)
	goto leave;

	err = mime_maker_add_header (mime, "Content-Type",
	"application/pgp-encrypted");
	if (err)
	goto leave;
	err = mime_maker_add_body (mime, "Version: 1\n");
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "Content-Type",
	"application/octet-stream");
	if (err)
	goto leave;

	err = mime_maker_add_stream (mime, &keyenc);
	if (err)
	goto leave;
	}

	err = wks_send_mime (mime);

	leave:
	mime_maker_release (mime);
	xfree (submission_to);
	free_uidinfo_list (uidlist);
	es_fclose (keyenc);
	es_fclose (key);
	wks_free_policy (&policy);
	xfree (addrspec);
	return err;
	}



	static void
	encrypt_response_status_cb (void opaque, const char keyword, char *args)
	{
	gpg_error_t *failure = opaque;
	char *fields[2];

	if (DBG_CRYPTO)
	log_debug ("gpg status: %s %s\n", keyword, args);

	if (!strcmp (keyword, "FAILURE"))
	{
	if (split_fields (args, fields, DIM (fields)) >= 2
	&& !strcmp (fields[0], "encrypt"))
	*failure = strtoul (fields[1], NULL, 10);
	}

	}


	/* Encrypt the INPUT stream to a new stream which is stored at success
	* at R_OUTPUT. Encryption is done for ADDRSPEC and for FINGERPRINT
	* (so that the sent message may later be inspected by the user). We
	* currently retrieve that key from the WKD, DANE, or from "local".
	* "local" is last to prefer the latest key version but use a local
	* copy in case we are working offline. It might be useful for the
	* server to send the fingerprint of its encryption key - or even the
	* entire key back. */
	static gpg_error_t
	encrypt_response (estream_t r_output, estream_t input, const char addrspec,
	const char *fingerprint)
	{
	gpg_error_t err;
	ccparray_t ccp;
	const char **argv;
	estream_t output;
	gpg_error_t gpg_err = 0;

	*r_output = NULL;

	output = es_fopenmem (0, "w+b");
	if (!output)
	{
	err = gpg_error_from_syserror ();
	log_error ("error allocating memory buffer: %s\n", gpg_strerror (err));
	return err;
	}

	ccparray_init (&ccp, 0);

	ccparray_put (&ccp, "--no-options");
	if (!opt.verbose)
	ccparray_put (&ccp, "--quiet");
	else if (opt.verbose > 1)
	ccparray_put (&ccp, "--verbose");
	ccparray_put (&ccp, "--batch");
	ccparray_put (&ccp, "--status-fd=2");
	ccparray_put (&ccp, "--always-trust");
	ccparray_put (&ccp, "--armor");
	if (fake_submission_addr)
	ccparray_put (&ccp, "--auto-key-locate=clear,local");
	else
	ccparray_put (&ccp, "--auto-key-locate=clear,wkd,dane,local");
	ccparray_put (&ccp, "--recipient");
	ccparray_put (&ccp, addrspec);
	ccparray_put (&ccp, "--recipient");
	ccparray_put (&ccp, fingerprint);
	ccparray_put (&ccp, "--encrypt");
	ccparray_put (&ccp, "--");

	ccparray_put (&ccp, NULL);
	argv = ccparray_get (&ccp, NULL);
	if (!argv)
	{
	err = gpg_error_from_syserror ();
	goto leave;
	}
	err = gnupg_exec_tool_stream (opt.gpg_program, argv, input,
	NULL, output,
	encrypt_response_status_cb, &gpg_err);
	if (err)
	{
	if (gpg_err)
	err = gpg_err;
	log_error ("encryption failed: %s\n", gpg_strerror (err));
	goto leave;
	}

	es_rewind (output);
	*r_output = output;
	output = NULL;

	leave:
	es_fclose (output);
	xfree (argv);
	return err;
	}


	static gpg_error_t
	send_confirmation_response (const char sender, const char address,
	const char *nonce, int encrypt,
	const char *fingerprint)
	{
	gpg_error_t err;
	estream_t body = NULL;
	estream_t bodyenc = NULL;
	mime_maker_t mime = NULL;

	body = es_fopenmem (0, "w+b");
	if (!body)
	{
	err = gpg_error_from_syserror ();
	log_error ("error allocating memory buffer: %s\n", gpg_strerror (err));
	return err;
	}

	/* It is fine to use 8 bit encoding because that is encrypted and
	* only our client will see it. */
	if (encrypt)
	{
	es_fputs ("Content-Type: application/vnd.gnupg.wks\n"
	"Content-Transfer-Encoding: 8bit\n"
	"\n",
	body);
	}

	es_fprintf (body, ("type: confirmation-response\n"
	"sender: %s\n"
	"address: %s\n"
	"nonce: %s\n"),
	sender,
	address,
	nonce);

	es_rewind (body);
	if (encrypt)
	{
	err = encrypt_response (&bodyenc, body, sender, fingerprint);
	if (err)
	goto leave;
	es_fclose (body);
	body = NULL;
	}

	err = mime_maker_new (&mime, NULL);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "From", address);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "To", sender);
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "Subject", "Key publication confirmation");
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "Wks-Draft-Version",
	STR2(WKS_DRAFT_VERSION));
	if (err)
	goto leave;

	if (encrypt)
	{
	err = mime_maker_add_header (mime, "Content-Type",
	"multipart/encrypted; "
	"protocol=\"application/pgp-encrypted\"");
	if (err)
	goto leave;
	err = mime_maker_add_container (mime);
	if (err)
	goto leave;

	err = mime_maker_add_header (mime, "Content-Type",
	"application/pgp-encrypted");
	if (err)
	goto leave;
	err = mime_maker_add_body (mime, "Version: 1\n");
	if (err)
	goto leave;
	err = mime_maker_add_header (mime, "Content-Type",
	"application/octet-stream");
	if (err)
	goto leave;

	err = mime_maker_add_stream (mime, &bodyenc);
	if (err)
	goto leave;
	}
	else
	{
	err = mime_maker_add_header (mime, "Content-Type",
	"application/vnd.gnupg.wks");
	if (err)
	goto leave;
	err = mime_maker_add_stream (mime, &body);
	if (err)
	goto leave;
	}

	err = wks_send_mime (mime);

	leave:
	mime_maker_release (mime);
	es_fclose (bodyenc);
	es_fclose (body);
	return err;
	}


	/* Reply to a confirmation request. The MSG has already been
	* decrypted and we only need to send the nonce back. MAINFPR is
	* either NULL or the primary key fingerprint of the key used to
	* decrypt the request. */
	static gpg_error_t
	process_confirmation_request (estream_t msg, const char *mainfpr)
	{
	gpg_error_t err;
	nvc_t nvc;
	nve_t item;
	const char value, sender, address, fingerprint, *nonce;

	err = nvc_parse (&nvc, NULL, msg);
	if (err)
	{
	log_error ("parsing the WKS message failed: %s\n", gpg_strerror (err));
	goto leave;
	}

	if (DBG_MIME)
	{
	log_debug ("request follows:\n");
	nvc_write (nvc, log_get_stream ());
	}

	/* Check that this is a confirmation request. */
	if (!((item = nvc_lookup (nvc, "type:")) && (value = nve_value (item))
	&& !strcmp (value, "confirmation-request")))
	{
	if (item && value)
	log_error ("received unexpected wks message '%s'\n", value);
	else
	log_error ("received invalid wks message: %s\n", "'type' missing");
	err = gpg_error (GPG_ERR_UNEXPECTED_MSG);
	goto leave;
	}

	/* Get the fingerprint. */
	if (!((item = nvc_lookup (nvc, "fingerprint:"))
	&& (value = nve_value (item))
	&& strlen (value) >= 40))
	{
	log_error ("received invalid wks message: %s\n",
	"'fingerprint' missing or invalid");
	err = gpg_error (GPG_ERR_INV_DATA);
	goto leave;
	}
	fingerprint = value;

	/* Check that the fingerprint matches the key used to decrypt the
	* message. In --read mode or with the old format we don't have the
	* decryption key; thus we can't bail out. */
	if (!mainfpr \|\| ascii_strcasecmp (mainfpr, fingerprint))
	{
	log_info ("target fingerprint: %s\n", fingerprint);
	log_info ("but decrypted with: %s\n", mainfpr);
	log_error ("confirmation request not decrypted with target key\n");
	if (mainfpr)
	{
	err = gpg_error (GPG_ERR_INV_DATA);
	goto leave;
	}
	}

	/* Get the address. */
	if (!((item = nvc_lookup (nvc, "address:")) && (value = nve_value (item))
	&& is_valid_mailbox (value)))
	{
	log_error ("received invalid wks message: %s\n",
	"'address' missing or invalid");
	err = gpg_error (GPG_ERR_INV_DATA);
	goto leave;
	}
	address = value;
	/* FIXME: Check that the "address" matches the User ID we want to
	* publish. */

	/* Get the sender. */
	if (!((item = nvc_lookup (nvc, "sender:")) && (value = nve_value (item))
	&& is_valid_mailbox (value)))
	{
	log_error ("received invalid wks message: %s\n",
	"'sender' missing or invalid");
	err = gpg_error (GPG_ERR_INV_DATA);
	goto leave;
	}
	sender = value;
	/* FIXME: Check that the "sender" matches the From: address. */

	/* Get the nonce. */
	if (!((item = nvc_lookup (nvc, "nonce:")) && (value = nve_value (item))
	&& strlen (value) > 16))
	{
	log_error ("received invalid wks message: %s\n",
	"'nonce' missing or too short");
	err = gpg_error (GPG_ERR_INV_DATA);
	goto leave;
	}
	nonce = value;

	/* Send the confirmation. If no key was found, try again without
	* encryption. */
	err = send_confirmation_response (sender, address, nonce, 1, fingerprint);
	if (gpg_err_code (err) == GPG_ERR_NO_PUBKEY)
	{
	log_info ("no encryption key found - sending response in the clear\n");
	err = send_confirmation_response (sender, address, nonce, 0, NULL);
	}

	leave:
	nvc_release (nvc);
	return err;
	}


	/* Read a confirmation request and decrypt it if needed. This
	* function may not be used with a mail or MIME message but only with
	* the actual encrypted or plaintext WKS data. */
	static gpg_error_t
	read_confirmation_request (estream_t msg)
	{
	gpg_error_t err;
	int c;
	estream_t plaintext = NULL;

	/* We take a really simple approach to check whether MSG is
	* encrypted: We know that an encrypted message is always armored
	* and thus starts with a few dashes. It is even sufficient to
	* check for a single dash, because that can never be a proper first
	* WKS data octet. We need to skip leading spaces, though. */
	while ((c = es_fgetc (msg)) == ' ' \|\| c == '\t' \|\| c == '\r' \|\| c == '\n')
	;
	if (c == EOF)
	{
	log_error ("can't process an empty message\n");
	return gpg_error (GPG_ERR_INV_DATA);
	}
	if (es_ungetc (c, msg) != c)
	{
	log_error ("error ungetting octet from message\n");
	return gpg_error (GPG_ERR_INTERNAL);
	}

	if (c != '-')
	err = process_confirmation_request (msg, NULL);
	else
	{
	struct decrypt_stream_parm_s decinfo;

	err = decrypt_stream (&plaintext, &decinfo, msg);
	if (err)
	log_error ("decryption failed: %s\n", gpg_strerror (err));
	else if (decinfo.otrust != 'u')
	{
	err = gpg_error (GPG_ERR_WRONG_SECKEY);
	log_error ("key used to decrypt the confirmation request"
	" was not generated by us\n");
	}
	else
	err = process_confirmation_request (plaintext, decinfo.mainfpr);
	xfree (decinfo.fpr);
	xfree (decinfo.mainfpr);
	}

	es_fclose (plaintext);
	return err;
	}


	/* Called from the MIME receiver to process the plain text data in MSG. */
	static gpg_error_t
	command_receive_cb (void opaque, const char mediatype,
	estream_t msg, unsigned int flags)
	{
	gpg_error_t err;

	(void)opaque;
	(void)flags;

	if (!strcmp (mediatype, "application/vnd.gnupg.wks"))
	err = read_confirmation_request (msg);
	else
	{
	log_info ("ignoring unexpected message of type '%s'\n", mediatype);
	err = gpg_error (GPG_ERR_UNEXPECTED_MSG);
	}

	return err;
	}

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