/*++
/* NAME
/*	tls_bio_ops 3
/* SUMMARY
/*	TLS network BIO management
/* SYNOPSIS
/*	#define TLS_INTERNAL
/*	#include <tls.h>
/*
/*	int tls_bio_connect(fd, timeout, context)
/*	int	fd;
/*	int	timeout;
/*	TLS_SESS_STATE *context;
/*
/*	int tls_bio_accept(fd, timeout, context)
/*	int	fd;
/*	int	timeout;
/*	TLS_SESS_STATE *context;
/*
/*	int tls_bio_shutdown(fd, timeout, context)
/*	int	fd;
/*	int	timeout;
/*	TLS_SESS_STATE *context;
/*
/*	int tls_bio_read(fd, buf, len, timeout, context)
/*	int	fd;
/*	void	*buf;
/*	int	len;
/*	int	timeout;
/*	TLS_SESS_STATE *context;
/*
/*	int tls_bio_write(fd, buf, len, timeout, context)
/*	int	fd;
/*	void	*buf;
/*	int	len;
/*	int	timeout;
/*	TLS_SESS_STATE *context;
/* DESCRIPTION
/*	This layer synchronizes the TLS network buffers with the network
/*	while performing TLS handshake or input/output operations.
/*
/*	When the TLS layer is active, it converts plain-text
/*	data from Postfix into encrypted network data and vice versa.
/*	However, to handle network timeout conditions, Postfix
/*	needs to maintain control over network input/output. This
/*	rules out the usual approach of placing the TLS layer
/*	between the application and the network socket.
/*
/*	As shown below, Postfix reads/writes plain-text data from/to
/*	the TLS layer. The TLS layer informs Postfix when it needs
/*	to read/write encrypted data from/to the network; Postfix
/*	then reads/writes encrypted data from/to the TLS layer and
/*	takes care of the network socket I/O.
/*
/*	The TLS layer to network interface is realized with a BIO pair:
/*
/*	 Postfix             |   TLS layer
/*	                     |
/*	smtp/smtpd           |
/*	 /\    ||            |
/*	 ||    \/            |
/*	vstream read/write <===> TLS read/write/etc
/*	                     |     /\    ||
/*	                     |     ||    \/
/*	                     |   BIO pair (internal_bio)
/*	                     |   BIO pair (network_bio)
/*	                     |     /\    ||
/*	                     |     ||    \/
/*	socket read/write  <===> BIO read/write
/*	 /\    ||            |
/*	 ||    \/            |
/*	 network             |
/*
/*	The Postfix VSTREAM read/write operations invoke the SSL
/*	read/write operations to send and retrieve plain-text data. Inside
/*	the TLS layer the data are converted to/from TLS protocol.
/*
/*	Whenever an SSL operation reports success, or whenever it
/*	indicates that network input/output needs to happen, Postfix
/*	uses the BIO read/write routines to synchronize the
/*	network_bio buffer with the network.  Writing data to the
/*	network has precedence over reading from the network. This
/*	is necessary to avoid deadlock.
/*
/*	The BIO pair buffer size is set to 8192 bytes. This is much
/*	larger than the typical Path MTU, and avoids sending tiny TCP
/*	segments.  It is also larger than the default VSTREAM_BUFSIZE
/*	(4096, see vstream.h), so that large write operations can
/*	be handled within one request.  The internal buffer in the
/*	network/network_bio handling layer is set to the same
/*	value, since this seems to be reasonable. The code is
/*	however able to handle arbitrary values smaller or larger
/*	than the buffer size in the BIO pair.
/*
/*	tls_bio_connect() performs the SSL_connect() operation while
/*	synchronizing the network_bio buffer with the network.
/*
/*	tls_bio_accept() performs the SSL_accept() operation while
/*	synchronizing the network_bio buffer with the network.
/*
/*	tls_bio_shutdown() performs the SSL_shutdown() operation while
/*	synchronizing the network_bio buffer with the network.
/*
/*	tls_bio_read() performs the SSL_read() operation while
/*	synchronizing the network_bio buffer with the network.
/*
/*	tls_bio_write() performs the SSL_write() operation while
/*	synchronizing the network_bio buffer with the network.
/*
/*	Arguments:
/* .IP fd
/*	Network socket.
/* .IP buf
/*	Read/write buffer.
/* .IP len
/*	Read/write request size.
/* .IP timeout
/*	Read/write timeout.
/* .IP TLScontext
/*	TLS session state.
/* DIAGNOSTICS
/*	The result value is -1 in case of a network read/write
/*	error, otherwise it is the result value of the TLS operation.
/* LICENSE
/* .ad
/* .fi
/*	This software is free. You can do with it whatever you want.
/*	The original author kindly requests that you acknowledge
/*	the use of his software.
/* AUTHOR(S)
/*	Originally written by:
/*	Lutz Jaenicke
/*	BTU Cottbus
/*	Allgemeine Elektrotechnik
/*	Universitaetsplatz 3-4
/*	D-03044 Cottbus, Germany
/*
/*	Updated by:
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Victor Duchovni
/*	Morgan Stanley
/*--*/

/* System library. */

#include <sys_defs.h>

#ifdef USE_TLS

/* Utility library. */

#include <msg.h>
#include <iostuff.h>

/* TLS library. */

#define TLS_INTERNAL
#include <tls.h>

/* Application-specific. */

#define NETLAYER_BUFFERSIZE 8192

/* network_biopair_interop - synchronize network with BIO pair */

static int network_biopair_interop(int fd, int timeout, BIO *network_bio)
{
    const char *myname = "network_biopair_interop";
    int     want_write;
    int     num_write;
    int     write_pos;
    int     from_bio;
    int     want_read;
    int     num_read;
    int     to_bio;
    char    buffer[NETLAYER_BUFFERSIZE];

    /*
     * To avoid deadlock, write all pending data to the network before
     * attempting to read from the network.
     */
    while ((want_write = BIO_ctrl_pending(network_bio)) > 0) {
	if (want_write > sizeof(buffer))
	    want_write = sizeof(buffer);
	from_bio = BIO_read(network_bio, buffer, want_write);

	/*
	 * Write the complete buffer contents to the network.
	 */
	for (write_pos = 0; write_pos < from_bio; /* see below */ ) {
	    if (timeout > 0 && write_wait(fd, timeout) < 0)
		return (-1);
	    num_write = write(fd, buffer + write_pos, from_bio - write_pos);
	    if (num_write <= 0) {
		if ((num_write < 0) && (timeout > 0) && (errno == EAGAIN)) {
		    msg_warn("write() returns EAGAIN on a writable file descriptor!");
		    msg_warn("pausing to avoid going into a tight select/write loop!");
		    sleep(1);
		} else {
		    msg_warn("%s: error writing %d bytes to the network: %m",
			     myname, from_bio - write_pos);
		    return (-1);
		}
	    } else {
		write_pos += num_write;
	    }
	}
    }

    /*
     * Read data from the network into the BIO pair.
     */
    while ((want_read = BIO_ctrl_get_read_request(network_bio)) > 0) {
	if (want_read > sizeof(buffer))
	    want_read = sizeof(buffer);
	if (timeout > 0 && read_wait(fd, timeout) < 0)
	    return (-1);
	num_read = read(fd, buffer, want_read);
	if (num_read == 0)
	    /* FIX 200412 Cannot return a zero read count. */
	    return (-1);
	if (num_read < 0) {
	    if ((num_read < 0) && (timeout > 0) && (errno == EAGAIN)) {
		msg_warn("read() returns EAGAIN on a readable file descriptor!");
		msg_warn("pausing to avoid going into a tight select/write loop!");
		sleep(1);
	    } else {
		msg_warn("%s: error reading %d bytes from the network: %m",
			 myname, want_read);
		return (-1);
	    }
	} else {
	    to_bio = BIO_write(network_bio, buffer, num_read);
	    if (to_bio != num_read)
		msg_panic("%s: BIO_write error: to_bio != num_read", myname);
	}
    }
    return (0);
}

/* tls_bio - perform SSL input/output operation with extreme prejudice */

int     tls_bio(int fd, int timeout, TLS_SESS_STATE *TLScontext,
		        int (*hsfunc) (SSL *),
		        int (*rfunc) (SSL *, void *, int),
		        int (*wfunc) (SSL *, const void *, int),
		        void *buf, int num)
{
    const char *myname = "tls_bio";
    int     status;
    int     err;
    int     retval = 0;
    int     biop_retval;
    int     done;

    /*
     * If necessary, retry the SSL handshake or read/write operation after
     * handling any pending network I/O.
     */
    for (done = 0; done == 0; /* void */ ) {
	if (hsfunc)
	    status = hsfunc(TLScontext->con);
	else if (rfunc)
	    status = rfunc(TLScontext->con, buf, num);
	else if (wfunc)
	    status = wfunc(TLScontext->con, buf, num);
	else
	    msg_panic("%s: nothing to do here", myname);
	err = SSL_get_error(TLScontext->con, status);

#if (OPENSSL_VERSION_NUMBER <= 0x0090581fL)

	/*
	 * There is a bug up to and including OpenSSL-0.9.5a: if an error
	 * occurs while checking the peers certificate due to some
	 * certificate error (e.g. as happend with a RSA-padding error), the
	 * error is put onto the error stack. If verification is not
	 * enforced, this error should be ignored, but the error-queue is not
	 * cleared, so we can find this error here. The bug has been fixed on
	 * May 28, 2000.
	 * 
	 * This bug so far has only manifested as 4800:error:0407006A:rsa
	 * routines:RSA_padding_check_PKCS1_type_1:block type is not
	 * 01:rsa_pk1.c:100: 4800:error:04067072:rsa
	 * routines:RSA_EAY_PUBLIC_DECRYPT:padding check
	 * failed:rsa_eay.c:396: 4800:error:0D079006:asn1 encoding
	 * routines:ASN1_verify:bad get asn1 object call:a_verify.c:109: so
	 * that we specifically test for this error. We print the errors to
	 * the logfile and automatically clear the error queue. Then we retry
	 * to get another error code. We cannot do better, since we can only
	 * retrieve the last entry of the error-queue without actually
	 * cleaning it on the way.
	 * 
	 * This workaround is secure, as verify_result is set to "failed"
	 * anyway.
	 */
	if (err == SSL_ERROR_SSL) {
	    if (ERR_peek_error() == 0x0407006AL) {
		tls_print_errors();
		msg_info("OpenSSL <= 0.9.5a workaround called: certificate errors ignored");
		err = SSL_get_error(TLScontext->con, status);
	    }
	}
#endif

	/*
	 * Find out if we must retry the operation and/or if there is pending
	 * network I/O.
	 * 
	 * XXX If we're the first to invoke SSL_shutdown(), then the operation
	 * isn't really complete when the call returns. We could hide that
	 * anomaly here and repeat the call.
	 */
	switch (err) {
	case SSL_ERROR_NONE:			/* success */
	    retval = status;
	    done = 1;
	    /* FALLTHROUGH */
	case SSL_ERROR_WANT_WRITE:		/* flush/update buffers */
	case SSL_ERROR_WANT_READ:
	    biop_retval =
		network_biopair_interop(fd, timeout, TLScontext->network_bio);
	    if (biop_retval < 0)
		return (-1);			/* network read/write error */
	    break;

	    /*
	     * With tls_timed_read() and tls_timed_write() the caller is the
	     * VSTREAM library module which is unaware of TLS, so we log the
	     * TLS error stack here. In a better world, each VSTREAM I/O
	     * object would provide an error reporting method in addition to
	     * the timed_read and timed_write methods, so that we would not
	     * need to have ad-hoc code like this.
	     */
	case SSL_ERROR_SSL:
	    if (rfunc || wfunc)
		tls_print_errors();
	    /* FALLTHROUGH */
	default:
	    retval = status;
	    done = 1;
	    break;
	}
    }
    return (retval);
}

#endif
