/*
 * Provides Custom BIO layer to interface OpenSSL with TCL. These functions
 * directly interface between the TCL IO channel and BIO buffers.
 *
 * Copyright (C) 1997-2000 Matt Newman <[email protected]>
 * Copyright (C) 2024 Brian O'Hagan
 *
 */

/*
		tlsBIO.c				tlsIO.c
  +------+                         +-----+                                     +------+
  |      |Tcl_WriteRaw <-- BioWrite| SSL |BIO_write <-- TlsOutputProc <-- Write|      |
  |socket|      <encrypted>        | BIO |            <unencrypted>            | App  |
  |      |Tcl_ReadRaw  -->  BioRead|     |BIO_Read  --> TlsInputProc  -->  Read|      |
  +------+                         +-----+                                     +------+
*/

#include "tlsInt.h"
#include <openssl/bio.h>

/* Define BIO methods structure */
static BIO_METHOD *BioMethods = NULL;

    return res;
}

/*
 *-----------------------------------------------------------------------------
 *
 * BioWrite --
 *
 *	This function is used to read encrypted data from the BIO and write it
 *	into the socket. This function will be called in response to the
 *	application calling the BIO_write_ex() or BIO_write() functions.
 *
 * Results:
 *	Returns the number of bytes written to channel, 0 for EOF, or -1 for
 *	error.
 *
 * Side effects:
 *	Writes BIO data to channel.
 *
 *-----------------------------------------------------------------------------
 */

static int BioWrite(BIO *bio, const char *buf, int bufLen) {
    Tcl_Size ret;
    int is_eof, tclErrno;
    State *statePtr = (State *) BIO_get_data(bio);
    Tcl_Channel chan = Tls_GetParent(statePtr, 0);

    dprintf("[chan=%p] BioWrite(bio=%p, buf=%p, len=%d)", (void *)chan, (void *) bio, buf, bufLen);


    BIO_clear_retry_flags(bio);
    Tcl_SetErrno(0);

    /* Write data to underlying channel */
    ret = Tcl_WriteRaw(chan, buf, (Tcl_Size) bufLen);
    is_eof = Tcl_Eof(chan);
    tclErrno = Tcl_GetErrno();

    dprintf("[chan=%p] BioWrite(%d) -> %" TCL_SIZE_MODIFIER "d [tclEof=%d; tclErrno=%d: %s]",
	(void *) chan, bufLen, ret, is_eof, tclErrno, Tcl_ErrnoMsg(tclErrno));

    if (ret > 0) {
	dprintf("Successfully wrote %" TCL_SIZE_MODIFIER "d bytes of data", ret);

    } else if (ret == 0) {
	if (is_eof) {

	    BIO_set_retry_write(bio);

	} else {
	    dprintf("Unexpected error: %i=%s", tclErrno, Tcl_ErrnoMsg(tclErrno));
	}
    }

    dprintf("BioWrite returning %" TCL_SIZE_MODIFIER "d", ret);
    return (int) ret;
}

/*
 *-----------------------------------------------------------------------------
 *
 * BioRead --
 *
 *	This function is used to read encrypted data from the socket and
 *	write it into the BIO. This function will be called in response to the
 *	application calling the BIO_read_ex() or BIO_read() functions.
 *
 * Results:
 *	Returns the number of bytes read from channel, 0 for EOF, or -1 for

 * returns the number of bytes which have been processed, buffered, and are
 * available inside ssl for immediate read. SSL_has_pending() returns 1 if
 * data is buffered (whether processed or unprocessed) and 0 otherwise.
 *
 *-----------------------------------------------------------------------------
 */

static int BioRead(BIO *bio, char *buf, int bufLen) {
    Tcl_Size ret = 0;
    int is_eof, tclErrno, is_blocked;
    State *statePtr = (State *) BIO_get_data(bio);
    Tcl_Channel chan = Tls_GetParent(statePtr, 0);

    dprintf("[chan=%p] BioRead(bio=%p, buf=%p, len=%d)", (void *) chan, (void *) bio, buf, bufLen);


    if (buf == NULL || bufLen <= 0) {
	return 0;
    }

    BIO_clear_retry_flags(bio);
    Tcl_SetErrno(0);

    /* Read data from underlying channel */
    ret = Tcl_ReadRaw(chan, buf, (Tcl_Size) bufLen);

    is_eof = Tcl_Eof(chan);
    tclErrno = Tcl_GetErrno();
    is_blocked = Tcl_InputBlocked(chan);

    dprintf("[chan=%p] BioRead(%d) -> %" TCL_SIZE_MODIFIER "d [tclEof=%d; blocked=%d; tclErrno=%d: %s]",
	(void *) chan, bufLen, ret, is_eof, is_blocked, tclErrno, Tcl_ErrnoMsg(tclErrno));

    if (ret > 0) {
	dprintf("Successfully read %" TCL_SIZE_MODIFIER "d bytes of data", ret);

    } else if (ret == 0) {
	if (is_eof) {

	    BIO_set_retry_read(bio);

	} else {
	    dprintf("Unexpected error: %i=%s", tclErrno, Tcl_ErrnoMsg(tclErrno));
	}
    }

    dprintf("BioRead returning %" TCL_SIZE_MODIFIER "d", ret);
    return (int) ret;
}

/*
 *-----------------------------------------------------------------------------
 *
 * BioPuts --

 *
 *-----------------------------------------------------------------------------
 */

static int BioPuts(BIO *bio, const char *str) {
    dprintf("BioPuts(%p) \"%s\"", bio, str);

    return BioWrite(bio, str, (int) strlen(str));
}

/*
 *-----------------------------------------------------------------------------
 *
 * BioCtrl --
 *

		break;
	case BIO_CTRL_FLUSH:
		/* opt - Flush any buffered output. Implements BIO_flush. */
		dprintf("Got BIO_CTRL_FLUSH");
		/* Use Tcl_WriteRaw instead of Tcl_Flush to operate on right chan in stack */
		/* Returns 1 for success, <=0 for error/retry. */
		ret = ((chan) && (Tcl_WriteRaw(chan, "", 0) >= 0) ? 1 : -1);
		/*ret = BioWrite(bio, NULL, 0);*/
		break;
	case BIO_CTRL_DUP:
		/* man - extra stuff for 'duped' BIO. Implements BIO_dup_state */
		dprintf("Got BIO_CTRL_DUP");
		ret = 1;
		break;
	case BIO_CTRL_WPENDING:

	BioMethods = BIO_meth_new(BIO_TYPE_BIO, "tcl");
	if (BioMethods == NULL) {
	    dprintf("Memory allocation error");

	    return NULL;
	}
	/* Not used BIO_meth_set_write_ex */
	BIO_meth_set_write(BioMethods, BioWrite);
	/* Not used BIO_meth_set_read_ex */
	BIO_meth_set_read(BioMethods, BioRead);
	BIO_meth_set_puts(BioMethods, BioPuts);
	BIO_meth_set_ctrl(BioMethods, BioCtrl);
	BIO_meth_set_create(BioMethods, BioNew);
	BIO_meth_set_destroy(BioMethods, BioFree);
    }

    if (statePtr == NULL) {
	dprintf("Asked to setup a NULL state, just creating the initial configuration");

	return NULL;
    }

#ifdef TCLTLS_SSL_USE_FASTPATH
    /*
     * If the channel can be mapped back to a file descriptor, just use the file descriptor
     * with the SSL library since it will likely be optimized for this.
     */
    parentChannel = Tls_GetParent(statePtr, 0);
    parentChannelType = Tcl_GetChannelType(parentChannel);

    validParentChannelFd = 0;
    if (strcmp(parentChannelType->typeName, "tcp") == 0) {
	void *parentChannelFdIn_p, *parentChannelFdOut_p;
	int tclGetChannelHandleRet;

	tclGetChannelHandleRet = Tcl_GetChannelHandle(parentChannel, TCL_READABLE, &parentChannelFdIn_p);

	if (tclGetChannelHandleRet == TCL_OK) {
	    tclGetChannelHandleRet = Tcl_GetChannelHandle(parentChannel, TCL_WRITABLE, &parentChannelFdOut_p);

	    if (tclGetChannelHandleRet == TCL_OK) {
		parentChannelFdIn = PTR2INT(parentChannelFdIn_p);
		parentChannelFdOut = PTR2INT(parentChannelFdOut_p);
		if (parentChannelFdIn == parentChannelFdOut) {
		    parentChannelFd = parentChannelFdIn;
		    validParentChannelFd = 1;
		}
	    }
	}
    }

    if (validParentChannelFd) {
	dprintf("We found a shortcut, this channel is backed by a socket: %i", parentChannelFdIn);

	bio = BIO_new_socket(parentChannelFd, flags);
	statePtr->flags |= TLS_TCL_FASTPATH;
	BIO_set_data(bio, statePtr);
	BIO_set_shutdown(bio, flags);
	BIO_set_init(bio, 1);
	return bio;
    }