1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
From 2d3ac49df11f0aed81f35ce9588eb2c578ec98f2 Mon Sep 17 00:00:00 2001
From: Kees Cook <kees@debian.org>
Date: Sun, 9 Feb 2014 16:10:06 +0000
Subject: Add DebianBanner server configuration option
Setting this to "no" causes sshd to omit the Debian revision from its
initial protocol handshake, for those scared by package-versioning.patch.
Bug-Debian: http://bugs.debian.org/562048
Forwarded: not-needed
Last-Update: 2023-01-02
Patch-Name: debian-banner.patch
---
kex.c | 5 +++--
kex.h | 2 +-
servconf.c | 9 +++++++++
servconf.h | 2 ++
sshconnect.c | 2 +-
sshd.c | 2 +-
sshd_config.5 | 5 +++++
7 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/kex.c b/kex.c
index 32858e65c..e7b7316c7 100644
--- a/kex.c
+++ b/kex.c
@@ -1272,7 +1272,7 @@ send_error(struct ssh *ssh, char *msg)
*/
int
kex_exchange_identification(struct ssh *ssh, int timeout_ms,
- const char *version_addendum)
+ int debian_banner, const char *version_addendum)
{
int remote_major, remote_minor, mismatch, oerrno = 0;
size_t len, n;
@@ -1290,7 +1290,8 @@ kex_exchange_identification(struct ssh *ssh, int timeout_ms,
if (version_addendum != NULL && *version_addendum == '\0')
version_addendum = NULL;
if ((r = sshbuf_putf(our_version, "SSH-%d.%d-%.100s%s%s\r\n",
- PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_RELEASE,
+ PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
+ debian_banner ? SSH_RELEASE : SSH_RELEASE_MINIMUM,
version_addendum == NULL ? "" : " ",
version_addendum == NULL ? "" : version_addendum)) != 0) {
oerrno = errno;
diff --git a/kex.h b/kex.h
index 240dca89d..e356f5ed0 100644
--- a/kex.h
+++ b/kex.h
@@ -200,7 +200,7 @@ char *kex_names_cat(const char *, const char *);
int kex_assemble_names(char **, const char *, const char *);
int kex_gss_names_valid(const char *);
-int kex_exchange_identification(struct ssh *, int, const char *);
+int kex_exchange_identification(struct ssh *, int, int, const char *);
struct kex *kex_new(void);
int kex_ready(struct ssh *, char *[PROPOSAL_MAX]);
diff --git a/servconf.c b/servconf.c
index 6529f2736..4ecbca8ed 100644
--- a/servconf.c
+++ b/servconf.c
@@ -203,6 +203,7 @@ initialize_server_options(ServerOptions *options)
options->channel_timeouts = NULL;
options->num_channel_timeouts = 0;
options->unused_connection_timeout = -1;
+ options->debian_banner = -1;
}
/* Returns 1 if a string option is unset or set to "none" or 0 otherwise. */
@@ -461,6 +462,8 @@ fill_default_server_options(ServerOptions *options)
options->required_rsa_size = SSH_RSA_MINIMUM_MODULUS_SIZE;
if (options->unused_connection_timeout == -1)
options->unused_connection_timeout = 0;
+ if (options->debian_banner == -1)
+ options->debian_banner = 1;
assemble_algorithms(options);
@@ -546,6 +549,7 @@ typedef enum {
sAllowStreamLocalForwarding, sFingerprintHash, sDisableForwarding,
sExposeAuthInfo, sRDomain, sPubkeyAuthOptions, sSecurityKeyProvider,
sRequiredRSASize, sChannelTimeout, sUnusedConnectionTimeout,
+ sDebianBanner,
sDeprecated, sIgnore, sUnsupported
} ServerOpCodes;
@@ -719,6 +723,7 @@ static struct {
{ "requiredrsasize", sRequiredRSASize, SSHCFG_ALL },
{ "channeltimeout", sChannelTimeout, SSHCFG_ALL },
{ "unusedconnectiontimeout", sUnusedConnectionTimeout, SSHCFG_ALL },
+ { "debianbanner", sDebianBanner, SSHCFG_GLOBAL },
{ NULL, sBadOption, 0 }
};
@@ -2596,6 +2601,10 @@ process_server_config_line_depth(ServerOptions *options, char *line,
}
goto parse_time;
+ case sDebianBanner:
+ intptr = &options->debian_banner;
+ goto parse_flag;
+
case sDeprecated:
case sIgnore:
case sUnsupported:
diff --git a/servconf.h b/servconf.h
index 38a68d576..e142cf77a 100644
--- a/servconf.h
+++ b/servconf.h
@@ -238,6 +238,8 @@ typedef struct {
u_int num_channel_timeouts;
int unused_connection_timeout;
+
+ int debian_banner;
} ServerOptions;
/* Information about the incoming connection as used by Match */
diff --git a/sshconnect.c b/sshconnect.c
index 77a3080ba..dbb3c98a7 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1574,7 +1574,7 @@ ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost,
lowercase(host);
/* Exchange protocol version identification strings with the server. */
- if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0)
+ if ((r = kex_exchange_identification(ssh, timeout_ms, 1, NULL)) != 0)
sshpkt_fatal(ssh, r, "banner exchange");
/* Put the connection into non-blocking mode. */
diff --git a/sshd.c b/sshd.c
index dd4a19131..b4ee435e5 100644
--- a/sshd.c
+++ b/sshd.c
@@ -2238,7 +2238,7 @@ main(int ac, char **av)
if (!debug_flag)
alarm(options.login_grace_time);
- if ((r = kex_exchange_identification(ssh, -1,
+ if ((r = kex_exchange_identification(ssh, -1, options.debian_banner,
options.version_addendum)) != 0)
sshpkt_fatal(ssh, r, "banner exchange");
diff --git a/sshd_config.5 b/sshd_config.5
index eb58750a5..2c6ec76cb 100644
--- a/sshd_config.5
+++ b/sshd_config.5
@@ -615,6 +615,11 @@ or
.Cm no .
The default is
.Cm yes .
+.It Cm DebianBanner
+Specifies whether the distribution-specified extra version suffix is
+included during initial protocol handshake.
+The default is
+.Cm yes .
.It Cm DenyGroups
This keyword can be followed by a list of group name patterns, separated
by spaces.
|
