/*
 * Message Digests Module
 *
 * Provides commands to calculate a message digest using a specified hash function.
 *
 * Copyright (C) 2023 Brian O'Hagan
 *
 */

#include "tlsInt.h"
#include "tclOpts.h"

/* Macros */
#define BUFFER_SIZE 65536
#define BIN_FORMAT 0
#define HEX_FORMAT 1
#define CHAN_EOF 0x10

/*
 * This structure defines the per-instance state of a digest operation.


 */
typedef struct DigestState {
	Tcl_Channel self;	/* This socket channel */
	Tcl_TimerToken timer;	/* Timer for read events */

	int flags;		/* Chan config flags */
	int watchMask;		/* Current WatchProc mask */

 *
 * Side effects:
 *	Creates structure
 *
 *-------------------------------------------------------------------
 */
DigestState *Tls_DigestNew(Tcl_Interp *interp, int format) {
    DigestState *statePtr;

    statePtr = (DigestState *) ckalloc((unsigned) sizeof(DigestState));
    if (statePtr != NULL) {
	memset(statePtr, 0, sizeof(DigestState));
	statePtr->self	= NULL;		/* This socket channel */
	statePtr->timer = NULL;		/* Timer to flush data */
	statePtr->flags = 0;		/* Chan config flags */

 *
 * Side effects:
 *	Removes structure
 *
 *-------------------------------------------------------------------
 */
void Tls_DigestFree(DigestState *statePtr) {
    if (statePtr == (DigestState *) NULL) {
	return;
    }

    if (statePtr->ctx != (EVP_MD_CTX *) NULL) {
	EVP_MD_CTX_free(statePtr->ctx);
    }
    if (statePtr->hctx != (HMAC_CTX *) NULL) {
	HMAC_CTX_free(statePtr->hctx);
    }

    /* Open file channel */
    chan = Tcl_FSOpenFileChannel(interp, filename, "rb", 0444);
    if (chan == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Configure channel */
    if ((res = Tcl_SetChannelOption(interp, chan, "-translation", "binary")) == TCL_ERROR) {

	goto done;
    }
    Tcl_SetChannelBufferSize(chan, BUFFER_SIZE);

    /* Create state data struct */
    if ((statePtr = Tls_DigestNew(interp, format)) == NULL) {
	res = TCL_ERROR;
	goto done;
    }

    /* Initialize hash function */
    if ((res = Tls_DigestInit(interp, statePtr, md, keyObj)) != TCL_OK) {

    /* Finalize hash function and calculate message digest */
    res = Tls_DigestFinialize(interp, statePtr);

done:
    /* Close channel */
    if (Tcl_Close(interp, chan) == TCL_ERROR) {

	res = TCL_ERROR;

    }

    /* Clean-up */
    Tls_DigestFree(statePtr);
    return res;
}

 *	queued output is flushed prior to calling this function.
 *
 * Returns:
 *	0 if successful or POSIX error code if failed.
 *
 * Side effects:
 *	Writes digest to output and closes the channel. Stores error
 *	messages in interp result using Tcl_GetChannelErrorInterp.
 *
 *-------------------------------------------------------------------
 */
int DigestCloseProc(ClientData clientData, Tcl_Interp *interp) {
    DigestState *statePtr = (DigestState *) clientData;

    /* Cancel active timer, if any */

 */
int DigestInputProc(ClientData clientData, char *buf, int toRead, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    int read, res;
    *errorCodePtr = 0;

    /* Abort if nothing to process */
    if (toRead <= 0 || statePtr->self == (Tcl_Channel) NULL) {
	return 0;
    }

    /* Get bytes from underlying channel */
    parent = Tcl_GetStackedChannel(statePtr->self);
    read = Tcl_ReadRaw(parent, buf, toRead);

	    
    } else if (read < 0) {
	/* Error */
	*errorCodePtr = Tcl_GetErrno();

    } else if (!(statePtr->flags & CHAN_EOF)) {
	/* EOF */

	unsigned char md_buf[EVP_MAX_MD_SIZE];
	unsigned int md_len = 0;

	/* Finalize hash function and calculate message digest */
	if (statePtr->ctx != NULL) {
	    res = EVP_DigestFinal_ex(statePtr->ctx, md_buf, &md_len);
	} else {
	    res = HMAC_Final(statePtr->hctx, md_buf, &md_len);
	}
	if (!res) {
	    Tcl_SetChannelError(statePtr->self, Tcl_ObjPrintf("Digest finalize failed: %s", REASON()));
	    *errorCodePtr = EINVAL;

	/* Write message digest to output channel as byte array or hex string */
	} else if (md_len > 0) {
	    if (statePtr->format == BIN_FORMAT && toRead >= (int) md_len) {
		read = md_len;
		memcpy(buf, md_buf, read);

 *
 *----------------------------------------------------------------------
 */
 int DigestOutputProc(ClientData clientData, const char *buf, int toWrite, int *errorCodePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    *errorCodePtr = 0;

    /* Abort if nothing to process */
    if (toWrite <= 0 || statePtr->self == (Tcl_Channel) NULL) {
	return 0;
    }

    /* Update hash function */
    if (toWrite > 0 && !Tls_DigestUpdate(statePtr, buf, (size_t) toWrite)) {
	Tcl_SetChannelError(statePtr->self, Tcl_ObjPrintf("Digest update failed: %s", REASON()));

 */
static int DigestSetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,
	const char *optionValue) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverSetOptionProc *setOptionProc;

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Delegate options downstream */
    parent = Tcl_GetStackedChannel(statePtr->self);
    setOptionProc = Tcl_ChannelSetOptionProc(Tcl_GetChannelType(parent));

 */
static int DigestGetOptionProc(ClientData clientData, Tcl_Interp *interp, const char *optionName,
	Tcl_DString *optionValue) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverGetOptionProc *getOptionProc;

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Delegate options downstream */
    parent = Tcl_GetStackedChannel(statePtr->self);
    getOptionProc = Tcl_ChannelGetOptionProc(Tcl_GetChannelType(parent));

 *	May call Tcl_NotifyChannel
 *
 *----------------------------------------------------------------------
 */
static void DigestTimerHandler(ClientData clientData) {
    DigestState *statePtr = (DigestState *) clientData;

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return;
    }

    /* Clear timer token */
    statePtr->timer = (Tcl_TimerToken) NULL;

 *----------------------------------------------------------------------
 *
 * DigestWatchProc --
 *
 *	Initialize the notifier to watch for events from this channel.
 *
 * Returns:
 *	Nothing (can't return error messages)
 *
 * Side effects:
 *	Configure notifier so future events on the channel will be seen by Tcl.
 *
 *----------------------------------------------------------------------
 */
#define READ_DELAY	5
void DigestWatchProc(ClientData clientData, int mask) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;
    Tcl_DriverWatchProc *watchProc;

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return;
    }

    /* Store OR-ed combination of TCL_READABLE, TCL_WRITABLE and TCL_EXCEPTION */
    statePtr->watchMask = mask;

 * Side effects:
 *	None
 *
 *----------------------------------------------------------------------
 */
int DigestGetHandleProc(ClientData clientData, int direction, ClientData *handlePtr) {
    DigestState *statePtr = (DigestState *) clientData;
    Tcl_Channel parent;

    /* Abort if no channel */
    if (statePtr->self == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    parent = Tcl_GetStackedChannel(statePtr->self);
    return Tcl_GetChannelHandle(parent, direction, handlePtr);
}

/*
 *----------------------------------------------------------------------
 *
 * DigestNotifyProc --
 *

 *
 *	Create a stacked channel for a message digest transformation.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Adds transform to channel and sets result to channel id or error message.
 *
 *----------------------------------------------------------------------
 */
static int
Tls_DigestChannel(Tcl_Interp *interp, const char *channel, const EVP_MD *md, int format,
	Tcl_Obj *keyObj) {
    int mode; /* OR-ed combination of TCL_READABLE and TCL_WRITABLE */
    Tcl_Channel chan;
    DigestState *statePtr;



    /* Validate args */
    if (channel == (const char *) NULL || md == (const EVP_MD *) NULL) {
	return TCL_ERROR;
    }

    /* Get channel Id */
    chan = Tcl_GetChannel(interp, channel, &mode);
    if (chan == (Tcl_Channel) NULL) {
	return TCL_ERROR;
    }

    /* Make sure to operate on the topmost channel */
    chan = Tcl_GetTopChannel(chan);

    /* Create state data struct */
    if ((statePtr = Tls_DigestNew(interp, format)) == NULL) {
	Tcl_AppendResult(interp, "Initialize digest error: memory allocation failure", (char *) NULL);
	return TCL_ERROR;
    }
    statePtr->self = chan;
    statePtr->mode = mode;

    /* Stack channel */
    statePtr->self = Tcl_StackChannel(interp, &digestChannelType, (ClientData) statePtr, mode, chan);
    if (statePtr->self == (Tcl_Channel) NULL) {
	Tls_DigestFree(statePtr);
	return TCL_ERROR;
    }

    /* Set result to channel Id */
    Tcl_SetResult(interp, (char *) Tcl_GetChannelName(chan), TCL_VOLATILE);
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Unstack Channel --
 *
 *	This function removes the stacked channel from the top of the
 *	channel stack if it is a digest channel.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Removes transform from channel or sets result to error message.
 *
 *----------------------------------------------------------------------
 */
static int
UnstackObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    Tcl_Channel chan;
    int mode; /* OR-ed combination of TCL_READABLE and TCL_WRITABLE  */

    /* Validate arg count */
    if (objc != 2) {
	Tcl_WrongNumArgs(interp, 1, objv, "channel");
	return TCL_ERROR;
    }

    /* Get channel */
    chan = Tcl_GetChannel(interp, Tcl_GetStringFromObj(objv[1], NULL), &mode);

    if (Tcl_GetChannelType(chan) != &digestChannelType) {
	Tcl_AppendResult(interp, "bad channel \"", Tcl_GetChannelName(chan),
	    "\": not a digest channel", NULL);
	Tcl_SetErrorCode(interp, "TLS", "UNSTACK", "CHANNEL", "INVALID", (char *) NULL);
	return TCL_ERROR;
    }

    /* Pop transform from channel */
    return Tcl_UnstackChannel(interp, chan);



    	clientData = clientData;
}

/*******************************************************************/

static const char *instance_fns [] = { "finalize", "update", NULL };

/*
 *-------------------------------------------------------------------
 *
 * InstanceObjCmd --
 *
 *	Handler for digest command instances. Used to add data to hash
 *	function or retrieve message digest.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Adds data to hash or returns message digest
 *
 *-------------------------------------------------------------------
 */
int InstanceObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    DigestState *statePtr = (DigestState *) clientData;
    int fn, len = 0;
    char *buf = NULL;

    /* Validate arg count */
    if (objc < 2 || objc > 3) {
	Tcl_WrongNumArgs(interp, 1, objv, "function ?data?");
	return TCL_ERROR;
    }

    /* Get function */
    if (Tcl_GetIndexFromObj(interp, objv[1], instance_fns, "function", 0, &fn) != TCL_OK) {
	return TCL_ERROR;
    }

    /* Do function */
    if (fn) {
	/* Get data or return error if none */
	if (objc == 3) {
	    buf = Tcl_GetByteArrayFromObj(objv[2], &len);
	} else {
	    Tcl_WrongNumArgs(interp, 1, objv, "update data");
	    return TCL_ERROR;
	}

	/* Update hash function */
	if (!Tls_DigestUpdate(statePtr, buf, (size_t) len)) {
	    Tcl_SetObjResult(interp, Tcl_ObjPrintf("Digest update failed: %s", REASON()));
	    return TCL_ERROR;
	}

    } else {
	/* Finalize hash function and calculate message digest */

 *-------------------------------------------------------------------
 */
int Tls_DigestInstance(Tcl_Interp *interp, Tcl_Obj *cmdObj, const EVP_MD *md, int format,
	Tcl_Obj *keyObj) {
    DigestState *statePtr;
    char *cmdName = Tcl_GetStringFromObj(cmdObj, NULL);

    /* Create state data struct */
    if ((statePtr = Tls_DigestNew(interp, format)) == NULL) {
	Tcl_AppendResult(interp, "Initialize digest error: memory allocation failure", (char *) NULL);
	return TCL_ERROR;
    }

    /* Initialize hash function */
    if (Tls_DigestInit(interp, statePtr, md, keyObj) != TCL_OK) {

/*******************************************************************/

/*
 *-------------------------------------------------------------------
 *
 * Tls_DigestData --
 *
 *	Return message digest for data using user specified hash function.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Sets result to message digest or error message
 *
 *-------------------------------------------------------------------
 */
int
Tls_DigestData(Tcl_Interp *interp, int objc, Tcl_Obj *const objv[],
	const EVP_MD *md, int format, Tcl_Obj *keyObj) {
    char *data;
    int len, res;
    unsigned int md_len;
    unsigned char md_buf[EVP_MAX_MD_SIZE];

    /* Validate arg count */
    if (objc != 2) {
	Tcl_WrongNumArgs(interp, 1, objv, "data");
	return TCL_ERROR;
    }

    /* Get data */
    data = Tcl_GetByteArrayFromObj(objv[1], &len);

 * Side effects:
 *	Sets result to message digest or error message
 *
 *-------------------------------------------------------------------
 */
static int
DigestObjCmd(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    int idx, len, format = HEX_FORMAT, res = TCL_OK;
    const char *digestname, *channel = NULL;
    Tcl_Obj *cmdObj = NULL, *dataObj = NULL, *fileObj = NULL, *keyObj = NULL;

    const EVP_MD *md;

    /* Clear interp result */
    Tcl_ResetResult(interp);

    /* Validate arg count */
    if (objc < 3 || objc > 7) {
	Tcl_WrongNumArgs(interp, 1, objv, "type ?-bin|-hex? ?-key hmac_key? [-channel chan | -command cmdName | -file filename | ?-data? data]");
	return TCL_ERROR;
    }

    /* Get digest */
    digestname = Tcl_GetStringFromObj(objv[1], &len);

	return Tls_DigestData(interp, --objc, ++objv, md, format, NULL);
    }

    /* Get options */
    for (idx = 2; idx < objc-1; idx++) {
	char *opt = Tcl_GetStringFromObj(objv[idx], NULL);

	if (opt[0] != '-') {
	    break;
	}

	OPTFLAG("-bin", format, BIN_FORMAT);
	OPTFLAG("-binary", format, BIN_FORMAT);
	OPTFLAG("-hex", format, HEX_FORMAT);
	OPTFLAG("-hexadecimal", format, HEX_FORMAT);

	OPTSTR("-chan", channel);
	OPTSTR("-channel", channel);
	OPTOBJ("-command", cmdObj);
	OPTOBJ("-data", dataObj);
	OPTOBJ("-file", fileObj);
	OPTOBJ("-filename", fileObj);
	OPTOBJ("-key", keyObj);

	OPTBAD("option", "-bin, -channel, -command, -data, -file, -filename, -hex, or -key");
	return TCL_ERROR;
    }

    /* If no option for last arg, then its the data */
    if (idx < objc) {
	dataObj = objv[idx];
    }

    /* Calc digest on file, stacked channel, using instance command, or data blob */
    if (fileObj != NULL) {
	res = Tls_DigestFile(interp, fileObj, md, format, keyObj);
    } else if (channel != NULL) {
	res = Tls_DigestChannel(interp, channel, md, format, keyObj);
    } else if (cmdObj != NULL) {
	res = Tls_DigestInstance(interp, cmdObj, md, format, keyObj);
    } else if (dataObj != NULL) {

 * Side effects:
 *	None.
 *
 *-------------------------------------------------------------------
 */
void NamesCallback(const OBJ_NAME *obj, void *arg) {
    Tcl_Obj *objPtr = (Tcl_Obj *) arg;

    /* Fields: (int) type and alias, (const char*) name and data */
    if (1 || !obj->alias) {
	/* Filter out signed digests (a.k.a signature algorithms) */
	if (strstr(obj->name, "rsa") == NULL && strstr(obj->name, "RSA") == NULL) {
	    Tcl_ListObjAppendElement(NULL, objPtr, Tcl_NewStringObj(obj->name,-1));
	}
    }
}