ref: ca8ca008f4ab7074971a35e08de9a46cb9b5d5ab
dir: /sys/src/cmd/upas/smtp/smtp.c/
#include "common.h"
#include "smtp.h"
#include <ctype.h>
#include <mp.h>
#include <libsec.h>
#include <auth.h>
static char* connect(char*);
static char* wraptls(void);
static char* dotls(char*);
static char* doauth(char*);
void addhostdom(String*, char*);
String* bangtoat(char*);
String* convertheader(String*);
int dBprint(char*, ...);
int dBputc(int);
char* data(String*, Biobuf*);
char* domainify(char*, char*);
String* fixrouteaddr(String*, Node*, Node*);
char* getcrnl(String*);
int getreply(void);
char* hello(char*, int);
char* mailfrom(char*);
int printdate(Node*);
int printheader(void);
void putcrnl(char*, int);
void quit(char*);
char* rcptto(char*);
char* rewritezone(char *);
#define Retry "Retry, Temporary Failure"
#define Giveup "Permanent Failure"
String *reply; /* last reply */
String *toline;
int alarmscale;
int autistic;
int debug; /* true if we're debugging */
int filter;
int insecure;
int last = 'n'; /* last character sent by putcrnl() */
int ping;
int quitting; /* when error occurs in quit */
int tryauth; /* Try to authenticate, if supported */
int trysecure; /* Try to use TLS if the other side supports it */
char *quitrv; /* deferred return value when in quit */
char ddomain[1024]; /* domain name of destination machine */
char *gdomain; /* domain name of gateway */
char *uneaten; /* first character after rfc822 headers */
char *farend; /* system we are trying to send to */
char *user; /* user we are authenticating as, if authenticating */
char hostdomain[256];
Biobuf bin;
Biobuf bout;
Biobuf berr;
Biobuf bfile;
static int bustedmx;
void
usage(void)
{
fprint(2, "usage: smtp [-aAdfipst] [-b busted-mx] [-g gw] [-h host] "
"[-u user] [.domain] net!host[!service] sender rcpt-list\n");
exits(Giveup);
}
int
timeout(void *x, char *msg)
{
USED(x);
syslog(0, "smtp.fail", "interrupt: %s: %s", farend, msg);
if(strstr(msg, "alarm")){
fprint(2, "smtp timeout: connection to %s timed out\n", farend);
if(quitting)
exits(quitrv);
exits(Retry);
}
if(strstr(msg, "closed pipe")){
/* call _exits() to prevent Bio from trying to flush closed pipe */
fprint(2, "smtp timeout: connection closed to %s\n", farend);
if(quitting){
syslog(0, "smtp.fail", "closed pipe to %s", farend);
_exits(quitrv);
}
_exits(Retry);
}
return 0;
}
void
removenewline(char *p)
{
int n = strlen(p)-1;
if(n < 0)
return;
if(p[n] == '\n')
p[n] = 0;
}
void
main(int argc, char **argv)
{
int i, ok, rcvrs;
char *addr, *rv, *trv, *host, *domain;
char **errs;
char hellodomain[256];
String *from, *fromm, *sender;
alarmscale = 60*1000; /* minutes */
quotefmtinstall();
fmtinstall('[', encodefmt);
errs = malloc(argc*sizeof(char*));
reply = s_new();
host = 0;
ARGBEGIN{
case 'a':
tryauth = 1;
if(trysecure == 0)
trysecure = 1;
break;
case 'A': /* autistic: won't talk to us until we talk (Verizon) */
autistic = 1;
break;
case 'b':
if (bustedmx >= Maxbustedmx)
sysfatal("more than %d busted mxs given", Maxbustedmx);
bustedmxs[bustedmx++] = EARGF(usage());
break;
case 'd':
debug = 1;
break;
case 'f':
filter = 1;
break;
case 'g':
gdomain = EARGF(usage());
break;
case 'h':
host = EARGF(usage());
break;
case 'i':
insecure = 1;
break;
case 'p':
alarmscale = 10*1000; /* tens of seconds */
ping = 1;
break;
case 's':
if(trysecure == 0)
trysecure = 1;
break;
case 't':
trysecure = 2;
break;
case 'u':
user = EARGF(usage());
break;
default:
usage();
break;
}ARGEND;
Binit(&berr, 2, OWRITE);
Binit(&bfile, 0, OREAD);
/*
* get domain and add to host name
*/
if(*argv && **argv=='.') {
domain = *argv;
argv++; argc--;
} else
domain = domainname_read();
if(host == 0)
host = sysname_read();
strcpy(hostdomain, domainify(host, domain));
strcpy(hellodomain, domainify(sysname_read(), domain));
/*
* get destination address
*/
if(*argv == 0)
usage();
addr = *argv++; argc--;
farend = addr;
/*
* get sender's machine.
* get sender in internet style. domainify if necessary.
*/
if(*argv == 0)
usage();
sender = unescapespecial(s_copy(*argv++));
argc--;
fromm = s_clone(sender);
rv = strrchr(s_to_c(fromm), '!');
if(rv)
*rv = 0;
else
*s_to_c(fromm) = 0;
from = bangtoat(s_to_c(sender));
/*
* send the mail
*/
if(filter){
Binit(&bout, 1, OWRITE);
rv = data(from, &bfile);
if(rv != 0)
goto error;
exits(0);
}
/* mxdial uses its own timeout handler */
if((rv = connect(addr)) != 0)
exits(rv);
/* 10 minutes to get through the initial handshake */
atnotify(timeout, 1);
alarm(10*alarmscale);
if((rv = hello(hellodomain, 0)) != 0)
goto error;
alarm(10*alarmscale);
if((rv = mailfrom(s_to_c(from))) != 0)
goto error;
ok = 0;
rcvrs = 0;
/* if any rcvrs are ok, we try to send the message */
for(i = 0; i < argc; i++){
if((trv = rcptto(argv[i])) != 0){
/* remember worst error */
if(rv != Giveup)
rv = trv;
errs[rcvrs] = strdup(s_to_c(reply));
removenewline(errs[rcvrs]);
} else {
ok++;
errs[rcvrs] = 0;
}
rcvrs++;
}
/* if no ok rcvrs or worst error is retry, give up */
if(ok == 0 || rv == Retry)
goto error;
if(ping){
quit(0);
exits(0);
}
rv = data(from, &bfile);
if(rv != 0)
goto error;
quit(0);
if(rcvrs == ok)
exits(0);
/*
* here when some but not all rcvrs failed
*/
fprint(2, "%s connect to %s:\n", thedate(), addr);
for(i = 0; i < rcvrs; i++){
if(errs[i]){
syslog(0, "smtp.fail", "delivery to %s at %s failed: %s", argv[i], addr, errs[i]);
fprint(2, " mail to %s failed: %s", argv[i], errs[i]);
}
}
exits(Giveup);
/*
* here when all rcvrs failed
*/
error:
removenewline(s_to_c(reply));
syslog(0, "smtp.fail", "%s to %s failed: %s",
ping ? "ping" : "delivery",
addr, s_to_c(reply));
fprint(2, "%s connect to %s:\n%s\n", thedate(), addr, s_to_c(reply));
if(!filter)
quit(rv);
exits(rv);
}
/*
* connect to the remote host
*/
static char *
connect(char* net)
{
char buf[Errlen];
int fd;
fd = mxdial(net, ddomain, gdomain);
if(fd < 0){
rerrstr(buf, sizeof(buf));
Bprint(&berr, "smtp: %s (%s)\n", buf, net);
syslog(0, "smtp.fail", "%s (%s)", buf, net);
if(strstr(buf, "illegal")
|| strstr(buf, "unknown")
|| strstr(buf, "can't translate"))
return Giveup;
else
return Retry;
}
Binit(&bin, fd, OREAD);
fd = dup(fd, -1);
Binit(&bout, fd, OWRITE);
return 0;
}
static char smtpthumbs[] = "/sys/lib/tls/smtp";
static char smtpexclthumbs[] = "/sys/lib/tls/smtp.exclude";
static char *
wraptls(void)
{
TLSconn *c;
Thumbprint *goodcerts;
char *h, *err;
int fd;
uchar hash[SHA1dlen];
goodcerts = nil;
err = Giveup;
c = mallocz(sizeof(*c), 1);
if (c == nil)
return err;
fd = tlsClient(Bfildes(&bout), c);
if (fd < 0) {
syslog(0, "smtp", "tlsClient to %q: %r", ddomain);
goto Out;
}
Bterm(&bout);
Binit(&bout, fd, OWRITE);
fd = dup(fd, Bfildes(&bin));
Bterm(&bin);
Binit(&bin, fd, OREAD);
goodcerts = initThumbprints(smtpthumbs, smtpexclthumbs);
if (goodcerts == nil) {
syslog(0, "smtp", "bad thumbprints in %s", smtpthumbs);
goto Out;
}
/* compute sha1 hash of remote's certificate, see if we know it */
sha1(c->cert, c->certlen, hash, nil);
if (!okThumbprint(hash, goodcerts)) {
/* TODO? if not excluded, add hash to thumb list */
h = malloc(2*sizeof hash + 1);
if (h == nil)
goto Out;
enc16(h, 2*sizeof hash + 1, hash, sizeof hash);
syslog(0, "smtp", "remote cert. has bad thumbprint: x509 sha1=%s server=%q",
h, ddomain);
free(h);
goto Out;
}
syslog(0, "smtp", "started TLS to %q", ddomain);
err = nil;
Out:
if(goodcerts != nil)
freeThumbprints(goodcerts);
free(c->cert);
free(c->sessionID);
free(c);
return err;
}
/*
* exchange names with remote host, attempt to
* enable encryption and optionally authenticate.
* not fatal if we can't.
*/
static char *
dotls(char *me)
{
char *err;
dBprint("STARTTLS\r\n");
if (getreply() != 2)
return Giveup;
err = wraptls();
if (err != nil)
return err;
return(hello(me, 1));
}
static char *
doauth(char *methods)
{
char *buf, *err;
UserPasswd *p;
int n;
DS ds;
dial_string_parse(ddomain, &ds);
if(user != nil)
p = auth_getuserpasswd(nil,
"proto=pass service=smtp server=%q user=%q", ds.host, user);
else
p = auth_getuserpasswd(nil,
"proto=pass service=smtp server=%q", ds.host);
if (p == nil)
return Giveup;
err = Retry;
if (strstr(methods, "LOGIN")){
dBprint("AUTH LOGIN\r\n");
if (getreply() != 3)
goto out;
dBprint("%.*[\r\n", strlen(p->user), p->user);
if (getreply() != 3)
goto out;
dBprint("%.*[\r\n", strlen(p->passwd), p->passwd);
if (getreply() != 2)
goto out;
err = nil;
}
else
if (strstr(methods, "PLAIN")){
n = strlen(p->user) + strlen(p->passwd) + 2;
buf = malloc(n+1);
if (buf == nil) {
free(buf);
goto out; /* Out of memory */
}
snprint(buf, n, "%c%s%c%s", 0, p->user, 0, p->passwd);
dBprint("AUTH PLAIN %.*[\r\n", n, buf);
memset(buf, 0, n);
free(buf);
if (getreply() != 2)
goto out;
err = nil;
} else
err = "No supported AUTH method";
out:
memset(p->user, 0, strlen(p->user));
memset(p->passwd, 0, strlen(p->passwd));
free(p);
return err;
}
char *
hello(char *me, int encrypted)
{
int ehlo;
String *r;
char *ret, *s, *t;
if (!encrypted) {
if(trysecure > 1){
if((ret = wraptls()) != nil)
return ret;
encrypted = 1;
}
/*
* Verizon fails to print the smtp greeting banner when it
* answers a call. Send a no-op in the hope of making it
* talk.
*/
if (autistic) {
dBprint("NOOP\r\n");
getreply(); /* consume the smtp greeting */
/* next reply will be response to noop */
}
switch(getreply()){
case 2:
break;
case 5:
return Giveup;
default:
return Retry;
}
}
ehlo = 1;
Again:
if(ehlo)
dBprint("EHLO %s\r\n", me);
else
dBprint("HELO %s\r\n", me);
switch (getreply()) {
case 2:
break;
case 5:
if(ehlo){
ehlo = 0;
goto Again;
}
return Giveup;
default:
return Retry;
}
r = s_clone(reply);
if(r == nil)
return Retry; /* Out of memory or couldn't get string */
/* Invariant: every line has a newline, a result of getcrlf() */
for(s = s_to_c(r); (t = strchr(s, '\n')) != nil; s = t + 1){
*t = '\0';
for (t = s; *t != '\0'; t++)
*t = toupper(*t);
if(!encrypted && trysecure &&
(strcmp(s, "250-STARTTLS") == 0 ||
strcmp(s, "250 STARTTLS") == 0)){
s_free(r);
return dotls(me);
}
if(tryauth && (encrypted || insecure) &&
(strncmp(s, "250 AUTH", strlen("250 AUTH")) == 0 ||
strncmp(s, "250-AUTH", strlen("250 AUTH")) == 0)){
ret = doauth(s + strlen("250 AUTH "));
s_free(r);
return ret;
}
}
s_free(r);
return 0;
}
/*
* report sender to remote
*/
char *
mailfrom(char *from)
{
if(!returnable(from))
dBprint("MAIL FROM:<>\r\n");
else
if(strchr(from, '@'))
dBprint("MAIL FROM:<%s>\r\n", from);
else
dBprint("MAIL FROM:<%s@%s>\r\n", from, hostdomain);
switch(getreply()){
case 2:
break;
case 5:
return Giveup;
default:
return Retry;
}
return 0;
}
/*
* report a recipient to remote
*/
char *
rcptto(char *to)
{
String *s;
s = unescapespecial(bangtoat(to));
if(toline == 0)
toline = s_new();
else
s_append(toline, ", ");
s_append(toline, s_to_c(s));
if(strchr(s_to_c(s), '@'))
dBprint("RCPT TO:<%s>\r\n", s_to_c(s));
else {
s_append(toline, "@");
s_append(toline, ddomain);
dBprint("RCPT TO:<%s@%s>\r\n", s_to_c(s), ddomain);
}
alarm(10*alarmscale);
switch(getreply()){
case 2:
break;
case 5:
return Giveup;
default:
return Retry;
}
return 0;
}
static char hex[] = "0123456789abcdef";
/*
* send the damn thing
*/
char *
data(String *from, Biobuf *b)
{
char *buf, *cp;
int i, n, nbytes, bufsize, eof, r;
String *fromline;
char errmsg[Errlen];
char id[40];
/*
* input the header.
*/
buf = malloc(1);
if(buf == 0){
s_append(s_restart(reply), "out of memory");
return Retry;
}
n = 0;
eof = 0;
for(;;){
cp = Brdline(b, '\n');
if(cp == nil){
eof = 1;
break;
}
nbytes = Blinelen(b);
buf = realloc(buf, n+nbytes+1);
if(buf == 0){
s_append(s_restart(reply), "out of memory");
return Retry;
}
strncpy(buf+n, cp, nbytes);
n += nbytes;
if(nbytes == 1) /* end of header */
break;
}
buf[n] = 0;
bufsize = n;
/*
* parse the header, turn all addresses into @ format
*/
yyinit(buf, n);
yyparse();
/*
* print message observing '.' escapes and using \r\n for \n
*/
alarm(20*alarmscale);
if(!filter){
dBprint("DATA\r\n");
switch(getreply()){
case 3:
break;
case 5:
free(buf);
return Giveup;
default:
free(buf);
return Retry;
}
}
/*
* send header. add a message-id, a sender, and a date if there
* isn't one
*/
nbytes = 0;
fromline = convertheader(from);
uneaten = buf;
srand(truerand());
if(messageid == 0){
for(i=0; i<16; i++){
r = rand()&0xFF;
id[2*i] = hex[r&0xF];
id[2*i+1] = hex[(r>>4)&0xF];
}
id[2*i] = '\0';
nbytes += Bprint(&bout, "Message-ID: <%s@%s>\r\n", id, hostdomain);
if(debug)
Bprint(&berr, "Message-ID: <%s@%s>\r\n", id, hostdomain);
}
if(originator==0){
nbytes += Bprint(&bout, "From: %s\r\n", s_to_c(fromline));
if(debug)
Bprint(&berr, "From: %s\r\n", s_to_c(fromline));
}
s_free(fromline);
if(destination == 0 && toline)
if(*s_to_c(toline) == '@'){ /* route addr */
nbytes += Bprint(&bout, "To: <%s>\r\n", s_to_c(toline));
if(debug)
Bprint(&berr, "To: <%s>\r\n", s_to_c(toline));
} else {
nbytes += Bprint(&bout, "To: %s\r\n", s_to_c(toline));
if(debug)
Bprint(&berr, "To: %s\r\n", s_to_c(toline));
}
if(date==0 && udate)
nbytes += printdate(udate);
if (usys)
uneaten = usys->end + 1;
nbytes += printheader();
if (*uneaten != '\n')
putcrnl("\n", 1);
/*
* send body
*/
putcrnl(uneaten, buf+n - uneaten);
nbytes += buf+n - uneaten;
if(eof == 0){
for(;;){
n = Bread(b, buf, bufsize);
if(n < 0){
rerrstr(errmsg, sizeof(errmsg));
s_append(s_restart(reply), errmsg);
free(buf);
return Retry;
}
if(n == 0)
break;
alarm(10*alarmscale);
putcrnl(buf, n);
nbytes += n;
}
}
free(buf);
if(!filter){
if(last != '\n')
dBprint("\r\n.\r\n");
else
dBprint(".\r\n");
alarm(10*alarmscale);
switch(getreply()){
case 2:
break;
case 5:
return Giveup;
default:
return Retry;
}
syslog(0, "smtp", "%s sent %d bytes to %s", s_to_c(from),
nbytes, s_to_c(toline));/**/
}
return 0;
}
/*
* we're leaving
*/
void
quit(char *rv)
{
/* 60 minutes to quit */
quitting = 1;
quitrv = rv;
alarm(60*alarmscale);
dBprint("QUIT\r\n");
getreply();
Bterm(&bout);
Bterm(&bfile);
}
/*
* read a reply into a string, return the reply code
*/
int
getreply(void)
{
char *line;
int rv;
reply = s_reset(reply);
for(;;){
line = getcrnl(reply);
if(debug)
Bflush(&berr);
if(line == 0)
return -1;
if(!isdigit(line[0]) || !isdigit(line[1]) || !isdigit(line[2]))
return -1;
if(line[3] != '-')
break;
}
if(debug)
Bflush(&berr);
rv = atoi(line)/100;
return rv;
}
void
addhostdom(String *buf, char *host)
{
s_append(buf, "@");
s_append(buf, host);
}
/*
* Convert from `bang' to `source routing' format.
*
* a.x.y!b.p.o!c!d -> @a.x.y:[email protected]
*/
String *
bangtoat(char *addr)
{
String *buf;
register int i;
int j, d;
char *field[128];
/* parse the '!' format address */
buf = s_new();
for(i = 0; addr; i++){
field[i] = addr;
addr = strchr(addr, '!');
if(addr)
*addr++ = 0;
}
if (i==1) {
s_append(buf, field[0]);
return buf;
}
/*
* count leading domain fields (non-domains don't count)
*/
for(d = 0; d<i-1; d++)
if(strchr(field[d], '.')==0)
break;
/*
* if there are more than 1 leading domain elements,
* put them in as source routing
*/
if(d > 1){
addhostdom(buf, field[0]);
for(j=1; j<d-1; j++){
s_append(buf, ",");
s_append(buf, "@");
s_append(buf, field[j]);
}
s_append(buf, ":");
}
/*
* throw in the non-domain elements separated by '!'s
*/
s_append(buf, field[d]);
for(j=d+1; j<=i-1; j++) {
s_append(buf, "!");
s_append(buf, field[j]);
}
if(d)
addhostdom(buf, field[d-1]);
return buf;
}
/*
* convert header addresses to @ format.
* if the address is a source address, and a domain is specified,
* make sure it falls in the domain.
*/
String*
convertheader(String *from)
{
Field *f;
Node *p, *lastp;
String *a;
if(!returnable(s_to_c(from))){
from = s_new();
s_append(from, "Postmaster");
addhostdom(from, hostdomain);
} else
if(strchr(s_to_c(from), '@') == 0){
a = username(from);
if(a) {
s_append(a, " <");
s_append(a, s_to_c(from));
addhostdom(a, hostdomain);
s_append(a, ">");
from = a;
} else {
from = s_copy(s_to_c(from));
addhostdom(from, hostdomain);
}
} else
from = s_copy(s_to_c(from));
for(f = firstfield; f; f = f->next){
lastp = 0;
for(p = f->node; p; lastp = p, p = p->next){
if(!p->addr)
continue;
a = bangtoat(s_to_c(p->s));
s_free(p->s);
if(strchr(s_to_c(a), '@') == 0)
addhostdom(a, hostdomain);
else if(*s_to_c(a) == '@')
a = fixrouteaddr(a, p->next, lastp);
p->s = a;
}
}
return from;
}
/*
* ensure route addr has brackets around it
*/
String*
fixrouteaddr(String *raddr, Node *next, Node *last)
{
String *a;
if(last && last->c == '<' && next && next->c == '>')
return raddr; /* properly formed already */
a = s_new();
s_append(a, "<");
s_append(a, s_to_c(raddr));
s_append(a, ">");
s_free(raddr);
return a;
}
/*
* print out the parsed header
*/
int
printheader(void)
{
int n, len;
Field *f;
Node *p;
char *cp;
char c[1];
n = 0;
for(f = firstfield; f; f = f->next){
for(p = f->node; p; p = p->next){
if(p->s)
n += dBprint("%s", s_to_c(p->s));
else {
c[0] = p->c;
putcrnl(c, 1);
n++;
}
if(p->white){
cp = s_to_c(p->white);
len = strlen(cp);
putcrnl(cp, len);
n += len;
}
uneaten = p->end;
}
putcrnl("\n", 1);
n++;
uneaten++; /* skip newline */
}
return n;
}
/*
* add a domain onto an name, return the new name
*/
char *
domainify(char *name, char *domain)
{
static String *s;
char *p;
if(domain==0 || strchr(name, '.')!=0)
return name;
s = s_reset(s);
s_append(s, name);
p = strchr(domain, '.');
if(p == 0){
s_append(s, ".");
p = domain;
}
s_append(s, p);
return s_to_c(s);
}
/*
* print message observing '.' escapes and using \r\n for \n
*/
void
putcrnl(char *cp, int n)
{
int c;
for(; n; n--, cp++){
c = *cp;
if(c == '\n')
dBputc('\r');
else if(c == '.' && last=='\n')
dBputc('.');
dBputc(c);
last = c;
}
}
/*
* Get a line including a crnl into a string. Convert crnl into nl.
*/
char *
getcrnl(String *s)
{
int c;
int count;
count = 0;
for(;;){
c = Bgetc(&bin);
if(debug)
Bputc(&berr, c);
switch(c){
case -1:
s_append(s, "connection closed unexpectedly by remote system");
s_terminate(s);
return 0;
case '\r':
c = Bgetc(&bin);
if(c == '\n'){
case '\n':
s_putc(s, c);
if(debug)
Bputc(&berr, c);
count++;
s_terminate(s);
return s->ptr - count;
}
Bungetc(&bin);
s_putc(s, '\r');
if(debug)
Bputc(&berr, '\r');
count++;
break;
default:
s_putc(s, c);
count++;
break;
}
}
}
/*
* print out a parsed date
*/
int
printdate(Node *p)
{
int n, sep = 0;
n = dBprint("Date: %s,", s_to_c(p->s));
for(p = p->next; p; p = p->next){
if(p->s){
if(sep == 0) {
dBputc(' ');
n++;
}
if (p->next)
n += dBprint("%s", s_to_c(p->s));
else
n += dBprint("%s", rewritezone(s_to_c(p->s)));
sep = 0;
} else {
dBputc(p->c);
n++;
sep = 1;
}
}
n += dBprint("\r\n");
return n;
}
char *
rewritezone(char *z)
{
int mindiff;
char s;
Tm *tm;
static char x[7];
tm = localtime(time(0));
mindiff = tm->tzoff/60;
/* if not in my timezone, don't change anything */
if(strcmp(tm->zone, z) != 0)
return z;
if(mindiff < 0){
s = '-';
mindiff = -mindiff;
} else
s = '+';
sprint(x, "%c%.2d%.2d", s, mindiff/60, mindiff%60);
return x;
}
/*
* stolen from libc/port/print.c
*/
#define SIZE 4096
int
dBprint(char *fmt, ...)
{
char buf[SIZE], *out;
va_list arg;
int n;
va_start(arg, fmt);
out = vseprint(buf, buf+SIZE, fmt, arg);
va_end(arg);
if(debug){
Bwrite(&berr, buf, (long)(out-buf));
Bflush(&berr);
}
n = Bwrite(&bout, buf, (long)(out-buf));
Bflush(&bout);
return n;
}
int
dBputc(int x)
{
if(debug)
Bputc(&berr, x);
return Bputc(&bout, x);
}