/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2026 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, see <https://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "syshead.h"

#if PROXY_DIGEST_AUTH

#include "crypto.h"
#include "httpdigest.h"

static void
CvtHex(IN HASH Bin, OUT HASHHEX Hex)
{
    unsigned short i;
    unsigned char j;

    for (i = 0; i < HASHLEN; i++)
    {
        j = (Bin[i] >> 4) & 0xf;
        if (j <= 9)
        {
            Hex[i * 2] = (j + '0');
        }
        else
        {
            Hex[i * 2] = (unsigned char)(j + 'a' - 10);
        }
        j = Bin[i] & 0xf;
        if (j <= 9)
        {
            Hex[i * 2 + 1] = (j + '0');
        }
        else
        {
            Hex[i * 2 + 1] = (unsigned char)(j + 'a' - 10);
        }
    }
    Hex[HASHHEXLEN] = '\0';
}

/* calculate H(A1) as per spec */
void
DigestCalcHA1(IN char *pszAlg, IN char *pszUserName, IN char *pszRealm, IN char *pszPassword,
              IN char *pszNonce, IN char *pszCNonce, OUT HASHHEX SessionKey)
{
    HASH HA1;
    md_ctx_t *md5_ctx = md_ctx_new();

    md_ctx_init(md5_ctx, "MD5");
    md_ctx_update(md5_ctx, (const uint8_t *)pszUserName, strlen(pszUserName));
    md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    md_ctx_update(md5_ctx, (const uint8_t *)pszRealm, strlen(pszRealm));
    md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    md_ctx_update(md5_ctx, (const uint8_t *)pszPassword, strlen(pszPassword));
    md_ctx_final(md5_ctx, HA1);
    if (pszAlg && strcasecmp(pszAlg, "md5-sess") == 0)
    {
        md_ctx_init(md5_ctx, "MD5");
        md_ctx_update(md5_ctx, HA1, HASHLEN);
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
        md_ctx_update(md5_ctx, (const uint8_t *)pszNonce, strlen(pszNonce));
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
        md_ctx_update(md5_ctx, (const uint8_t *)pszCNonce, strlen(pszCNonce));
        md_ctx_final(md5_ctx, HA1);
    }
    md_ctx_cleanup(md5_ctx);
    md_ctx_free(md5_ctx);
    CvtHex(HA1, SessionKey);
}

/* calculate request-digest/response-digest as per HTTP Digest spec */
void
DigestCalcResponse(IN HASHHEX HA1,         /* H(A1) */
                   IN char *pszNonce,      /* nonce from server */
                   IN char *pszNonceCount, /* 8 hex digits */
                   IN char *pszCNonce,     /* client nonce */
                   IN char *pszQop,        /* qop-value: "", "auth", "auth-int" */
                   IN char *pszMethod,     /* method from the request */
                   IN char *pszDigestUri,  /* requested URL */
                   IN HASHHEX HEntity,     /* H(entity body) if qop="auth-int" */
                   OUT HASHHEX Response    /* request-digest or response-digest */
)
{
    HASH HA2;
    HASH RespHash;
    HASHHEX HA2Hex;

    md_ctx_t *md5_ctx = md_ctx_new();

    /* calculate H(A2) */
    md_ctx_init(md5_ctx, "MD5");
    md_ctx_update(md5_ctx, (const uint8_t *)pszMethod, strlen(pszMethod));
    md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    md_ctx_update(md5_ctx, (const uint8_t *)pszDigestUri, strlen(pszDigestUri));
    if (strcasecmp(pszQop, "auth-int") == 0)
    {
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
        md_ctx_update(md5_ctx, HEntity, HASHHEXLEN);
    }
    md_ctx_final(md5_ctx, HA2);
    CvtHex(HA2, HA2Hex);

    /* calculate response */
    md_ctx_init(md5_ctx, "MD5");
    md_ctx_update(md5_ctx, HA1, HASHHEXLEN);
    md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    md_ctx_update(md5_ctx, (const uint8_t *)pszNonce, strlen(pszNonce));
    md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    if (*pszQop)
    {
        md_ctx_update(md5_ctx, (const uint8_t *)pszNonceCount, strlen(pszNonceCount));
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
        md_ctx_update(md5_ctx, (const uint8_t *)pszCNonce, strlen(pszCNonce));
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
        md_ctx_update(md5_ctx, (const uint8_t *)pszQop, strlen(pszQop));
        md_ctx_update(md5_ctx, (const uint8_t *)":", 1);
    }
    md_ctx_update(md5_ctx, HA2Hex, HASHHEXLEN);
    md_ctx_final(md5_ctx, RespHash);
    md_ctx_cleanup(md5_ctx);
    md_ctx_free(md5_ctx);
    CvtHex(RespHash, Response);
}

#endif /* if PROXY_DIGEST_AUTH */
