prot.c

/* prot.c -- stdio-like module that handles SASL protection mechanisms
 *
 * Copyright (c) 1994-2008 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * $Id: prot.c,v 1.100 2010/06/28 12:06:43 brong Exp $
 */

#include <config.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <syslog.h>
#include <signal.h>
#include <stdarg.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <netinet/in.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#include "assert.h"
#include "exitcodes.h"
#include "imparse.h"
#include "libcyr_cfg.h"
#include "map.h"
#include "nonblock.h"
#include "prot.h"
#include "signals.h"
#include "util.h"
#include "xmalloc.h"

/* Transparant protgroup structure */
struct protgroup
{
    size_t nalloced; /* Number of nodes in the group */
    size_t next_element; /* Node number of next group member */
    struct protstream **group;
};

/*
 * Create a new protection stream for file descriptor 'fd'.  Stream
 * will be used for writing iff 'write' is nonzero.
 */
struct protstream *prot_new(int fd, int write)
{
    struct protstream *newstream;

    newstream = (struct protstream *) xzmalloc(sizeof(struct protstream));
    newstream->buf = (unsigned char *) 
	xmalloc(sizeof(char) * (PROT_BUFSIZE));
    newstream->buf_size = PROT_BUFSIZE;
    newstream->ptr = newstream->buf;
    newstream->maxplain = PROT_BUFSIZE;
    newstream->fd = fd;
    newstream->write = write;
    newstream->logfd = PROT_NO_FD;
    newstream->big_buffer = PROT_NO_FD;
    if(write)
	newstream->cnt = PROT_BUFSIZE;

    return newstream;
}

struct protstream *prot_writebuf(struct buf *buf)
{
    struct protstream *newstream;

    newstream = (struct protstream *) xzmalloc(sizeof(struct protstream));
    /* dodgy, but the alternative is two pointers */
    newstream->buf = (unsigned char *) 
	xmalloc(sizeof(char) * (PROT_BUFSIZE));
    newstream->buf_size = PROT_BUFSIZE;
    newstream->ptr = newstream->buf;
    newstream->cnt = PROT_BUFSIZE;
    newstream->maxplain = PROT_BUFSIZE;
    newstream->write = 1;
    newstream->writetobuf = buf;
    newstream->fd = PROT_NO_FD;
    newstream->logfd = PROT_NO_FD;
    newstream->big_buffer = PROT_NO_FD;

    return newstream;
}

/* Create a protstream which is just an interface to a mapped piece of
 * memory, allowing prot commands to be used to read from it */
struct protstream *prot_readmap(const char *base, uint32_t len)
{
    struct protstream *newstream;

    newstream = (struct protstream *) xzmalloc(sizeof(struct protstream));
    /* dodgy, but the alternative is two pointers */
    newstream->ptr = (unsigned char *)base;
    newstream->cnt = len;
    newstream->fixedsize = 1;
    newstream->fd = PROT_NO_FD;
    newstream->logfd = PROT_NO_FD;
    newstream->big_buffer = PROT_NO_FD;

    return newstream;
}

/*
 * Free a protection stream
 */
int prot_free(struct protstream *s)
{
    if (s->error) free(s->error);
    free(s->buf);

    if(s->big_buffer != PROT_NO_FD) {
	map_free(&(s->bigbuf_base), &(s->bigbuf_siz));
	close(s->big_buffer);
    }

#ifdef HAVE_ZLIB
    if (s->zstrm) {
	if (s->write) deflateEnd(s->zstrm);
	else inflateEnd(s->zstrm);
	free(s->zstrm);
    }
    if (s->zbuf) free(s->zbuf);
#endif

    free(s);

    return 0;
}

/*
 * Set the logging file descriptor for stream 's' to be 'fd'.
 */
int prot_setlog(struct protstream *s, int fd)
{
    s->logfd = fd;
    return 0;
}

int prot_setisclient(struct protstream *s, int val)
{
    s->isclient = val;
    return 0;
}

#ifdef HAVE_SSL

/*
 * Turn on TLS for this connection
 */

int prot_settls(struct protstream *s, SSL *tlsconn)
{
    s->tls_conn = tlsconn;

    /* Make nonblocking stuff to work similar to write() */
    SSL_set_mode(tlsconn,
		 SSL_MODE_ENABLE_PARTIAL_WRITE
		 | SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);

    return 0;
}

#endif /* HAVE_SSL */

/*
 * Decode data sent via a SASL security layer. Returns EOF on error.
 */
int prot_sasldecode(struct protstream *s, int n)
{
    int result;
    const char *out;
    unsigned outlen;
    
    assert(!s->write);

    /* decode the input */
    result = sasl_decode(s->conn, (const char *) s->buf, n, 
			 &out, &outlen);

    if (result != SASL_OK) {
	char errbuf[256];
	const char *ed = sasl_errdetail(s->conn);

	snprintf(errbuf, 256, "decoding error: %s; %s",
		 sasl_errstring(result, NULL, NULL),
		 ed ? ed : "no detail");
	s->error = xstrdup(errbuf);
	return EOF;
    }
   
    if (outlen > 0) {
      /* The contents of 'out' is static until next call to
	 sasl_decode(), so serve data directly from 'out' */
	s->ptr = (unsigned char *) out;
	s->cnt = outlen;
    } else {		/* didn't decode anything */
	s->cnt = 0;
    }

    return 0;
}

/*
 * Turn on SASL for this connection
 */

int prot_setsasl(struct protstream *s, sasl_conn_t *conn)
{
    const void *ssfp;
    int result;

    if (s->write && s->ptr != s->buf) {
	/* flush any pending output */
	if (prot_flush_internal(s, 0) == EOF)
	    return EOF;
    }
   
    s->conn = conn;

    result = sasl_getprop(conn, SASL_SSF, &ssfp);
    if (result != SASL_OK) {
	return -1;
    }
    s->saslssf = *((const int *) ssfp);

    if (s->write) {
	const void *maxp;
	unsigned int max;

	/* ask SASL for layer max */
	result = sasl_getprop(conn, SASL_MAXOUTBUF, &maxp);
	max = *((const unsigned int *) maxp);
	if (result != SASL_OK) {
	    return -1;
	}

	if (max == 0 || max > PROT_BUFSIZE) {
	    /* max = 0 means unlimited, and we can't go bigger */
	    max = PROT_BUFSIZE;
	}
    
	s->maxplain = max;
	s->cnt = max;
    }
    else if (s->cnt) {  
	/* decode any pending input */
	if (prot_sasldecode(s, s->cnt) == EOF) return EOF;
    }

    return 0;
}

/*
 * Turn off SASL for this connection
 */

void prot_unsetsasl(struct protstream *s)
{
    s->conn = NULL;
    s->maxplain = PROT_BUFSIZE;
    s->saslssf = 0;
}

#ifdef HAVE_ZLIB

#define ZLARGE_DIFF_CHUNK (5120) /* 5K */

/* Wrappers for our memory management functions */
static voidpf zalloc(voidpf opaque __attribute__((unused)),
		     uInt items, uInt size)
{
    return (voidpf) xmalloc(items * size);
}

static void zfree(voidpf opaque __attribute__((unused)),
		  voidpf address)
{
    free(address);
}

/*
 * Turn on (de)compression for this connection
 * If its an output stream, initialize a compressor,
 * otherwise initialize a decompressor.
 */

int prot_setcompress(struct protstream *s)
{
    int zr = Z_OK;
    z_stream *zstrm = (z_stream *) xmalloc(sizeof(z_stream));

    zstrm->zalloc = zalloc;
    zstrm->zfree = zfree;
    zstrm->opaque = Z_NULL;

    if (s->write) {
	if (s->ptr != s->buf) {
	    /* flush any pending output */
	    if (prot_flush_internal(s, 0) == EOF)
	        goto error;
	}

	s->zlevel = Z_DEFAULT_COMPRESSION;
	zr = deflateInit2(zstrm, s->zlevel, Z_DEFLATED,
		          -MAX_WBITS,		/* raw deflate */
			  MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY);
    }
    else {
	zstrm->next_in = Z_NULL;
	zstrm->avail_in = 0;
	zr = inflateInit2(zstrm, -MAX_WBITS);	/* raw inflate */
    }

    if (zr != Z_OK)
	goto error;

    /* RFC 1951 says:
     * A simple counting argument shows that no lossless compression
     * algorithm can compress every possible input data set.  For the
     * format defined here, the worst case expansion is 5 bytes per 32K-
     * byte block, i.e., a size increase of 0.015% for large data sets.
     *
     * We say: maxplain can never be bigger than PROT_BUFSIZE, which
     * is currently 4096, so adding 5 bytes will do it!
     * 
     * Add another spare byte and we'll never totally fill the buffer,
     * which saves a loop.
     *
     * NOTE: we do double check and handle buffer filling gracefully
     * anyway, but starting with the right size is good.
     */
    s->zbuf_size = s->maxplain + 6;
    s->zbuf = (unsigned char *) xmalloc(sizeof(unsigned char) * s->zbuf_size);
    syslog(LOG_DEBUG, "created %scompress buffer of %u bytes",
	   s->write ? "" : "de", s->zbuf_size);
    s->zstrm = zstrm;

    return 0;

error:
    syslog(LOG_NOTICE, "failed to start %scompression",
	   s->write ? "" : "de");
    free(zstrm);
    return EOF;
}

/* Table of incompressible file type signatures */
static struct file_sig {
    const char *type;
    size_t len;
    const char *sig;
} sig_tbl[] = {
    { "GIF87a",	6, "GIF87a" },
    { "GIF89a",	6, "GIF89a" },
    { "GZIP",	2, "\x1F\x8B" },
    { "JPEG",	4, "\xFF\xD8\xFF\xE0" },
    { "PNG",	8, "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A" },
    { NULL,	0, NULL }
};

/* Check if a chunk of data is incompressible */
static int is_incompressible(const char *p, size_t n)
{
    struct file_sig *sig = sig_tbl;

    /* is it worth checking? */
    if (n < ZLARGE_DIFF_CHUNK) return 0;

    while (sig->type) {
	if (n >= sig->len && !memcmp(p, sig->sig, sig->len)) {
	    syslog(LOG_DEBUG, "data is %s", sig->type);
	    return 1;
	}
	sig++;
    }

    return 0;
}

#endif /* HAVE_ZLIB */

/* Tell the protstream that the type of data is about to change.
 * Since we might want to look at the data, we only set a flag and delay
 * any changes to the stream layers until the next prot_write().
 */
int prot_data_boundary(struct protstream *s)
{
    s->boundary = 1;
    return 0;
}

/*
 * Set the read timeout for the stream 's' to 'timeout' seconds.
 * 's' must have been created for reading.
 */
int prot_settimeout(struct protstream *s, int timeout)
{
    assert(!s->write);

    s->read_timeout = timeout;
    s->timeout_mark = time(NULL) + timeout;
    return 0;
}

/*
 * Reset the read timeout_mark for the stream 's'.
 * 'S' must have been created for reading.
 */
int prot_resettimeout(struct protstream *s)
{
    assert(!s->write);

    s->timeout_mark = time(NULL) + s->read_timeout;
    return 0;
}

/*
 * Set the stream 's' to flush the stream 'flushs' before
 * blocking for reading. 's' must have been created for reading,
 * 'flushs' for writing.
 */
int prot_setflushonread(struct protstream *s, struct protstream *flushs)
{
    assert(!s->write);
    if(flushs) assert(flushs->write);

    s->flushonread = flushs;
    return 0;
}

/*
 * Set on stream 's' the callback 'proc' and 'rock'
 * to make the next time we have to wait for input.
 */
int prot_setreadcallback(struct protstream *s, 
			 prot_readcallback_t *proc, void *rock)
{
    assert(!s->write);

    s->readcallback_proc = proc;
    s->readcallback_rock = rock;
    return 0;
}

/*
 * Add an event on stream 's' so that the callback 'proc' taking
 * argument 'rock' will be called at 'mark' (in seconds) while
 * waiting for input.
 */
struct prot_waitevent *prot_addwaitevent(struct protstream *s, time_t mark,
					 prot_waiteventcallback_t *proc,
					 void *rock)
{
    struct prot_waitevent *new, *cur;

    /* if we aren't passed a callback function, don't bother */
    if (!proc) return s->waitevent;

    /* create new timer struct */
    new = (struct prot_waitevent *) xmalloc(sizeof(struct prot_waitevent));
    new->mark = mark;
    new->proc = proc;
    new->rock = rock;
    new->next = NULL;

    /* add the new event to the end of the list */
    if (!s->waitevent)
	s->waitevent = new;
    else {
	cur = s->waitevent;
	while (cur && cur->next) cur = cur->next;
	cur->next = new;
    }

    return new;
}

/*
 * Remove 'event' from stream 's'.
 */
void prot_removewaitevent(struct protstream *s, struct prot_waitevent *event)
{
    struct prot_waitevent *prev, *cur;

    prev = NULL;
    cur = s->waitevent;

    while (cur && cur != event) {
	prev = cur;
	cur = cur->next;
    }

    if (!cur) return;

    if (!prev)
	s->waitevent = cur->next;
    else
	prev->next = cur->next;

    free(cur);
}

/*
 * Return a pointer to a statically-allocated string describing the
 * error encountered on 's'.  If there is no error condition, return a
 * null pointer.
 */
const char *prot_error(struct protstream *s)
{
    if(!s) return "bad protstream passed to prot_error";
    else if(s->error) return s->error;
    else if(s->eof) return PROT_EOF_STRING;
    else return NULL;
}

/*
 * Rewind the stream 's'.  's' must have been created for reading.
 */
int prot_rewind(struct protstream *s)
{
    assert(!s->write);

    if (lseek(s->fd, 0L, 0) == -1) {
	s->error = xstrdup(strerror(errno));
	return EOF;
    }
    s->cnt = 0;
    s->error = 0;
    s->eof = 0;
    s->can_unget = 0;
    s->bytes_in = 0;
    return 0;
}

/*
 * Read data into the empty buffer for the stream 's' and return the
 * first character.  Returns EOF on EOF or error.
 */
int prot_fill(struct protstream *s)
{
    int n;
    unsigned char *ptr;
    int left;
    int r;
    struct timeval timeout;
    fd_set rfds;
    int haveinput; 
    time_t read_timeout;
    struct prot_waitevent *event, *next;
   
    assert(!s->write);

    /* Zero errno just in case */
    errno = 0;

    if (s->fixedsize) s->eof = 1;
    if (s->eof || s->error) return EOF;

    do {
#ifdef HAVE_ZLIB
	/* check if there's anything in the zlib buffer already */
	if (s->zstrm && s->zstrm->avail_in) {
	    /* Decompress the data */
	    int zr = Z_OK;

	    s->zstrm->next_out = s->zbuf;
	    s->zstrm->avail_out = s->zbuf_size;
	    zr = inflate(s->zstrm, Z_SYNC_FLUSH);
	    if (!(zr == Z_OK || zr == Z_BUF_ERROR || zr == Z_STREAM_END)) {
		/* Error decompressing */
		syslog(LOG_ERR, "zlib inflate error: %d %s", zr, s->zstrm->msg);
		s->error = xstrdup("Error decompressing data");
		return EOF;
	    }

	    if (s->zstrm->avail_out < s->zbuf_size) {
		/* inflated some data */
		s->ptr = s->zbuf;
		s->cnt = s->zbuf_size - s->zstrm->avail_out;

		/* drop straight to logging and returning the first char */
		break;
	    }
	}
#endif

	/* wait until get input */
	haveinput = 0;

#ifdef HAVE_SSL
	/* maybe there's data stuck in the SSL buffer? */
	if (s->tls_conn != NULL) {
	    haveinput = SSL_pending(s->tls_conn);
	}
#endif

	/* if we've promised to call something before blocking or
	   flush an output stream, check to see if we're going to block */
	if (s->readcallback_proc ||
	    (s->flushonread && s->flushonread->ptr != s->flushonread->buf)) {
	    timeout.tv_sec = timeout.tv_usec = 0;
	    FD_ZERO(&rfds);
	    FD_SET(s->fd, &rfds);

	    if (!haveinput &&
		(select(s->fd + 1, &rfds, (fd_set *)0, (fd_set *)0,
			&timeout) <= 0)) {
		if (s->readcallback_proc) {
		    (*s->readcallback_proc)(s, s->readcallback_rock);
		    s->readcallback_proc = 0;
		    s->readcallback_rock = 0;
		}
		/* Request a flush of the buffer.  If we are a blocking
		   read stream, force the flush */
		if (s->flushonread)
		    prot_flush_internal(s->flushonread, !s->dontblock);
	    }
	    else {
		haveinput = 1;
	    }
	}

	if (!haveinput && (s->read_timeout || s->dontblock)) {
	    time_t now = time(NULL);
	    time_t sleepfor;

	    read_timeout = s->dontblock ? now : s->timeout_mark;
	    do {
		if (read_timeout < now)
		    sleepfor = 0;
		else
		    sleepfor = read_timeout - now;
		/* execute each callback that has timed out */
		for (event = s->waitevent; event; event = next)
		{
		    next = event->next;
		    if (now >= event->mark) {
			event = (*event->proc)(s, event, event->rock);
		    }
		    /* if event == NULL, the callback has removed itself */
		    if (event && sleepfor > (event->mark - now)) {
			sleepfor = event->mark - now;
		    }
		}

		/* check for input */
		timeout.tv_sec = sleepfor;
		timeout.tv_usec = 0;
		FD_ZERO(&rfds);
		FD_SET(s->fd, &rfds);
		r = select(s->fd + 1, &rfds, (fd_set *)0, (fd_set *)0,
			   &timeout);
		now = time(NULL);
	    } while ((r == 0 || (r == -1 && errno == EINTR && !signals_poll())) &&
		     (now < read_timeout));
	    if ((r == 0) || 
                /* ignore EINTR if we've timed out */
                (r == -1 && errno == EINTR && !signals_poll() && now >= read_timeout)) {
		if (!s->dontblock) {
		    s->error = xstrdup("idle for too long");
		    return EOF;
		} else {
		    errno = EAGAIN;
		    return EOF;
		}
	    }
	    else if (r == -1) {
		syslog(LOG_ERR, "select() failed: %m");
		s->error = xstrdup(strerror(errno));
		return EOF;
	    }
	}

	/* we have data, reset the timeout_mark */
	s->timeout_mark = time(NULL) + s->read_timeout;
	
	do {
	    cmdtime_netstart();
#ifdef HAVE_SSL	  
	    /* just do a SSL read instead if we're under a tls layer */
	    if (s->tls_conn != NULL) {
		n = SSL_read(s->tls_conn, (char *) s->buf, PROT_BUFSIZE);
	    } else {
		n = read(s->fd, s->buf, PROT_BUFSIZE);
	    }
#else  /* HAVE_SSL */
	    n = read(s->fd, s->buf, PROT_BUFSIZE);
#endif /* HAVE_SSL */
	    cmdtime_netend();
	} while (n == -1 && errno == EINTR && !signals_poll());

	if (n <= 0) {
	    if (n) s->error = xstrdup(strerror(errno));
	    else s->eof = 1;
	    return EOF;
	}
	
	if (s->saslssf) { /* decode it */
	    if (prot_sasldecode(s, n) == EOF) return EOF;
	} else {
	    /* No protection function, just use the raw data */
	    s->ptr = s->buf;
	    s->cnt = n;
	}

#ifdef HAVE_ZLIB
	if (s->zstrm) {
	    /* transfer the data we have to the input of 
	     * the z_stream and loop to process it */

	    s->zstrm->next_in = s->ptr;
	    s->zstrm->avail_in = s->cnt;
	    s->cnt = 0;
	}
#endif /* HAVE_ZLIB */
    } while (!s->cnt);

    if (s->logfd != -1) {
	time_t newtime;
	char timebuf[20];

	time(&newtime);
	snprintf(timebuf, sizeof(timebuf), "<%ld<", newtime);
	n = write(s->logfd, timebuf, strlen(timebuf));

	left = s->cnt;
	ptr = s->ptr;
	do {
	    n = write(s->logfd, ptr, left);
	    if (n == -1 && (errno != EINTR || signals_poll())) {
		break;
	    }

	    if (n > 0) {
		ptr += n;
		left -= n;
	    }
	} while (left);
    }

    s->cnt--;		/* we return the first char */
    s->can_unget = 1;
    s->bytes_in++;
    return *s->ptr++;
}

/*
 * If 's' is an input stream, discard any pending/buffered data.  Otherwise,
 * Write out any buffered data in the stream 's'
 */
int prot_flush(struct protstream *s) 
{
    if (!s->write) {
	int c, save_dontblock = s->dontblock;

	/* Set stream to nonblocking mode */
	if (!save_dontblock) nonblock(s->fd, (s->dontblock = 1));

	/* Ingest any pending input */
	while ((c = prot_fill(s)) != EOF);

	/* Reset stream to previous blocking mode */
	if (!save_dontblock) nonblock(s->fd, (s->dontblock = 0));

	/* Discard any buffered input */
	s->cnt = 0;
	s->can_unget = 0;

	return 0;
    }

    return prot_flush_internal(s, 1);
}

/* Do the logging part of prot_flush */
static void prot_flush_log(struct protstream *s) 
{
    if(s->logfd != PROT_NO_FD) {
	unsigned char *ptr = s->buf;
	int left = s->ptr - s->buf;
	int n;
	time_t newtime;
	char timebuf[20];
	
	time(&newtime);
	snprintf(timebuf, sizeof(timebuf), ">%ld>", newtime);
	n = write(s->logfd, timebuf, strlen(timebuf));

	do {
	    n = write(s->logfd, ptr, left);
	    if (n == -1 && (errno != EINTR || signals_poll())) {
		break;
	    }
	    if (n > 0) {
		ptr += n;
		left -= n;
	    }
	} while (left);

	(void)fsync(s->logfd);
    }
}

/* Do the encoding part of prot_flush */
static int prot_flush_encode(struct protstream *s,
			     const char **output_buf,
			     unsigned *output_len) 
{
    unsigned char *ptr = s->buf;
    int left = s->ptr - s->buf;

#ifdef HAVE_ZLIB
    if (s->zstrm) {
	/* Compress the data */
	int zr = Z_OK;

	s->zstrm->next_in = ptr;
	s->zstrm->avail_in = left;
	s->zstrm->next_out = s->zbuf;
	s->zstrm->avail_out = s->zbuf_size;

	do {
	    /* should never be needed, but it's better to always check! */
	    if (!s->zstrm->avail_out) {
		syslog(LOG_DEBUG, "growing compress buffer from %u to %u bytes",
		       s->zbuf_size, s->zbuf_size + PROT_BUFSIZE);

		s->zbuf = (unsigned char *)
		    xrealloc(s->zbuf, s->zbuf_size + PROT_BUFSIZE);
		s->zstrm->next_out = s->zbuf + s->zbuf_size;
		s->zstrm->avail_out = PROT_BUFSIZE;
		s->zbuf_size += PROT_BUFSIZE;
	    }

	    zr = deflate(s->zstrm, Z_SYNC_FLUSH);
	    if (!(zr == Z_OK || zr == Z_STREAM_END || zr == Z_BUF_ERROR)) {
		/* something went wrong */
		syslog(LOG_ERR, "zlib deflate error: %d %s", zr, s->zstrm->msg);
		s->error = xstrdup("Error compressing data");
		return EOF;
	    }

	    /* http://www.zlib.net/manual.html says:
	     * If deflate returns with avail_out == 0, this function must be 
	     * called again with the same value of the flush parameter and
	     * more output space (updated avail_out), until the flush is 
	     * complete (deflate returns with non-zero avail_out). 
	     */
	} while (!s->zstrm->avail_out);

	ptr = s->zbuf;
	left = s->zbuf_size - s->zstrm->avail_out;
    }
#endif /* HAVE_ZLIB */

    if (s->saslssf != 0) {
	/* encode the data */
	int result = sasl_encode(s->conn, (char *) ptr, left, 
				 output_buf, output_len);
	if (result != SASL_OK) {
	    char errbuf[256];
	    const char *ed = sasl_errdetail(s->conn);
	    
	    snprintf(errbuf, 256, "encoding error: %s; %s",
		     sasl_errstring(result, NULL, NULL),
		     ed ? ed : "no detail");
	    s->error = xstrdup(errbuf);
	    
	    return EOF;
	}
    } else {
	*output_buf = (char *) ptr;
	*output_len = left;
    }
    return 0;
}

/* A wrapper for write() that handles SSL and EINTR */
static int prot_flush_writebuffer(struct protstream *s,
				  const char *buf, size_t len) 
{
    int n;
    
    do {
	cmdtime_netstart();
#ifdef HAVE_SSL
	if (s->tls_conn != NULL) {
	    n = SSL_write(s->tls_conn, (char *)buf, len);
	} else {
	    n = write(s->fd, buf, len);
	}
#else  /* HAVE_SSL */
	n = write(s->fd, buf, len);
#endif /* HAVE_SSL */
	cmdtime_netend();
    } while (n == -1 && errno == EINTR && !signals_poll());

    return n;
}

int prot_flush_internal(struct protstream *s, int force)
{
    int n;
    int save_dontblock = s->dontblock;

    const char *ptr = (char *) s->buf; /* Memory buffer info */
    unsigned left = s->ptr - s->buf;

    assert(s->write);

    /* Is this protstream finished? */
    if (s->eof || s->error) {
	s->ptr = s->buf;
	s->cnt = 1;
	return EOF;
    }

    /* make sure that the main file descriptor is set up to
     * be blocking or nonblocking based on the configuration of the
     * protstream and the force flag */
    if(force)
	s->dontblock = 0;
    
    if(s->dontblock != s->dontblock_isset) {
	nonblock(s->fd,s->dontblock);
	s->dontblock_isset = s->dontblock;
    }
    
    /* end protstream setup */

    /* if writing to a buffer, just append the lot.  Always works */
    if (s->writetobuf) {
	buf_appendmap(s->writetobuf, ptr, left);
    }

    /* If we're doing a blocking write, flush the buffers, bigbuffer first */
    else if (!s->dontblock) {
	if(s->big_buffer != PROT_NO_FD) {
	    /* Write the bigbuffer */
	    do {
		n = prot_flush_writebuffer(s, s->bigbuf_base + s->bigbuf_pos,
					   s->bigbuf_len - s->bigbuf_pos);
		if(n == -1) {
		    s->error = xstrdup(strerror(errno));
		    goto done;
		} else if (n > 0) {
		    s->bigbuf_pos += n;
		}
	    } while(s->bigbuf_len != s->bigbuf_pos);

	    /* Free the bigbuffer */
	    map_free(&(s->bigbuf_base), &(s->bigbuf_siz));
	    close(s->big_buffer);
	    s->bigbuf_len = s->bigbuf_pos = 0;
	    s->big_buffer = PROT_NO_FD;
	}

	/* Is there anything in the memory buffer? */
	if(!left) {
	    goto done;
	}

	/* Do a regular write of whatever is left */

	/* Log and Encode it */
	prot_flush_log(s);

	if(prot_flush_encode(s, &ptr, &left) == EOF) {
	    /* s->error set by prot_flush_encode */
	    goto done;
	}

	/* Write it to descriptor */
	do {
	    n = prot_flush_writebuffer(s, ptr, left);
	    if(n == -1) {
		s->error = xstrdup(strerror(errno));
		goto done;
	    } else if (n > 0) {
		ptr += n;
		left -= n;
	    }
	} while(left);
    }

    /* Nonblocking */
    else {
	/* If we've been feeding a bigbuffer, write out from the current
	 * position as much as we can */
	if (s->big_buffer != PROT_NO_FD) {
	    /* Write what we can. */
	    n = prot_flush_writebuffer(s, s->bigbuf_base + s->bigbuf_pos,
				       s->bigbuf_len - s->bigbuf_pos);

	    if(n == -1 && errno == EAGAIN) {
		/* No room in the pipe, but we don't care */
		n = 0;
	    } else if(n == -1) {
		s->error = xstrdup(strerror(errno));
		goto done;
	    }

	    if (n > 0) {
		s->bigbuf_pos += n;
	    }
	}

	/* If there isn't anything in the memory buffer, we're done now */
	if(!left) {
	    goto done;
	}

	/* Prepare the data in the memory buffer */
	prot_flush_log(s);
	
	/* Encode it */
	if(prot_flush_encode(s, &ptr, &left) == EOF) {
	    /* prot_flush_encode set s->error */
	    goto done;
	}

	if(s->big_buffer == PROT_NO_FD || s->bigbuf_pos == s->bigbuf_len) {
	    /* No bigbuffer currently open (or we've written the current
	       one to its entirety), so write what we can from memory */

	    n = prot_flush_writebuffer(s, ptr, left);

	    if(n == -1 && errno == EAGAIN) {
		/* No room in the pipe, but we don't care */
		n = 0;
	    } else if(n == -1) {
		s->error = xstrdup(strerror(errno));
		goto done;
	    }

	    if(n > 0) {
		ptr += n;
		left -= n;
	    }
	}

	/* if there is data still to send, it needs to go to the bigbuffer */
	if(left) {
	    struct stat sbuf;
	    
	    if(s->big_buffer == PROT_NO_FD) {
		/* open new bigbuffer */
		int fd = create_tempfile(libcyrus_config_getstring(CYRUSOPT_TEMP_PATH));
		if(fd == -1) {
		    s->error = xstrdup(strerror(errno));
		    goto done;
		}

		s->big_buffer = fd;
	    }

	    do {
		n = write(s->big_buffer, ptr, left);
		if (n == -1 && (errno != EINTR || signals_poll())) {
		    syslog(LOG_ERR, "write to protstream buffer failed: %s",
			   strerror(errno));
		    
		    fatal("write to big buffer failed", EC_OSFILE);
		}
		if (n > 0) {
		    ptr += n;
		    left -= n;
		}
	    } while (left);

	    /* We did a write to the bigbuffer, refresh the memory map */
	    if (fstat(s->big_buffer, &sbuf) == -1) {
		syslog(LOG_ERR, "IOERROR: fstating temp protlayer buffer: %m");
		fatal("failed to fstat protlayer buffer", EC_IOERR);
	    }
	    
	    s->bigbuf_len = sbuf.st_size;

	    map_refresh(s->big_buffer, 0, &(s->bigbuf_base), &(s->bigbuf_siz),
			s->bigbuf_len, "temp protlayer buffer", NULL);
	}
	
    } /* end of blocking/nonblocking if statment */

    /* Reset the memory buffer -- should be done on EOF or on success. */
    s->ptr = s->buf;
    s->cnt = s->maxplain;
        
 done:
    /* are we done with the big buffer? If so, free it. This includes
     * when we exit with error */
    if (s->big_buffer != PROT_NO_FD &&
       (s->bigbuf_pos == s->bigbuf_len || s->error)) {
	map_free(&(s->bigbuf_base), &(s->bigbuf_siz));
	close(s->big_buffer);
	s->bigbuf_len = s->bigbuf_pos = 0;
	s->big_buffer = PROT_NO_FD;
    }

    if (force) {
	/* we don't need to call nonblock() again, because it will be
	 * set correctly on the next prot_flush_internal() anyway */
	s->dontblock = save_dontblock;
    }
    
    /* If we are exiting with an error, we should clear our memory buffer 
     * and set our return code */
    if(s->error) {
        s->ptr = s->buf;
        s->cnt = s->maxplain;
	return EOF;
    }

    return 0;
}

/*
 * Write to the output stream 's' the 'len' bytes of data at 'buf'
 */
int prot_write(struct protstream *s, const char *buf, unsigned len)
{
    assert(s->write);
    if(s->error || s->eof) return EOF;
    if(len == 0) return 0;
    
    /* Different type of data, adjust layers accordingly */
    if (s->boundary) {
#ifdef HAVE_ZLIB
	if (s->zstrm) {
	    int zr = Z_OK;
	    int zlevel = Z_DEFAULT_COMPRESSION;

	    if (is_incompressible(buf, len))
		zlevel = Z_NO_COMPRESSION;

	    if (zlevel != s->zlevel) {
		s->zlevel = zlevel;

		/* flush any pending data */
		if (s->ptr != s->buf) {
		    if (prot_flush_internal(s, 1) == EOF) return EOF;
		}

		/* Set new compression level */
		zr = deflateParams(s->zstrm, s->zlevel, Z_DEFAULT_STRATEGY);
		if (zr != Z_OK) {
		    s->error = xstrdup("Error setting compression level");
		    return EOF;
		}
	    }
	}
#endif /* HAVE_ZLIB */

	s->boundary = 0;
    }

    while (len >= s->cnt) {
	/* XXX can we manage to write data from 'buf' without copying it
	   to s->ptr ? */
	memcpy(s->ptr, buf, s->cnt);
	s->ptr += s->cnt;
	buf += s->cnt;
	len -= s->cnt;
	s->cnt = 0;
	if (prot_flush_internal(s,0) == EOF) return EOF;
    }
    memcpy(s->ptr, buf, len);
    s->ptr += len;
    s->cnt -= len;
    s->bytes_out += len;
    if (s->error || s->eof) return EOF;

    assert(s->cnt > 0);
    return 0;
}

int prot_putbuf(struct protstream *s, struct buf *buf)
{
    return prot_write(s, buf->s, buf->len);
}

/*
 * Stripped-down version of printf() that works on protection streams
 * Only understands '%lld', '%llu', '%ld', '%lu', '%d', %u', '%s',
 * '%tu', '%td', '%c', and '%%' in the format string.
 */
int prot_printf(struct protstream *s, const char *fmt, ...)
{
    va_list pvar;
    char *percent, *p;
    long l;
    unsigned long ul;
    int i;
    unsigned u;
    char buf[30];
    va_start(pvar, fmt);

    assert(s->write);

    while ((percent = strchr(fmt, '%')) != 0) {
	prot_write(s, fmt, percent-fmt);
	switch (*++percent) {
	case '%':
	    (void)prot_putc('%', s);
	    break;

	case 'l':
	    switch (*++percent) {
	    case 'd':
		l = va_arg(pvar, long);
		snprintf(buf, sizeof(buf), "%ld", l);
		prot_write(s, buf, strlen(buf));
		break;

	    case 'u':
		ul = va_arg(pvar, long);
		snprintf(buf, sizeof(buf), "%lu", ul);
		prot_write(s, buf, strlen(buf));
		break;

            case 'l': {
		long long int ll;
		unsigned long long int ull;

	        switch (*++percent) {
		case 'd':
		    ll = va_arg(pvar, long long int);
		    snprintf(buf, sizeof(buf), "%lld", ll);
		    prot_write(s, buf, strlen(buf));
		    break;

		case 'u':
		    ull = va_arg(pvar, unsigned long long int);
		    snprintf(buf, sizeof(buf), "%llu", ull);
		    prot_write(s, buf, strlen(buf));
		    break;

	        default:
		    abort();
		}
		break;
	    }

	    default:
		abort();
	    }
	    break;

	case 'd':
	    i = va_arg(pvar, int);
	    snprintf(buf, sizeof(buf), "%d", i);
	    prot_write(s, buf, strlen(buf));
	    break;

	case 'u':
	    u = va_arg(pvar, int);
	    snprintf(buf, sizeof(buf), "%u", u);
	    prot_write(s, buf, strlen(buf));
	    break;

	case 't': {
	    size_t tu;
	    ssize_t td;

	    switch (*++percent) {
	    case 'u':
		tu = va_arg(pvar, size_t);
		snprintf(buf, sizeof(buf), "%tu", tu);
		prot_write(s, buf, strlen(buf));
		break;

	    case 'd':
		td = va_arg(pvar, ssize_t);
		snprintf(buf, sizeof(buf), "%td", td);
		prot_write(s, buf, strlen(buf));
		break;

	    default:
		abort();
	    }
	    break;
	}

	case 's':
	    p = va_arg(pvar, char *);
	    prot_write(s, p, strlen(p));
	    break;

	case 'c':
	    i = va_arg(pvar, int);
	    (void)prot_putc(i, s);
	    break;

	default:
	    abort();
	}
	fmt = percent+1;
    }
    prot_write(s, fmt, strlen(fmt));
    va_end(pvar);
    if (s->error || s->eof) return EOF;
    return 0;
}

int prot_printliteral(struct protstream *out, const char *s, size_t size)
{
    int r;
    if (out->isclient)
	r = prot_printf(out, "{" SIZE_T_FMT "+}\r\n", size);
    else
	r = prot_printf(out, "{" SIZE_T_FMT "}\r\n", size);
    if (r) return r;
    return prot_write(out, s, size);
}

#define isQCHAR(c) \
	(!((c) & 0x80 || *p == '\r' || (c) == '\n' \
	    || (c) == '\"' || (c) == '%' || (c) == '\\'))
#define MAXQSTRING  1024

/*
 * Print 's' as a quoted-string or literal (but not an atom)
 */
int prot_printstring(struct protstream *out, const char *s)
{
    const char *p;

    if (!s) return prot_printf(out, "NIL");

    /* Look for any non-QCHAR characters */
    for (p = s; *p && (p-s) < MAXQSTRING; p++) {
	if (!isQCHAR(*p)) break;
    }

    /* if it's too long, literal it */
    if (*p || (p-s) >= MAXQSTRING) {
	return prot_printliteral(out, s, strlen(s));
    }

    return prot_printf(out, "\"%s\"", s);
}

/*
 * Print the @n bytes at @s as a quoted-string or literal.
 * Handles embedded NULs.
 */
int prot_printmap(struct protstream *out, const char *s, size_t n)
{
    const char *p;
    int r;

    if (!s) return prot_printf(out, "NIL");

    /* if it's too long, literal it */
    if (n >= MAXQSTRING)
	return prot_printliteral(out, s, n);

    /* Look for NULs or any non-QCHAR characters */
    for (p = s; (size_t)(p-s) < n; p++) {
	if (!*p || !isQCHAR(*p))
	    return prot_printliteral(out, s, n);
    }

    prot_putc('"', out);
    r = prot_write(out, s, n);
    if (r < 0)
	return r;
    prot_putc('"', out);
    return r+2;
}

/*
 * Print 's' as an atom, quoted-string, or literal
 */
int prot_printastring(struct protstream *out, const char *s)
{
    if (!s) return prot_printf(out, "NIL");

    /* special cases for atoms */
    if (!*s) return prot_printf(out, "\"\"");
    if (imparse_isatom(s)) return prot_printf(out, "%s", s);

    /* not an atom, so pass to printstring */
    return prot_printstring(out, s);
}

/*
 * Read from the protections stream 's' up to 'size' bytes into the buffer
 * 'buf'.  Returns the number of bytes read, or 0 for some error.
 */
int prot_read(struct protstream *s, char *buf, unsigned size)
{
    int c;

    assert(!s->write);

    if (!size) return 0;

    /* If no data in the input buffer, get some */
    if (!s->cnt) {
	c = prot_fill(s);
	if (c == EOF) return 0;
	prot_ungetc(c, s);
    }

    if (size > s->cnt) size = s->cnt;
    memcpy(buf, s->ptr, size);
    s->ptr += size;
    s->cnt -= size;
    s->can_unget += size;
    s->bytes_in += size;  /* prot_fill added the 1 already */
    return size;
}

/*
 * select() for protection streams, read only
 * Also supports selecting on an extra file descriptor
 *
 * returns # of protstreams with pending data (including the extra fd)
 *
 * Only works for readable protstreams
 */ 
int prot_select(struct protgroup *readstreams, int extra_read_fd,
		struct protgroup **out, int *extra_read_flag,
		struct timeval *timeout) 
{
    struct protstream *s, *timeout_prot = NULL;
    struct protgroup *retval = NULL;
    int max_fd, found_fds = 0;
    unsigned i;
    fd_set rfds;
    int have_readtimeout = 0;
    struct timeval my_timeout;
    struct prot_waitevent *event;
    time_t now = time(NULL);
    time_t read_timeout = 0;
    
    assert(readstreams || extra_read_fd != PROT_NO_FD);
    assert(extra_read_fd == PROT_NO_FD || extra_read_flag);
    assert(out);

    /* Initialize things we might use */
    errno = 0;
    found_fds = 0;
    FD_ZERO(&rfds);

    /* If extra_read_fd is PROT_NO_FD, then the first protstream
     * will override it */
    max_fd = extra_read_fd;

    for(i = 0; i<readstreams->next_element; i++) {
	int have_thistimeout = 0; /* used to compute the minimal timeout for */
	time_t this_timeout = 0;  /* this stream */
	
	s = readstreams->group[i];
	if (!s) continue;

	assert(!s->write);

	/* scan for waitevent callbacks */
	for (event = s->waitevent; event; event = event->next)
	{
	    if(!have_thistimeout || event->mark - now < this_timeout) {
		this_timeout = event->mark - now;
		have_thistimeout = 1;
	    }
	}
	
	/* check the idle timeout on this one as well */
	if(s->read_timeout &&
	   (!have_thistimeout || s->timeout_mark - now < this_timeout)) {
	    this_timeout = s->timeout_mark - now;
	    have_thistimeout = 1;
	}

	if(!s->dontblock && have_thistimeout &&
	   (!have_readtimeout || now + this_timeout < read_timeout)) {
	    read_timeout = now + this_timeout;
	    have_readtimeout = 1;
	    if(!timeout || this_timeout <= timeout->tv_sec)
		timeout_prot = s;
	}
	    
	FD_SET(s->fd, &rfds);
	if(s->fd > max_fd)
	    max_fd = s->fd;

	/* Is something currently pending in our protstream's buffer? */
	if(s->cnt > 0) {
	    found_fds++;

	    if(!retval)
		retval = protgroup_new(readstreams->next_element + 1);

	    protgroup_insert(retval, s);
	    
	}
#ifdef HAVE_SSL
	else if(s->tls_conn != NULL && SSL_pending(s->tls_conn)) {
	    found_fds++;

	    if(!retval)
		retval = protgroup_new(readstreams->next_element + 1);

	    protgroup_insert(retval, s);
	}
#endif
    }

    /* xxx we should probably do a nonblocking select on the remaining
     * protstreams instead of skipping this part entirely */
    if(!retval) {
	time_t sleepfor;

	/* do a select */
	if(extra_read_fd != PROT_NO_FD) {
	    /* max_fd started with atleast extra_read_fd */
	    FD_SET(extra_read_fd, &rfds);
	}

	if(read_timeout < now)
	    sleepfor = 0;
	else
	    sleepfor = read_timeout - now;

	/* If we don't have a timeout structure, and we need one, use
	 * a local version.  Otherwise, make sure that we are timing out
	 * for the right reason */
	if(have_readtimeout &&
	   (!timeout || sleepfor < timeout->tv_sec)) {
	    if(!timeout) timeout = &my_timeout;
	    timeout->tv_sec = sleepfor;
	    timeout->tv_usec = 0;
	}

	if(select(max_fd + 1, &rfds, NULL, NULL, timeout) == -1)
	    return -1;

	/* Reset now */
	now = time(NULL);

	if(extra_read_fd != PROT_NO_FD && FD_ISSET(extra_read_fd, &rfds)) {
	    *extra_read_flag = 1;
	    found_fds++;
	} else if(extra_read_flag) {
	    *extra_read_flag = 0;
	}
	
	for(i = 0; i<readstreams->next_element; i++) {
	    s = readstreams->group[i];
	    if (!s) continue;

	    if(FD_ISSET(s->fd, &rfds)) {
		found_fds++;

		if(!retval)
		    retval = protgroup_new(readstreams->next_element + 1);

		protgroup_insert(retval, s);
	    } else if(s == timeout_prot && now >= read_timeout) {
		/* If we timed out, be sure to add the protstream we were
		 * waiting for, even if it didn't show up */
		found_fds++;

		if(!retval)
		    retval = protgroup_new(readstreams->next_element + 1);

		protgroup_insert(retval, s);
	    }
	}	
    }
    
    *out = retval;
    return found_fds;
}

/*
 * Version of fgets() that works with protection streams.
 */
char *prot_fgets(char *buf, unsigned size, struct protstream *s)
{
    char *p = buf;
    int c;

    assert(!s->write);

    if (size < 2 || s->eof) return 0;
    size--;

    while (size && (c = prot_getc(s)) != EOF) {
	size--;
	*p++ = c;
        s->bytes_in++;
	if (c == '\n') break;
    }
    if (p == buf) return 0;
    *p++ = '\0';
    return buf;
}

/* Handle protgroups */
/* Create a new protgroup of the given size, or 32 if size is 0 */
struct protgroup *protgroup_new(size_t size) 
{
    struct protgroup *ret = xmalloc(sizeof(struct protgroup));

    if(!size) size = PROTGROUP_SIZE_DEFAULT;

    ret->nalloced = size;
    ret->next_element = 0;
    ret->group = xzmalloc(size * sizeof(struct protstream *));

    return ret;
}

struct protgroup *protgroup_copy(struct protgroup *src)
{
    struct protgroup *dest;
    assert(src);
    dest = protgroup_new(src->nalloced);
    if(src->next_element) {
	memcpy(dest->group, src->group,
	       src->next_element * sizeof(struct protstream *));
    }
    return dest;
}

void protgroup_reset(struct protgroup *group) 
{
    if(group) {
	memset(group->group, 0,
	       group->nalloced * sizeof(struct protstream *));
	group->next_element = 0;
    }
}

void protgroup_free(struct protgroup *group) 
{
    if(group) {
	assert(group->group);
	free(group->group);
	free(group);
    }
}

void protgroup_insert(struct protgroup *group, struct protstream *item) 
{
    unsigned i, empty;

    assert(group);
    assert(item);

    /* See if we already have this protstream */
    for (i = 0, empty = group->next_element; i < group->next_element; i++) {
	if (!group->group[i]) empty = i;
	else if (group->group[i] == item) return;
    }
    /* Double size of the protgroup if we're at our limit */ 
    if (empty == group->next_element &&
	group->next_element++ == group->nalloced) {
	group->nalloced *= 2;
	group->group = xrealloc(group->group,
				group->nalloced * sizeof(struct protstream *));
    }
    /* Insert the item at the empty location */
    group->group[empty] = item;
}

void protgroup_delete(struct protgroup *group, struct protstream *item) 
{
    unsigned i;

    assert(group);
    assert(item);

    /* find the protstream */
    for (i = 0; i < group->next_element; i++) {
	if (group->group[i] == item) {
	    /* slide all remaining elements down one slot */
	    group->next_element--;
	    for (; i < group->next_element; i++) {
		group->group[i] = group->group[i+1];
	    }
	    group->group[i] = NULL;
	    return;
	}
    }
    syslog(LOG_ERR, "protgroup_delete(): can't find protstream in group");
}

struct protstream *protgroup_getelement(struct protgroup *group,
					size_t element) 
{
    assert(group);

    if (element >= group->next_element)
	return NULL;

    return group->group[element];
}

int prot_getc(struct protstream *s)
{
    assert(!s->write);

    if (s->cnt > 0) {
	--s->cnt;
	s->can_unget++;
	s->bytes_in++;
	return *(s->ptr)++;
    }

    return prot_fill(s);
}

int prot_ungetc(int c, struct protstream *s)
{
    assert(!s->write);

    if (c == EOF) return EOF;

    if (!s->can_unget)
	fatal("Can't unwind any more", EC_SOFTWARE);

    s->cnt++;
    s->can_unget--;
    s->bytes_in--;
    s->ptr--;
    if (*s->ptr != c)
	fatal("Trying to unput wrong character", EC_SOFTWARE);

    return c;
}

int prot_putc(int c, struct protstream *s)
{
    assert(s->write);
    assert(s->cnt > 0);

    *s->ptr++ = c;

    s->bytes_out++;
    if (--s->cnt == 0)
	return prot_flush_internal(s,0);

    return 0;
}