// SPDX-License-Identifier: GPL-2.0-or-later
/* Cache manager security.
 *
 * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <crypto/krb5.h>
#include "internal.h"
#include "afs_cm.h"
#include "afs_fs.h"
#include "protocol_yfs.h"
#define RXRPC_TRACE_ONLY_DEFINE_ENUMS
#include <trace/events/rxrpc.h>

#define RXGK_SERVER_ENC_TOKEN 1036U // 0x40c
#define xdr_round_up(x) (round_up((x), sizeof(__be32)))
#define xdr_len_object(x) (4 + round_up((x), sizeof(__be32)))

#ifdef CONFIG_RXGK
static int afs_create_yfs_cm_token(struct sk_buff *challenge,
                                   struct afs_server *server);
#endif

/*
 * Respond to an RxGK challenge, adding appdata.
 */
static int afs_respond_to_challenge(struct sk_buff *challenge)
{
#ifdef CONFIG_RXGK
        struct krb5_buffer appdata = {};
        struct afs_server *server;
#endif
        struct rxrpc_peer *peer;
        unsigned long peer_data;
        u16 service_id;
        u8 security_index;

        rxrpc_kernel_query_challenge(challenge, &peer, &peer_data,
                                     &service_id, &security_index);

        _enter("%u,%u", service_id, security_index);

        switch (service_id) {
                /* We don't send CM_SERVICE RPCs, so don't expect a challenge
                 * therefrom.
                 */
        case FS_SERVICE:
        case VL_SERVICE:
        case YFS_FS_SERVICE:
        case YFS_VL_SERVICE:
                break;
        default:
                pr_warn("Can't respond to unknown challenge %u:%u",
                        service_id, security_index);
                return rxrpc_kernel_reject_challenge(challenge, RX_USER_ABORT, -EPROTO,
                                                     afs_abort_unsupported_sec_class);
        }

        switch (security_index) {
#ifdef CONFIG_RXKAD
        case RXRPC_SECURITY_RXKAD:
                return rxkad_kernel_respond_to_challenge(challenge);
#endif

#ifdef CONFIG_RXGK
        case RXRPC_SECURITY_RXGK:
                return rxgk_kernel_respond_to_challenge(challenge, &appdata);

        case RXRPC_SECURITY_YFS_RXGK:
                switch (service_id) {
                case FS_SERVICE:
                case YFS_FS_SERVICE:
                        server = (struct afs_server *)peer_data;
                        if (!server->cm_rxgk_appdata.data) {
                                mutex_lock(&server->cm_token_lock);
                                if (!server->cm_rxgk_appdata.data)
                                        afs_create_yfs_cm_token(challenge, server);
                                mutex_unlock(&server->cm_token_lock);
                        }
                        if (server->cm_rxgk_appdata.data)
                                appdata = server->cm_rxgk_appdata;
                        break;
                }
                return rxgk_kernel_respond_to_challenge(challenge, &appdata);
#endif

        default:
                return rxrpc_kernel_reject_challenge(challenge, RX_USER_ABORT, -EPROTO,
                                                     afs_abort_unsupported_sec_class);
        }
}

/*
 * Process the OOB message queue, processing challenge packets.
 */
void afs_process_oob_queue(struct work_struct *work)
{
        struct afs_net *net = container_of(work, struct afs_net, rx_oob_work);
        struct sk_buff *oob;
        enum rxrpc_oob_type type;

        while ((oob = rxrpc_kernel_dequeue_oob(net->socket, &type))) {
                switch (type) {
                case RXRPC_OOB_CHALLENGE:
                        afs_respond_to_challenge(oob);
                        break;
                }
                rxrpc_kernel_free_oob(oob);
        }
}

#ifdef CONFIG_RXGK
/*
 * Create a securities keyring for the cache manager and attach a key to it for
 * the RxGK tokens we want to use to secure the callback connection back from
 * the fileserver.
 */
int afs_create_token_key(struct afs_net *net, struct socket *socket)
{
        const struct krb5_enctype *krb5;
        struct key *ring;
        key_ref_t key;
        char K0[32], *desc;
        int ret;

        ring = keyring_alloc("kafs",
                             GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
                             KEY_POS_SEARCH | KEY_POS_WRITE |
                             KEY_USR_VIEW | KEY_USR_READ | KEY_USR_SEARCH,
                             KEY_ALLOC_NOT_IN_QUOTA,
                             NULL, NULL);
        if (IS_ERR(ring))
                return PTR_ERR(ring);

        ret = rxrpc_sock_set_security_keyring(socket->sk, ring);
        if (ret < 0)
                goto out;

        ret = -ENOPKG;
        krb5 = crypto_krb5_find_enctype(KRB5_ENCTYPE_AES128_CTS_HMAC_SHA1_96);
        if (!krb5)
                goto out;

        if (WARN_ON_ONCE(krb5->key_len > sizeof(K0)))
                goto out;

        ret = -ENOMEM;
        desc = kasprintf(GFP_KERNEL, "%u:%u:%u:%u",
                         YFS_CM_SERVICE, RXRPC_SECURITY_YFS_RXGK, 1, krb5->etype);
        if (!desc)
                goto out;

        wait_for_random_bytes();
        get_random_bytes(K0, krb5->key_len);

        key = key_create(make_key_ref(ring, true),
                         "rxrpc_s", desc,
                         K0, krb5->key_len,
                         KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_USR_VIEW,
                         KEY_ALLOC_NOT_IN_QUOTA);
        kfree(desc);
        if (IS_ERR(key)) {
                ret = PTR_ERR(key);
                goto out;
        }

        net->fs_cm_token_key = key_ref_to_ptr(key);
        ret = 0;
out:
        key_put(ring);
        return ret;
}

/*
 * Create an YFS RxGK GSS token to use as a ticket to the specified fileserver.
 */
static int afs_create_yfs_cm_token(struct sk_buff *challenge,
                                   struct afs_server *server)
{
        const struct krb5_enctype *conn_krb5, *token_krb5;
        const struct krb5_buffer *token_key;
        struct crypto_aead *aead;
        struct scatterlist sg;
        struct afs_net *net = server->cell->net;
        const struct key *key = net->fs_cm_token_key;
        size_t keysize, uuidsize, authsize, toksize, encsize, contsize, adatasize, offset;
        __be32 caps[1] = {
                [0] = htonl(AFS_CAP_ERROR_TRANSLATION),
        };
        __be32 *xdr;
        void *appdata, *K0, *encbase;
        u32 enctype;
        int ret;

        if (!key)
                return -ENOKEY;

        /* Assume that the fileserver is happy to use the same encoding type as
         * we were told to use by the token obtained by the user.
         */
        enctype = rxgk_kernel_query_challenge(challenge);

        conn_krb5 = crypto_krb5_find_enctype(enctype);
        if (!conn_krb5)
                return -ENOPKG;
        token_krb5 = key->payload.data[0];
        token_key = (const struct krb5_buffer *)&key->payload.data[2];

        /* struct rxgk_key {
         *      afs_uint32      enctype;
         *      opaque          key<>;
         * };
         */
        keysize = 4 + xdr_len_object(conn_krb5->key_len);

        /* struct RXGK_AuthName {
         *      afs_int32       kind;
         *      opaque          data<AUTHDATAMAX>;
         *      opaque          display<AUTHPRINTABLEMAX>;
         * };
         */
        uuidsize = sizeof(server->uuid);
        authsize = 4 + xdr_len_object(uuidsize) + xdr_len_object(0);

        /* struct RXGK_Token {
         *      rxgk_key                K0;
         *      RXGK_Level              level;
         *      rxgkTime                starttime;
         *      afs_int32               lifetime;
         *      afs_int32               bytelife;
         *      rxgkTime                expirationtime;
         *      struct RXGK_AuthName    identities<>;
         * };
         */
        toksize = keysize + 8 + 4 + 4 + 8 + xdr_len_object(authsize);

        offset = 0;
        encsize = crypto_krb5_how_much_buffer(token_krb5, KRB5_ENCRYPT_MODE, toksize, &offset);

        /* struct RXGK_TokenContainer {
         *      afs_int32       kvno;
         *      afs_int32       enctype;
         *      opaque          encrypted_token<>;
         * };
         */
        contsize = 4 + 4 + xdr_len_object(encsize);

        /* struct YFSAppData {
         *      opr_uuid        initiatorUuid;
         *      opr_uuid        acceptorUuid;
         *      Capabilities    caps;
         *      afs_int32       enctype;
         *      opaque          callbackKey<>;
         *      opaque          callbackToken<>;
         * };
         */
        adatasize = 16 + 16 +
                xdr_len_object(sizeof(caps)) +
                4 +
                xdr_len_object(conn_krb5->key_len) +
                xdr_len_object(contsize);

        ret = -ENOMEM;
        appdata = kzalloc(adatasize, GFP_KERNEL);
        if (!appdata)
                goto out;
        xdr = appdata;

        memcpy(xdr, &net->uuid, 16);            /* appdata.initiatorUuid */
        xdr += 16 / 4;
        memcpy(xdr, &server->uuid, 16);         /* appdata.acceptorUuid */
        xdr += 16 / 4;
        *xdr++ = htonl(ARRAY_SIZE(caps));       /* appdata.caps.len */
        memcpy(xdr, &caps, sizeof(caps));       /* appdata.caps */
        xdr += ARRAY_SIZE(caps);
        *xdr++ = htonl(conn_krb5->etype);       /* appdata.enctype */

        *xdr++ = htonl(conn_krb5->key_len);     /* appdata.callbackKey.len */
        K0 = xdr;
        get_random_bytes(K0, conn_krb5->key_len); /* appdata.callbackKey.data */
        xdr += xdr_round_up(conn_krb5->key_len) / 4;

        *xdr++ = htonl(contsize);               /* appdata.callbackToken.len */
        *xdr++ = htonl(1);                      /* cont.kvno */
        *xdr++ = htonl(token_krb5->etype);      /* cont.enctype */
        *xdr++ = htonl(encsize);                /* cont.encrypted_token.len */

        encbase = xdr;
        xdr += offset / 4;
        *xdr++ = htonl(conn_krb5->etype);       /* token.K0.enctype */
        *xdr++ = htonl(conn_krb5->key_len);     /* token.K0.key.len */
        memcpy(xdr, K0, conn_krb5->key_len);    /* token.K0.key.data */
        xdr += xdr_round_up(conn_krb5->key_len) / 4;

        *xdr++ = htonl(RXRPC_SECURITY_ENCRYPT); /* token.level */
        *xdr++ = htonl(0);                      /* token.starttime */
        *xdr++ = htonl(0);                      /* " */
        *xdr++ = htonl(0);                      /* token.lifetime */
        *xdr++ = htonl(0);                      /* token.bytelife */
        *xdr++ = htonl(0);                      /* token.expirationtime */
        *xdr++ = htonl(0);                      /* " */
        *xdr++ = htonl(1);                      /* token.identities.count */
        *xdr++ = htonl(0);                      /* token.identities[0].kind */
        *xdr++ = htonl(uuidsize);               /* token.identities[0].data.len */
        memcpy(xdr, &server->uuid, uuidsize);
        xdr += xdr_round_up(uuidsize) / 4;
        *xdr++ = htonl(0);                      /* token.identities[0].display.len */

        xdr = encbase + xdr_round_up(encsize);

        if ((unsigned long)xdr - (unsigned long)appdata != adatasize)
                pr_err("Appdata size incorrect %lx != %zx\n",
                       (unsigned long)xdr - (unsigned long)appdata, adatasize);

        aead = crypto_krb5_prepare_encryption(token_krb5, token_key, RXGK_SERVER_ENC_TOKEN,
                                              GFP_KERNEL);
        if (IS_ERR(aead)) {
                ret = PTR_ERR(aead);
                goto out_token;
        }

        sg_init_one(&sg, encbase, encsize);
        ret = crypto_krb5_encrypt(token_krb5, aead, &sg, 1, encsize, offset, toksize, false);
        if (ret < 0)
                goto out_aead;

        server->cm_rxgk_appdata.len  = adatasize;
        server->cm_rxgk_appdata.data = appdata;
        appdata = NULL;

out_aead:
        crypto_free_aead(aead);
out_token:
        kfree(appdata);
out:
        return ret;
}
#endif /* CONFIG_RXGK */