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	/* decrypt.c - Decrypt function.
	Copyright (C) 2000 Werner Koch (dd9jn)
	Copyright (C) 2001, 2002, 2003, 2004, 2017 g10 Code GmbH

	This file is part of GPGME.

	GPGME 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.

	GPGME 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, write to the Free Software
	Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
	02111-1307, USA. */

	#if HAVE_CONFIG_H
	#include <config.h>
	#endif
	#include <stdlib.h>
	#include <string.h>
	#include <errno.h>
	#include <assert.h>

	#include "debug.h"
	#include "gpgme.h"
	#include "util.h"
	#include "context.h"
	#include "ops.h"



	typedef struct
	{
	struct _gpgme_op_decrypt_result result;

	/* The error code from a FAILURE status line or 0. */
	gpg_error_t failure_code;

	int okay;

	/* A flag telling that the a decryption failed and an optional error
	* code to further specify the failure. */
	int failed;
	gpg_error_t pkdecrypt_failed;

	/* At least one secret key is not available. gpg issues NO_SECKEY
	* status lines for each key the message has been encrypted to but
	* that secret key is not available. This can't be done for hidden
	* recipients, though. We track it here to allow for a better error
	* message that the general DECRYPTION_FAILED. */
	int any_no_seckey;

	/* A pointer to the next pointer of the last recipient in the list.
	This makes appending new invalid signers painless while
	preserving the order. */
	gpgme_recipient_t *last_recipient_p;
	} *op_data_t;


	static void
	release_op_data (void *hook)
	{
	op_data_t opd = (op_data_t) hook;
	gpgme_recipient_t recipient = opd->result.recipients;

	if (opd->result.unsupported_algorithm)
	free (opd->result.unsupported_algorithm);

	if (opd->result.file_name)
	free (opd->result.file_name);

	if (opd->result.session_key)
	free (opd->result.session_key);

	while (recipient)
	{
	gpgme_recipient_t next = recipient->next;
	free (recipient);
	recipient = next;
	}
	}


	gpgme_decrypt_result_t
	gpgme_op_decrypt_result (gpgme_ctx_t ctx)
	{
	void *hook;
	op_data_t opd;
	gpgme_error_t err;

	TRACE_BEG (DEBUG_CTX, "gpgme_op_decrypt_result", ctx);

	err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook, -1, NULL);
	opd = hook;
	if (err \|\| !opd)
	{
	TRACE_SUC0 ("result=(null)");
	return NULL;
	}

	if (_gpgme_debug_trace ())
	{
	gpgme_recipient_t rcp;

	if (opd->result.unsupported_algorithm)
	{
	TRACE_LOG1 ("result: unsupported_algorithm: %s",
	opd->result.unsupported_algorithm);
	}
	if (opd->result.wrong_key_usage)
	{
	TRACE_LOG ("result: wrong key usage");
	}
	rcp = opd->result.recipients;
	while (rcp)
	{
	TRACE_LOG3 ("result: recipient: keyid=%s, pubkey_algo=%i, "
	"status=%s", rcp->keyid, rcp->pubkey_algo,
	gpg_strerror (rcp->status));
	rcp = rcp->next;
	}
	if (opd->result.file_name)
	{
	TRACE_LOG1 ("result: original file name: %s", opd->result.file_name);
	}
	}

	TRACE_SUC1 ("result=%p", &opd->result);
	return &opd->result;
	}



	/* Parse the ARGS of an error status line and record some error
	* conditions at OPD. Returns 0 on success. */
	static gpgme_error_t
	parse_status_error (char *args, op_data_t opd)
	{
	gpgme_error_t err;
	char *field[3];
	int nfields;
	char *args2;

	if (!args)
	return trace_gpg_error (GPG_ERR_INV_ENGINE);

	args2 = strdup (args); /* Split modifies the input string. */
	nfields = _gpgme_split_fields (args2, field, DIM (field));
	if (nfields < 1)
	{
	free (args2);
	return trace_gpg_error (GPG_ERR_INV_ENGINE); /* Required arg missing. */
	}
	err = nfields < 2 ? 0 : atoi (field[1]);

	if (!strcmp (field[0], "decrypt.algorithm"))
	{
	if (gpg_err_code (err) == GPG_ERR_UNSUPPORTED_ALGORITHM
	&& nfields > 2
	&& strcmp (field[2], "?"))
	{
	opd->result.unsupported_algorithm = strdup (field[2]);
	if (!opd->result.unsupported_algorithm)
	{
	free (args2);
	return gpg_error_from_syserror ();
	}
	}
	}
	else if (!strcmp (field[0], "decrypt.keyusage"))
	{
	if (gpg_err_code (err) == GPG_ERR_WRONG_KEY_USAGE)
	opd->result.wrong_key_usage = 1;
	}
	else if (!strcmp (field[0], "pkdecrypt_failed"))
	{
	switch (gpg_err_code (err))
	{
	case GPG_ERR_CANCELED:
	case GPG_ERR_FULLY_CANCELED:
	/* It is better to return with a cancel error code than the
	* general decryption failed error code. */
	opd->pkdecrypt_failed = gpg_err_make (gpg_err_source (err),
	GPG_ERR_CANCELED);
	break;

	case GPG_ERR_BAD_PASSPHRASE:
	/* A bad passphrase is severe enough that we return this
	* error code. */
	opd->pkdecrypt_failed = err;
	break;

	default:
	/* For now all other error codes are ignored and the
	* standard DECRYPT_FAILED is returned. */
	break;
	}
	}


	free (args2);
	return 0;
	}


	static gpgme_error_t
	parse_enc_to (char args, gpgme_recipient_t recp, gpgme_protocol_t protocol)
	{
	gpgme_recipient_t rec;
	char *tail;
	int i;

	rec = malloc (sizeof (*rec));
	if (!rec)
	return gpg_error_from_syserror ();

	rec->next = NULL;
	rec->keyid = rec->_keyid;
	rec->status = 0;

	for (i = 0; i < sizeof (rec->_keyid) - 1; i++)
	{
	if (args[i] == '\0' \|\| args[i] == ' ')
	break;

	rec->_keyid[i] = args[i];
	}
	rec->_keyid[i] = '\0';

	args = &args[i];
	if (args != '\0' && args != ' ')
	{
	free (rec);
	return trace_gpg_error (GPG_ERR_INV_ENGINE);
	}

	while (*args == ' ')
	args++;

	if (*args)
	{
	gpg_err_set_errno (0);
	rec->pubkey_algo = _gpgme_map_pk_algo (strtol (args, &tail, 0), protocol);
	if (errno \|\| args == tail \|\| *tail != ' ')
	{
	/* The crypto backend does not behave. */
	free (rec);
	return trace_gpg_error (GPG_ERR_INV_ENGINE);
	}
	}

	/* FIXME: The key length is always 0 right now, so no need to parse
	it. */

	*recp = rec;
	return 0;
	}


	gpgme_error_t
	_gpgme_decrypt_status_handler (void *priv, gpgme_status_code_t code,
	char *args)
	{
	gpgme_ctx_t ctx = (gpgme_ctx_t) priv;
	gpgme_error_t err;
	void *hook;
	op_data_t opd;

	err = _gpgme_passphrase_status_handler (priv, code, args);
	if (err)
	return err;

	err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook, -1, NULL);
	opd = hook;
	if (err)
	return err;

	switch (code)
	{
	case GPGME_STATUS_FAILURE:
	opd->failure_code = _gpgme_parse_failure (args);
	break;

	case GPGME_STATUS_EOF:
	/* FIXME: These error values should probably be attributed to
	the underlying crypto engine (as error source). */
	if (opd->failed && opd->pkdecrypt_failed)
	return opd->pkdecrypt_failed;
	else if (opd->failed && opd->any_no_seckey)
	return gpg_error (GPG_ERR_NO_SECKEY);
	else if (opd->failed)
	return gpg_error (GPG_ERR_DECRYPT_FAILED);
	else if (!opd->okay)
	return gpg_error (GPG_ERR_NO_DATA);
	else if (opd->failure_code)
	return opd->failure_code;
	break;

	case GPGME_STATUS_DECRYPTION_INFO:
	/* Fixme: Provide a way to return the used symmetric algorithm. */
	break;

	case GPGME_STATUS_DECRYPTION_OKAY:
	opd->okay = 1;
	break;

	case GPGME_STATUS_DECRYPTION_FAILED:
	opd->failed = 1;
	break;

	case GPGME_STATUS_ERROR:
	/* Note that this is an informational status code which should
	not lead to an error return unless it is something not
	related to the backend. */
	err = parse_status_error (args, opd);
	if (err)
	return err;
	break;

	case GPGME_STATUS_ENC_TO:
	err = parse_enc_to (args, opd->last_recipient_p, ctx->protocol);
	if (err)
	return err;

	opd->last_recipient_p = &(*opd->last_recipient_p)->next;
	break;

	case GPGME_STATUS_SESSION_KEY:
	if (opd->result.session_key)
	free (opd->result.session_key);
	opd->result.session_key = strdup(args);
	break;

	case GPGME_STATUS_NO_SECKEY:
	{
	gpgme_recipient_t rec = opd->result.recipients;
	while (rec)
	{
	if (!strcmp (rec->keyid, args))
	{
	rec->status = gpg_error (GPG_ERR_NO_SECKEY);
	break;
	}
	rec = rec->next;
	}
	/* FIXME: Is this ok? */
	if (!rec)
	return trace_gpg_error (GPG_ERR_INV_ENGINE);
	opd->any_no_seckey = 1;
	}
	break;

	case GPGME_STATUS_PLAINTEXT:
	err = _gpgme_parse_plaintext (args, &opd->result.file_name);
	if (err)
	return err;
	break;

	case GPGME_STATUS_INQUIRE_MAXLEN:
	if (ctx->status_cb && !ctx->full_status)
	{
	err = ctx->status_cb (ctx->status_cb_value, "INQUIRE_MAXLEN", args);
	if (err)
	return err;
	}
	break;

	case GPGME_STATUS_DECRYPTION_COMPLIANCE_MODE:
	PARSE_COMPLIANCE_FLAGS (args, &opd->result);
	break;

	default:
	break;
	}

	return 0;
	}


	static gpgme_error_t
	decrypt_status_handler (void priv, gpgme_status_code_t code, char args)
	{
	gpgme_error_t err;

	err = _gpgme_progress_status_handler (priv, code, args);
	if (!err)
	err = _gpgme_decrypt_status_handler (priv, code, args);
	return err;
	}


	gpgme_error_t
	_gpgme_op_decrypt_init_result (gpgme_ctx_t ctx)
	{
	gpgme_error_t err;
	void *hook;
	op_data_t opd;

	err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook,
	sizeof (*opd), release_op_data);
	opd = hook;
	if (err)
	return err;

	opd->last_recipient_p = &opd->result.recipients;
	return 0;
	}


	gpgme_error_t
	_gpgme_decrypt_start (gpgme_ctx_t ctx, int synchronous,
	gpgme_decrypt_flags_t flags,
	gpgme_data_t cipher, gpgme_data_t plain)
	{
	gpgme_error_t err;

	assert (!(flags & GPGME_DECRYPT_VERIFY));

	err = _gpgme_op_reset (ctx, synchronous);
	if (err)
	return err;

	err = _gpgme_op_decrypt_init_result (ctx);
	if (err)
	return err;

	if (!cipher)
	return gpg_error (GPG_ERR_NO_DATA);
	if (!plain)
	return gpg_error (GPG_ERR_INV_VALUE);

	if (err)
	return err;

	if (ctx->passphrase_cb)
	{
	err = _gpgme_engine_set_command_handler
	(ctx->engine, _gpgme_passphrase_command_handler, ctx, NULL);
	if (err)
	return err;
	}

	_gpgme_engine_set_status_handler (ctx->engine, decrypt_status_handler, ctx);

	return _gpgme_engine_op_decrypt (ctx->engine,
	flags,
	cipher, plain,
	ctx->export_session_keys,
	ctx->override_session_key,
	ctx->auto_key_retrieve);
	}


	gpgme_error_t
	gpgme_op_decrypt_start (gpgme_ctx_t ctx, gpgme_data_t cipher,
	gpgme_data_t plain)
	{
	gpgme_error_t err;

	TRACE_BEG2 (DEBUG_CTX, "gpgme_op_decrypt_start", ctx,
	"cipher=%p, plain=%p", cipher, plain);

	if (!ctx)
	return TRACE_ERR (gpg_error (GPG_ERR_INV_VALUE));

	err = _gpgme_decrypt_start (ctx, 0, 0, cipher, plain);
	return TRACE_ERR (err);
	}


	/* Decrypt ciphertext CIPHER within CTX and store the resulting
	plaintext in PLAIN. */
	gpgme_error_t
	gpgme_op_decrypt (gpgme_ctx_t ctx, gpgme_data_t cipher, gpgme_data_t plain)
	{
	gpgme_error_t err;

	TRACE_BEG2 (DEBUG_CTX, "gpgme_op_decrypt", ctx,
	"cipher=%p, plain=%p", cipher, plain);

	if (!ctx)
	return TRACE_ERR (gpg_error (GPG_ERR_INV_VALUE));

	err = _gpgme_decrypt_start (ctx, 1, 0, cipher, plain);
	if (!err)
	err = _gpgme_wait_one (ctx);
	return TRACE_ERR (err);
	}

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