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diff --git a/readconf.c b/readconf.c
index 724974b7..97a1ffd8 100644
--- a/readconf.c
+++ b/readconf.c
@@ -161,6 +161,7 @@ typedef enum {
oClearAllForwardings, oNoHostAuthenticationForLocalhost,
oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
oAddressFamily, oGssAuthentication, oGssDelegateCreds,
+ oGssTrustDns,
oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
oSendEnv, oSetEnv, oControlPath, oControlMaster, oControlPersist,
oHashKnownHosts,
@@ -206,9 +207,11 @@ static struct {
#if defined(GSSAPI)
{ "gssapiauthentication", oGssAuthentication },
{ "gssapidelegatecredentials", oGssDelegateCreds },
+ { "gssapitrustdns", oGssTrustDns },
# else
{ "gssapiauthentication", oUnsupported },
{ "gssapidelegatecredentials", oUnsupported },
+ { "gssapitrustdns", oUnsupported },
#endif
#ifdef ENABLE_PKCS11
{ "pkcs11provider", oPKCS11Provider },
@@ -1083,6 +1086,10 @@ parse_time:
intptr = &options->gss_deleg_creds;
goto parse_flag;
+ case oGssTrustDns:
+ intptr = &options->gss_trust_dns;
+ goto parse_flag;
+
case oBatchMode:
intptr = &options->batch_mode;
goto parse_flag;
@@ -2183,6 +2190,7 @@ initialize_options(Options * options)
options->challenge_response_authentication = -1;
options->gss_authentication = -1;
options->gss_deleg_creds = -1;
+ options->gss_trust_dns = -1;
options->password_authentication = -1;
options->kbd_interactive_authentication = -1;
options->kbd_interactive_devices = NULL;
@@ -2340,6 +2348,8 @@ fill_default_options(Options * options)
options->gss_authentication = 0;
if (options->gss_deleg_creds == -1)
options->gss_deleg_creds = 0;
+ if (options->gss_trust_dns == -1)
+ options->gss_trust_dns = 0;
if (options->password_authentication == -1)
options->password_authentication = 1;
if (options->kbd_interactive_authentication == -1)
diff --git a/readconf.h b/readconf.h
index 2fba866e..da3ce87a 100644
--- a/readconf.h
+++ b/readconf.h
@@ -42,6 +42,7 @@ typedef struct {
/* Try S/Key or TIS, authentication. */
int gss_authentication; /* Try GSS authentication */
int gss_deleg_creds; /* Delegate GSS credentials */
+ int gss_trust_dns; /* Trust DNS for GSS canonicalization */
int password_authentication; /* Try password
* authentication. */
int kbd_interactive_authentication; /* Try keyboard-interactive auth. */
diff --git a/ssh_config.5 b/ssh_config.5
index f8119189..e0fd0d76 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -783,6 +783,16 @@ The default is
Forward (delegate) credentials to the server.
The default is
.Cm no .
+Note that this option applies to protocol version 2 connections using GSSAPI.
+.It Cm GSSAPITrustDns
+Set to
+.Dq yes to indicate that the DNS is trusted to securely canonicalize
+the name of the host being connected to. If
+.Dq no, the hostname entered on the
+command line will be passed untouched to the GSSAPI library.
+The default is
+.Dq no .
+This option only applies to protocol version 2 connections using GSSAPI.
.It Cm HashKnownHosts
Indicates that
.Xr ssh 1
diff --git a/sshconnect2.c b/sshconnect2.c
index 059c9480..ab6f6832 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -770,6 +770,13 @@ userauth_gssapi(struct ssh *ssh)
OM_uint32 min;
int r, ok = 0;
gss_OID mech = NULL;
+ const char *gss_host;
+
+ if (options.gss_trust_dns) {
+ extern const char *auth_get_canonical_hostname(struct ssh *ssh, int use_dns);
+ gss_host = auth_get_canonical_hostname(ssh, 1);
+ } else
+ gss_host = authctxt->host;
/* Try one GSSAPI method at a time, rather than sending them all at
* once. */
@@ -784,7 +791,7 @@ userauth_gssapi(struct ssh *ssh)
elements[authctxt->mech_tried];
/* My DER encoding requires length<128 */
if (mech->length < 128 && ssh_gssapi_check_mechanism(&gssctxt,
- mech, authctxt->host)) {
+ mech, gss_host)) {
ok = 1; /* Mechanism works */
} else {
authctxt->mech_tried++;
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