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kdcpreauth_plugin.h
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/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */ /* * Copyright (c) 2006 Red Hat, Inc. * Portions copyright (c) 2006, 2011 Massachusetts Institute of Technology * All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 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. * * Neither the name of Red Hat, Inc., nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER * OR CONTRIBUTORS 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. */ /* * Declarations for kdcpreauth plugin module implementors. * * The kdcpreauth interface has a single supported major version, which is 1. * Major version 1 has a current minor version of 2. kdcpreauth modules should * define a function named kdcpreauth_<modulename>_initvt, matching the * signature: * * krb5_error_code * kdcpreauth_modname_initvt(krb5_context context, int maj_ver, int min_ver, * krb5_plugin_vtable vtable); * * The initvt function should: * * - Check that the supplied maj_ver number is supported by the module, or * return KRB5_PLUGIN_VER_NOTSUPP if it is not. * * - Cast the vtable pointer as appropriate for the interface and maj_ver: * kdcpreauth, maj_ver == 1: Cast to krb5_kdcpreauth_vtable * * - Initialize the methods of the vtable, stopping as appropriate for the * supplied min_ver. Optional methods may be left uninitialized. * * Memory for the vtable is allocated by the caller, not by the module. */ #ifndef KRB5_KDCPREAUTH_PLUGIN_H #define KRB5_KDCPREAUTH_PLUGIN_H #include <krb5/krb5.h> #include <krb5/plugin.h> /* kdcpreauth mechanism property flags */ /* * Causes the KDC to include this mechanism in a list of supported preauth * types if the user's DB entry flags the user as requiring hardware-based * preauthentication. */ #define PA_HARDWARE 0x00000004 /* * Causes the KDC to include this mechanism in a list of supported preauth * types if the user's DB entry flags the user as requiring preauthentication, * and to fail preauthentication if we can't verify the client data. The * flipside of PA_SUFFICIENT. */ #define PA_REQUIRED 0x00000008 /* * Causes the KDC to include this mechanism in a list of supported preauth * types if the user's DB entry flags the user as requiring preauthentication, * and to mark preauthentication as successful if we can verify the client * data. The flipside of PA_REQUIRED. */ #define PA_SUFFICIENT 0x00000010 /* * Marks this preauthentication mechanism as one which changes the key which is * used for encrypting the response to the client. Modules which have this * flag have their server_return_fn called before modules which do not, and are * passed over if a previously-called module has modified the encrypting key. */ #define PA_REPLACES_KEY 0x00000020 /* * Not really a padata type, so don't include it in any list of preauth types * which gets sent over the wire. */ #define PA_PSEUDO 0x00000080 /* * Indicates that e_data in non-FAST errors should be encoded as typed data * instead of padata. */ #define PA_TYPED_E_DATA 0x00000100 /* Abstract type for a KDC callback data handle. */ typedef struct krb5_kdcpreauth_rock_st *krb5_kdcpreauth_rock; /* Abstract type for module data and per-request module data. */ typedef struct krb5_kdcpreauth_moddata_st *krb5_kdcpreauth_moddata; typedef struct krb5_kdcpreauth_modreq_st *krb5_kdcpreauth_modreq; /* The verto context structure type (typedef is in verto.h; we want to avoid a * header dependency for the moment). */ struct verto_ctx; /* Before using a callback after version 1, modules must check the vers * field of the callback structure. */ typedef struct krb5_kdcpreauth_callbacks_st { int vers; krb5_deltat (*max_time_skew)(krb5_context context, krb5_kdcpreauth_rock rock); /* * Get an array of krb5_keyblock structures containing the client keys * matching the request enctypes, terminated by an entry with key type = 0. * Returns ENOENT if no keys are available for the request enctypes. Free * the resulting object with the free_keys callback. */ krb5_error_code (*client_keys)(krb5_context context, krb5_kdcpreauth_rock rock, krb5_keyblock **keys_out); /* Free the result of client_keys. */ void (*free_keys)(krb5_context context, krb5_kdcpreauth_rock rock, krb5_keyblock *keys); /* * Get the encoded request body, which is sometimes needed for checksums. * For a FAST request this is the encoded inner request body. The returned * pointer is an alias and should not be freed. */ krb5_data *(*request_body)(krb5_context context, krb5_kdcpreauth_rock rock); /* Get a pointer to the FAST armor key, or NULL if the request did not use * FAST. The returned pointer is an alias and should not be freed. */ krb5_keyblock *(*fast_armor)(krb5_context context, krb5_kdcpreauth_rock rock); /* Retrieve a string attribute from the client DB entry, or NULL if no such * attribute is set. Free the result with the free_string callback. */ krb5_error_code (*get_string)(krb5_context context, krb5_kdcpreauth_rock rock, const char *key, char **value_out); /* Free the result of get_string. */ void (*free_string)(krb5_context context, krb5_kdcpreauth_rock rock, char *string); /* Get a pointer to the client DB entry (returned as a void pointer to * avoid a dependency on a libkdb5 type). */ void *(*client_entry)(krb5_context context, krb5_kdcpreauth_rock rock); /* Get a pointer to the verto context which should be used by an * asynchronous edata or verify method. */ struct verto_ctx *(*event_context)(krb5_context context, krb5_kdcpreauth_rock rock); /* End of version 1 kdcpreauth callbacks. */ /* Return true if the client DB entry contains any keys matching the * request enctypes. */ krb5_boolean (*have_client_keys)(krb5_context context, krb5_kdcpreauth_rock rock); /* End of version 2 kdcpreauth callbacks. */ /* * Get the current reply key. Initially the reply key is the decrypted * client long-term key chosen according to the request enctype list, or * NULL if no matching key was found. The value may be changed by the * replace_reply_key callback or a return_padata method modifying * encrypting_key. The returned pointer is an alias and should not be * freed. */ const krb5_keyblock *(*client_keyblock)(krb5_context context, krb5_kdcpreauth_rock rock); /* Assert an authentication indicator in the AS-REP authdata. Duplicate * indicators will be ignored. */ krb5_error_code (*add_auth_indicator)(krb5_context context, krb5_kdcpreauth_rock rock, const char *indicator); /* * Read a data value for pa_type from the request cookie, placing it in * *out. The value placed there is an alias and must not be freed. * Returns true if a value for pa_type was retrieved, false if not. */ krb5_boolean (*get_cookie)(krb5_context context, krb5_kdcpreauth_rock rock, krb5_preauthtype pa_type, krb5_data *out); /* * Set a data value for pa_type to be sent in a secure cookie in the next * error response. If pa_type is already present, the value is ignored. * If the preauth mechanism has different preauth types for requests and * responses, use the request type. Secure cookies are encrypted in a key * known only to the KDCs, but can be replayed within a short time window * for requests using the same client principal. */ krb5_error_code (*set_cookie)(krb5_context context, krb5_kdcpreauth_rock rock, krb5_preauthtype pa_type, const krb5_data *data); /* End of version 3 kdcpreauth callbacks. */ /* * Return true if princ matches the principal named in the request or the * client principal (possibly canonicalized). If princ does not match, * attempt a database lookup of princ with aliases allowed and compare the * result to the client principal, returning true if it matches. * Otherwise, return false. */ krb5_boolean (*match_client)(krb5_context context, krb5_kdcpreauth_rock rock, krb5_principal princ); /* * Get an alias to the client DB entry principal (possibly canonicalized). */ krb5_principal (*client_name)(krb5_context context, krb5_kdcpreauth_rock rock); /* End of version 4 kdcpreauth callbacks. */ /* * Instruct the KDC to send a freshness token in the method data * accompanying a PREAUTH_REQUIRED or PREAUTH_FAILED error, if the client * indicated support for freshness tokens. This callback should only be * invoked from the edata method. */ void (*send_freshness_token)(krb5_context context, krb5_kdcpreauth_rock rock); /* Validate a freshness token sent by the client. Return 0 on success, * KRB5KDC_ERR_PREAUTH_EXPIRED on error. */ krb5_error_code (*check_freshness_token)(krb5_context context, krb5_kdcpreauth_rock rock, const krb5_data *token); /* End of version 5 kdcpreauth callbacks. */ /* * Replace the reply key with key. If is_strengthen is true, key must be a * derivative of the client long-term key. This callback may be invoked * from the verify or return_padata methods. If it is invoked from the * verify method, the new key will appear as the encrypting_key input to * return_padata. */ krb5_error_code (*replace_reply_key)(krb5_context context, krb5_kdcpreauth_rock rock, const krb5_keyblock *key, krb5_boolean is_strengthen); /* End of version 6 kdcpreauth callbacks. */ } *krb5_kdcpreauth_callbacks; /* Optional: preauth plugin initialization function. */ typedef krb5_error_code (*krb5_kdcpreauth_init_fn)(krb5_context context, krb5_kdcpreauth_moddata *moddata_out, const char **realmnames); /* Optional: preauth plugin cleanup function. */ typedef void (*krb5_kdcpreauth_fini_fn)(krb5_context context, krb5_kdcpreauth_moddata moddata); /* * Optional: return the flags which the KDC should use for this module. This * is a callback instead of a static value because the module may or may not * wish to count itself as a hardware preauthentication module (in other words, * the flags may be affected by the configuration, for example if a site * administrator can force a particular preauthentication type to be supported * using only hardware). This function is called for each entry entry in the * server_pa_type_list. */ typedef int (*krb5_kdcpreauth_flags_fn)(krb5_context context, krb5_preauthtype pa_type); /* * Responder for krb5_kdcpreauth_edata_fn. If invoked with a non-zero code, pa * will be ignored and the padata type will not be included in the hint list. * If invoked with a zero code and a null pa value, the padata type will be * included in the list with an empty value. If invoked with a zero code and a * non-null pa value, pa will be included in the hint list and will later be * freed by the KDC. */ typedef void (*krb5_kdcpreauth_edata_respond_fn)(void *arg, krb5_error_code code, krb5_pa_data *pa); /* * Optional: provide pa_data to send to the client as part of the "you need to * use preauthentication" error. The implementation must invoke the respond * when complete, whether successful or not, either before returning or * asynchronously using the verto context returned by cb->event_context(). * * This function is not allowed to create a modreq object because we have no * guarantee that the client will ever make a follow-up request, or that it * will hit this KDC if it does. */ typedef void (*krb5_kdcpreauth_edata_fn)(krb5_context context, krb5_kdc_req *request, krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock, krb5_kdcpreauth_moddata moddata, krb5_preauthtype pa_type, krb5_kdcpreauth_edata_respond_fn respond, void *arg); /* * Responder for krb5_kdcpreauth_verify_fn. Invoke with the arg parameter * supplied to verify, the error code (0 for success), an optional module * request state object to be consumed by return_fn or free_modreq_fn, optional * e_data to be passed to the caller if code is nonzero, and optional * authorization data to be included in the ticket. In non-FAST replies, * e_data will be encoded as typed-data if the module sets the PA_TYPED_E_DATA * flag, and as pa-data otherwise. e_data and authz_data will be freed by the * KDC. */ typedef void (*krb5_kdcpreauth_verify_respond_fn)(void *arg, krb5_error_code code, krb5_kdcpreauth_modreq modreq, krb5_pa_data **e_data, krb5_authdata **authz_data); /* * Optional: verify preauthentication data sent by the client, setting the * TKT_FLG_PRE_AUTH or TKT_FLG_HW_AUTH flag in the enc_tkt_reply's "flags" * field as appropriate. The implementation must invoke the respond function * when complete, whether successful or not, either before returning or * asynchronously using the verto context returned by cb->event_context(). */ typedef void (*krb5_kdcpreauth_verify_fn)(krb5_context context, krb5_data *req_pkt, krb5_kdc_req *request, krb5_enc_tkt_part *enc_tkt_reply, krb5_pa_data *data, krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock, krb5_kdcpreauth_moddata moddata, krb5_kdcpreauth_verify_respond_fn respond, void *arg); /* * Optional: generate preauthentication response data to send to the client as * part of the AS-REP. If it needs to override the key which is used to * encrypt the response, it can do so by modifying encrypting_key, but it is * preferrable to use the replace_reply_key callback. */ typedef krb5_error_code (*krb5_kdcpreauth_return_fn)(krb5_context context, krb5_pa_data *padata, krb5_data *req_pkt, krb5_kdc_req *request, krb5_kdc_rep *reply, krb5_keyblock *encrypting_key, krb5_pa_data **send_pa_out, krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock, krb5_kdcpreauth_moddata moddata, krb5_kdcpreauth_modreq modreq); /* Optional: free a per-request context. */ typedef void (*krb5_kdcpreauth_free_modreq_fn)(krb5_context, krb5_kdcpreauth_moddata moddata, krb5_kdcpreauth_modreq modreq); /* Optional: invoked after init_fn to provide the module with a pointer to the * verto main loop. */ typedef krb5_error_code (*krb5_kdcpreauth_loop_fn)(krb5_context context, krb5_kdcpreauth_moddata moddata, struct verto_ctx *ctx); typedef struct krb5_kdcpreauth_vtable_st { /* Mandatory: name of module. */ const char *name; /* Mandatory: pointer to zero-terminated list of pa_types which this module * can provide services for. */ krb5_preauthtype *pa_type_list; krb5_kdcpreauth_init_fn init; krb5_kdcpreauth_fini_fn fini; krb5_kdcpreauth_flags_fn flags; krb5_kdcpreauth_edata_fn edata; krb5_kdcpreauth_verify_fn verify; krb5_kdcpreauth_return_fn return_padata; krb5_kdcpreauth_free_modreq_fn free_modreq; /* Minor 1 ends here. */ krb5_kdcpreauth_loop_fn loop; /* Minor 2 ends here. */ } *krb5_kdcpreauth_vtable; #endif /* KRB5_KDCPREAUTH_PLUGIN_H */