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/*
* Copyright (c) 1990,1993 Regents of The University of Michigan.
* Copyright (c) 1999 Adrian Sun (asun@u.washington.edu)
* Copyright (c) 2003 The Reed Institute
* Copyright (c) 2004 Bjoern Fernhomberg
* All Rights Reserved. See COPYRIGHT.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif /* HAVE_CONFIG_H */
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <atalk/logger.h>
#include <atalk/afp.h>
#include <atalk/uam.h>
#include <atalk/util.h>
#include <atalk/compat.h>
#include <atalk/globals.h>
/* Kerberos includes */
#ifdef HAVE_GSSAPI_GSSAPI_H
#include <gssapi/gssapi.h>
#else
#include <gssapi.h>
#endif // HAVE_GSSAPI_GSSAPI_H
#ifdef HAVE_KERBEROS
#ifdef HAVE_KRB5_KRB5_H
#include <krb5/krb5.h>
#else
#include <krb5.h>
#endif /* HAVE_KRB5_KRB5_H */
#endif /* HAVE_KERBEROS */
#define LOG_UAMS(log_level, ...) \
LOG(log_level, logtype_uams, __VA_ARGS__)
#define LOG_LOGINCONT(log_level, ...) \
LOG_UAMS(log_level, "FPLoginCont: " __VA_ARGS__)
static void log_status(char *s,
OM_uint32 major_status,
OM_uint32 minor_status)
{
gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
OM_uint32 min_status, maj_status;
OM_uint32 maj_ctx = 0, min_ctx = 0;
while (1) {
maj_status = gss_display_status( &min_status, major_status,
GSS_C_GSS_CODE, GSS_C_NULL_OID,
&maj_ctx, &msg );
LOG_UAMS(log_error, "%s %.*s (error %s)",
s, msg.length, msg.value, strerror(errno));
gss_release_buffer(&min_status, &msg);
if (!maj_ctx)
break;
}
while (1) {
maj_status = gss_display_status( &min_status, minor_status,
GSS_C_MECH_CODE, GSS_C_NULL_OID,
&min_ctx, &msg );
LOG_UAMS(log_error, "%s %.*s (error %s)",
s, msg.length, msg.value, strerror(errno));
gss_release_buffer(&min_status, &msg);
if (!min_ctx)
break;
}
}
static void log_ctx_flags(OM_uint32 flags)
{
if (flags & GSS_C_DELEG_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_DELEG_FLAG");
if (flags & GSS_C_MUTUAL_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_MUTUAL_FLAG");
if (flags & GSS_C_REPLAY_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_REPLAY_FLAG");
if (flags & GSS_C_SEQUENCE_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_SEQUENCE_FLAG");
if (flags & GSS_C_CONF_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_CONF_FLAG");
if (flags & GSS_C_INTEG_FLAG)
LOG_LOGINCONT(log_debug, "context flag: GSS_C_INTEG_FLAG");
}
static void log_service_name(gss_ctx_id_t context)
{
OM_uint32 major_status = 0, minor_status = 0;
gss_name_t service_name;
gss_buffer_desc service_name_buffer;
major_status = gss_inquire_context(&minor_status,
context,
NULL,
&service_name,
NULL,
NULL,
NULL,
NULL,
NULL);
if (major_status != GSS_S_COMPLETE) {
log_status("gss_inquire_context", major_status, minor_status);
return;
}
major_status = gss_display_name(&minor_status,
service_name,
&service_name_buffer,
NULL);
if (major_status == GSS_S_COMPLETE) {
LOG_LOGINCONT(log_debug,
"service principal is `%s'",
service_name_buffer.value);
gss_release_buffer(&minor_status, &service_name_buffer);
} else
log_status("gss_display_name", major_status, minor_status);
gss_release_name(&minor_status, &service_name);
}
static int get_client_username(char *username,
int ulen,
gss_name_t *client_name)
{
OM_uint32 major_status = 0, minor_status = 0;
gss_buffer_desc client_name_buffer;
char *p;
int ret = 0;
/*
* To extract the unix username, use gss_display_name on client_name.
* We do rely on gss_display_name returning a zero terminated string.
* The username returned contains the realm and possibly an instance.
* We only want the username for afpd, so we have to strip those from
* the username before copying it to afpd's buffer.
*/
major_status = gss_display_name(&minor_status,
*client_name,
&client_name_buffer,
NULL);
if (major_status != GSS_S_COMPLETE) {
log_status("gss_display_name", major_status, minor_status);
return 1;
}
LOG_LOGINCONT(log_debug,
"user principal is `%s'",
client_name_buffer.value);
/* chop off realm */
p = strchr(client_name_buffer.value, '@');
if (p)
*p = 0;
/* FIXME: chop off instance? */
p = strchr(client_name_buffer.value, '/');
if (p)
*p = 0;
/* check if this username fits into afpd's username buffer */
size_t cnblen = strlen(client_name_buffer.value);
if (cnblen >= ulen) {
/* The username is too long for afpd's buffer, bail out */
LOG_LOGINCONT(log_info,
"username `%s' too long (%d)",
client_name_buffer.value, cnblen);
ret = 1;
} else {
/* copy stripped username to afpd's buffer */
strlcpy(username, client_name_buffer.value, ulen);
}
gss_release_buffer(&minor_status, &client_name_buffer);
return ret;
}
/* wrap afpd's sessionkey */
static int wrap_sessionkey(gss_ctx_id_t context, struct session_info *sinfo)
{
OM_uint32 major_status = 0, minor_status = 0;
gss_buffer_desc sesskey_buff, wrap_buff;
int ret = 0;
/*
* gss_wrap afpd's session_key.
* This is needed fo OS X 10.3 clients. They request this information
* with type 8 (kGetKerberosSessionKey) on FPGetSession.
* See AFP 3.1 specs, page 77.
*/
sesskey_buff.value = sinfo->sessionkey;
sesskey_buff.length = sinfo->sessionkey_len;
/* gss_wrap the session key with the default mechanism.
Require both confidentiality and integrity services */
major_status = gss_wrap(&minor_status,
context,
true,
GSS_C_QOP_DEFAULT,
&sesskey_buff,
NULL,
&wrap_buff);
if (major_status != GSS_S_COMPLETE) {
log_status("gss_wrap", major_status, minor_status);
return 1;
}
/* store the wrapped session key in afpd's session_info struct */
if (NULL == (sinfo->cryptedkey = malloc(wrap_buff.length))) {
LOG_UAMS(log_error,
"wrap_sessionkey: out of memory tyring to allocate %u bytes",
wrap_buff.length);
ret = 1;
} else {
/* cryptedkey is binary data */
memcpy(sinfo->cryptedkey, wrap_buff.value, wrap_buff.length);
sinfo->cryptedkey_len = wrap_buff.length;
}
/* we're done with buffer, release */
gss_release_buffer(&minor_status, &wrap_buff);
return ret;
}
static int accept_sec_context(gss_ctx_id_t *context,
gss_buffer_desc *ticket_buffer,
gss_name_t *client_name,
gss_buffer_desc *authenticator_buff)
{
OM_uint32 major_status = 0, minor_status = 0, flags = 0;
/* Initialize autheticator buffer. */
authenticator_buff->length = 0;
authenticator_buff->value = NULL;
LOG_LOGINCONT(log_debug,
"accepting context (ticketlen: %u)",
ticket_buffer->length);
/*
* Try to accept the secondary context using the token in ticket_buffer.
* We don't care about the principals or mechanisms used, nor for the time.
* We don't act as a proxy either.
*/
major_status = gss_accept_sec_context(&minor_status,
context,
GSS_C_NO_CREDENTIAL,
ticket_buffer,
GSS_C_NO_CHANNEL_BINDINGS,
client_name,
NULL,
authenticator_buff,
&flags,
NULL,
NULL);
if (major_status != GSS_S_COMPLETE) {
log_status("gss_accept_sec_context", major_status, minor_status);
return 1;
}
log_ctx_flags(flags);
return 0;
}
static int do_gss_auth(void *obj,
char *ibuf, size_t ibuflen,
char *rbuf, int *rbuflen,
char *username, size_t ulen,
struct session_info *sinfo )
{
OM_uint32 status = 0;
gss_name_t client_name;
gss_ctx_id_t context = GSS_C_NO_CONTEXT;
gss_buffer_desc ticket_buffer, authenticator_buff;
int ret = 0;
/*
* Try to accept the secondary context, using the ticket/token the
* client sent us. Ticket is stored at current ibuf position.
* Don't try to release ticket_buffer later, it points into ibuf!
*/
ticket_buffer.length = ibuflen;
ticket_buffer.value = ibuf;
if ((ret = accept_sec_context(&context,
&ticket_buffer,
&client_name,
&authenticator_buff)))
return ret;
log_service_name(context);
/* We succesfully acquired the secondary context, now get the
username for afpd and gss_wrap the sessionkey */
if ((ret = get_client_username(username, ulen, &client_name)))
goto cleanup_client_name;
if ((ret = wrap_sessionkey(context, sinfo)))
goto cleanup_client_name;
/* Authenticated, construct the reply using:
* authenticator length (uint16_t)
* authenticator
*/
/* copy the authenticator length into the reply buffer */
uint16_t auth_len = htons(authenticator_buff.length);
memcpy(rbuf, &auth_len, sizeof(auth_len));
*rbuflen += sizeof(auth_len);
rbuf += sizeof(auth_len);
/* copy the authenticator value into the reply buffer */
memcpy(rbuf, authenticator_buff.value, authenticator_buff.length);
*rbuflen += authenticator_buff.length;
cleanup_client_name:
gss_release_name(&status, &client_name);
gss_release_buffer(&status, &authenticator_buff);
gss_delete_sec_context(&status, &context, NULL);
return ret;
}
/* -------------------------- */
/*
* For the gss uam, this function only needs to return a two-byte
* login-session id. None of the data provided by the client up to this
* point is trustworthy as we'll have a signed ticket to parse in logincont.
*/
static int gss_login(void *obj,
struct passwd **uam_pwd,
char *ibuf, size_t ibuflen,
char *rbuf, size_t *rbuflen)
{
*rbuflen = 0;
/* The reply contains a two-byte ID value - note
* that Apple's implementation seems to always return 1 as well
*/
uint16_t temp16 = htons(1);
memcpy(rbuf, &temp16, sizeof(temp16));
*rbuflen += sizeof(temp16);
return AFPERR_AUTHCONT;
}
static int gss_logincont(void *obj,
struct passwd **uam_pwd,
char *ibuf, size_t ibuflen,
char *rbuf, size_t *rbuflen)
{
struct passwd *pwd = NULL;
uint16_t login_id;
char *username;
uint16_t ticket_len;
char *p;
int rblen;
size_t userlen;
struct session_info *sinfo;
/* Apple's AFP 3.1 documentation specifies that this command
* takes the following format:
* pad (byte)
* id returned in LoginExt response (uint16_t)
* username (format unspecified)
* padded, when necessary, to end on an even boundary
* ticket length (uint16_t)
* ticket
*/
/* Observation of AFP clients in the wild indicate that the actual
* format of this request is as follows:
* pad (byte) [consumed before login_ext is called]
* ?? (byte) - always observed to be 0
* id returned in LoginExt response (uint16_t)
* username, encoding unspecified, null terminated C string,
* padded when the terminating null is an even numbered byte.
* The packet is formated such that the username begins on an
* odd numbered byte. E.g. if the username is 3 characters and the
* terminating null makes 4, expect to pad the the result.
* The encoding of this string is unknown.
* ticket length (uint16_t)
* ticket
*/
rblen = *rbuflen = 0;
if (ibuflen < 1 +sizeof(login_id)) {
LOG_LOGINCONT(log_info, "received incomplete packet");
return AFPERR_PARAM;
}
ibuf++, ibuflen--; /* ?? */
/* 2 byte ID from LoginExt -- always '00 01' in this implementation */
memcpy(&login_id, ibuf, sizeof(login_id));
ibuf += sizeof(login_id), ibuflen -= sizeof(login_id);
login_id = ntohs(login_id);
/* get the username buffer from apfd */
if (uam_afpserver_option(obj, UAM_OPTION_USERNAME, &username, &userlen) < 0)
return AFPERR_MISC;
/* get the session_info structure from afpd. We need the session key */
if (uam_afpserver_option(obj, UAM_OPTION_SESSIONINFO, &sinfo, NULL) < 0)
return AFPERR_MISC;
if (sinfo->sessionkey == NULL || sinfo->sessionkey_len == 0) {
/* Should never happen. Most likely way too old afpd version */
LOG_LOGINCONT(log_error, "internal error: afpd's sessionkey not set");
return AFPERR_MISC;
}
/* We skip past the 'username' parameter because all that matters is the ticket */
p = ibuf;
while ( *ibuf && ibuflen ) { ibuf++, ibuflen--; }
if (ibuflen < 4) {
LOG_LOGINCONT(log_info, "user is %s, no ticket", p);
return AFPERR_PARAM;
}
ibuf++, ibuflen--; /* null termination */
if ((ibuf - p + 1) % 2) ibuf++, ibuflen--; /* deal with potential padding */
LOG_LOGINCONT(log_debug, "client thinks user is %s", p);
/* get the length of the ticket the client sends us */
memcpy(&ticket_len, ibuf, sizeof(ticket_len));
ibuf += sizeof(ticket_len); ibuflen -= sizeof(ticket_len);
ticket_len = ntohs(ticket_len);
/* a little bounds checking */
if (ticket_len > ibuflen) {
LOG_LOGINCONT(log_info,
"invalid ticket length (%u > %u)",
ticket_len, ibuflen);
return AFPERR_PARAM;
}
/* now try to authenticate */
if (do_gss_auth(obj, ibuf, ticket_len, rbuf, &rblen, username, userlen, sinfo)) {
LOG_LOGINCONT(log_info, "do_gss_auth() failed" );
*rbuflen = 0;
return AFPERR_MISC;
}
/* We use the username we got back from the gssapi client_name.
Should we compare this to the username the client sent in the clear?
We know the character encoding of the cleartext username (UTF8), what
encoding is the gssapi name in? */
if ((pwd = uam_getname( obj, username, userlen )) == NULL) {
LOG_LOGINCONT(log_info, "uam_getname() failed for %s", username);
return AFPERR_NOTAUTH;
}
if (uam_checkuser(pwd) < 0) {
LOG_LOGINCONT(log_info, "`%s'' not a valid user", username);
return AFPERR_NOTAUTH;
}
*rbuflen = rblen;
*uam_pwd = pwd;
return AFP_OK;
}
/* logout */
static void gss_logout() {
}
static int gss_login_ext(void *obj,
char *uname,
struct passwd **uam_pwd,
char *ibuf, size_t ibuflen,
char *rbuf, size_t *rbuflen)
{
return gss_login(obj, uam_pwd, ibuf, ibuflen, rbuf, rbuflen);
}
static int set_principal(AFPObj *obj, char *principal)
{
size_t len = strlen(principal);
if (len > 255) {
LOG(log_error, logtype_afpd, "set_principal: principal '%s' too long (max=255)", principal, len);
return -1;
}
/* We store: 1 byte number principals (1) + 1 byte principal name length + zero terminated principal */
if ((obj->options.k5principal = malloc(len + 3)) == NULL) {
LOG(log_error, logtype_afpd, "set_principal: OOM");
return -1;
}
LOG(log_info, logtype_afpd, "Using AFP Kerberos service principal name: %s", principal);
obj->options.k5principal[0] = 1;
obj->options.k5principal[1] = (unsigned char)len;
obj->options.k5principal_buflen = len + 2;
strncpy(obj->options.k5principal + 2, principal, len);
return 0;
}
static int gss_create_principal(AFPObj *obj)
{
int rv = -1;
#ifdef HAVE_KERBEROS
krb5_context context;
krb5_error_code ret;
const char *error_msg;
krb5_keytab keytab;
krb5_keytab_entry entry;
krb5_principal service_principal;
char *principal;
krb5_kt_cursor cursor;
if (krb5_init_context(&context)) {
LOG(log_error, logtype_afpd, "gss_create_principal: failed to initialize a krb5_context");
goto exit;
}
if ((ret = krb5_kt_default(context, &keytab)))
goto krb5_error;
if (obj->options.k5service && obj->options.fqdn && obj->options.k5realm) {
LOG(log_debug, logtype_afpd, "gss_create_principal: using service principal specified in options");
if ((ret = krb5_build_principal(context,
&service_principal,
strlen(obj->options.k5realm),
obj->options.k5realm,
obj->options.k5service,
obj->options.fqdn,
NULL)))
goto krb5_error;
if ((ret = krb5_kt_get_entry(context,
keytab,
service_principal,
0, // kvno - wildcard
0, // enctype - wildcard
&entry)) == KRB5_KT_NOTFOUND) {
krb5_unparse_name(context, service_principal, &principal);
LOG(log_error, logtype_afpd, "gss_create_principal: specified service principal '%s' not found in keytab", principal);
#ifdef HAVE_KRB5_FREE_UNPARSED_NAME
krb5_free_unparsed_name(context, principal);
#else
krb5_xfree(principal);
#endif
goto krb5_cleanup;
}
krb5_free_principal(context, service_principal);
if (ret)
goto krb5_error;
} else {
LOG(log_debug, logtype_afpd, "gss_create_principal: using first entry from keytab as service principal");
if ((ret = krb5_kt_start_seq_get(context, keytab, &cursor)))
goto krb5_error;
ret = krb5_kt_next_entry(context, keytab, &entry, &cursor);
krb5_kt_end_seq_get(context, keytab, &cursor);
if (ret)
goto krb5_error;
}
krb5_unparse_name(context, entry.principal, &principal);
#ifdef HAVE_KRB5_FREE_KEYTAB_ENTRY_CONTENTS
krb5_free_keytab_entry_contents(context, &entry);
#elif defined(HAVE_KRB5_KT_FREE_ENTRY)
krb5_kt_free_entry(context, &entry);
#endif
set_principal(obj, principal);
free(principal);
rv = 0;
goto krb5_cleanup;
krb5_error:
if (ret) {
error_msg = krb5_get_error_message(context, ret);
LOG(log_note, logtype_afpd, "Can't get principal from default keytab: %s",
(char *)error_msg);
#ifdef HAVE_KRB5_FREE_ERROR_MESSAGE
krb5_free_error_message(context, error_msg);
#else
krb5_xfree(error_msg);
#endif
}
krb5_cleanup:
krb5_kt_close(context, keytab);
krb5_free_context(context);
#else /* ! HAVE_KERBEROS */
if (!obj->options.k5service || !obj->options.fqdn || !obj->options.k5realm)
goto exit;
char principal[255];
size_t len = snprintf(principal, sizeof(principal), "%s/%s@%s",
obj->options.k5service, obj->options.fqdn, obj->options.k5realm);
(void)set_principal(obj, principal);
rv = 0;
#endif /* HAVE_KERBEROS */
exit:
return rv;
}
static int uam_setup(void *handle, const char *path)
{
AFPObj *obj = (AFPObj *)handle;
if (gss_create_principal(obj) != 0)
return -1;
return uam_register(UAM_SERVER_LOGIN_EXT, path, "Client Krb v2",
gss_login, gss_logincont, gss_logout, gss_login_ext);
}
static void uam_cleanup(void)
{
uam_unregister(UAM_SERVER_LOGIN_EXT, "Client Krb v2");
}
UAM_MODULE_EXPORT struct uam_export uams_gss = {
UAM_MODULE_SERVER,
UAM_MODULE_VERSION,
uam_setup,
uam_cleanup
};
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