diff options
Diffstat (limited to 'usr.sbin/sendmail/src/srvrsmtp.c')
| -rw-r--r-- | usr.sbin/sendmail/src/srvrsmtp.c | 112 |
1 files changed, 83 insertions, 29 deletions
diff --git a/usr.sbin/sendmail/src/srvrsmtp.c b/usr.sbin/sendmail/src/srvrsmtp.c index 895cce5e3a92..83bd46389a92 100644 --- a/usr.sbin/sendmail/src/srvrsmtp.c +++ b/usr.sbin/sendmail/src/srvrsmtp.c @@ -36,9 +36,9 @@ #ifndef lint #if SMTP -static char sccsid[] = "@(#)srvrsmtp.c 8.131 (Berkeley) 12/1/96 (with SMTP)"; +static char sccsid[] = "@(#)srvrsmtp.c 8.136 (Berkeley) 1/17/97 (with SMTP)"; #else -static char sccsid[] = "@(#)srvrsmtp.c 8.131 (Berkeley) 12/1/96 (without SMTP)"; +static char sccsid[] = "@(#)srvrsmtp.c 8.136 (Berkeley) 1/17/97 (without SMTP)"; #endif #endif /* not lint */ @@ -121,7 +121,11 @@ char *CurSmtpClient; /* who's at the other end of channel */ static char *skipword(); -#define MAXBADCOMMANDS 25 /* maximum number of bad commands */ +#define MAXBADCOMMANDS 25 /* maximum number of bad commands */ +#define MAXNOOPCOMMANDS 20 /* max "noise" commands before slowdown */ +#define MAXHELOCOMMANDS 3 /* max HELO/EHLO commands before slowdown */ +#define MAXVRFYCOMMANDS 6 /* max VRFY/EXPN commands before slowdown */ +#define MAXETRNCOMMANDS 8 /* max ETRN commands before slowdown */ void smtp(nullserver, e) @@ -146,6 +150,8 @@ smtp(nullserver, e) volatile int badcommands = 0; /* count of bad commands */ volatile int nverifies = 0; /* count of VRFY/EXPN commands */ volatile int n_etrn = 0; /* count of ETRN commands */ + volatile int n_noop = 0; /* count of NOOP/VERB/ONEX etc cmds */ + volatile int n_helo = 0; /* count of HELO/EHLO commands */ bool ok; char inp[MAXLINE]; char cmdbuf[MAXLINE]; @@ -154,6 +160,7 @@ smtp(nullserver, e) extern void settime __P((ENVELOPE *)); extern bool enoughdiskspace __P((long)); extern int runinchild __P((char *, ENVELOPE *)); + extern void checksmtpattack __P((volatile int *, int, char *)); if (fileno(OutChannel) != fileno(stdout)) { @@ -303,10 +310,23 @@ smtp(nullserver, e) ** to everything. */ - if (nullserver && c->cmdcode != CMDQUIT) + if (nullserver) { - message("550 Access denied"); - continue; + switch (c->cmdcode) + { + case CMDQUIT: + case CMDHELO: + case CMDEHLO: + case CMDNOOP: + /* process normally */ + break; + + default: + if (++badcommands > MAXBADCOMMANDS) + sleep(1); + message("550 Access denied"); + continue; + } } /* non-null server */ @@ -325,6 +345,17 @@ smtp(nullserver, e) SmtpPhase = "server HELO"; } + /* avoid denial-of-service */ + checksmtpattack(&n_helo, MAXHELOCOMMANDS, "HELO/EHLO"); + + /* check for duplicate HELO/EHLO per RFC 1651 4.2 */ + if (gothello) + { + message("503 %s Duplicate HELO/EHLO", + MyHostName); + break; + } + /* check for valid domain name (re 1123 5.2.5) */ if (*p == '\0' && !AllowBogusHELO) { @@ -355,20 +386,15 @@ smtp(nullserver, e) if (!AllowBogusHELO) message("501 Invalid domain name"); else + { message("250 %s Invalid domain name, accepting anyway", MyHostName); + gothello = TRUE; + } break; } } - /* check for duplicate HELO/EHLO per RFC 1651 4.2 */ - if (gothello) - { - message("503 %s Duplicate HELO/EHLO", - MyHostName); - break; - } - sendinghost = newstr(p); gothello = TRUE; if (c->cmdcode != CMDEHLO) @@ -484,7 +510,7 @@ smtp(nullserver, e) /* must parse sender first */ delimptr = NULL; - setsender(p, e, &delimptr, FALSE); + setsender(p, e, &delimptr, ' ', FALSE); if (delimptr != NULL && *delimptr != '\0') *delimptr++ = '\0'; @@ -775,18 +801,8 @@ smtp(nullserver, e) case CMDVRFY: /* vrfy -- verify address */ case CMDEXPN: /* expn -- expand address */ - if (++nverifies >= MAXBADCOMMANDS) - { -#ifdef LOG - if (nverifies == MAXBADCOMMANDS && - LogLevel > 5) - { - syslog(LOG_INFO, "%.100s: VRFY attack?", - CurSmtpClient); - } -#endif - sleep(1); - } + checksmtpattack(&nverifies, MAXVRFYCOMMANDS, + c->cmdcode == CMDVRFY ? "VRFY" : "EXPN"); vrfy = c->cmdcode == CMDVRFY; if (bitset(vrfy ? PRIV_NOVRFY : PRIV_NOEXPN, PrivacyFlags)) @@ -867,8 +883,8 @@ smtp(nullserver, e) } /* crude way to avoid denial-of-service attacks */ - if (n_etrn++ >= 3) - sleep(3); + checksmtpattack(&n_etrn, MAXETRNCOMMANDS, "ETRN"); + id = p; if (*id == '@') id++; @@ -892,6 +908,7 @@ smtp(nullserver, e) break; case CMDNOOP: /* noop -- do nothing */ + checksmtpattack(&n_noop, MAXNOOPCOMMANDS, "NOOP"); message("250 OK"); break; @@ -916,17 +933,20 @@ doquit: message("502 Verbose unavailable"); break; } + checksmtpattack(&n_noop, MAXNOOPCOMMANDS, "VERB"); Verbose = TRUE; e->e_sendmode = SM_DELIVER; message("250 Verbose mode"); break; case CMDONEX: /* doing one transaction only */ + checksmtpattack(&n_noop, MAXNOOPCOMMANDS, "ONEX"); OneXact = TRUE; message("250 Only one transaction"); break; case CMDXUSR: /* initial (user) submission */ + checksmtpattack(&n_noop, MAXNOOPCOMMANDS, "XUSR"); UserSubmission = TRUE; message("250 Initial submission"); break; @@ -976,6 +996,40 @@ doquit: } } /* +** CHECKSMTPATTACK -- check for denial-of-service attack by repetition +** +** Parameters: +** pcounter -- pointer to a counter for this command. +** maxcount -- maximum value for this counter before we +** slow down. +** cname -- command name for logging. +** +** Returns: +** none. +** +** Side Effects: +** Slows down if we seem to be under attack. +*/ + +void +checksmtpattack(pcounter, maxcount, cname) + volatile int *pcounter; + int maxcount; + char *cname; +{ + if (++(*pcounter) >= maxcount) + { +#ifdef LOG + if (*pcounter == maxcount && LogLevel > 5) + { + syslog(LOG_INFO, "%.100s: %.40s attack?", + CurSmtpClient, cname); + } +#endif + sleep(*pcounter / maxcount); + } +} + /* ** SKIPWORD -- skip a fixed word. ** ** Parameters: |