// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * The ASB.1/BER parsing code is derived from ip_nat_snmp_basic.c which was in
 * turn derived from the gxsnmp package by Gregory McLean & Jochen Friedrich
 *
 * Copyright (c) 2000 RP Internet (www.rpi.net.au).
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/oid_registry.h>

#include "glob.h"

#include "asn1.h"
#include "connection.h"
#include "auth.h"
#include "ksmbd_spnego_negtokeninit.asn1.h"
#include "ksmbd_spnego_negtokentarg.asn1.h"

#define NTLMSSP_OID_LEN  10

static char NTLMSSP_OID_STR[NTLMSSP_OID_LEN] = { 0x2b, 0x06, 0x01, 0x04, 0x01,
        0x82, 0x37, 0x02, 0x02, 0x0a };

int
ksmbd_decode_negTokenInit(unsigned char *security_blob, int length,
                          struct ksmbd_conn *conn)
{
        return asn1_ber_decoder(&ksmbd_spnego_negtokeninit_decoder, conn,
                                security_blob, length);
}

int
ksmbd_decode_negTokenTarg(unsigned char *security_blob, int length,
                          struct ksmbd_conn *conn)
{
        return asn1_ber_decoder(&ksmbd_spnego_negtokentarg_decoder, conn,
                                security_blob, length);
}

static int compute_asn_hdr_len_bytes(int len)
{
        if (len > 0xFFFFFF)
                return 4;
        else if (len > 0xFFFF)
                return 3;
        else if (len > 0xFF)
                return 2;
        else if (len > 0x7F)
                return 1;
        else
                return 0;
}

static void encode_asn_tag(char *buf, unsigned int *ofs, char tag, char seq,
                           int length)
{
        int i;
        int index = *ofs;
        char hdr_len = compute_asn_hdr_len_bytes(length);
        int len = length + 2 + hdr_len;

        /* insert tag */
        buf[index++] = tag;

        if (!hdr_len) {
                buf[index++] = len;
        } else {
                buf[index++] = 0x80 | hdr_len;
                for (i = hdr_len - 1; i >= 0; i--)
                        buf[index++] = (len >> (i * 8)) & 0xFF;
        }

        /* insert seq */
        len = len - (index - *ofs);
        buf[index++] = seq;

        if (!hdr_len) {
                buf[index++] = len;
        } else {
                buf[index++] = 0x80 | hdr_len;
                for (i = hdr_len - 1; i >= 0; i--)
                        buf[index++] = (len >> (i * 8)) & 0xFF;
        }

        *ofs += (index - *ofs);
}

int build_spnego_ntlmssp_neg_blob(unsigned char **pbuffer, u16 *buflen,
                                  char *ntlm_blob, int ntlm_blob_len)
{
        char *buf;
        unsigned int ofs = 0;
        int neg_result_len = 4 + compute_asn_hdr_len_bytes(1) * 2 + 1;
        int oid_len = 4 + compute_asn_hdr_len_bytes(NTLMSSP_OID_LEN) * 2 +
                NTLMSSP_OID_LEN;
        int ntlmssp_len = 4 + compute_asn_hdr_len_bytes(ntlm_blob_len) * 2 +
                ntlm_blob_len;
        int total_len = 4 + compute_asn_hdr_len_bytes(neg_result_len +
                        oid_len + ntlmssp_len) * 2 +
                        neg_result_len + oid_len + ntlmssp_len;

        buf = kmalloc(total_len, KSMBD_DEFAULT_GFP);
        if (!buf)
                return -ENOMEM;

        /* insert main gss header */
        encode_asn_tag(buf, &ofs, 0xa1, 0x30, neg_result_len + oid_len +
                        ntlmssp_len);

        /* insert neg result */
        encode_asn_tag(buf, &ofs, 0xa0, 0x0a, 1);
        buf[ofs++] = 1;

        /* insert oid */
        encode_asn_tag(buf, &ofs, 0xa1, 0x06, NTLMSSP_OID_LEN);
        memcpy(buf + ofs, NTLMSSP_OID_STR, NTLMSSP_OID_LEN);
        ofs += NTLMSSP_OID_LEN;

        /* insert response token - ntlmssp blob */
        encode_asn_tag(buf, &ofs, 0xa2, 0x04, ntlm_blob_len);
        memcpy(buf + ofs, ntlm_blob, ntlm_blob_len);
        ofs += ntlm_blob_len;

        *pbuffer = buf;
        *buflen = total_len;
        return 0;
}

int build_spnego_ntlmssp_auth_blob(unsigned char **pbuffer, u16 *buflen,
                                   int neg_result)
{
        char *buf;
        unsigned int ofs = 0;
        int neg_result_len = 4 + compute_asn_hdr_len_bytes(1) * 2 + 1;
        int total_len = 4 + compute_asn_hdr_len_bytes(neg_result_len) * 2 +
                neg_result_len;

        buf = kmalloc(total_len, KSMBD_DEFAULT_GFP);
        if (!buf)
                return -ENOMEM;

        /* insert main gss header */
        encode_asn_tag(buf, &ofs, 0xa1, 0x30, neg_result_len);

        /* insert neg result */
        encode_asn_tag(buf, &ofs, 0xa0, 0x0a, 1);
        if (neg_result)
                buf[ofs++] = 2;
        else
                buf[ofs++] = 0;

        *pbuffer = buf;
        *buflen = total_len;
        return 0;
}

int ksmbd_gssapi_this_mech(void *context, size_t hdrlen, unsigned char tag,
                           const void *value, size_t vlen)
{
        enum OID oid;

        oid = look_up_OID(value, vlen);
        if (oid != OID_spnego) {
                char buf[50];

                sprint_oid(value, vlen, buf, sizeof(buf));
                ksmbd_debug(AUTH, "Unexpected OID: %s\n", buf);
                return -EBADMSG;
        }

        return 0;
}

int ksmbd_neg_token_init_mech_type(void *context, size_t hdrlen,
                                   unsigned char tag, const void *value,
                                   size_t vlen)
{
        struct ksmbd_conn *conn = context;
        enum OID oid;
        int mech_type;

        oid = look_up_OID(value, vlen);
        if (oid == OID_ntlmssp) {
                mech_type = KSMBD_AUTH_NTLMSSP;
        } else if (oid == OID_mskrb5) {
                mech_type = KSMBD_AUTH_MSKRB5;
        } else if (oid == OID_krb5) {
                mech_type = KSMBD_AUTH_KRB5;
        } else if (oid == OID_krb5u2u) {
                mech_type = KSMBD_AUTH_KRB5U2U;
        } else {
                char buf[50];

                sprint_oid(value, vlen, buf, sizeof(buf));
                ksmbd_debug(AUTH, "Unexpected OID: %s\n", buf);
                return -EBADMSG;
        }

        conn->auth_mechs |= mech_type;
        if (conn->preferred_auth_mech == 0)
                conn->preferred_auth_mech = mech_type;

        return 0;
}

static int ksmbd_neg_token_alloc(void *context, size_t hdrlen,
                                 unsigned char tag, const void *value,
                                 size_t vlen)
{
        struct ksmbd_conn *conn = context;

        if (!vlen)
                return -EINVAL;

        conn->mechToken = kmemdup_nul(value, vlen, KSMBD_DEFAULT_GFP);
        if (!conn->mechToken)
                return -ENOMEM;

        conn->mechTokenLen = (unsigned int)vlen;

        return 0;
}

int ksmbd_neg_token_init_mech_token(void *context, size_t hdrlen,
                                    unsigned char tag, const void *value,
                                    size_t vlen)
{
        return ksmbd_neg_token_alloc(context, hdrlen, tag, value, vlen);
}

int ksmbd_neg_token_targ_resp_token(void *context, size_t hdrlen,
                                    unsigned char tag, const void *value,
                                    size_t vlen)
{
        return ksmbd_neg_token_alloc(context, hdrlen, tag, value, vlen);
}