243 lines
8.1 KiB
Diff
243 lines
8.1 KiB
Diff
The patch below adds support for the deprecated 'gssapi' authentication
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mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
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in this release. The use of 'gssapi' is deprecated due to the presence of
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potential man-in-the-middle attacks, which 'gssapi-with-mic' is not
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susceptible to.
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To use the patch apply it to a OpenSSH 3.8p1 source tree. After compiling,
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backwards compatibility may be obtained by supplying the
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'GssapiEnableMitmAttack yes' option to either the client or server.
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It should be noted that this patch is being made available purely as a means
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of easing the process of moving to OpenSSH 3.8p1. Any new installations are
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recommended to use the 'gssapi-with-mic' mechanism. Existing installations
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are encouraged to upgrade as soon as possible.
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Index: auth2-gss.c
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================================================================================
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--- auth2-gss.c
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+++ auth2-gss.c
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@@ -177,6 +177,15 @@
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dispatch_set(
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SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
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&input_gssapi_exchange_complete);
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+
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+ /*
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+ * Old style 'gssapi' didn't have the GSSAPI_MIC
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+ * and went straight to sending exchange_complete
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+ */
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+ if (options.gss_enable_mitm)
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+ dispatch_set(
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+ SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
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+ &input_gssapi_exchange_complete);
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}
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}
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@@ -298,4 +307,10 @@
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&options.gss_authentication
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};
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+Authmethod method_gssapi_old = {
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+ "gssapi",
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+ userauth_gssapi,
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+ &options.gss_enable_mitm
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+};
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+
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#endif /* GSSAPI */
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--- auth2.c
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+++ auth2.c
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@@ -65,6 +65,7 @@
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extern Authmethod method_hostbased;
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#ifdef GSSAPI
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extern Authmethod method_gssapi;
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+extern Authmethod method_gssapi_old;
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#endif
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Authmethod *authmethods[] = {
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@@ -72,6 +73,7 @@
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&method_pubkey,
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#ifdef GSSAPI
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&method_gssapi,
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+ &method_gssapi_old,
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#endif
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&method_passwd,
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&method_kbdint,
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--- readconf.c
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+++ readconf.c
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@@ -126,7 +126,7 @@
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oHostKeyAlgorithms, oBindAddress, oSmartcardDevice,
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oClearAllForwardings, oNoHostAuthenticationForLocalhost,
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oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout,
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- oAddressFamily, oGssAuthentication, oGssDelegateCreds,
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+ oAddressFamily, oGssAuthentication, oGssDelegateCreds, oGssEnableMITM,
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oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly,
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oSendEnv, oControlPath, oControlMaster, oHashKnownHosts,
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oTunnel, oTunnelDevice, oLocalCommand, oPermitLocalCommand,
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@@ -164,9 +164,11 @@
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#if defined(GSSAPI)
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{ "gssapiauthentication", oGssAuthentication },
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{ "gssapidelegatecredentials", oGssDelegateCreds },
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+ { "gssapienablemitmattack", oGssEnableMITM },
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#else
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{ "gssapiauthentication", oUnsupported },
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{ "gssapidelegatecredentials", oUnsupported },
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+ { "gssapienablemitmattack", oUnsupported },
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#endif
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{ "fallbacktorsh", oDeprecated },
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{ "usersh", oDeprecated },
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@@ -445,6 +447,10 @@
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case oGssDelegateCreds:
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intptr = &options->gss_deleg_creds;
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goto parse_flag;
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+
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+ case oGssEnableMITM:
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+ intptr = &options->gss_enable_mitm;
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+ goto parse_flag;
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case oBatchMode:
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intptr = &options->batch_mode;
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@@ -1012,6 +1018,7 @@
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options->challenge_response_authentication = -1;
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options->gss_authentication = -1;
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options->gss_deleg_creds = -1;
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+ options->gss_enable_mitm = -1;
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options->password_authentication = -1;
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options->kbd_interactive_authentication = -1;
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options->kbd_interactive_devices = NULL;
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@@ -1102,6 +1109,8 @@
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options->gss_authentication = 0;
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if (options->gss_deleg_creds == -1)
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options->gss_deleg_creds = 0;
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+ if (options->gss_enable_mitm == -1)
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+ options->gss_enable_mitm = 0;
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if (options->password_authentication == -1)
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options->password_authentication = 1;
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if (options->kbd_interactive_authentication == -1)
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--- readconf.h
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+++ readconf.h
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@@ -45,6 +45,7 @@
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/* Try S/Key or TIS, authentication. */
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int gss_authentication; /* Try GSS authentication */
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int gss_deleg_creds; /* Delegate GSS credentials */
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+ int gss_enable_mitm; /* Enable old style gssapi auth */
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int password_authentication; /* Try password
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* authentication. */
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int kbd_interactive_authentication; /* Try keyboard-interactive auth. */
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--- servconf.c
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+++ servconf.c
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@@ -91,6 +91,7 @@
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options->kerberos_get_afs_token = -1;
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options->gss_authentication=-1;
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options->gss_cleanup_creds = -1;
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+ options->gss_enable_mitm = -1;
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options->password_authentication = -1;
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options->kbd_interactive_authentication = -1;
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options->challenge_response_authentication = -1;
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@@ -206,6 +207,8 @@
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options->gss_authentication = 0;
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if (options->gss_cleanup_creds == -1)
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options->gss_cleanup_creds = 1;
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+ if (options->gss_enable_mitm == -1)
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+ options->gss_enable_mitm = 0;
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if (options->password_authentication == -1)
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options->password_authentication = 1;
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if (options->kbd_interactive_authentication == -1)
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@@ -290,7 +293,7 @@
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sBanner, sUseDNS, sHostbasedAuthentication,
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sHostbasedUsesNameFromPacketOnly, sClientAliveInterval,
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sClientAliveCountMax, sAuthorizedKeysFile, sAuthorizedKeysFile2,
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- sGssAuthentication, sGssCleanupCreds, sAcceptEnv, sPermitTunnel,
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+ sGssAuthentication, sGssCleanupCreds, sAcceptEnv, sPermitTunnel, sGssEnableMITM,
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sMatch, sPermitOpen, sForceCommand,
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sUsePrivilegeSeparation,
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sDeprecated, sUnsupported
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@@ -351,9 +354,11 @@
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#ifdef GSSAPI
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{ "gssapiauthentication", sGssAuthentication, SSHCFG_ALL },
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{ "gssapicleanupcredentials", sGssCleanupCreds, SSHCFG_GLOBAL },
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+ { "gssapienablemitmattack", sGssEnableMITM },
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#else
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{ "gssapiauthentication", sUnsupported, SSHCFG_ALL },
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{ "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL },
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+ { "gssapienablemitmattack", sUnsupported },
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#endif
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{ "passwordauthentication", sPasswordAuthentication, SSHCFG_ALL },
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{ "kbdinteractiveauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL },
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@@ -877,6 +882,10 @@
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case sGssCleanupCreds:
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intptr = &options->gss_cleanup_creds;
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goto parse_flag;
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+
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+ case sGssEnableMITM:
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+ intptr = &options->gss_enable_mitm;
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+ goto parse_flag;
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case sPasswordAuthentication:
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intptr = &options->password_authentication;
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--- servconf.h
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+++ servconf.h
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@@ -88,6 +88,7 @@
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* authenticated with Kerberos. */
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int gss_authentication; /* If true, permit GSSAPI authentication */
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int gss_cleanup_creds; /* If true, destroy cred cache on logout */
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+ int gss_enable_mitm; /* If true, enable old style GSSAPI */
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int password_authentication; /* If true, permit password
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* authentication. */
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int kbd_interactive_authentication; /* If true, permit */
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--- ssh_config
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+++ ssh_config
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@@ -53,3 +53,13 @@
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# Tunnel no
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# TunnelDevice any:any
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# PermitLocalCommand no
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+# GSSAPIAuthentication no
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+# GSSAPIDelegateCredentials no
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+
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+# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication
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+# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
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+# in this release. The use of 'gssapi' is deprecated due to the presence of
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+# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to.
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+# GSSAPIEnableMITMAttack no
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+
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+>>>>>>>
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--- sshconnect2.c
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+++ sshconnect2.c
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@@ -242,6 +242,10 @@
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userauth_gssapi,
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&options.gss_authentication,
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NULL},
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+ {"gssapi",
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+ userauth_gssapi,
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+ &options.gss_enable_mitm,
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+ NULL},
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#endif
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{"hostbased",
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userauth_hostbased,
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@@ -576,7 +580,9 @@
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if (status == GSS_S_COMPLETE) {
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/* send either complete or MIC, depending on mechanism */
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- if (!(flags & GSS_C_INTEG_FLAG)) {
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+
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+ if (strcmp(authctxt->method->name,"gssapi")==0 ||
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+ (!(flags & GSS_C_INTEG_FLAG))) {
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packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE);
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packet_send();
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} else {
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--- sshd_config
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+++ sshd_config
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@@ -69,6 +69,13 @@
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#GSSAPIAuthentication no
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#GSSAPICleanupCredentials yes
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+# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication
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+# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
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+# in this release. The use of 'gssapi' is deprecated due to the presence of
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+# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to.
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+#GSSAPIEnableMITMAttack no
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+
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+
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# Set this to 'yes' to enable PAM authentication, account processing,
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# and session processing. If this is enabled, PAM authentication will
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# be allowed through the ChallengeResponseAuthentication and
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