source: trunk/third/openssh/gss-serv.c @ 18772

/*
 * Copyright (c) 2001,2002 Simon Wilkinson. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"

#ifdef GSSAPI

#include "ssh.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "packet.h"
#include "compat.h"
#include <openssl/evp.h>
#include "cipher.h"
#include "kex.h"
#include "auth.h"
#include "log.h"
#include "channels.h"
#include "session.h"
#include "dispatch.h"
#include "servconf.h"
#include "compat.h"
#include "monitor_wrap.h"

#include "ssh-gss.h"

extern ServerOptions options;
extern u_char *session_id2;
extern int session_id2_len;
extern int is_local_acct;

typedef struct ssh_gssapi_cred_cache {
        char *filename;
        char *envvar;
        char *envval;
        void *data;
} ssh_gssapi_cred_cache;

static struct ssh_gssapi_cred_cache gssapi_cred_store = {NULL,NULL,NULL};

#ifdef KRB5

#ifdef HEIMDAL
#include <krb5.h>
#else
#include <gssapi_krb5.h>
#define krb5_get_err_text(context,code) error_message(code)
#endif

/* Initialise the krb5 library, so we can use it for those bits that
 * GSSAPI won't do */

int ssh_gssapi_krb5_init(Authctxt *authctxt) {
        krb5_error_code problem;
        
        if (authctxt->krb5_ctx != NULL)
          return 1;

        problem = krb5_init_context(&authctxt->krb5_ctx);
        if (problem) {
                log("Cannot initialize krb5 context");
                return 0;
        }
        krb5_init_ets(authctxt->krb5_ctx);

        return 1;       
}                       

/* Check if this user is OK to login. This only works with krb5 - other 
 * GSSAPI mechanisms will need their own.
 * Returns true if the user is OK to log in, otherwise returns 0
 */

int
ssh_gssapi_krb5_userok(Authctxt *authctxt) {
        krb5_principal princ;
        int retval;

        if (ssh_gssapi_krb5_init(authctxt) == 0)
                return 0;

        /* If this isn't a local account and the user hasn't specified
         * ticket forwarding, fail through to password authentication.
         * The shell the user gets won't be useful without tickets anyway.
         */
        if (!is_local_acct && !gssapi_client_creds)
                return 0;
                
        if ((retval=krb5_parse_name(authctxt->krb5_ctx,
                                    gssapi_client_name.value, 
                                    &princ))) {
                log("krb5_parse_name(): %.100s", 
                        krb5_get_err_text(authctxt->krb5_ctx,retval));
                return 0;
        }
        if (krb5_kuserok(authctxt->krb5_ctx, princ, authctxt->user)) {
                retval = 1;
                log("Authorized to %s, krb5 principal %s (krb5_kuserok)",
                    authctxt->user, (char *)gssapi_client_name.value);
        }
        else
                retval = 0;
        
        krb5_free_principal(authctxt->krb5_ctx, princ);
        return retval;
}
        
/* Make sure that this is called _after_ we've setuid to the user */

/* This writes out any forwarded credentials. Its specific to the Kerberos
 * GSSAPI mechanism
 *
 * We assume that our caller has made sure that the user has selected
 * delegated credentials, and that the client_creds structure is correctly
 * populated.
 */

void
ssh_gssapi_krb5_storecreds(Authctxt *authctxt) {
        krb5_ccache ccache;
        krb5_error_code problem;
        krb5_principal princ;
        char ccname[35];
        static char name[40];
        int tmpfd;
        OM_uint32 maj_status,min_status;


        if (gssapi_client_creds==NULL) {
                debug("No credentials stored"); 
                return;
        }
                
        if (ssh_gssapi_krb5_init(authctxt) == 0)
                return;

        if (options.gss_use_session_ccache) {
                snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_p%d",getpid());
       
                if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
                        log("fchmod(): %.100s", strerror(errno));
                        close(tmpfd);
                        return;
                }
        } else {
                snprintf(ccname,sizeof(ccname),"/tmp/krb5cc_p%d",getpid());
                tmpfd = open(ccname, O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
                if (tmpfd == -1) {
                        log("open(): %.100s", strerror(errno));
                        return;
                }
        }

        close(tmpfd);
        snprintf(name, sizeof(name), "FILE:%s",ccname);
 
        if ((problem = krb5_cc_resolve(authctxt->krb5_ctx, name, &ccache))) {
                log("krb5_cc_default(): %.100s", 
                        krb5_get_err_text(authctxt->krb5_ctx,problem));
                return;
        }

        if ((problem = krb5_parse_name(authctxt->krb5_ctx, gssapi_client_name.value, 
                                       &princ))) {
                log("krb5_parse_name(): %.100s", 
                        krb5_get_err_text(authctxt->krb5_ctx,problem));
                krb5_cc_destroy(authctxt->krb5_ctx,ccache);
                return;
        }
        
        if ((problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache, princ))) {
                log("krb5_cc_initialize(): %.100s", 
                        krb5_get_err_text(authctxt->krb5_ctx,problem));
                krb5_free_principal(authctxt->krb5_ctx,princ);
                krb5_cc_destroy(authctxt->krb5_ctx,ccache);
                return;
        }
        
        krb5_free_principal(authctxt->krb5_ctx,princ);

        #ifdef HEIMDAL
        if ((problem = krb5_cc_copy_cache(authctxt->krb5_ctx, 
                                           gssapi_client_creds->ccache,
                                           ccache))) {
                log("krb5_cc_copy_cache(): %.100s", 
                        krb5_get_err_text(authctxt->krb5_ctx,problem));
                krb5_cc_destroy(authctxt->krb5_ctx,ccache);
                return;
        }
        #else
        if ((maj_status = gss_krb5_copy_ccache(&min_status, 
                                               gssapi_client_creds, 
                                               ccache))) {
                log("gss_krb5_copy_ccache() failed");
                ssh_gssapi_error(maj_status,min_status);
                krb5_cc_destroy(authctxt->krb5_ctx,ccache);
                return;
        }
        #endif
        
#ifdef USE_PAM
        do_pam_putenv("KRB5CCNAME",name);
#endif

        gssapi_cred_store.filename=strdup(ccname);
        gssapi_cred_store.envvar="KRB5CCNAME";
        gssapi_cred_store.envval=strdup(name);

        /* Populate the Kerberos specific members of the authctxt.
         * We'll need them later.
         */
        krb5_copy_principal(authctxt->krb5_ctx, princ, &authctxt->krb5_user);
        krb5_free_principal(authctxt->krb5_ctx, princ);

        authctxt->krb5_fwd_ccache = ccache;
        authctxt->krb5_ticket_file = 
          (char *)krb5_cc_get_name(authctxt->krb5_ctx, 
                                   authctxt->krb5_fwd_ccache);

        return;
}

#endif /* KRB5 */

#ifdef GSI
#include <globus_gss_assist.h>

/*
 * Check if this user is OK to login under GSI. User has been authenticated
 * as identity in global 'client_name.value' and is trying to log in as passed
 * username in 'name'.
 *
 * Returns non-zero if user is authorized, 0 otherwise.
 */
int
ssh_gssapi_gsi_userok(char *name)
{
    int authorized = 0;
    
    /* This returns 0 on success */
    authorized = (globus_gss_assist_userok(gssapi_client_name.value,
                                           name) == 0);
    
    debug("GSI user %s is%s authorized as target user %s",
          (char *) gssapi_client_name.value,
          (authorized ? "" : " not"),
          name);
    
    return authorized;
}

/*
 * Handle setting up child environment for GSI.
 *
 * Make sure that this is called _after_ we've setuid to the user.
 */
void
ssh_gssapi_gsi_storecreds()
{
        OM_uint32       major_status;
        OM_uint32       minor_status;
        
        
        if (gssapi_client_creds != NULL)
        {
                char *creds_env = NULL;

                /*
                 * This is the current hack with the GSI gssapi library to
                 * export credentials to disk.
                 */

                debug("Exporting delegated credentials");
                
                minor_status = 0xdee0;  /* Magic value */
                major_status =
                        gss_inquire_cred(&minor_status,
                                         gssapi_client_creds,
                                         (gss_name_t *) &creds_env,
                                         NULL,
                                         NULL,
                                         NULL);

                if ((major_status == GSS_S_COMPLETE) &&
                    (minor_status == 0xdee1) &&
                    (creds_env != NULL))
                {
                        char            *value;
                                
                        /*
                         * String is of the form:
                         * X509_USER_DELEG_PROXY=filename
                         * so we parse out the filename
                         * and then set X509_USER_PROXY
                         * to point at it.
                         */
                        value = strchr(creds_env, '=');
                        
                        if (value != NULL)
                        {
                                *value = '\0';
                                value++;
#ifdef USE_PAM
                                do_pam_putenv("X509_USER_PROXY",value);
#endif
                                gssapi_cred_store.filename=NULL;
                                gssapi_cred_store.envvar="X509_USER_PROXY";
                                gssapi_cred_store.envval=strdup(value);

                                return;
                        }
                        else
                        {
                                log("Failed to parse delegated credentials string '%s'",
                                    creds_env);
                        }
                }
                else
                {
                        log("Failed to export delegated credentials (error %ld)",
                            major_status);
                }
        }       
}

#endif /* GSI */

void
ssh_gssapi_cleanup_creds(void *ignored)
{
        if (gssapi_cred_store.filename!=NULL) {
                /* Unlink probably isn't sufficient */
                debug("removing gssapi cred file\"%s\"",gssapi_cred_store.filename);
                unlink(gssapi_cred_store.filename);
        }
}

void 
ssh_gssapi_storecreds(Authctxt *authctxt)
{
        switch (gssapi_client_type) {
#ifdef KRB5
        case GSS_KERBEROS:
                ssh_gssapi_krb5_storecreds(authctxt);
                break;
#endif
#ifdef GSI
        case GSS_GSI:
                ssh_gssapi_gsi_storecreds();
                break;
#endif /* GSI */
        case GSS_LAST_ENTRY:
                /* GSSAPI not used in this authentication */
                debug("No GSSAPI credentials stored");
                break;
        default:
                log("ssh_gssapi_do_child: Unknown mechanism");
        
        }
        
        if (options.gss_cleanup_creds) {
                fatal_add_cleanup(ssh_gssapi_cleanup_creds, NULL);
        }

}

/* This allows GSSAPI methods to do things to the childs environment based
 * on the passed authentication process and credentials.
 *
 * Question: If we didn't use userauth_external for some reason, should we
 * still delegate credentials?
 */
void 
ssh_gssapi_do_child(char ***envp, u_int *envsizep) 
{

        if (gssapi_cred_store.envvar!=NULL && 
            gssapi_cred_store.envval!=NULL) {
            
                debug("Setting %s to %s", gssapi_cred_store.envvar,
                                          gssapi_cred_store.envval);                              
                child_set_env(envp, envsizep, gssapi_cred_store.envvar, 
                                              gssapi_cred_store.envval);
        }

        switch(gssapi_client_type) {
#ifdef KRB5
        case GSS_KERBEROS: break;
#endif
#ifdef GSI
        case GSS_GSI: break;
#endif
        case GSS_LAST_ENTRY:
                debug("No GSSAPI credentials stored");
                break;
        default:
                log("ssh_gssapi_do_child: Unknown mechanism");
        }
}

int
ssh_gssapi_userok(Authctxt *authctxt)
{
        if (gssapi_client_name.length==0 || 
            gssapi_client_name.value==NULL) {
                debug("No suitable client data");
                return 0;
        }
        switch (gssapi_client_type) {
#ifdef KRB5
        case GSS_KERBEROS:
                return(ssh_gssapi_krb5_userok(authctxt));
                break; /* Not reached */
#endif
#ifdef GSI
        case GSS_GSI:
                return(ssh_gssapi_gsi_userok(authctxt->user));
                break; /* Not reached */
#endif /* GSI */
        case GSS_LAST_ENTRY:
                debug("Client not GSSAPI");
                break;
        default:
                debug("Unknown client authentication type");
        }
        return(0);
}

/* Stuff to play nicely with privsep */

#if 0
extern struct monitor *pmonitor;

OM_uint32
mm_ssh_gssapi_server_ctxt(Gssctxt **ctx, gss_OID oid) {
        Buffer m;
        
        /* Client doesn't get to see the context */
        *ctx=NULL;

        buffer_init(&m)
        buffer_put_string(&m,oid->elements,oid->length);
        
        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSETUP, &m);

        debug3("%s: waiting for MONITOR_ANS_GSSSIGN",__func__);
        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_SIGN, &m);
        major=buffer_get_int(&m);

        return(major);
}
        
int
mm_answer_gss_server_ctxt(int socket, Buffer *m) {
        gss_OID_desc oid;
        OM_uint32 major;
        
        oid.elements=buffer_get_string(m,&oid.length);
                
        major=ssh_gssapi_server_ctxt(&gsscontext,&oid);

        xfree(oid.elements);
        
        buffer_clear(m);
        buffer_put_int(m,result);
        
        mm_request_send(socket,MONITOR_ANS_GSSSIGN,m);
        
        return(0);
}

OM_uint32
mm_ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *in,
                         gss_buffer_desc *out, OM_uint32 *flags) {

        Buffer m;
        OM_uint32, major;
        
        buffer_init(&m);
        buffer_put_string(&m, in->value, in->length);
        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSTEP, &m);
        
        debug3("%s: waiting for MONITOR_ANS_GSSSTEP", &m);
        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSTEP, &m);
        
        major=buffer_get_int(&m);
        *out->value=buffer->get_string(&m,&out->length);
        flags=buffer_get_int(&m);

        return(major);
}

int
mm_answer_gss_accept_ctxt(int socket, Buffer *m) {
        gss_buffer_desc in,out;
        OM_uint32 major;
        OM_uint32 flags = 0; /* GSI needs this */
        
        in.value = buffer_get_string(m,&in.length);
        major=ssh_gssapi_accept_ctxt(gsscontext,&in,&out,&flags);
        xfree(in.value);
        
        buffer_clear(m);
        buffer_put_int(m, major);
        buffer_put_string(m, out.value, out.length);
        buffer_put_int(m, flags);
        mm_request_send(socket,MONITOR_ANS_STEP,m);
        
        gss_release_buffer(out);
        
        return(0);
}

int
mm_ssh_gssapi_userok(char *user) {
        Buffer m;
        
        buffer_init(&m);
        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUSEROK, &m);
        
        debug3("%s: waiting for MONTIOR_ANS_GSSUSEROK", __func__);
        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSUSEROK),
                                  &m);
        
        authenticated = buffer_get_int(&m);
        
        buffer_free(&m);
        debug3("%s: user %sauthetnicated",__func__, authenticated ? "" : "not ");
        return(authenticated);
}

int
mm_answer_gss_userok(int socket, Buffer *m) {
        authenticated = authctxt->valid && ssh_gssapi_userok(authctxt);
        
        buffer_clear(m);
        buffer_put_int(m, authenticated);
        
        debug3("%s: sending result %d", __func__, authenticated);
        mm_request_send(socket, MONITOR_ANS_GSSUSEROK, m);
        
        /* Monitor loop will terminate if authenticated */
        return(authenticated);
}

OM_uint32
mm_ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_desc *data, gss_buffer_desc *hash) {
        Buffer m;
        OM_uint32 major, minor;
        
        buffer_init(&m);
        buffer_put_string(&m, data->value, data->length);
        
        mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSIGN, &m);
        
        debug3("%s: waiting for MONITOR_ANS_GSSSIGN",__func__);
        mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSIGN, &m);
        major=buffer_get_int(&m);
        *hash->value = buffer_get_string(&m, &hash->length);
        
        return(major);
}
        
int
mm_answer_gss_sign(int socket, Buffer *m) {
        gss_buffer_desc data,hash;
        OM_uint32 major;
        
        data.value = buffer_get_string(m,&data.length);
        if (data.length != 20)
                fatal("%s: data length incorrect: %d", __func__, datlen);
        
        /* Save the session ID - only first time round */
        if (session_id2_len == 0) {
                session_id2_len=data.length;
                session_id2 = xmalloc(session_id2_len);
                memcpy(session_id2, data.value, session_id2_len);
        }
        major=ssh_gssapi_sign(gsscontext, &data, &hash);
        
        xfree(data.value);
        
        buffer_clear(m);
        buffer_put_int(m, major);
        buffer_put_string(m, hash.value, hash.length);

        mm_request_send(socket,MONITOR_ANS_GSSSIGN,m);
                
        gss_release_buffer(hash);
        
        return(0);
}
#endif
#endif /* GSSAPI */