From 31ac6ab23fefb113ffff194975f5da386c4fd95f Mon Sep 17 00:00:00 2001 From: djm Date: Fri, 22 May 2015 03:50:02 +0000 Subject: [PATCH] add knob to relax GSSAPI host credential check for multihomed hosts bz#928, patch by Simon Wilkinson; ok dtucker (kerberos/GSSAPI is not compiled by default on OpenBSD) --- usr.bin/ssh/gss-serv.c | 40 ++++++++++++++++++++++++--------------- usr.bin/ssh/servconf.c | 14 ++++++++++++-- usr.bin/ssh/servconf.h | 3 ++- usr.bin/ssh/sshd_config.5 | 19 +++++++++++++++++-- 4 files changed, 56 insertions(+), 20 deletions(-) diff --git a/usr.bin/ssh/gss-serv.c b/usr.bin/ssh/gss-serv.c index ffe41c8d6d0..f26db425964 100644 --- a/usr.bin/ssh/gss-serv.c +++ b/usr.bin/ssh/gss-serv.c @@ -1,4 +1,4 @@ -/* $OpenBSD: gss-serv.c,v 1.28 2015/01/20 23:14:00 deraadt Exp $ */ +/* $OpenBSD: gss-serv.c,v 1.29 2015/05/22 03:50:02 djm Exp $ */ /* * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. @@ -40,9 +40,12 @@ #include "channels.h" #include "session.h" #include "misc.h" +#include "servconf.h" #include "ssh-gss.h" +extern ServerOptions options; + static ssh_gssapi_client gssapi_client = { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}}; @@ -95,25 +98,32 @@ ssh_gssapi_acquire_cred(Gssctxt *ctx) char lname[NI_MAXHOST]; gss_OID_set oidset; - gss_create_empty_oid_set(&status, &oidset); - gss_add_oid_set_member(&status, ctx->oid, &oidset); + if (options.gss_strict_acceptor) { + gss_create_empty_oid_set(&status, &oidset); + gss_add_oid_set_member(&status, ctx->oid, &oidset); - if (gethostname(lname, sizeof(lname))) { - gss_release_oid_set(&status, &oidset); - return (-1); - } + if (gethostname(lname, MAXHOSTNAMELEN)) { + gss_release_oid_set(&status, &oidset); + return (-1); + } + + if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { + gss_release_oid_set(&status, &oidset); + return (ctx->major); + } + + if ((ctx->major = gss_acquire_cred(&ctx->minor, + ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, + NULL, NULL))) + ssh_gssapi_error(ctx); - if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) { gss_release_oid_set(&status, &oidset); return (ctx->major); + } else { + ctx->name = GSS_C_NO_NAME; + ctx->creds = GSS_C_NO_CREDENTIAL; } - - if ((ctx->major = gss_acquire_cred(&ctx->minor, - ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL))) - ssh_gssapi_error(ctx); - - gss_release_oid_set(&status, &oidset); - return (ctx->major); + return GSS_S_COMPLETE; } /* Privileged */ diff --git a/usr.bin/ssh/servconf.c b/usr.bin/ssh/servconf.c index d64ba6b7533..ea254b06e60 100644 --- a/usr.bin/ssh/servconf.c +++ b/usr.bin/ssh/servconf.c @@ -1,5 +1,5 @@ -/* $OpenBSD: servconf.c,v 1.270 2015/05/21 06:43:30 djm Exp $ */ +/* $OpenBSD: servconf.c,v 1.271 2015/05/22 03:50:02 djm Exp $ */ /* * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved @@ -107,6 +107,7 @@ initialize_server_options(ServerOptions *options) options->kerberos_get_afs_token = -1; options->gss_authentication=-1; options->gss_cleanup_creds = -1; + options->gss_strict_acceptor = -1; options->password_authentication = -1; options->kbd_interactive_authentication = -1; options->challenge_response_authentication = -1; @@ -260,6 +261,8 @@ fill_default_server_options(ServerOptions *options) options->gss_authentication = 0; if (options->gss_cleanup_creds == -1) options->gss_cleanup_creds = 1; + if (options->gss_strict_acceptor == -1) + options->gss_strict_acceptor = 0; if (options->password_authentication == -1) options->password_authentication = 1; if (options->kbd_interactive_authentication == -1) @@ -368,7 +371,8 @@ typedef enum { sBanner, sUseDNS, sHostbasedAuthentication, sHostbasedUsesNameFromPacketOnly, sHostbasedAcceptedKeyTypes, sClientAliveInterval, sClientAliveCountMax, sAuthorizedKeysFile, - sGssAuthentication, sGssCleanupCreds, sAcceptEnv, sPermitTunnel, + sGssAuthentication, sGssCleanupCreds, sGssStrictAcceptor, + sAcceptEnv, sPermitTunnel, sMatch, sPermitOpen, sForceCommand, sChrootDirectory, sUsePrivilegeSeparation, sAllowAgentForwarding, sHostCertificate, @@ -428,9 +432,11 @@ static struct { #ifdef GSSAPI { "gssapiauthentication", sGssAuthentication, SSHCFG_ALL }, { "gssapicleanupcredentials", sGssCleanupCreds, SSHCFG_GLOBAL }, + { "gssapistrictacceptorcheck", sGssStrictAcceptor, SSHCFG_GLOBAL }, #else { "gssapiauthentication", sUnsupported, SSHCFG_ALL }, { "gssapicleanupcredentials", sUnsupported, SSHCFG_GLOBAL }, + { "gssapistrictacceptorcheck", sUnsupported, SSHCFG_GLOBAL }, #endif { "passwordauthentication", sPasswordAuthentication, SSHCFG_ALL }, { "kbdinteractiveauthentication", sKbdInteractiveAuthentication, SSHCFG_ALL }, @@ -1165,6 +1171,10 @@ process_server_config_line(ServerOptions *options, char *line, intptr = &options->gss_cleanup_creds; goto parse_flag; + case sGssStrictAcceptor: + intptr = &options->gss_strict_acceptor; + goto parse_flag; + case sPasswordAuthentication: intptr = &options->password_authentication; goto parse_flag; diff --git a/usr.bin/ssh/servconf.h b/usr.bin/ssh/servconf.h index 4c4867b010e..0b72d492ae2 100644 --- a/usr.bin/ssh/servconf.h +++ b/usr.bin/ssh/servconf.h @@ -1,4 +1,4 @@ -/* $OpenBSD: servconf.h,v 1.118 2015/05/21 06:43:31 djm Exp $ */ +/* $OpenBSD: servconf.h,v 1.119 2015/05/22 03:50:02 djm Exp $ */ /* * Author: Tatu Ylonen @@ -118,6 +118,7 @@ typedef struct { * authenticated with Kerberos. */ int gss_authentication; /* If true, permit GSSAPI authentication */ int gss_cleanup_creds; /* If true, destroy cred cache on logout */ + int gss_strict_acceptor; /* If true, restrict the GSSAPI acceptor name */ int password_authentication; /* If true, permit password * authentication. */ int kbd_interactive_authentication; /* If true, permit */ diff --git a/usr.bin/ssh/sshd_config.5 b/usr.bin/ssh/sshd_config.5 index 507a8bf3354..72403e53e8d 100644 --- a/usr.bin/ssh/sshd_config.5 +++ b/usr.bin/ssh/sshd_config.5 @@ -33,8 +33,8 @@ .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.\" $OpenBSD: sshd_config.5,v 1.202 2015/05/21 06:43:31 djm Exp $ -.Dd $Mdocdate: May 21 2015 $ +.\" $OpenBSD: sshd_config.5,v 1.203 2015/05/22 03:50:02 djm Exp $ +.Dd $Mdocdate: May 22 2015 $ .Dt SSHD_CONFIG 5 .Os .Sh NAME @@ -623,6 +623,21 @@ on logout. The default is .Dq yes . Note that this option applies to protocol version 2 only. +.It Cm GSSAPIStrictAcceptorCheck +Determines whether to be strict about the identity of the GSSAPI acceptor +a client authenticates against. +If set to +.Dq yes +then the client must authenticate against the +.Pa host +service on the current hostname. +If set to +.Dq no +then the client may authenticate against any service key stored in the +machine's default store. +This facility is provided to assist with operation on multi homed machines. +The default is +.Dq yes . .It Cm HostbasedAcceptedKeyTypes Specifies the key types that will be accepted for hostbased authentication as a comma-separated pattern list. -- 2.20.1