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commit 72c678024d5f7b97bae8c20cc3fb2e0299778d5b
Author: Tomas Korbar <tkorbar@redhat.com>
Date: Mon Sep 7 12:41:05 2020 +0200
Backport confTLS_FALLBACK_TO_CLEAR Configuration option
diff --git a/cf/README b/cf/README
index 91e69a9..e8941ad 100644
--- a/cf/README
+++ b/cf/README
@@ -4011,6 +4011,10 @@ confUSERDB_SPEC UserDatabaseSpec
confFALLBACK_MX FallbackMXhost [undefined] Fallback MX host.
confFALLBACK_SMARTHOST FallbackSmartHost
[undefined] Fallback smart host.
+confTLS_FALLBACK_TO_CLEAR TLSFallbacktoClear
+ [undefined] If set, immediately try
+ a connection again without STARTTLS
+ after a TLS handshake failure.
confTRY_NULL_MX_LIST TryNullMXList [False] If this host is the best MX
for a host and other arrangements
haven't been made, try connecting
diff --git a/cf/m4/proto.m4 b/cf/m4/proto.m4
index 0df3416..a741d97 100644
--- a/cf/m4/proto.m4
+++ b/cf/m4/proto.m4
@@ -656,6 +656,8 @@ _OPTION(CipherList, `confCIPHER_LIST', `')
_OPTION(ServerSSLOptions, `confSERVER_SSL_OPTIONS', `')
# client side SSL options
_OPTION(ClientSSLOptions, `confCLIENT_SSL_OPTIONS', `')
+# TLS: fall back to clear text after handshake failure?
+_OPTION(TLSFallbacktoClear, `confTLS_FALLBACK_TO_CLEAR', `')
# Input mail filters
_OPTION(InputMailFilters, `confINPUT_MAIL_FILTERS', `')
@@ -2856,6 +2858,7 @@ R<$-:$+><VERIFY $*> <$*> FAIL $#error $@ $2 $: $1 " authentication failed"
R<$-:$+><VERIFY $*> <$*> NO $#error $@ $2 $: $1 " not authenticated"
R<$-:$+><VERIFY $*> <$*> NOT $#error $@ $2 $: $1 " no authentication requested"
R<$-:$+><VERIFY $*> <$*> NONE $#error $@ $2 $: $1 " other side does not support STARTTLS"
+R<$-:$+><VERIFY $*> <$*> CLEAR $#error $@ $2 $: $1 " STARTTLS disabled locally"
dnl some other value for ${verify}
R<$-:$+><VERIFY $*> <$*> $+ $#error $@ $2 $: $1 " authentication failure " $4
dnl some level of encryption required: get the maximum level (case 2.)
diff --git a/doc/op/op.me b/doc/op/op.me
index 57e25cd..97d3b9c 100644
--- a/doc/op/op.me
+++ b/doc/op/op.me
@@ -8340,6 +8340,22 @@ PostMilter is useful only when
.i sendmail
is running as an SMTP server; in all other situations it
acts the same as True.
+.ip TLSFallbacktoClear
+[no short name]
+If set,
+.i sendmail
+immediately tries an outbound connection again without STARTTLS
+after a TLS handshake failure.
+Note:
+this applies to all connections even if TLS specific requirements are set
+(see rulesets
+.i tls_rcpt
+and
+.i tls_client
+).
+Hence such requirements will cause an error on a retry without STARTTLS.
+Therefore they should only trigger a temporary failure so the connection
+is later on tried again.
.ip TLSSrvOptions
[no short name]
List of options for SMTP STARTTLS for the server
diff --git a/sendmail/deliver.c b/sendmail/deliver.c
index 8027a50..af42e8f 100644
--- a/sendmail/deliver.c
+++ b/sendmail/deliver.c
@@ -1334,6 +1334,10 @@ deliver(e, firstto)
char *pv[MAXPV + 1];
char buf[MAXNAME + 1];
char cbuf[MAXPATHLEN];
+#if STARTTLS
+ /* 0: try TLS, 1: try without TLS again, >1: don't try again */
+ int tlsstate;
+#endif
errno = 0;
SM_REQUIRE(firstto != NULL); /* same as to */
@@ -1349,7 +1353,9 @@ deliver(e, firstto)
e->e_statmsg = NULL;
SmtpError[0] = '\0';
xstart = curtime();
-
+#if STARTTLS
+ tlsstate = 0;
+#endif
if (tTd(10, 1))
sm_dprintf("\n--deliver, id=%s, mailer=%s, host=`%s', first user=`%s'\n",
e->e_id, m->m_name, host, to->q_user);
@@ -2073,6 +2079,9 @@ tryhost:
hostnum++;
if (endp != NULL)
*endp = sep;
+#if STARTTLS
+ tlsstate = 0;
+#endif
one_last_try:
/* see if we already know that this host is fried */
@@ -2960,6 +2969,8 @@ reconnect: /* after switching to an encrypted connection */
usetls = bitset(MCIF_TLS, mci->mci_flags);
if (usetls)
usetls = !iscltflgset(e, D_NOTLS);
+ if (usetls)
+ usetls = tlsstate == 0;
host = macvalue(macid("{server_name}"), e);
if (usetls)
@@ -3025,8 +3036,11 @@ reconnect: /* after switching to an encrypted connection */
}
}
else
+ {
+ p = tlsstate == 0 ? "NONE": "CLEAR";
macdefine(&e->e_macro, A_PERM,
- macid("{verify}"), "NONE");
+ macid("{verify}"), p);
+ }
olderrors = Errors;
QuickAbort = false;
SuprErrs = true;
@@ -3077,6 +3091,10 @@ reconnect: /* after switching to an encrypted connection */
}
mci->mci_flags &= ~MCIF_TLSACT;
(void) endmailer(mci, e, pv);
+ if (TLSFallbacktoClear)
+ {
+ ++tlsstate;
+ }
}
else
{
@@ -3119,6 +3137,27 @@ reconnect: /* after switching to an encrypted connection */
mci_clr_extensions(mci);
goto reconnect;
}
+ if (tlsstate == 1)
+ {
+ if (tTd(11, 1))
+ {
+ sm_syslog(LOG_DEBUG, NOQID,
+ "STARTTLS=client, relay=%.100s, tlsstate=%d, status=trying_again",
+ mci->mci_host, tlsstate);
+ mci_dump(NULL, mci, true);
+ }
+ ++tlsstate;
+ /*
+ ** Fake the status so a new connection is
+ ** tried, otherwise the TLS error will
+ ** "persist" during this delivery attempt.
+ */
+
+ mci->mci_errno = 0;
+ rcode = EX_OK;
+ mci_setstat(mci, rcode, NULL, NULL);
+ goto one_last_try;
+ }
}
# endif /* STARTTLS */
# if SASL
diff --git a/sendmail/readcf.c b/sendmail/readcf.c
index 86892f5..82660f4 100644
--- a/sendmail/readcf.c
+++ b/sendmail/readcf.c
@@ -2911,7 +2911,10 @@ static struct optioninfo
#endif
#define O_USECOMPRESSEDIPV6ADDRESSES 0xec
{ "UseCompressedIPv6Addresses", O_USECOMPRESSEDIPV6ADDRESSES, OI_NONE },
-
+#if STARTTLS
+# define O_TLSFB2CLEAR 0xef
+ { "TLSFallbacktoClear", O_TLSFB2CLEAR, OI_NONE },
+#endif
{ NULL, '\0', OI_NONE }
};
@@ -4305,6 +4308,9 @@ setoption(opt, val, safe, sticky, e)
#endif /* SASL */
#if STARTTLS
+ case O_TLSFB2CLEAR:
+ TLSFallbacktoClear = atobool(val);
+ break;
case O_SRVCERTFILE:
SET_STRING_EXP(SrvCertFile);
case O_SRVKEYFILE:
diff --git a/sendmail/sendmail.h b/sendmail/sendmail.h
index 441399c..9be1e76 100644
--- a/sendmail/sendmail.h
+++ b/sendmail/sendmail.h
@@ -2032,6 +2032,7 @@ EXTERN char *CRLPath; /* path to CRLs (dir. with hashes) */
#endif /* _FFR_CRLPATH */
EXTERN unsigned long TLS_Srv_Opts; /* TLS server options */
EXTERN unsigned long Srv_SSL_Options, Clt_SSL_Options; /* SSL options */
+EXTERN bool TLSFallbacktoClear;
#endif /* STARTTLS */
/*
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