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openssh-4.1p1-gssapimitm.patch
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File openssh-4.1p1-gssapimitm.patch of Package opensuse
The patch below adds support for the deprecated 'gssapi' authentication mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included in this release. The use of 'gssapi' is deprecated due to the presence of potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to. To use the patch apply it to a OpenSSH 3.8p1 source tree. After compiling, backwards compatibility may be obtained by supplying the 'GssapiEnableMitmAttack yes' option to either the client or server. It should be noted that this patch is being made available purely as a means of easing the process of moving to OpenSSH 3.8p1. Any new installations are recommended to use the 'gssapi-with-mic' mechanism. Existing installations are encouraged to upgrade as soon as possible. Index: auth2-gss.c ================================================================================ --- auth2-gss.c +++ auth2-gss.c @@ -171,6 +171,15 @@ dispatch_set( SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, &input_gssapi_exchange_complete); + + /* + * Old style 'gssapi' didn't have the GSSAPI_MIC + * and went straight to sending exchange_complete + */ + if (options.gss_enable_mitm) + dispatch_set( + SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, + &input_gssapi_exchange_complete); } } @@ -292,4 +301,10 @@ &options.gss_authentication }; +Authmethod method_gssapi_old = { + "gssapi", + userauth_gssapi, + &options.gss_enable_mitm +}; + #endif /* GSSAPI */ --- auth2.c +++ auth2.c @@ -54,6 +54,7 @@ extern Authmethod method_hostbased; #ifdef GSSAPI extern Authmethod method_gssapi; +extern Authmethod method_gssapi_old; #endif Authmethod *authmethods[] = { @@ -61,6 +62,7 @@ &method_pubkey, #ifdef GSSAPI &method_gssapi, + &method_gssapi_old, #endif &method_passwd, &method_kbdint, --- readconf.c +++ readconf.c @@ -104,7 +104,7 @@ oHostKeyAlgorithms, oBindAddress, oSmartcardDevice, oClearAllForwardings, oNoHostAuthenticationForLocalhost, oEnableSSHKeysign, oRekeyLimit, oVerifyHostKeyDNS, oConnectTimeout, - oAddressFamily, oGssAuthentication, oGssDelegateCreds, + oAddressFamily, oGssAuthentication, oGssDelegateCreds, oGssEnableMITM, oServerAliveInterval, oServerAliveCountMax, oIdentitiesOnly, oSendEnv, oControlPath, oControlMaster, oDeprecated, oUnsupported @@ -140,9 +140,11 @@ #if defined(GSSAPI) { "gssapiauthentication", oGssAuthentication }, { "gssapidelegatecredentials", oGssDelegateCreds }, + { "gssapienablemitmattack", oGssEnableMITM }, #else { "gssapiauthentication", oUnsupported }, { "gssapidelegatecredentials", oUnsupported }, + { "gssapienablemitmattack", oUnsupported }, #endif { "fallbacktorsh", oDeprecated }, { "usersh", oDeprecated }, @@ -399,6 +401,10 @@ case oGssDelegateCreds: intptr = &options->gss_deleg_creds; goto parse_flag; + + case oGssEnableMITM: + intptr = &options->gss_enable_mitm; + goto parse_flag; case oBatchMode: intptr = &options->batch_mode; @@ -869,6 +875,7 @@ options->challenge_response_authentication = -1; options->gss_authentication = -1; options->gss_deleg_creds = -1; + options->gss_enable_mitm = -1; options->password_authentication = -1; options->kbd_interactive_authentication = -1; options->kbd_interactive_devices = NULL; @@ -951,6 +958,8 @@ options->gss_authentication = 0; if (options->gss_deleg_creds == -1) options->gss_deleg_creds = 0; + if (options->gss_enable_mitm == -1) + options->gss_enable_mitm = 0; if (options->password_authentication == -1) options->password_authentication = 1; if (options->kbd_interactive_authentication == -1) --- readconf.h +++ readconf.h @@ -45,6 +45,7 @@ /* Try S/Key or TIS, authentication. */ int gss_authentication; /* Try GSS authentication */ int gss_deleg_creds; /* Delegate GSS credentials */ + int gss_enable_mitm; /* Enable old style gssapi auth */ int password_authentication; /* Try password * authentication. */ int kbd_interactive_authentication; /* Try keyboard-interactive auth. */ --- servconf.c +++ servconf.c @@ -74,6 +74,7 @@ options->kerberos_get_afs_token = -1; options->gss_authentication=-1; options->gss_cleanup_creds = -1; + options->gss_enable_mitm = -1; options->password_authentication = -1; options->kbd_interactive_authentication = -1; options->challenge_response_authentication = -1; @@ -189,6 +190,8 @@ options->gss_authentication = 0; if (options->gss_cleanup_creds == -1) options->gss_cleanup_creds = 1; + if (options->gss_enable_mitm == -1) + options->gss_enable_mitm = 0; if (options->password_authentication == -1) options->password_authentication = 1; if (options->kbd_interactive_authentication == -1) @@ -270,7 +273,7 @@ sBanner, sUseDNS, sHostbasedAuthentication, sHostbasedUsesNameFromPacketOnly, sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile, sAuthorizedKeysFile2, - sGssAuthentication, sGssCleanupCreds, sAcceptEnv, + sGssAuthentication, sGssCleanupCreds, sAcceptEnv, sGssEnableMITM, sUsePrivilegeSeparation, sDeprecated, sUnsupported } ServerOpCodes; @@ -325,9 +328,11 @@ #ifdef GSSAPI { "gssapiauthentication", sGssAuthentication }, { "gssapicleanupcredentials", sGssCleanupCreds }, + { "gssapienablemitmattack", sGssEnableMITM }, #else { "gssapiauthentication", sUnsupported }, { "gssapicleanupcredentials", sUnsupported }, + { "gssapienablemitmattack", sUnsupported }, #endif { "passwordauthentication", sPasswordAuthentication }, { "kbdinteractiveauthentication", sKbdInteractiveAuthentication }, @@ -657,6 +662,10 @@ case sGssCleanupCreds: intptr = &options->gss_cleanup_creds; goto parse_flag; + + case sGssEnableMITM: + intptr = &options->gss_enable_mitm; + goto parse_flag; case sPasswordAuthentication: intptr = &options->password_authentication; --- servconf.h +++ servconf.h @@ -88,6 +88,7 @@ * authenticated with Kerberos. */ int gss_authentication; /* If true, permit GSSAPI authentication */ int gss_cleanup_creds; /* If true, destroy cred cache on logout */ + int gss_enable_mitm; /* If true, enable old style GSSAPI */ int password_authentication; /* If true, permit password * authentication. */ int kbd_interactive_authentication; /* If true, permit */ --- ssh_config +++ ssh_config @@ -46,3 +46,12 @@ # Cipher 3des # Ciphers aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc # EscapeChar ~ +# GSSAPIAuthentication no +# GSSAPIDelegateCredentials no + +# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication +# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included +# in this release. The use of 'gssapi' is deprecated due to the presence of +# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to. +# GSSAPIEnableMITMAttack no + --- sshconnect2.c +++ sshconnect2.c @@ -227,6 +227,10 @@ userauth_gssapi, &options.gss_authentication, NULL}, + {"gssapi", + userauth_gssapi, + &options.gss_enable_mitm, + NULL}, #endif {"hostbased", userauth_hostbased, @@ -564,7 +568,9 @@ if (status == GSS_S_COMPLETE) { /* send either complete or MIC, depending on mechanism */ - if (!(flags & GSS_C_INTEG_FLAG)) { + + if (strcmp(authctxt->method->name,"gssapi")==0 || + (!(flags & GSS_C_INTEG_FLAG))) { packet_start(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE); packet_send(); } else { --- sshd_config +++ sshd_config @@ -68,6 +68,13 @@ #GSSAPIAuthentication no #GSSAPICleanupCredentials yes +# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication +# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included +# in this release. The use of 'gssapi' is deprecated due to the presence of +# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to. +#GSSAPIEnableMITMAttack no + + # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication mechanism.
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