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postfix: Backport fix for CVE-2023-51764

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Import patches from ubuntu launchpad  fix CVE-2023-51764

Upstream-Status: Backport from [https://launchpad.net/ubuntu/+source/postfix/3.6.4-1ubuntu1.3]
Signed-off-by: Ashish Sharma <asharma@mvista.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
This commit is contained in:
Ashish Sharma
2024-01-31 21:53:42 +05:30
committed by Armin Kuster
parent f81b181933
commit 667850f086
3 changed files with 1357 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
meta-networking/recipes-daemons/postfix/files/CVE-2023-51764-1.patch
+377
View File
@@ -0,0 +1,377 @@
From a6596ec37a4892e1d9c2498ecbfc4b8e6be5156a Mon Sep 17 00:00:00 2001
From: Wietse Venema <wietse@porcupine.org>
Date: Fri, 22 Dec 2023 00:00:00 -0500
Subject: [PATCH] postfix-3.6.13
---
Upstream-Status: Backport from [https://launchpad.net/ubuntu/+source/postfix/3.6.4-1ubuntu1.3]
CVE: CVE-2023-51764
Signed-off-by: Ashish Sharma <asharma@mvista.com>
man/man5/postconf.5 | 55 +++++++++++++++++++++++++++++++++++++++++++++++
man/man8/smtpd.8 | 9 +++++++
mantools/postlink | 2 +
proto/postconf.proto | 52 ++++++++++++++++++++++++++++++++++++++++++++
src/global/mail_params.h | 11 ++++++++-
src/global/smtp_stream.c | 14 +++++++++++
src/global/smtp_stream.h | 2 +
src/smtpd/smtpd.c | 42 +++++++++++++++++++++++++++++++++++
8 files changed, 185 insertions(+), 2 deletions(-)
--- a/man/man5/postconf.5
+++ b/man/man5/postconf.5
@@ -10412,6 +10412,61 @@
parameter $name expansion.
.PP
This feature is available in Postfix 2.0 and later.
+.SH smtpd_forbid_bare_newline (default: Postfix < 3.9: no)
+Reply with "Error: bare <LF> received" and disconnect
+when a remote SMTP client sends a line ending in <LF>, violating
+the RFC 5321 requirement that lines must end in <CR><LF>.
+This feature is disbled by default with Postfix < 3.9. Use
+smtpd_forbid_bare_newline_exclusions to exclude non\-standard clients
+such as netcat. Specify "smtpd_forbid_bare_newline = no" to disable
+(not recommended for an Internet\-connected MTA).
+.PP
+See
+https://www.postfix.org/smtp\-smuggling.html for details.
+.PP
+Example:
+.sp
+.in +4
+.nf
+.na
+.ft C
+# Disconnect remote SMTP clients that send bare newlines, but allow
+# local clients with non\-standard SMTP implementations such as netcat,
+# fax machines, or load balancer health checks.
+#
+smtpd_forbid_bare_newline = yes
+smtpd_forbid_bare_newline_exclusions = $mynetworks
+.fi
+.ad
+.ft R
+.in -4
+.PP
+This feature is available in Postfix >= 3.9, 3.8.4, 3.7.9,
+3.6.13, and 3.5.23.
+.SH smtpd_forbid_bare_newline_exclusions (default: $mynetworks)
+Exclude the specified clients from smtpd_forbid_bare_newline
+enforcement. It uses the same syntax and parent\-domain matching
+behavior as mynetworks.
+.PP
+Example:
+.sp
+.in +4
+.nf
+.na
+.ft C
+# Disconnect remote SMTP clients that send bare newlines, but allow
+# local clients with non\-standard SMTP implementations such as netcat,
+# fax machines, or load balancer health checks.
+#
+smtpd_forbid_bare_newline = yes
+smtpd_forbid_bare_newline_exclusions = $mynetworks
+.fi
+.ad
+.ft R
+.in -4
+.PP
+This feature is available in Postfix >= 3.9, 3.8.4, 3.7.9,
+3.6.13, and 3.5.23.
.SH smtpd_forbidden_commands (default: CONNECT, GET, POST)
List of commands that cause the Postfix SMTP server to immediately
terminate the session with a 221 code. This can be used to disconnect
--- a/man/man8/smtpd.8
+++ b/man/man8/smtpd.8
@@ -808,6 +808,15 @@
The maximal number of AUTH commands that any client is allowed to
send to this service per time unit, regardless of whether or not
Postfix actually accepts those commands.
+.PP
+Available in Postfix 3.9, 3.8.4, 3.7.9, 3.6.13, 3.5.23 and later:
+.IP "\fBsmtpd_forbid_bare_newline (Postfix < 3.9: no)\fR"
+Reply with "Error: bare <LF> received" and disconnect
+when a remote SMTP client sends a line ending in <LF>, violating
+the RFC 5321 requirement that lines must end in <CR><LF>.
+.IP "\fBsmtpd_forbid_bare_newline_exclusions ($mynetworks)\fR"
+Exclude the specified clients from smtpd_forbid_bare_newline
+enforcement.
.SH "TARPIT CONTROLS"
.na
.nf
--- a/mantools/postlink
+++ b/mantools/postlink
@@ -547,6 +547,8 @@
s;\bsmtpd_error_sleep_time\b;<a href="postconf.5.html#smtpd_error_sleep_time">$&</a>;g;
s;\bsmtpd_etrn_restrictions\b;<a href="postconf.5.html#smtpd_etrn_restrictions">$&</a>;g;
s;\bsmtpd_expansion_filter\b;<a href="postconf.5.html#smtpd_expansion_filter">$&</a>;g;
+ s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_newline\b;<a href="postconf.5.html#smtpd_forbi d_bare_newline">$&</a>;g;
+ s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_newline_exclusions\b;<a href="postconf.5.html# smtpd_forbid_bare_newline_exclusions">$&</a>;g;
s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bidden_commands\b;<a href="postconf.5.html#smtpd_forbidden_commands">$&</a>;g;
s;\bsmtpd_hard_error_limit\b;<a href="postconf.5.html#smtpd_hard_error_limit">$&</a>;g;
s;\bsmtpd_helo_required\b;<a href="postconf.5.html#smtpd_helo_required">$&</a>;g;
--- a/proto/postconf.proto
+++ b/proto/postconf.proto
@@ -18058,3 +18058,55 @@
name or port number. </p>
<p> This feature is available in Postfix 3.6 and later. </p>
+
+%PARAM smtpd_forbid_bare_newline Postfix &lt; 3.9: no
+
+<p> Reply with "Error: bare &lt;LF&gt; received" and disconnect
+when a remote SMTP client sends a line ending in &lt;LF&gt;, violating
+the RFC 5321 requirement that lines must end in &lt;CR&gt;&lt;LF&gt;.
+This feature is disbled by default with Postfix &lt; 3.9. Use
+smtpd_forbid_bare_newline_exclusions to exclude non-standard clients
+such as netcat. Specify "smtpd_forbid_bare_newline = no" to disable
+(not recommended for an Internet-connected MTA). </p>
+
+<p> See <a href="https://www.postfix.org/smtp-smuggling.html">
+https://www.postfix.org/smtp-smuggling.html</a> for details.
+
+<p> Example: </p>
+
+<blockquote>
+<pre>
+# Disconnect remote SMTP clients that send bare newlines, but allow
+# local clients with non-standard SMTP implementations such as netcat,
+# fax machines, or load balancer health checks.
+#
+smtpd_forbid_bare_newline = yes
+smtpd_forbid_bare_newline_exclusions = $mynetworks
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix &ge; 3.9, 3.8.4, 3.7.9,
+3.6.13, and 3.5.23. </p>
+
+%PARAM smtpd_forbid_bare_newline_exclusions $mynetworks
+
+<p> Exclude the specified clients from smtpd_forbid_bare_newline
+enforcement. It uses the same syntax and parent-domain matching
+behavior as mynetworks. </p>
+
+<p> Example: </p>
+
+<blockquote>
+<pre>
+# Disconnect remote SMTP clients that send bare newlines, but allow
+# local clients with non-standard SMTP implementations such as netcat,
+# fax machines, or load balancer health checks.
+#
+smtpd_forbid_bare_newline = yes
+smtpd_forbid_bare_newline_exclusions = $mynetworks
+</pre>
+</blockquote>
+
+<p> This feature is available in Postfix &ge; 3.9, 3.8.4, 3.7.9,
+3.6.13, and 3.5.23. </p>
+
--- a/src/global/mail_params.h
+++ b/src/global/mail_params.h
@@ -4170,7 +4170,16 @@
extern char *var_smtpd_dns_re_filter;
/*
- * Share TLS sessions through tlproxy(8).
+ * Backwards compatibility.
+ */
+#define VAR_SMTPD_FORBID_BARE_LF "smtpd_forbid_bare_newline"
+#define DEF_SMTPD_FORBID_BARE_LF 0
+
+#define VAR_SMTPD_FORBID_BARE_LF_EXCL "smtpd_forbid_bare_newline_exclusions"
+#define DEF_SMTPD_FORBID_BARE_LF_EXCL "$" VAR_MYNETWORKS
+
+ /*
+ * Share TLS sessions through tlsproxy(8).
*/
#define VAR_SMTP_TLS_CONN_REUSE "smtp_tls_connection_reuse"
#define DEF_SMTP_TLS_CONN_REUSE 0
--- a/src/global/smtp_stream.c
+++ b/src/global/smtp_stream.c
@@ -50,6 +50,8 @@
/* VSTREAM *stream;
/* char *format;
/* va_list ap;
+/*
+/* int smtp_forbid_bare_lf;
/* AUXILIARY API
/* int smtp_get_noexcept(vp, stream, maxlen, flags)
/* VSTRING *vp;
@@ -124,11 +126,16 @@
/* smtp_vprintf() is the machine underneath smtp_printf().
/*
/* smtp_get_noexcept() implements the subset of smtp_get()
-/* without timeouts and without making long jumps. Instead,
+/* without long jumps for timeout or EOF errors. Instead,
/* query the stream status with vstream_feof() etc.
+/* This function will make a VSTREAM long jump (error code
+/* SMTP_ERR_LF) when rejecting input with a bare newline byte.
/*
/* smtp_timeout_setup() is a backwards-compatibility interface
/* for programs that don't require per-record deadline support.
+/*
+/* smtp_forbid_bare_lf controls whether smtp_get_noexcept()
+/* will reject input with a bare newline byte.
/* DIAGNOSTICS
/* .fi
/* .ad
@@ -201,6 +208,8 @@
#include "smtp_stream.h"
+int smtp_forbid_bare_lf;
+
/* smtp_timeout_reset - reset per-stream error flags, restart deadline timer */
static void smtp_timeout_reset(VSTREAM *stream)
@@ -404,6 +413,9 @@
*/
case '\n':
vstring_truncate(vp, VSTRING_LEN(vp) - 1);
+ if (smtp_forbid_bare_lf
+ && (VSTRING_LEN(vp) == 0 || vstring_end(vp)[-1] != '\r'))
+ vstream_longjmp(stream, SMTP_ERR_LF);
while (VSTRING_LEN(vp) > 0 && vstring_end(vp)[-1] == '\r')
vstring_truncate(vp, VSTRING_LEN(vp) - 1);
VSTRING_TERMINATE(vp);
--- a/src/global/smtp_stream.h
+++ b/src/global/smtp_stream.h
@@ -32,6 +32,7 @@
#define SMTP_ERR_QUIET 3 /* silent cleanup (application) */
#define SMTP_ERR_NONE 4 /* non-error case */
#define SMTP_ERR_DATA 5 /* application data error */
+#define SMTP_ERR_LF 6 /* bare <LF> protocol error */
extern void smtp_stream_setup(VSTREAM *, int, int);
extern void PRINTFLIKE(2, 3) smtp_printf(VSTREAM *, const char *,...);
@@ -43,6 +44,7 @@
extern void smtp_fwrite(const char *, ssize_t len, VSTREAM *);
extern void smtp_fread_buf(VSTRING *, ssize_t len, VSTREAM *);
extern void smtp_fputc(int, VSTREAM *);
+extern int smtp_forbid_bare_lf;
extern void smtp_vprintf(VSTREAM *, const char *, va_list);
--- a/src/smtpd/smtpd.c
+++ b/src/smtpd/smtpd.c
@@ -762,6 +762,15 @@
/* The maximal number of AUTH commands that any client is allowed to
/* send to this service per time unit, regardless of whether or not
/* Postfix actually accepts those commands.
+/* .PP
+/* Available in Postfix 3.9, 3.8.4, 3.7.9, 3.6.13, 3.5.23 and later:
+/* .IP "\fBsmtpd_forbid_bare_newline (Postfix < 3.9: no)\fR"
+/* Reply with "Error: bare <LF> received" and disconnect
+/* when a remote SMTP client sends a line ending in <LF>, violating
+/* the RFC 5321 requirement that lines must end in <CR><LF>.
+/* .IP "\fBsmtpd_forbid_bare_newline_exclusions ($mynetworks)\fR"
+/* Exclude the specified clients from smtpd_forbid_bare_newline
+/* enforcement.
/* TARPIT CONTROLS
/* .ad
/* .fi
@@ -1467,6 +1476,10 @@
int var_smtpd_uproxy_tmout;
bool var_relay_before_rcpt_checks;
+bool var_smtpd_forbid_bare_lf;
+char *var_smtpd_forbid_bare_lf_excl;
+static NAMADR_LIST *bare_lf_excl;
+
/*
* Silly little macros.
*/
@@ -1541,6 +1554,7 @@
#define REASON_TIMEOUT "timeout"
#define REASON_LOST_CONNECTION "lost connection"
#define REASON_ERROR_LIMIT "too many errors"
+#define REASON_BARE_LF "bare <LF> received"
#ifdef USE_TLS
@@ -3967,6 +3981,7 @@
*/
done = 0;
do {
+ int payload_err;
/*
* Do not skip the smtp_fread_buf() call if read_len == 0. We still
@@ -3980,6 +3995,10 @@
smtp_fread_buf(state->buffer, read_len, state->client);
state->bdat_get_stream = vstream_memreopen(
state->bdat_get_stream, state->buffer, O_RDONLY);
+ vstream_control(state->bdat_get_stream, CA_VSTREAM_CTL_EXCEPT,
+ CA_VSTREAM_CTL_END);
+ if ((payload_err = vstream_setjmp(state->bdat_get_stream)) != 0)
+ vstream_longjmp(state->client, payload_err);
/*
* Read lines from the fragment. The last line may continue in the
@@ -4655,6 +4674,9 @@
*/
xclient_allowed =
namadr_list_match(xclient_hosts, state->name, state->addr);
+ smtp_forbid_bare_lf = SMTPD_STAND_ALONE((state)) == 0
+ && var_smtpd_forbid_bare_lf
+ && !namadr_list_match(bare_lf_excl, state->name, state->addr);
/* NOT: tls_reset() */
if (got_helo == 0)
helo_reset(state);
@@ -5446,6 +5468,13 @@
var_myhostname);
break;
+ case SMTP_ERR_LF:
+ state->reason = REASON_BARE_LF;
+ if (vstream_setjmp(state->client) == 0)
+ smtpd_chat_reply(state, "521 5.5.2 %s Error: bare <LF> received",
+ var_myhostname);
+ break;
+
case 0:
/*
@@ -5995,6 +6024,13 @@
namadr_list_match(xforward_hosts, state.name, state.addr);
/*
+ * Enforce strict SMTP line endings, with compatibility exclusions.
+ */
+ smtp_forbid_bare_lf = SMTPD_STAND_ALONE((&state)) == 0
+ && var_smtpd_forbid_bare_lf
+ && !namadr_list_match(bare_lf_excl, state.name, state.addr);
+
+ /*
* See if we need to turn on verbose logging for this client.
*/
debug_peer_check(state.name, state.addr);
@@ -6055,6 +6091,10 @@
hogger_list = namadr_list_init(VAR_SMTPD_HOGGERS, MATCH_FLAG_RETURN
| match_parent_style(VAR_SMTPD_HOGGERS),
var_smtpd_hoggers);
+ bare_lf_excl = namadr_list_init(VAR_SMTPD_FORBID_BARE_LF_EXCL,
+ MATCH_FLAG_RETURN
+ | match_parent_style(VAR_MYNETWORKS),
+ var_smtpd_forbid_bare_lf_excl);
/*
* Open maps before dropping privileges so we can read passwords etc.
@@ -6412,6 +6452,7 @@
VAR_SMTPD_PEERNAME_LOOKUP, DEF_SMTPD_PEERNAME_LOOKUP, &var_smtpd_peername_lookup,
VAR_SMTPD_DELAY_OPEN, DEF_SMTPD_DELAY_OPEN, &var_smtpd_delay_open,
VAR_SMTPD_CLIENT_PORT_LOG, DEF_SMTPD_CLIENT_PORT_LOG, &var_smtpd_client_port_log,
+ VAR_SMTPD_FORBID_BARE_LF, DEF_SMTPD_FORBID_BARE_LF, &var_smtpd_forbid_bare_lf,
0,
};
static const CONFIG_NBOOL_TABLE nbool_table[] = {
@@ -6527,6 +6568,7 @@
VAR_SMTPD_POLICY_CONTEXT, DEF_SMTPD_POLICY_CONTEXT, &var_smtpd_policy_context, 0, 0,
VAR_SMTPD_DNS_RE_FILTER, DEF_SMTPD_DNS_RE_FILTER, &var_smtpd_dns_re_filter, 0, 0,
VAR_SMTPD_REJ_FTR_MAPS, DEF_SMTPD_REJ_FTR_MAPS, &var_smtpd_rej_ftr_maps, 0, 0,
+ VAR_SMTPD_FORBID_BARE_LF_EXCL, DEF_SMTPD_FORBID_BARE_LF_EXCL, &var_smtpd_forbid_bare_lf_excl, 0, 0,
0,
};
static const CONFIG_RAW_TABLE raw_table[] = {
meta-networking/recipes-daemons/postfix/files/CVE-2023-51764-2.patch
+978
View File
@@ -0,0 +1,978 @@
From cb3b1cbda3dec086a7f4541fe64751d9bb2988bd Mon Sep 17 00:00:00 2001
From: Wietse Venema <wietse@porcupine.org>
Date: Sun, 21 Jan 2024 00:00:00 -0500
Subject: [PATCH] postfix-3.6.14
---
Upstream-Status: Backport from [https://launchpad.net/ubuntu/+source/postfix/3.6.4-1ubuntu1.3]
CVE: CVE-2023-51764
Signed-off-by: Ashish Sharma <asharma@mvista.com>
man/man5/postconf.5 | 173 +++++++++++++++++++++++++++++++++++-------
man/man8/cleanup.8 | 8 +
man/man8/smtpd.8 | 11 +-
mantools/postlink | 6 -
proto/postconf.proto | 142 +++++++++++++++++++++++++++-------
src/cleanup/cleanup.c | 8 +
src/cleanup/cleanup_init.c | 2
src/cleanup/cleanup_message.c | 17 ++++
src/global/cleanup_strerror.c | 1
src/global/cleanup_user.h | 6 +
src/global/mail_params.h | 9 +-
src/global/smtp_stream.c | 34 +++++---
src/global/smtp_stream.h | 4
src/smtpd/smtpd.c | 114 ++++++++++++++++++++-------
src/smtpd/smtpd_check.c | 14 ++-
src/smtpd/smtpd_check.h | 1
16 files changed, 443 insertions(+), 107 deletions(-)
--- a/man/man5/postconf.5
+++ b/man/man5/postconf.5
@@ -845,6 +845,32 @@
.fi
.ad
.ft R
+.SH cleanup_replace_stray_cr_lf (default: yes)
+Replace each stray <CR> or <LF> character in message
+content with a space character, to prevent outbound SMTP smuggling,
+and to make the evaluation of Postfix\-added DKIM or other signatures
+independent from how a remote mail server handles such characters.
+.PP
+SMTP does not allow such characters unless they are part of a
+<CR><LF> sequence, and different mail systems handle
+such stray characters in an implementation\-dependent manner. Stray
+<CR> or <LF> characters could be used for outbound
+SMTP smuggling, where an attacker uses a Postfix server to send
+message content with a non\-standard End\-of\-DATA sequence that
+triggers inbound SMTP smuggling at a remote SMTP server.
+.PP
+The replacement happens before all other content management,
+and before Postfix may add a DKIM etc. signature; if the signature
+were created first, the replacement could invalidate the signature.
+.PP
+In addition to preventing SMTP smuggling, replacing stray
+<CR> or <LF> characters ensures that the result of
+signature validation by later mail system will not depend on how
+that mail system handles those stray characters in an
+implementation\-dependent manner.
+.PP
+This feature is available in Postfix >= 3.9, 3.8.5, 3.7.10,
+3.6.14, and 3.5.24.
.SH cleanup_service_name (default: cleanup)
The name of the \fBcleanup\fR(8) service. This service rewrites addresses
into the standard form, and performs \fBcanonical\fR(5) address mapping
@@ -10413,60 +10439,153 @@
.PP
This feature is available in Postfix 2.0 and later.
.SH smtpd_forbid_bare_newline (default: Postfix < 3.9: no)
-Reply with "Error: bare <LF> received" and disconnect
-when a remote SMTP client sends a line ending in <LF>, violating
-the RFC 5321 requirement that lines must end in <CR><LF>.
-This feature is disbled by default with Postfix < 3.9. Use
-smtpd_forbid_bare_newline_exclusions to exclude non\-standard clients
-such as netcat. Specify "smtpd_forbid_bare_newline = no" to disable
-(not recommended for an Internet\-connected MTA).
-.PP
-See
-https://www.postfix.org/smtp\-smuggling.html for details.
+Reject or restrict input lines from an SMTP client that end in
+<LF> instead of the standard <CR><LF>. Such line
+endings are commonly allowed with UNIX\-based SMTP servers, but they
+violate RFC 5321, and allowing such line endings can make a server
+vulnerable to
+SMTP smuggling.
+.PP
+Specify one of the following values (case does not matter):
+.IP "\fBnormalize\fR"
+Require the standard
+End\-of\-DATA sequence <CR><LF>.<CR><LF>.
+Otherwise, allow command or message content lines ending in the
+non\-standard <LF>, and process them as if the client sent the
+standard <CR><LF>.
+.br
+.br
+This maintains compatibility
+with many legitimate SMTP client applications that send a mix of
+standard and non\-standard line endings, but will fail to receive
+email from client implementations that do not terminate DATA content
+with the standard End\-of\-DATA sequence
+<CR><LF>.<CR><LF>.
+.br
+.br
+Such clients
+can be excluded with smtpd_forbid_bare_newline_exclusions.
+.br
+.IP "\fByes\fR"
+Compatibility alias for \fBnormalize\fR.
+.br
+.IP "\fBreject\fR"
+Require the standard End\-of\-DATA
+sequence <CR><LF>.<CR><LF>. Reject a command
+or message content when a line contains bare <LF>, log a "bare
+<LF> received" error, and reply with the SMTP status code in
+$smtpd_forbid_bare_newline_reject_code.
+.br
+.br
+This will reject
+email from SMTP clients that send any non\-standard line endings
+such as web applications, netcat, or load balancer health checks.
+.br
+.br
+This will also reject email from services that use BDAT
+to send MIME text containing a bare newline (RFC 3030 Section 3
+requires canonical MIME format for text message types, defined in
+RFC 2045 Sections 2.7 and 2.8).
+.br
+.br
+Such clients can be
+excluded with smtpd_forbid_bare_newline_exclusions (or, in the case
+of BDAT violations, BDAT can be selectively disabled with
+smtpd_discard_ehlo_keyword_address_maps, or globally disabled with
+smtpd_discard_ehlo_keywords).
+.br
+.IP "\fBno\fR (default)"
+Do not require the standard
+End\-of\-DATA
+sequence <CR><LF>.<CR><LF>. Always process
+a bare <LF> as if the client sent <CR><LF>. This
+option is fully backwards compatible, but is not recommended for
+an Internet\-facing SMTP server, because it is vulnerable to SMTP smuggling.
+.br
+.br
.PP
-Example:
+Recommended settings:
.sp
.in +4
.nf
.na
.ft C
-# Disconnect remote SMTP clients that send bare newlines, but allow
-# local clients with non\-standard SMTP implementations such as netcat,
-# fax machines, or load balancer health checks.
+# Require the standard End\-of\-DATA sequence <CR><LF>.<CR><LF>.
+# Otherwise, allow bare <LF> and process it as if the client sent
+# <CR><LF>.
#
-smtpd_forbid_bare_newline = yes
+# This maintains compatibility with many legitimate SMTP client
+# applications that send a mix of standard and non\-standard line
+# endings, but will fail to receive email from client implementations
+# that do not terminate DATA content with the standard End\-of\-DATA
+# sequence <CR><LF>.<CR><LF>.
+#
+# Such clients can be allowlisted with smtpd_forbid_bare_newline_exclusions.
+# The example below allowlists SMTP clients in trusted networks.
+#
+smtpd_forbid_bare_newline = normalize
smtpd_forbid_bare_newline_exclusions = $mynetworks
.fi
.ad
.ft R
.in -4
.PP
-This feature is available in Postfix >= 3.9, 3.8.4, 3.7.9,
-3.6.13, and 3.5.23.
-.SH smtpd_forbid_bare_newline_exclusions (default: $mynetworks)
-Exclude the specified clients from smtpd_forbid_bare_newline
-enforcement. It uses the same syntax and parent\-domain matching
-behavior as mynetworks.
-.PP
-Example:
+Alternative:
.sp
.in +4
.nf
.na
.ft C
-# Disconnect remote SMTP clients that send bare newlines, but allow
-# local clients with non\-standard SMTP implementations such as netcat,
-# fax machines, or load balancer health checks.
+# Reject input lines that contain <LF> and log a "bare <LF> received"
+# error. Require that input lines end in <CR><LF>, and require the
+# standard End\-of\-DATA sequence <CR><LF>.<CR><LF>.
+#
+# This will reject email from SMTP clients that send any non\-standard
+# line endings such as web applications, netcat, or load balancer
+# health checks.
#
-smtpd_forbid_bare_newline = yes
+# This will also reject email from services that use BDAT to send
+# MIME text containing a bare newline (RFC 3030 Section 3 requires
+# canonical MIME format for text message types, defined in RFC 2045
+# Sections 2.7 and 2.8).
+#
+# Such clients can be allowlisted with smtpd_forbid_bare_newline_exclusions.
+# The example below allowlists SMTP clients in trusted networks.
+#
+smtpd_forbid_bare_newline = reject
smtpd_forbid_bare_newline_exclusions = $mynetworks
+#
+# Alternatively, in the case of BDAT violations, BDAT can be selectively
+# disabled with smtpd_discard_ehlo_keyword_address_maps, or globally
+# disabled with smtpd_discard_ehlo_keywords.
+#
+# smtpd_discard_ehlo_keyword_address_maps = cidr:/path/to/file
+# /path/to/file:
+# 10.0.0.0/24 chunking, silent\-discard
+# smtpd_discard_ehlo_keywords = chunking, silent\-discard
.fi
.ad
.ft R
.in -4
.PP
+This feature with settings \fByes\fR and \fBno\fR is available
+in Postfix 3.8.4, 3.7.9, 3.6.13, and 3.5.23. Additionally, the
+settings \fBreject\fR, and \fBnormalize\fR are available with
+Postfix >= 3.9, 3.8.5, 3.7.10, 3.6.14, and 3.5.24.
+.SH smtpd_forbid_bare_newline_exclusions (default: $mynetworks)
+Exclude the specified clients from smtpd_forbid_bare_newline
+enforcement. This setting uses the same syntax and parent\-domain
+matching behavior as mynetworks.
+.PP
This feature is available in Postfix >= 3.9, 3.8.4, 3.7.9,
3.6.13, and 3.5.23.
+.SH smtpd_forbid_bare_newline_reject_code (default: 550)
+The numerical Postfix SMTP server response code when rejecting a
+request with "smtpd_forbid_bare_newline = reject".
+Specify a 5XX status code (521 to disconnect).
+.PP
+This feature is available in Postfix >= 3.9, 3.8.5, 3.7.10,
+3.6.14, and 3.5.24.
.SH smtpd_forbidden_commands (default: CONNECT, GET, POST)
List of commands that cause the Postfix SMTP server to immediately
terminate the session with a 221 code. This can be used to disconnect
--- a/man/man8/cleanup.8
+++ b/man/man8/cleanup.8
@@ -163,6 +163,14 @@
.IP "\fBmessage_strip_characters (empty)\fR"
The set of characters that Postfix will remove from message
content.
+.PP
+Available in Postfix version 3.9, 3.8.5, 3.7.10, 3.6.14,
+3.5.24, and later:
+.IP "\fBcleanup_replace_stray_cr_lf (yes)\fR"
+Replace each stray <CR> or <LF> character in message
+content with a space character, to prevent outbound SMTP smuggling,
+and to make the evaluation of Postfix\-added DKIM or other signatures
+independent from how a remote mail server handles such characters.
.SH "BEFORE QUEUE MILTER CONTROLS"
.na
.nf
--- a/man/man8/smtpd.8
+++ b/man/man8/smtpd.8
@@ -811,12 +811,17 @@
.PP
Available in Postfix 3.9, 3.8.4, 3.7.9, 3.6.13, 3.5.23 and later:
.IP "\fBsmtpd_forbid_bare_newline (Postfix < 3.9: no)\fR"
-Reply with "Error: bare <LF> received" and disconnect
-when a remote SMTP client sends a line ending in <LF>, violating
-the RFC 5321 requirement that lines must end in <CR><LF>.
+Reject or restrict input lines from an SMTP client that end in
+<LF> instead of the standard <CR><LF>.
.IP "\fBsmtpd_forbid_bare_newline_exclusions ($mynetworks)\fR"
Exclude the specified clients from smtpd_forbid_bare_newline
enforcement.
+.PP
+Available in Postfix 3.9, 3.8.5, 3.7.10, 3.6.14, 3.5.24 and
+later:
+.IP "\fBsmtpd_forbid_bare_newline_reject_code (550)\fR"
+The numerical Postfix SMTP server response code when rejecting a
+request with "smtpd_forbid_bare_newline = reject".
.SH "TARPIT CONTROLS"
.na
.nf
--- a/mantools/postlink
+++ b/mantools/postlink
@@ -547,8 +547,10 @@
s;\bsmtpd_error_sleep_time\b;<a href="postconf.5.html#smtpd_error_sleep_time">$&</a>;g;
s;\bsmtpd_etrn_restrictions\b;<a href="postconf.5.html#smtpd_etrn_restrictions">$&</a>;g;
s;\bsmtpd_expansion_filter\b;<a href="postconf.5.html#smtpd_expansion_filter">$&</a>;g;
- s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_newline\b;<a href="postconf.5.html#smtpd_forbi d_bare_newline">$&</a>;g;
- s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_newline_exclusions\b;<a href="postconf.5.html# smtpd_forbid_bare_newline_exclusions">$&</a>;g;
+ s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_new[-</bB>]*\n*[ <bB>]*line\b;<a href="postconf.5.html#smtpd_forbid_bare_newline">$&</a>;g;
+ s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_new[-</bB>]*\n*[ <bB>]*line_reject_code\b;<a href="postconf.5.html#smtpd_forbid_bare_newline_reject_code">$&</a>;g;
+ s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bid_bare_new[-</bB>]*\n*[ <bB>]*line_exclusions\b;<a href="postconf.5.html#smtpd_forbid_bare_newline_exclusions">$&</a>;g;
+ s;\bcleanup_replace_stray_cr_lf\b;<a href="postconf.5.html#cleanup_replace_stray_cr_lf">$&</a>;g;
s;\bsmtpd_for[-</bB>]*\n*[ <bB>]*bidden_commands\b;<a href="postconf.5.html#smtpd_forbidden_commands">$&</a>;g;
s;\bsmtpd_hard_error_limit\b;<a href="postconf.5.html#smtpd_hard_error_limit">$&</a>;g;
s;\bsmtpd_helo_required\b;<a href="postconf.5.html#smtpd_helo_required">$&</a>;g;
--- a/proto/postconf.proto
+++ b/proto/postconf.proto
@@ -18061,52 +18061,138 @@
%PARAM smtpd_forbid_bare_newline Postfix &lt; 3.9: no
-<p> Reply with "Error: bare &lt;LF&gt; received" and disconnect
-when a remote SMTP client sends a line ending in &lt;LF&gt;, violating
-the RFC 5321 requirement that lines must end in &lt;CR&gt;&lt;LF&gt;.
-This feature is disbled by default with Postfix &lt; 3.9. Use
-smtpd_forbid_bare_newline_exclusions to exclude non-standard clients
-such as netcat. Specify "smtpd_forbid_bare_newline = no" to disable
-(not recommended for an Internet-connected MTA). </p>
+<p> Reject or restrict input lines from an SMTP client that end in
+&lt;LF&gt; instead of the standard &lt;CR&gt;&lt;LF&gt;. Such line
+endings are commonly allowed with UNIX-based SMTP servers, but they
+violate RFC 5321, and allowing such line endings can make a server
+vulnerable to <a href="https://www.postfix.org/smtp-smuggling.html">
+SMTP smuggling</a>. </p>
+
+<p> Specify one of the following values (case does not matter): </p>
+
+<dl compact>
+
+<dt> <b>normalize</b></dt> <dd> Require the standard
+End-of-DATA sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;.
+Otherwise, allow command or message content lines ending in the
+non-standard &lt;LF&gt;, and process them as if the client sent the
+standard &lt;CR&gt;&lt;LF&gt;. <br> <br> This maintains compatibility
+with many legitimate SMTP client applications that send a mix of
+standard and non-standard line endings, but will fail to receive
+email from client implementations that do not terminate DATA content
+with the standard End-of-DATA sequence
+&lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;. <br> <br> Such clients
+can be excluded with smtpd_forbid_bare_newline_exclusions. </dd>
+
+<dt> <b>yes</b> </dt> <dd> Compatibility alias for <b>normalize</b>. </dd>
+
+<dt> <b>reject</b> </dt> <dd> Require the standard End-of-DATA
+sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;. Reject a command
+or message content when a line contains bare &lt;LF&gt;, log a "bare
+&lt;LF&gt; received" error, and reply with the SMTP status code in
+$smtpd_forbid_bare_newline_reject_code. <br> <br> This will reject
+email from SMTP clients that send any non-standard line endings
+such as web applications, netcat, or load balancer health checks.
+<br> <br> This will also reject email from services that use BDAT
+to send MIME text containing a bare newline (RFC 3030 Section 3
+requires canonical MIME format for text message types, defined in
+RFC 2045 Sections 2.7 and 2.8). <br> <br> Such clients can be
+excluded with smtpd_forbid_bare_newline_exclusions (or, in the case
+of BDAT violations, BDAT can be selectively disabled with
+smtpd_discard_ehlo_keyword_address_maps, or globally disabled with
+smtpd_discard_ehlo_keywords). </dd>
+
+<dt> <b>no</b> (default)</dt> <dd> Do not require the standard
+End-of-DATA
+sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;. Always process
+a bare &lt;LF&gt; as if the client sent &lt;CR&gt;&lt;LF&gt;. This
+option is fully backwards compatible, but is not recommended for
+an Internet-facing SMTP server, because it is vulnerable to <a
+href="https://www.postfix.org/smtp-smuggling.html"> SMTP smuggling</a>.
+</dd>
-<p> See <a href="https://www.postfix.org/smtp-smuggling.html">
-https://www.postfix.org/smtp-smuggling.html</a> for details.
+</dl>
-<p> Example: </p>
+<p> Recommended settings: </p>
<blockquote>
<pre>
-# Disconnect remote SMTP clients that send bare newlines, but allow
-# local clients with non-standard SMTP implementations such as netcat,
-# fax machines, or load balancer health checks.
+# Require the standard End-of-DATA sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;.
+# Otherwise, allow bare &lt;LF&gt; and process it as if the client sent
+# &lt;CR&gt;&lt;LF&gt;.
#
-smtpd_forbid_bare_newline = yes
+# This maintains compatibility with many legitimate SMTP client
+# applications that send a mix of standard and non-standard line
+# endings, but will fail to receive email from client implementations
+# that do not terminate DATA content with the standard End-of-DATA
+# sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;.
+#
+# Such clients can be allowlisted with smtpd_forbid_bare_newline_exclusions.
+# The example below allowlists SMTP clients in trusted networks.
+#
+smtpd_forbid_bare_newline = normalize
smtpd_forbid_bare_newline_exclusions = $mynetworks
</pre>
</blockquote>
-<p> This feature is available in Postfix &ge; 3.9, 3.8.4, 3.7.9,
-3.6.13, and 3.5.23. </p>
-
-%PARAM smtpd_forbid_bare_newline_exclusions $mynetworks
-
-<p> Exclude the specified clients from smtpd_forbid_bare_newline
-enforcement. It uses the same syntax and parent-domain matching
-behavior as mynetworks. </p>
-
-<p> Example: </p>
+<p> Alternative: </p>
<blockquote>
<pre>
-# Disconnect remote SMTP clients that send bare newlines, but allow
-# local clients with non-standard SMTP implementations such as netcat,
-# fax machines, or load balancer health checks.
+# Reject input lines that contain &lt;LF&gt; and log a "bare &lt;LF&gt; received"
+# error. Require that input lines end in &lt;CR&gt;&lt;LF&gt;, and require the
+# standard End-of-DATA sequence &lt;CR&gt;&lt;LF&gt;.&lt;CR&gt;&lt;LF&gt;.
+#
+# This will reject email from SMTP clients that send any non-standard
+# line endings such as web applications, netcat, or load balancer
+# health checks.
+#
+# This will also reject email from services that use BDAT to send
+# MIME text containing a bare newline (RFC 3030 Section 3 requires
+# canonical MIME format for text message types, defined in RFC 2045
+# Sections 2.7 and 2.8).
+#
+# Such clients can be allowlisted with smtpd_forbid_bare_newline_exclusions.
+# The example below allowlists SMTP clients in trusted networks.
#
-smtpd_forbid_bare_newline = yes
+smtpd_forbid_bare_newline = reject
smtpd_forbid_bare_newline_exclusions = $mynetworks
+#
+# Alternatively, in the case of BDAT violations, BDAT can be selectively
+# disabled with smtpd_discard_ehlo_keyword_address_maps, or globally
+# disabled with smtpd_discard_ehlo_keywords.
+#
+# smtpd_discard_ehlo_keyword_address_maps = cidr:/path/to/file
+# /path/to/file:
+# 10.0.0.0/24 chunking, silent-discard
+# smtpd_discard_ehlo_keywords = chunking, silent-discard
</pre>
</blockquote>
+<p> This feature with settings <b>yes</b> and <b>no</b> is available
+in Postfix 3.8.4, 3.7.9, 3.6.13, and 3.5.23. Additionally, the
+settings <b>reject</b>, and <b>normalize</b> are available with
+Postfix &ge; 3.9, 3.8.5, 3.7.10, 3.6.14, and 3.5.24. </p>
+
+%PARAM smtpd_forbid_bare_newline_exclusions $mynetworks
+
+<p> Exclude the specified clients from smtpd_forbid_bare_newline
+enforcement. This setting uses the same syntax and parent-domain
+matching behavior as mynetworks. </p>
+
<p> This feature is available in Postfix &ge; 3.9, 3.8.4, 3.7.9,
3.6.13, and 3.5.23. </p>
+%PARAM smtpd_forbid_bare_newline_reject_code 550
+
+<p>
+The numerical Postfix SMTP server response code when rejecting a
+request with "smtpd_forbid_bare_newline = reject".
+Specify a 5XX status code (521 to disconnect).
+</p>
+
+<p> This feature is available in Postfix &ge; 3.9, 3.8.5, 3.7.10,
+3.6.14, and 3.5.24. </p>
+
+%PARAM cleanup_replace_stray_cr_lf yes
+
--- a/src/cleanup/cleanup.c
+++ b/src/cleanup/cleanup.c
@@ -145,6 +145,14 @@
/* .IP "\fBmessage_strip_characters (empty)\fR"
/* The set of characters that Postfix will remove from message
/* content.
+/* .PP
+/* Available in Postfix version 3.9, 3.8.5, 3.7.10, 3.6.14,
+/* 3.5.24, and later:
+/* .IP "\fBcleanup_replace_stray_cr_lf (yes)\fR"
+/* Replace each stray <CR> or <LF> character in message
+/* content with a space character, to prevent outbound SMTP smuggling,
+/* and to make the evaluation of Postfix-added DKIM or other signatures
+/* independent from how a remote mail server handles such characters.
/* BEFORE QUEUE MILTER CONTROLS
/* .ad
/* .fi
--- a/src/cleanup/cleanup_init.c
+++ b/src/cleanup/cleanup_init.c
@@ -173,6 +173,7 @@
int var_always_add_hdrs; /* always add missing headers */
int var_virt_addrlen_limit; /* stop exponential growth */
char *var_hfrom_format; /* header_from_format */
+int var_cleanup_mask_stray_cr_lf; /* replace stray CR or LF with space */
const CONFIG_INT_TABLE cleanup_int_table[] = {
VAR_HOPCOUNT_LIMIT, DEF_HOPCOUNT_LIMIT, &var_hopcount_limit, 1, 0,
@@ -189,6 +190,7 @@
VAR_VERP_BOUNCE_OFF, DEF_VERP_BOUNCE_OFF, &var_verp_bounce_off,
VAR_AUTO_8BIT_ENC_HDR, DEF_AUTO_8BIT_ENC_HDR, &var_auto_8bit_enc_hdr,
VAR_ALWAYS_ADD_HDRS, DEF_ALWAYS_ADD_HDRS, &var_always_add_hdrs,
+ VAR_CLEANUP_MASK_STRAY_CR_LF, DEF_CLEANUP_MASK_STRAY_CR_LF, &var_cleanup_mask_stray_cr_lf,
0,
};
--- a/src/cleanup/cleanup_message.c
+++ b/src/cleanup/cleanup_message.c
@@ -930,6 +930,23 @@
char *dst;
/*
+ * Replace each stray CR or LF with one space. These are not allowed in
+ * SMTP, and can be used to enable outbound (remote) SMTP smuggling.
+ * Replacing these early ensures that our later DKIM etc. signature will
+ * not be invalidated. Besides preventing SMTP smuggling, replacing stray
+ * <CR> or <LF> ensures that the result of signature validation by a
+ * later mail system will not depend on how that mail system handles
+ * those stray characters in an implementation-dependent manner.
+ *
+ * The input length is not changed, therefore it is safe to overwrite the
+ * input.
+ */
+ if (var_cleanup_mask_stray_cr_lf)
+ for (dst = (char *) buf; dst < buf + len; dst++)
+ if (*dst == '\r' || *dst == '\n')
+ *dst = ' ';
+
+ /*
* Reject unwanted characters.
*
* XXX Possible optimization: simplify the loop when the "reject" set
--- a/src/global/cleanup_strerror.c
+++ b/src/global/cleanup_strerror.c
@@ -73,6 +73,7 @@
CLEANUP_STAT_CONT, 550, "5.7.1", "message content rejected",
CLEANUP_STAT_WRITE, 451, "4.3.0", "queue file write error",
CLEANUP_STAT_NOPERM, 550, "5.7.1", "service denied",
+ CLEANUP_STAT_BARE_LF, 521, "5.5.2", "bare <LF> received",
};
static CLEANUP_STAT_DETAIL cleanup_stat_success = {
--- a/src/global/cleanup_user.h
+++ b/src/global/cleanup_user.h
@@ -65,6 +65,12 @@
#define CLEANUP_STAT_NOPERM (1<<9) /* Denied by non-content policy */
/*
+ * Non-cleanup errors that live in the same bitmask space, to centralize
+ * error handling.
+ */
+#define CLEANUP_STAT_BARE_LF (1<<16) /* Bare <LF> received */
+
+ /*
* These are set when we can't bounce even if we were asked to.
*/
#define CLEANUP_STAT_MASK_CANT_BOUNCE \
--- a/src/global/mail_params.h
+++ b/src/global/mail_params.h
@@ -4173,11 +4173,18 @@
* Backwards compatibility.
*/
#define VAR_SMTPD_FORBID_BARE_LF "smtpd_forbid_bare_newline"
-#define DEF_SMTPD_FORBID_BARE_LF 0
+#define DEF_SMTPD_FORBID_BARE_LF "no"
#define VAR_SMTPD_FORBID_BARE_LF_EXCL "smtpd_forbid_bare_newline_exclusions"
#define DEF_SMTPD_FORBID_BARE_LF_EXCL "$" VAR_MYNETWORKS
+#define VAR_SMTPD_FORBID_BARE_LF_CODE "smtpd_forbid_bare_newline_reject_code"
+#define DEF_SMTPD_FORBID_BARE_LF_CODE 550
+
+#define VAR_CLEANUP_MASK_STRAY_CR_LF "cleanup_replace_stray_cr_lf"
+#define DEF_CLEANUP_MASK_STRAY_CR_LF 1
+extern int var_cleanup_mask_stray_cr_lf;
+
/*
* Share TLS sessions through tlsproxy(8).
*/
--- a/src/global/smtp_stream.c
+++ b/src/global/smtp_stream.c
@@ -51,7 +51,8 @@
/* char *format;
/* va_list ap;
/*
-/* int smtp_forbid_bare_lf;
+/* int smtp_detect_bare_lf;
+/* int smtp_got_bare_lf;
/* AUXILIARY API
/* int smtp_get_noexcept(vp, stream, maxlen, flags)
/* VSTRING *vp;
@@ -126,16 +127,16 @@
/* smtp_vprintf() is the machine underneath smtp_printf().
/*
/* smtp_get_noexcept() implements the subset of smtp_get()
-/* without long jumps for timeout or EOF errors. Instead,
+/* without timeouts and without making long jumps. Instead,
/* query the stream status with vstream_feof() etc.
-/* This function will make a VSTREAM long jump (error code
-/* SMTP_ERR_LF) when rejecting input with a bare newline byte.
+/*
+/* This function assigns smtp_got_bare_lf = smtp_detect_bare_lf,
+/* if smtp_detect_bare_lf is non-zero and the last read line
+/* was terminated with a bare newline. Otherwise, this function
+/* sets smtp_got_bare_lf to zero.
/*
/* smtp_timeout_setup() is a backwards-compatibility interface
/* for programs that don't require per-record deadline support.
-/*
-/* smtp_forbid_bare_lf controls whether smtp_get_noexcept()
-/* will reject input with a bare newline byte.
/* DIAGNOSTICS
/* .fi
/* .ad
@@ -208,7 +209,8 @@
#include "smtp_stream.h"
-int smtp_forbid_bare_lf;
+int smtp_detect_bare_lf;
+int smtp_got_bare_lf;
/* smtp_timeout_reset - reset per-stream error flags, restart deadline timer */
@@ -371,6 +373,8 @@
int last_char;
int next_char;
+ smtp_got_bare_lf = 0;
+
/*
* It's painful to do I/O with records that may span multiple buffers.
* Allow for partial long lines (we will read the remainder later) and
@@ -413,11 +417,15 @@
*/
case '\n':
vstring_truncate(vp, VSTRING_LEN(vp) - 1);
- if (smtp_forbid_bare_lf
- && (VSTRING_LEN(vp) == 0 || vstring_end(vp)[-1] != '\r'))
- vstream_longjmp(stream, SMTP_ERR_LF);
- while (VSTRING_LEN(vp) > 0 && vstring_end(vp)[-1] == '\r')
- vstring_truncate(vp, VSTRING_LEN(vp) - 1);
+ if (smtp_detect_bare_lf) {
+ if (VSTRING_LEN(vp) == 0 || vstring_end(vp)[-1] != '\r')
+ smtp_got_bare_lf = smtp_detect_bare_lf;
+ else
+ vstring_truncate(vp, VSTRING_LEN(vp) - 1);
+ } else {
+ while (VSTRING_LEN(vp) > 0 && vstring_end(vp)[-1] == '\r')
+ vstring_truncate(vp, VSTRING_LEN(vp) - 1);
+ }
VSTRING_TERMINATE(vp);
/* FALLTRHOUGH */
--- a/src/global/smtp_stream.h
+++ b/src/global/smtp_stream.h
@@ -32,7 +32,6 @@
#define SMTP_ERR_QUIET 3 /* silent cleanup (application) */
#define SMTP_ERR_NONE 4 /* non-error case */
#define SMTP_ERR_DATA 5 /* application data error */
-#define SMTP_ERR_LF 6 /* bare <LF> protocol error */
extern void smtp_stream_setup(VSTREAM *, int, int);
extern void PRINTFLIKE(2, 3) smtp_printf(VSTREAM *, const char *,...);
@@ -44,7 +43,8 @@
extern void smtp_fwrite(const char *, ssize_t len, VSTREAM *);
extern void smtp_fread_buf(VSTRING *, ssize_t len, VSTREAM *);
extern void smtp_fputc(int, VSTREAM *);
-extern int smtp_forbid_bare_lf;
+extern int smtp_detect_bare_lf;
+extern int smtp_got_bare_lf;
extern void smtp_vprintf(VSTREAM *, const char *, va_list);
--- a/src/smtpd/smtpd.c
+++ b/src/smtpd/smtpd.c
@@ -765,12 +765,17 @@
/* .PP
/* Available in Postfix 3.9, 3.8.4, 3.7.9, 3.6.13, 3.5.23 and later:
/* .IP "\fBsmtpd_forbid_bare_newline (Postfix < 3.9: no)\fR"
-/* Reply with "Error: bare <LF> received" and disconnect
-/* when a remote SMTP client sends a line ending in <LF>, violating
-/* the RFC 5321 requirement that lines must end in <CR><LF>.
+/* Reject or restrict input lines from an SMTP client that end in
+/* <LF> instead of the standard <CR><LF>.
/* .IP "\fBsmtpd_forbid_bare_newline_exclusions ($mynetworks)\fR"
/* Exclude the specified clients from smtpd_forbid_bare_newline
/* enforcement.
+/* .PP
+/* Available in Postfix 3.9, 3.8.5, 3.7.10, 3.6.14, 3.5.24 and
+/* later:
+/* .IP "\fBsmtpd_forbid_bare_newline_reject_code (550)\fR"
+/* The numerical Postfix SMTP server response code when rejecting a
+/* request with "smtpd_forbid_bare_newline = reject".
/* TARPIT CONTROLS
/* .ad
/* .fi
@@ -1476,8 +1481,10 @@
int var_smtpd_uproxy_tmout;
bool var_relay_before_rcpt_checks;
-bool var_smtpd_forbid_bare_lf;
+char *var_smtpd_forbid_bare_lf;
char *var_smtpd_forbid_bare_lf_excl;
+int var_smtpd_forbid_bare_lf_code;
+static int bare_lf_mask;
static NAMADR_LIST *bare_lf_excl;
/*
@@ -1554,7 +1561,6 @@
#define REASON_TIMEOUT "timeout"
#define REASON_LOST_CONNECTION "lost connection"
#define REASON_ERROR_LIMIT "too many errors"
-#define REASON_BARE_LF "bare <LF> received"
#ifdef USE_TLS
@@ -1573,6 +1579,40 @@
*/
static DICT *smtpd_cmd_filter;
+ /*
+ * Bare LF and End-of-DATA controls (bare CR is handled elsewhere).
+ *
+ * At the smtp_get*() line reader level, setting any of these flags in the
+ * smtp_detect_bare_lf variable enables the detection of bare newlines. The
+ * line reader will set the same flags in the smtp_got_bare_lf variable
+ * after it detects a bare newline, otherwise it clears smtp_got_bare_lf.
+ *
+ * At the SMTP command level, the flags in smtp_got_bare_lf control whether
+ * commands ending in a bare newline are rejected.
+ *
+ * At the DATA and BDAT content level, the flags in smtp_got_bare_lf control
+ * whether the standard End-of-DATA sequence CRLF.CRLF is required, and
+ * whether lines ending in bare newlines are rejected.
+ *
+ * Postfix implements "delayed reject" after detecting a bare newline in BDAT
+ * or DATA content. The SMTP server delays a REJECT response until the
+ * command is finished, instead of replying and hanging up immediately. The
+ * End-of-DATA detection is secured with BARE_LF_FLAG_WANT_STD_EOD.
+ */
+#define BARE_LF_FLAG_WANT_STD_EOD (1<<0) /* Require CRLF.CRLF */
+#define BARE_LF_FLAG_REPLY_REJECT (1<<1) /* Reject bare newline */
+
+#define IS_BARE_LF_WANT_STD_EOD(m) ((m) & BARE_LF_FLAG_WANT_STD_EOD)
+#define IS_BARE_LF_REPLY_REJECT(m) ((m) & BARE_LF_FLAG_REPLY_REJECT)
+
+static const NAME_CODE bare_lf_mask_table[] = {
+ "normalize", BARE_LF_FLAG_WANT_STD_EOD, /* Default */
+ "yes", BARE_LF_FLAG_WANT_STD_EOD, /* Migration aid */
+ "reject", BARE_LF_FLAG_WANT_STD_EOD | BARE_LF_FLAG_REPLY_REJECT,
+ "no", 0,
+ 0, -1, /* error */
+};
+
#ifdef USE_SASL_AUTH
/*
@@ -3515,6 +3555,7 @@
int curr_rec_type;
int prev_rec_type;
int first = 1;
+ int prev_got_bare_lf = 0;
/*
* Copy the message content. If the cleanup process has a problem, keep
@@ -3528,12 +3569,15 @@
* XXX Deal with UNIX-style From_ lines at the start of message content
* because sendmail permits it.
*/
- for (prev_rec_type = 0; /* void */ ; prev_rec_type = curr_rec_type) {
+ for (prev_rec_type = 0; /* void */ ; prev_rec_type = curr_rec_type,
+ prev_got_bare_lf = smtp_got_bare_lf) {
if (smtp_get(state->buffer, state->client, var_line_limit,
SMTP_GET_FLAG_NONE) == '\n')
curr_rec_type = REC_TYPE_NORM;
else
curr_rec_type = REC_TYPE_CONT;
+ if (IS_BARE_LF_REPLY_REJECT(smtp_got_bare_lf))
+ state->err |= CLEANUP_STAT_BARE_LF;
start = vstring_str(state->buffer);
len = VSTRING_LEN(state->buffer);
if (first) {
@@ -3546,9 +3590,14 @@
if (len > 0 && IS_SPACE_TAB(start[0]))
out_record(out_stream, REC_TYPE_NORM, "", 0);
}
- if (prev_rec_type != REC_TYPE_CONT && *start == '.'
- && (proxy == 0 ? (++start, --len) == 0 : len == 1))
- break;
+ if (prev_rec_type != REC_TYPE_CONT && *start == '.') {
+ if (len == 1 && IS_BARE_LF_WANT_STD_EOD(smtp_detect_bare_lf)
+ && (smtp_got_bare_lf || prev_got_bare_lf))
+ /* Do not store or send to proxy filter. */
+ continue;
+ if (proxy == 0 ? (++start, --len) == 0 : len == 1)
+ break;
+ }
if (state->err == CLEANUP_STAT_OK) {
if (ENFORCING_SIZE_LIMIT(var_message_limit)
&& var_message_limit - state->act_size < len + 2) {
@@ -3701,6 +3750,11 @@
else
smtpd_chat_reply(state,
"250 2.0.0 Ok: queued as %s", state->queue_id);
+ } else if ((state->err & CLEANUP_STAT_BARE_LF) != 0) {
+ state->error_mask |= MAIL_ERROR_PROTOCOL;
+ log_whatsup(state, "reject", "bare <LF> received");
+ smtpd_chat_reply(state, "%d 5.5.2 %s Error: bare <LF> received",
+ var_smtpd_forbid_bare_lf_code, var_myhostname);
} else if (why && IS_SMTP_REJECT(STR(why))) {
state->error_mask |= MAIL_ERROR_POLICY;
smtpd_chat_reply(state, "%s", STR(why));
@@ -3981,7 +4035,6 @@
*/
done = 0;
do {
- int payload_err;
/*
* Do not skip the smtp_fread_buf() call if read_len == 0. We still
@@ -3995,10 +4048,6 @@
smtp_fread_buf(state->buffer, read_len, state->client);
state->bdat_get_stream = vstream_memreopen(
state->bdat_get_stream, state->buffer, O_RDONLY);
- vstream_control(state->bdat_get_stream, CA_VSTREAM_CTL_EXCEPT,
- CA_VSTREAM_CTL_END);
- if ((payload_err = vstream_setjmp(state->bdat_get_stream)) != 0)
- vstream_longjmp(state->client, payload_err);
/*
* Read lines from the fragment. The last line may continue in the
@@ -4023,6 +4072,8 @@
/* Skip the out_record() and VSTRING_RESET() calls below. */
break;
}
+ if (IS_BARE_LF_REPLY_REJECT(smtp_got_bare_lf))
+ state->err |= CLEANUP_STAT_BARE_LF;
start = vstring_str(state->bdat_get_buffer);
len = VSTRING_LEN(state->bdat_get_buffer);
if (state->err == CLEANUP_STAT_OK) {
@@ -4674,9 +4725,9 @@
*/
xclient_allowed =
namadr_list_match(xclient_hosts, state->name, state->addr);
- smtp_forbid_bare_lf = SMTPD_STAND_ALONE((state)) == 0
- && var_smtpd_forbid_bare_lf
- && !namadr_list_match(bare_lf_excl, state->name, state->addr);
+ smtp_detect_bare_lf = (SMTPD_STAND_ALONE((state)) == 0 && bare_lf_mask
+ && !namadr_list_match(bare_lf_excl, state->name, state->addr)) ?
+ bare_lf_mask : 0;
/* NOT: tls_reset() */
if (got_helo == 0)
helo_reset(state);
@@ -5468,13 +5519,6 @@
var_myhostname);
break;
- case SMTP_ERR_LF:
- state->reason = REASON_BARE_LF;
- if (vstream_setjmp(state->client) == 0)
- smtpd_chat_reply(state, "521 5.5.2 %s Error: bare <LF> received",
- var_myhostname);
- break;
-
case 0:
/*
@@ -5676,6 +5720,13 @@
}
watchdog_pat();
smtpd_chat_query(state);
+ if (IS_BARE_LF_REPLY_REJECT(smtp_got_bare_lf)) {
+ log_whatsup(state, "reject", "bare <LF> received");
+ state->error_mask |= MAIL_ERROR_PROTOCOL;
+ smtpd_chat_reply(state, "%d 5.5.2 %s Error: bare <LF> received",
+ var_smtpd_forbid_bare_lf_code, var_myhostname);
+ break;
+ }
/* Safety: protect internal interfaces against malformed UTF-8. */
if (var_smtputf8_enable && valid_utf8_string(STR(state->buffer),
LEN(state->buffer)) == 0) {
@@ -6024,11 +6075,11 @@
namadr_list_match(xforward_hosts, state.name, state.addr);
/*
- * Enforce strict SMTP line endings, with compatibility exclusions.
+ * Reject or normalize bare LF, with compatibility exclusions.
*/
- smtp_forbid_bare_lf = SMTPD_STAND_ALONE((&state)) == 0
- && var_smtpd_forbid_bare_lf
- && !namadr_list_match(bare_lf_excl, state.name, state.addr);
+ smtp_detect_bare_lf = (SMTPD_STAND_ALONE((&state)) == 0 && bare_lf_mask
+ && !namadr_list_match(bare_lf_excl, state.name, state.addr)) ?
+ bare_lf_mask : 0;
/*
* See if we need to turn on verbose logging for this client.
@@ -6095,6 +6146,10 @@
MATCH_FLAG_RETURN
| match_parent_style(VAR_MYNETWORKS),
var_smtpd_forbid_bare_lf_excl);
+ if ((bare_lf_mask = name_code(bare_lf_mask_table, NAME_CODE_FLAG_NONE,
+ var_smtpd_forbid_bare_lf)) < 0)
+ msg_fatal("bad parameter value: '%s = %s'",
+ VAR_SMTPD_FORBID_BARE_LF, var_smtpd_forbid_bare_lf);
/*
* Open maps before dropping privileges so we can read passwords etc.
@@ -6390,6 +6445,7 @@
VAR_VIRT_MAILBOX_CODE, DEF_VIRT_MAILBOX_CODE, &var_virt_mailbox_code, 0, 0,
VAR_RELAY_RCPT_CODE, DEF_RELAY_RCPT_CODE, &var_relay_rcpt_code, 0, 0,
VAR_PLAINTEXT_CODE, DEF_PLAINTEXT_CODE, &var_plaintext_code, 0, 0,
+ VAR_SMTPD_FORBID_BARE_LF_CODE, DEF_SMTPD_FORBID_BARE_LF_CODE, &var_smtpd_forbid_bare_lf_code, 500, 599,
VAR_SMTPD_CRATE_LIMIT, DEF_SMTPD_CRATE_LIMIT, &var_smtpd_crate_limit, 0, 0,
VAR_SMTPD_CCONN_LIMIT, DEF_SMTPD_CCONN_LIMIT, &var_smtpd_cconn_limit, 0, 0,
VAR_SMTPD_CMAIL_LIMIT, DEF_SMTPD_CMAIL_LIMIT, &var_smtpd_cmail_limit, 0, 0,
@@ -6452,7 +6508,6 @@
VAR_SMTPD_PEERNAME_LOOKUP, DEF_SMTPD_PEERNAME_LOOKUP, &var_smtpd_peername_lookup,
VAR_SMTPD_DELAY_OPEN, DEF_SMTPD_DELAY_OPEN, &var_smtpd_delay_open,
VAR_SMTPD_CLIENT_PORT_LOG, DEF_SMTPD_CLIENT_PORT_LOG, &var_smtpd_client_port_log,
- VAR_SMTPD_FORBID_BARE_LF, DEF_SMTPD_FORBID_BARE_LF, &var_smtpd_forbid_bare_lf,
0,
};
static const CONFIG_NBOOL_TABLE nbool_table[] = {
@@ -6569,6 +6624,7 @@
VAR_SMTPD_DNS_RE_FILTER, DEF_SMTPD_DNS_RE_FILTER, &var_smtpd_dns_re_filter, 0, 0,
VAR_SMTPD_REJ_FTR_MAPS, DEF_SMTPD_REJ_FTR_MAPS, &var_smtpd_rej_ftr_maps, 0, 0,
VAR_SMTPD_FORBID_BARE_LF_EXCL, DEF_SMTPD_FORBID_BARE_LF_EXCL, &var_smtpd_forbid_bare_lf_excl, 0, 0,
+ VAR_SMTPD_FORBID_BARE_LF, DEF_SMTPD_FORBID_BARE_LF, &var_smtpd_forbid_bare_lf, 1, 0,
0,
};
static const CONFIG_RAW_TABLE raw_table[] = {
--- a/src/smtpd/smtpd_check.c
+++ b/src/smtpd/smtpd_check.c
@@ -48,6 +48,11 @@
/*
/* char *smtpd_check_queue(state)
/* SMTPD_STATE *state;
+/* AUXILIARY FUNCTIONS
+/* void log_whatsup(state, action, text)
+/* SMTPD_STATE *state;
+/* const char *action;
+/* const char *text;
/* DESCRIPTION
/* This module implements additional checks on SMTP client requests.
/* A client request is validated in the context of the session state.
@@ -146,6 +151,11 @@
/* The recipient address given with the RCPT TO or VRFY command.
/* .IP size
/* The message size given with the MAIL FROM command (zero if unknown).
+/* .PP
+/* log_whatsup() logs "<queueid>: <action>: <protocol state>
+/* from: <client-name[client-addr]>: <text>" plus the protocol
+/* (SMTP or ESMTP), and if available, EHLO, MAIL FROM, or RCPT
+/* TO.
/* BUGS
/* Policies like these should not be hard-coded in C, but should
/* be user-programmable instead.
@@ -987,8 +997,8 @@
/* log_whatsup - log as much context as we have */
-static void log_whatsup(SMTPD_STATE *state, const char *whatsup,
- const char *text)
+void log_whatsup(SMTPD_STATE *state, const char *whatsup,
+ const char *text)
{
VSTRING *buf = vstring_alloc(100);
--- a/src/smtpd/smtpd_check.h
+++ b/src/smtpd/smtpd_check.h
@@ -25,6 +25,7 @@
extern char *smtpd_check_data(SMTPD_STATE *);
extern char *smtpd_check_eod(SMTPD_STATE *);
extern char *smtpd_check_policy(SMTPD_STATE *, char *);
+extern void log_whatsup(SMTPD_STATE *, const char *, const char *);
/* LICENSE
/* .ad
meta-networking/recipes-daemons/postfix/postfix_3.6.7.bb
+2
View File
@@ -13,6 +13,8 @@ SRC_URI += "ftp://ftp.porcupine.org/mirrors/postfix-release/official/postfix-${P
file://0004-Fix-icu-config.patch \
file://0005-makedefs-add-lnsl-and-lresolv-to-SYSLIBS-by-default.patch \
file://0006-makedefs-Account-for-linux-6.x-version.patch \
file://CVE-2023-51764-1.patch \
file://CVE-2023-51764-2.patch \
"
SRC_URI[sha256sum] = "e471df7e0eb11c4a1e574b6d7298f635386e2843b6b3584c25a04543d587e07f"
UPSTREAM_CHECK_REGEX = "postfix\-(?P<pver>3\.6(\.\d+)+).tar.gz"