/*
 * HttpAuth
 *
 * Copyright (C) 2004 Stefan Walter
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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, write to the
 * Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* Ideas and Guidance from Apache 2.0's mod_auth_digest */

#include "usuals.h"
#include "md5.h"
#include "httpauthd.h"
#include "digest.h"
#include "stringx.h"

#include <ctype.h>
#include <syslog.h>
#include <assert.h>

/* A globally unique counter used to guarantee uniqueness of nonces */
static unsigned int g_digest_unique = 0;

/* All the various HTTP methods to try when ignoring the method */
static const char* g_http_methods[] = {
	"GET", "HEAD", "POST", "PUT", "DELETE", "TRACE", "CONNECT", NULL
};

typedef struct internal_nonce
{
    unsigned char hash[MD5_LEN];
    time_t tm;
    unsigned int unique;
}
internal_nonce_t __attribute__((packed));

void digest_makenonce(unsigned char* nonce, unsigned char* secret, unsigned char* old)
{
    internal_nonce_t in;
    md5_ctx_t md5;

    ASSERT(nonce && secret);
    ASSERT(sizeof(internal_nonce_t) == DIGEST_NONCE_LEN);

    if(old)
    {
        internal_nonce_t* nold = (internal_nonce_t*)old;
        in.tm = nold->tm;
        in.unique = nold->unique;
    }
    else
    {
        in.tm = time(NULL);
        ha_lock(NULL);
            in.unique = g_digest_unique++;
        ha_unlock(NULL);
    }

    md5_init(&md5);
    md5_update(&md5, secret, DIGEST_SECRET_LEN);
    md5_update(&md5, &(in.tm), sizeof(in.tm));
    md5_update(&md5, &(in.unique), sizeof(in.unique));
    md5_final(in.hash, &md5);

    memcpy(nonce, &in, DIGEST_NONCE_LEN);
}

int digest_checknonce(unsigned char* nonce, unsigned char* secret, time_t* tm)
{
    internal_nonce_t in;

    ASSERT(nonce && secret);
    ASSERT(sizeof(internal_nonce_t) == DIGEST_NONCE_LEN);

    digest_makenonce((unsigned char*)&in, secret, nonce);

    if(memcmp((unsigned char*)&in, nonce, DIGEST_SECRET_LEN) == 0)
    {
        if(tm)
            *tm = in.tm;

        return HA_OK;
    }

    return HA_FALSE;
}

const char* digest_challenge(ha_buffer_t* buf, const char* nonce_str,
                             const char* realm, const char* domains, int stale)
{
    ASSERT(buf && realm && nonce_str);

    ha_bufmcat(buf, HA_PREFIX_DIGEST, " realm=\"", realm, "\", nonce=\"",
               nonce_str, "\", qop=\"auth\", algorithm=\"MD5\"", NULL);

    if(domains)
    {
        ha_bufjoin(buf);
        ha_bufmcat(buf, ", domain=\"", domains, "\"", NULL);
    }

    if(stale)
    {
        ha_bufjoin(buf);
        ha_bufcat(buf, ", stale=true");
    }

    return ha_bufdata(buf);
}

/*
 * Copyright 1999-2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

int digest_parse(const char* head, ha_buffer_t* buf, digest_header_t* rec)
{
    char next;
    char* key;
    char* value;
    char* header;

    ASSERT(head && buf && rec);

    header = ha_bufcpy(buf, head);

    if(!header)
        return HA_CRITERROR;

    memset(rec, 0, sizeof(*rec));

    while(header[0])
    {
        /* find key */
        header = (char*)trim_start(header);
        key = header;

        while(header[0] && header[0] != '=' && header[0] != ',' &&
              !isspace(header[0]))
            header++;

        /* null terminate and move on */
        next = header[0];
        header[0] = '\0';
        header++;

        if(!next)
            break;

        if(isspace(header[0]))
        {
            header = (char*)trim_start(header);
            next = header[0];
        }

        /* find value */

        if(next == '=')
        {
            header = (char*)trim_start(header);

            if(header[0] == '\"')          /* quoted string */
            {
                header++;
                value = header;

                while(header[0] && header[0] != '\"')
                    header++;

                next = header[0];
                header[0] = 0;
                header++;
            }

            else                          /* token */
            {
                value = header;

                while(header[0] && header[0] != ',' && !isspace(header[0]))
                    header++;

                next = header[0];
                header[0] = 0;
                header++;
            }

            if(next != ',')
            {
                while(header[0] && header[0] != ',')
                    header++;

                if(header[0])
                    header++;
            }

            if(!strcasecmp(key, "username"))
                rec->username = value;
            else if(!strcasecmp(key, "realm"))
                rec->realm = value;
            else if (!strcasecmp(key, "nonce"))
                rec->nonce = value;
            else if (!strcasecmp(key, "uri"))
                rec->uri = value;
            else if (!strcasecmp(key, "response"))
                rec->digest = value;
            else if (!strcasecmp(key, "algorithm"))
                rec->algorithm = value;
            else if (!strcasecmp(key, "cnonce"))
                rec->cnonce = value;
            else if (!strcasecmp(key, "opaque"))
                rec->opaque = value;
            else if (!strcasecmp(key, "qop"))
                rec->qop = value;
            else if (!strcasecmp(key, "nc"))
                rec->nc = value;
        }
    }

    return HA_OK;
}

int digest_check(digest_context_t* dg, const ha_context_t* opts, ha_buffer_t* buf, int *stale)
{
    int r;

    r = digest_pre_check(dg, opts, buf, stale);
    if(r == HA_OK)
        r = digest_complete_check(dg, opts, buf);

    return r;
}

int digest_pre_check(digest_context_t* dg, const ha_context_t* opts,
                     ha_buffer_t* buf, int *stale)
{
    ASSERT(buf && buf && dg);
    ASSERT(stale);

    /* Check for digest */
    if(!dg->client.digest || !dg->client.digest[0])
    {
        ha_messagex(NULL, LOG_WARNING, "digest response missing digest");
        return HA_BADREQ;
    }

    /* Username */
    if(!dg->client.username || !dg->client.username[0])
    {
        ha_messagex(NULL, LOG_WARNING, "digest response missing username");
        return HA_BADREQ;
    }

    /* The realm */
    if(!dg->client.realm)
    {
        ha_messagex(NULL, LOG_WARNING, "digest response contains missing realm");
        return HA_BADREQ;
    }

    if(strcmp(dg->client.realm, opts->realm) != 0)
    {
        ha_messagex(NULL, LOG_ERR, "digest response contains invalid realm: %s", dg->client.realm);
        return HA_FALSE;
    }

    /* Components in the new RFC */
    if(dg->client.qop)
    {
        /*
         * We only support 'auth' qop. We don't have access to the data
         * and wouldn't be able to support anything else.
         */
        if(strcmp(dg->client.qop, "auth") != 0)
        {
            ha_messagex(NULL, LOG_WARNING, "digest response contains unknown or unsupported qop: '%s'",
                        dg->client.qop ? dg->client.qop : "");
            return HA_BADREQ;
        }

        /* The cnonce */
        if(!dg->client.cnonce || !dg->client.cnonce[0])
        {
            ha_messagex(NULL, LOG_WARNING, "digest response is missing cnonce value");
            return HA_BADREQ;
        }

        if(!opts->digest_ignorenc)
        {
            /* The nonce count */
            if(!dg->client.nc || !dg->client.nc[0])
            {
                ha_messagex(NULL, LOG_WARNING, "digest response is missing nc value");
                return HA_BADREQ;
            }

            /* Validate the nc */
            else
            {
                /* TODO: We need to validate the nc properly. Somehow that's not
                 * happening here. */
                char* e;
                long nc = strtol(dg->client.nc, &e, 16);

                if(*e)
                {
                    ha_messagex(NULL, LOG_ERR, "digest response has invalid nc value: %s", dg->client.nc);
                    return HA_BADREQ;
                }

                /* If we didn't a nc then save it away */
                if(!*e && dg->server_nc == 0)
                    dg->server_nc = nc;

                if(*e || nc != dg->server_nc)
                {
                    ha_messagex(NULL, LOG_WARNING, "digest response has wrong nc value: %s "
                                                   "possible replay attack, should be: %d",
                                                   dg->client.nc, dg->server_nc);
                    *stale = 1;
                    return HA_FALSE;
                }
            }
        }
    }

    /* The algorithm */
    if(dg->client.algorithm && strcasecmp(dg->client.algorithm, "MD5") != 0)
    {
        ha_messagex(NULL, LOG_WARNING, "digest response contains unknown or unsupported algorithm: '%s'",
                    dg->client.algorithm ? dg->client.algorithm : "");
        return HA_BADREQ;
    }

    /* Request URI */
    if(!dg->client.uri)
    {
        ha_messagex(NULL, LOG_WARNING, "digest response is missing uri");
        return HA_BADREQ;
    }

    if(!opts->digest_allowany && strcmp(dg->client.uri, dg->server_uri) != 0)
    {
        ha_uri_t d_uri;
        ha_uri_t s_uri;

        if(ha_uriparse(buf, dg->client.uri, &d_uri) < 0)
        {
            if(CHECK_BUF(buf))
                return HA_CRITERROR;

            ha_messagex(NULL, LOG_WARNING, "digest response constains invalid uri: %s", dg->client.uri);
            return HA_BADREQ;
        }

        ASSERT(dg->server_uri);

        if(ha_uriparse(buf, dg->server_uri, &s_uri) < 0)
        {
            if(CHECK_BUF(buf))
                return HA_CRITERROR;

            ha_messagex(NULL, LOG_ERR, "server sent us an invalid uri: %s", dg->server_uri);
            return HA_BADREQ;
        }

        if(ha_uricmp(&d_uri, &s_uri) != 0)
        {
            ha_messagex(NULL, LOG_ERR, "digest response contains wrong uri: %s "
                                 "(should be %s)", dg->client.uri, dg->server_uri);
            return HA_FALSE;
        }
    }

    /*
     * nonce: should have already been validated by the caller who
     * found this nice rec structure to pass us.
     *
     * opaque: We also don't use opaque. The caller should have validated it
     * if it's used there.
     */

    return HA_OK;
}


static int internal_check(digest_context_t* dg, const char* http_method, ha_buffer_t* buf)
{
    unsigned char hash[MD5_LEN];
    md5_ctx_t md5;
    const char* t;
    const char* digest;

    ASSERT(dg && buf);

    /*
     * Now we validate the digest response
     */

    /* Encode ha1 */
    t = ha_bufenchex(buf, dg->server_ha1, MD5_LEN);

    if(t == NULL)
        return HA_CRITERROR;

    ASSERT(dg->server_method);

    /* Encode ha2 */
    md5_init(&md5);
    md5_update(&md5, http_method, strlen(http_method));
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.uri, strlen(dg->client.uri));
    md5_final(hash, &md5);

    ha_bufenchex(buf, hash, MD5_LEN);

    if(!ha_bufdata(buf))
        return HA_CRITERROR;

    ASSERT(dg->client.nonce);

    /* Old style digest (RFC 2069) */
    if(!dg->client.qop)
    {
        md5_init(&md5);
        md5_update(&md5, t, MD5_LEN * 2);                /* ha1 */
        md5_update(&md5, ":", 1);
        md5_update(&md5, dg->client.nonce, strlen(dg->client.nonce));  /* nonce */
        md5_update(&md5, ":", 1);
        md5_update(&md5, ha_bufdata(buf), MD5_LEN * 2);  /* ha1 */
        md5_final(hash, &md5);
    }

    /* New style 'auth' digest (RFC 2617) */
    else
    {
        ASSERT(dg->client.nc);
        ASSERT(dg->client.cnonce);
        ASSERT(dg->client.qop);

        md5_init(&md5);
        md5_update(&md5, t, MD5_LEN * 2);                                /* ha1 */
        md5_update(&md5, ":", 1);
        md5_update(&md5, dg->client.nonce, strlen(dg->client.nonce));    /* nonce */
        md5_update(&md5, ":", 1);
        md5_update(&md5, dg->client.nc, strlen(dg->client.nc));          /* nc */
        md5_update(&md5, ":", 1);
        md5_update(&md5, dg->client.cnonce, strlen(dg->client.cnonce));  /* cnonce */
        md5_update(&md5, ":", 1);
        md5_update(&md5, dg->client.qop, strlen(dg->client.qop));        /* qop */
        md5_update(&md5, ":", 1);
        md5_update(&md5, ha_bufdata(buf), MD5_LEN * 2);    /* ha2 */
        md5_final(hash, &md5);
    }

    /* Encode the digest */
    digest = ha_bufenchex(buf, hash, MD5_LEN);

    if(digest == NULL)
        return HA_CRITERROR;

    ASSERT(dg->client.digest);

    if(strcasecmp(dg->client.digest, digest) != 0)
        return HA_FALSE;

    return HA_OK;
}

int digest_complete_check(digest_context_t* dg, const ha_context_t* opts, ha_buffer_t* buf)
{
	const char** m;
	int ret;

	/* Use the method sent to us */
	ret = internal_check (dg, dg->server_method, buf);
	if(ret != HA_FALSE)
		return ret;

	if(opts->digest_allowany)
	{
		/* Try out each and every method in HTTP */
		for(m = g_http_methods; *m; ++m)
		{
			ret = internal_check (dg, *m, buf);
			if(ret != HA_FALSE)
				break;
		}
	}

	return ret;
}

const char* digest_respond(digest_context_t* dg, ha_buffer_t* buf,
                           unsigned char* next)
{
    unsigned char hash[MD5_LEN];
    md5_ctx_t md5;
    const char* nextnonce = NULL;
    const char* t;

    ASSERT(buf && dg);

    /* This makes a new buffer */
    ha_bufcpy(buf, "");

    if(next)
    {
        nextnonce = ha_bufenc64(buf, next, DIGEST_NONCE_LEN);

        if(nextnonce == NULL)
            return NULL;
    }

    /* For older clients RFC 2069 */
    if(!dg->client.qop)
    {
        if(nextnonce)
            ha_bufmcat(buf, "nextnonce=\"", nextnonce, "\"", NULL);

        return ha_bufdata(buf);
    }

    /* Otherwise we do the whole song and dance */

    /* Encode ha1 */
    t = ha_bufenchex(buf, dg->server_ha1, MD5_LEN);

    if(t == NULL)
        return NULL;

    ASSERT(dg->client.uri);

    /* Encode ha2 */
    md5_init(&md5);
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.uri, strlen(dg->client.uri));
    md5_final(hash, &md5);

    ha_bufenchex(buf, hash, MD5_LEN);

    if(!ha_bufdata(buf))
        return NULL;

    ASSERT(dg->client.nonce);
    ASSERT(dg->client.nc);
    ASSERT(dg->client.cnonce);
    ASSERT(dg->client.qop);

    /* New style 'auth' digest (RFC 2617) */
    md5_init(&md5);
    md5_update(&md5, t, MD5_LEN * 2);                                /* ha1 */
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.nonce, strlen(dg->client.nonce));    /* nonce */
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.nc, strlen(dg->client.nc));          /* nc */
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.cnonce, strlen(dg->client.cnonce));  /* cnonce */
    md5_update(&md5, ":", 1);
    md5_update(&md5, dg->client.qop, strlen(dg->client.qop));        /* qop */
    md5_update(&md5, ":", 1);
    md5_update(&md5, ha_bufdata(buf), MD5_LEN * 2);                  /* ha2 */
    md5_final(hash, &md5);

    /* Encode the digest */
    t = ha_bufenchex(buf, hash, MD5_LEN);

    if(t == NULL)
        return NULL;

    ha_bufmcat(buf, "rspauth=\"", t, "\"",
                    ", qop=", dg->client.qop,
                    ", nc=", dg->client.nc,
                    ", cnonce=\"", dg->client.cnonce, "\"", NULL);

    if(nextnonce)
    {
        ha_bufjoin(buf);
        ha_bufmcat(buf, ", nextnonce=\"", nextnonce, "\"", NULL);
    }

    return ha_bufdata(buf);
}

void digest_makeha1(unsigned char* digest, const char* user,
                    const char* realm, const char* password)
{
    md5_ctx_t md5;

    ASSERT(digest && user && realm && password);

    md5_init(&md5);
    md5_update(&md5, user, strlen(user));
    md5_update(&md5, ":", 1);
    md5_update(&md5, realm, strlen(realm));
    md5_update(&md5, ":", 1);
    md5_update(&md5, password, strlen(password));
    md5_final(digest, &md5);
}

#define MUST_ESCAPE "\"\' \t\n\r\v\\"

void
digest_escape (ha_buffer_t *buf, const char *orig)
{
	const char* t;
	size_t pos;

	assert (orig);
	assert (buf);

	ha_bufcpy(buf, "");

	t = orig;
	while (*t) {
		pos = strcspn (t, MUST_ESCAPE);

		if(pos > 0) {
			ha_bufjoin (buf);
			ha_bufncpy (buf, t, pos);
			t += pos;
		}

		while (*t && !strchr (MUST_ESCAPE, *t)) {
			char esc[3];
			esc[0] = '\\';
			esc[1] = *t;
			esc[2] = '\0';
			ha_bufjoin (buf);
			ha_bufcpy (buf, esc);
			t++;
		}
	}
}