/* mmutf8fix.c
 * fix invalid UTF8 sequences. This is begun as a very simple replacer
 * of non-control characters, and actually breaks some UTF-8 encoding
 * right now. If the module turns out to be useful, it should be enhanced
 * to support modes that really detect invalid UTF8. In the longer term
 * it could also be evolved into an any-charset-to-UTF8 converter. But
 * first let's see if it really gets into widespread enough use.
 *
 * Copyright 2013-2016 Adiscon GmbH.
 *
 * This file is part of rsyslog.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *       -or-
 *       see COPYING.ASL20 in the source distribution
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "config.h"
#include "rsyslog.h"
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>
#include <stdint.h>
#include "conf.h"
#include "syslogd-types.h"
#include "srUtils.h"
#include "template.h"
#include "module-template.h"
#include "errmsg.h"

MODULE_TYPE_OUTPUT
MODULE_TYPE_NOKEEP
MODULE_CNFNAME("mmutf8fix")


DEF_OMOD_STATIC_DATA

/* define operation modes we have */
#define MODE_CC 0	 /* just fix control characters */
#define MODE_UTF8 1	 /* do real UTF-8 fixing */

/* config variables */
typedef struct _instanceData {
	uchar replChar;
	uint8_t mode;		/* operations mode */
} instanceData;

typedef struct wrkrInstanceData {
	instanceData *pData;
} wrkrInstanceData_t;

struct modConfData_s {
	rsconf_t *pConf;	/* our overall config object */
};
static modConfData_t *loadModConf = NULL;/* modConf ptr to use for the current load process */
static modConfData_t *runModConf = NULL;/* modConf ptr to use for the current exec process */


/* tables for interfacing with the v6 config system */
/* action (instance) parameters */
static struct cnfparamdescr actpdescr[] = {
	{ "mode", eCmdHdlrGetWord, 0 },
	{ "replacementchar", eCmdHdlrGetChar, 0 }
};
static struct cnfparamblk actpblk =
	{ CNFPARAMBLK_VERSION,
	  sizeof(actpdescr)/sizeof(struct cnfparamdescr),
	  actpdescr
	};

BEGINbeginCnfLoad
CODESTARTbeginCnfLoad
	loadModConf = pModConf;
	pModConf->pConf = pConf;
ENDbeginCnfLoad

BEGINendCnfLoad
CODESTARTendCnfLoad
ENDendCnfLoad

BEGINcheckCnf
CODESTARTcheckCnf
ENDcheckCnf

BEGINactivateCnf
CODESTARTactivateCnf
	runModConf = pModConf;
ENDactivateCnf

BEGINfreeCnf
CODESTARTfreeCnf
ENDfreeCnf


BEGINcreateInstance
CODESTARTcreateInstance
ENDcreateInstance


BEGINcreateWrkrInstance
CODESTARTcreateWrkrInstance
ENDcreateWrkrInstance


BEGINisCompatibleWithFeature
CODESTARTisCompatibleWithFeature
ENDisCompatibleWithFeature


BEGINfreeInstance
CODESTARTfreeInstance
ENDfreeInstance


BEGINfreeWrkrInstance
CODESTARTfreeWrkrInstance
ENDfreeWrkrInstance


static inline void
setInstParamDefaults(instanceData *pData)
{
	pData->mode = MODE_UTF8;
	pData->replChar = ' ';
}

BEGINnewActInst
	struct cnfparamvals *pvals;
	int i;
CODESTARTnewActInst
	DBGPRINTF("newActInst (mmutf8fix)\n");
	if((pvals = nvlstGetParams(lst, &actpblk, NULL)) == NULL) {
		ABORT_FINALIZE(RS_RET_MISSING_CNFPARAMS);
	}

	CODE_STD_STRING_REQUESTnewActInst(1)
	CHKiRet(OMSRsetEntry(*ppOMSR, 0, NULL, OMSR_TPL_AS_MSG));
	CHKiRet(createInstance(&pData));
	setInstParamDefaults(pData);

	for(i = 0 ; i < actpblk.nParams ; ++i) {
		if(!pvals[i].bUsed)
			continue;
		if(!strcmp(actpblk.descr[i].name, "mode")) {
			if(!es_strbufcmp(pvals[i].val.d.estr, (uchar*)"utf-8",
					 sizeof("utf-8")-1)) {
				pData->mode = MODE_UTF8;
			} else if(!es_strbufcmp(pvals[i].val.d.estr, (uchar*)"controlcharacters",
					 sizeof("controlcharacters")-1)) {
				pData->mode = MODE_CC;
			} else {
				char *cstr = es_str2cstr(pvals[i].val.d.estr, NULL);
				LogError(0, RS_RET_INVLD_MODE,
					"mmutf8fix: invalid mode '%s' - ignored",
					cstr);
				free(cstr);
			}
		} else if(!strcmp(actpblk.descr[i].name, "replacementchar")) {
			pData->replChar = es_getBufAddr(pvals[i].val.d.estr)[0];
		} else {
			dbgprintf("mmutf8fix: program error, non-handled "
			  "param '%s'\n", actpblk.descr[i].name);
		}
	}

CODE_STD_FINALIZERnewActInst
	cnfparamvalsDestruct(pvals, &actpblk);
ENDnewActInst


BEGINdbgPrintInstInfo
CODESTARTdbgPrintInstInfo
ENDdbgPrintInstInfo


BEGINtryResume
CODESTARTtryResume
ENDtryResume


static void
doCC(instanceData *pData, uchar *msg, int lenMsg)
{
	int i;

	for(i = 0 ; i < lenMsg ; ++i) {
		if(msg[i] < 32 || msg[i] > 126) {
			msg[i] = pData->replChar;
		}
	}
}

/* fix an invalid multibyte sequence */
static void
fixInvldMBSeq(instanceData *pData, uchar *msg, int lenMsg, int strtIdx, int cnt)
{
	int i, endIdx;

	/* Actually strtIdx + cnt will not exceed msgLen,
	   but this check does bring peace of mind */
	endIdx = strtIdx + cnt;
	if(endIdx > lenMsg)
		endIdx = lenMsg;
	for(i = strtIdx ; i < endIdx ; ++i)
		msg[i] = pData->replChar;
}

static void
doUTF8(instanceData *pData, uchar *msg, int lenMsg)
{
	uchar c;
	int8_t bytesLeft = 0;
	uint32_t codepoint;
	int strtIdx = 0;
	int i;

	for(i = 0 ; i < lenMsg ; ++i) {
		c = msg[i];
		if(bytesLeft) {
			if((c & 0xc0) != 0x80) {
				/* invalid continuation byte, invalidate all bytes
				   up to (but not including) the current byte
				   startIdx is always set if bytesLeft is set */
				fixInvldMBSeq(pData, msg, lenMsg, strtIdx, i - strtIdx);
				bytesLeft = 0;
				goto startOfSequence;
			} else {
				codepoint = (codepoint << 6) | (c & 0x3f);
				--bytesLeft;
				if(bytesLeft == 0) {
					int seqLen = i - strtIdx + 1;

					if (
					    /* an overlong encoding? (a codepoint must use only
					       the minimum number of bytes to represent its value) */
					    (((2 == seqLen) && (codepoint < 0x80)) ||
					     ((3 == seqLen) && (codepoint < 0x800)) ||
					     ((4 == seqLen) && (codepoint < 0x10000)))
					    ||
					    /* UTF-16 surrogates? */
					    ((codepoint >= 0xD800) && (codepoint <= 0xDFFF))
					    ||
					    /* too-large codepoint? */
					    (codepoint > 0x10FFFF)
					) {
						/* sequence invalid, invalidate all bytes
						   startIdx is always set if bytesLeft is set */
						fixInvldMBSeq(pData, msg, lenMsg, strtIdx, seqLen);
					}
				}
			}
		} else {
startOfSequence:
			if((c & 0x80) == 0) {
				/* 1-byte sequence, US-ASCII */
				; /* nothing to do, all well */
			} else if((c & 0xe0) == 0xc0) {
				/* 2-byte sequence */
				strtIdx = i;
				bytesLeft = 1;
				codepoint = c & 0x1f;
			} else if((c & 0xf0) == 0xe0) {
				/* 3-byte sequence */
				strtIdx = i;
				bytesLeft = 2;
				codepoint = c & 0x0f;
			} else if((c & 0xf8) == 0xf0) {
				/* 4-byte sequence */
				strtIdx = i;
				bytesLeft = 3;
				codepoint = c & 0x07;
			} else {   /* invalid, either:
				      - stray continuation byte (0x80 <= x <= 0xBF)
				      - 5&6 byte sequence start (x >= 0xF8) forbidden by RFC3629
				    */
				msg[i] = pData->replChar;
			}
		}
	}
	if (bytesLeft) {
		/* invalid, there was not enough bytes to complete a sequence
		   startIdx is always set if bytesLeft is set */
		fixInvldMBSeq(pData, msg, lenMsg, strtIdx, i - strtIdx);
	}
}

BEGINdoAction_NoStrings
	smsg_t **ppMsg = (smsg_t **) pMsgData;
	smsg_t *pMsg = ppMsg[0];
	uchar *msg;
	int lenMsg;
CODESTARTdoAction
	lenMsg = getMSGLen(pMsg);
	msg = getMSG(pMsg);
	if(pWrkrData->pData->mode == MODE_CC) {
		doCC(pWrkrData->pData, msg, lenMsg);
	} else {
		doUTF8(pWrkrData->pData, msg, lenMsg);
	}
ENDdoAction


NO_LEGACY_CONF_parseSelectorAct


BEGINmodExit
CODESTARTmodExit
ENDmodExit


BEGINqueryEtryPt
CODESTARTqueryEtryPt
CODEqueryEtryPt_STD_OMOD_QUERIES
CODEqueryEtryPt_STD_OMOD8_QUERIES
CODEqueryEtryPt_STD_CONF2_OMOD_QUERIES
CODEqueryEtryPt_STD_CONF2_QUERIES
ENDqueryEtryPt


BEGINmodInit()
CODESTARTmodInit
	*ipIFVersProvided = CURR_MOD_IF_VERSION; /* we only support the current interface specification */
CODEmodInit_QueryRegCFSLineHdlr
	DBGPRINTF("mmutf8fix: module compiled with rsyslog version %s.\n", VERSION);
ENDmodInit