/* ====================================================================
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 *    if and wherever such third-party acknowledgments normally appear.
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 *
 * This software consists of voluntary contributions made by many
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 *
 * Portions of this software are based upon public domain software
 * originally written at the National Center for Supercomputing Applications,
 * University of Illinois, Urbana-Champaign.
 */
/*
 * mod_digest: MD5 digest authentication
 * 
 * by Alexei Kosut <akosut@nueva.pvt.k12.ca.us>
 * based on mod_auth, by Rob McCool and Robert S. Thau
 *
 */
#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "http_log.h"
#include "http_protocol.h"
#include "util_md5.h"
typedef struct digest_config_struct {
    char *pwfile;
} digest_config_rec;
typedef struct digest_header_struct {
    char *username;
    char *realm;
    char *nonce;
    char *requested_uri;
    char *digest;
} digest_header_rec;
static void *create_digest_dir_config(pool *p, char *d)
{
    return ap_pcalloc(p, sizeof(digest_config_rec));
}
static const char *set_digest_slot(cmd_parms *cmd, void *offset, char *f, char *t)
{
    if (t && strcmp(t, "standard"))
        return ap_pstrcat(cmd->pool, "Invalid auth file type: ", t, NULL);
    return ap_set_string_slot(cmd, offset, f);
}
static const command_rec digest_cmds[] =
{
    {"AuthDigestFile", set_digest_slot,
  (void *) XtOffsetOf(digest_config_rec, pwfile), OR_AUTHCFG, TAKE12, NULL},
    {NULL}
};
module MODULE_VAR_EXPORT digest_module;
static char *get_hash(request_rec *r, char *user, char *auth_pwfile)
{
    configfile_t *f;
    char l[MAX_STRING_LEN];
    const char *rpw;
    char *w, *x;
    if (!(f = ap_pcfg_openfile(r->pool, auth_pwfile))) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
                    "Could not open password file: %s", auth_pwfile);
        return NULL;
    }
    while (!(ap_cfg_getline(l, MAX_STRING_LEN, f))) {
        if ((l[0] == '#') || (!l[0]))
            continue;
        rpw = l;
        w = ap_getword(r->pool, &rpw, ':');
        x = ap_getword(r->pool, &rpw, ':');
        if (x && w && !strcmp(user, w) && !strcmp(ap_auth_name(r), x)) {
            ap_cfg_closefile(f);
            return ap_pstrdup(r->pool, rpw);
        }
    }
    ap_cfg_closefile(f);
    return NULL;
}
/* Parse the Authorization header, if it exists */
static int get_digest_rec(request_rec *r, digest_header_rec * response)
{
    const char *auth_line;
    int l;
    int s, vk = 0, vv = 0;
    const char *t;
    char *key, *value;
    const char *scheme;
    if (!(t = ap_auth_type(r)) || strcasecmp(t, "Digest"))
        return DECLINED;
    if (!ap_auth_name(r)) {
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                    "need AuthName: %s", r->uri);
        return SERVER_ERROR;
    }
    auth_line = ap_table_get(r->headers_in,
                             r->proxyreq == STD_PROXY ? "Proxy-Authorization"
                                                      : "Authorization");
    if (!auth_line) {
        ap_note_digest_auth_failure(r);
        return AUTH_REQUIRED;
    }
    if (strcasecmp(scheme = ap_getword_white(r->pool, &auth_line), "Digest")) {
        /* Client tried to authenticate using wrong auth scheme */
        ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r->server,
                    "client used wrong authentication scheme: %s for %s", 
                    scheme, r->uri);
        ap_note_digest_auth_failure(r);
        return AUTH_REQUIRED;
    }
    l = strlen(auth_line);
    /* Note we don't allocate l + 1 bytes for these deliberately, because
     * there has to be at least one '=' character for either of these two
     * new strings to be terminated.  That takes care of the need for +1.
     */
    key = ap_palloc(r->pool, l);
    value = ap_palloc(r->pool, l);
    /* There's probably a better way to do this, but for the time being... */
#define D_KEY 0
#define D_VALUE 1
#define D_STRING 2
#define D_EXIT -1
    s = D_KEY;
    while (s != D_EXIT) {
        switch (s) {
        case D_STRING:
            if (auth_line[0] == '\"') {
                s = D_VALUE;
            }
            else {
                value[vv] = auth_line[0];
                vv++;
            }
            auth_line++;
            break;
        case D_VALUE:
            if (ap_isalnum(auth_line[0])) {
                value[vv] = auth_line[0];
                vv++;
            }
            else if (auth_line[0] == '\"') {
                s = D_STRING;
            }
            else {
                value[vv] = '\0';
                if (!strcasecmp(key, "username"))
                    response->username = ap_pstrdup(r->pool, value);
                else if (!strcasecmp(key, "realm"))
                    response->realm = ap_pstrdup(r->pool, value);
                else if (!strcasecmp(key, "nonce"))
                    response->nonce = ap_pstrdup(r->pool, value);
                else if (!strcasecmp(key, "uri"))
                    response->requested_uri = ap_pstrdup(r->pool, value);
                else if (!strcasecmp(key, "response"))
                    response->digest = ap_pstrdup(r->pool, value);
                vv = 0;
                s = D_KEY;
            }
            auth_line++;
            break;
        case D_KEY:
            if (ap_isalnum(auth_line[0])) {
                key[vk] = auth_line[0];
                vk++;
            }
            else if (auth_line[0] == '=') {
                key[vk] = '\0';
                vk = 0;
                s = D_VALUE;
            }
            auth_line++;
            break;
        }
        if (auth_line[-1] == '\0')
            s = D_EXIT;
    }
    if (!response->username || !response->realm || !response->nonce ||
        !response->requested_uri || !response->digest) {
        ap_note_digest_auth_failure(r);
        return AUTH_REQUIRED;
    }
    r->connection->user = response->username;
    r->connection->ap_auth_type = "Digest";
    return OK;
}
/* The actual MD5 code... whee */
static char *find_digest(request_rec *r, digest_header_rec * h, char *a1)
{
    return ap_md5(r->pool,
                  (unsigned char *)ap_pstrcat(r->pool, a1, ":", h->nonce, ":",
                                           ap_md5(r->pool,
                           (unsigned char *)ap_pstrcat(r->pool, r->method, ":",
                                                    h->requested_uri, NULL)),
                                           NULL));
}
/* These functions return 0 if client is OK, and proper error status
 * if not... either AUTH_REQUIRED, if we made a check, and it failed, or
 * SERVER_ERROR, if things are so totally confused that we couldn't
 * figure out how to tell if the client is authorized or not.
 *
 * If they return DECLINED, and all other modules also decline, that's
 * treated by the server core as a configuration error, logged and
 * reported as such.
 */
/* Determine user ID, and check if it really is that user, for HTTP
 * basic authentication...
 */
static int authenticate_digest_user(request_rec *r)
{
    digest_config_rec *sec =
    (digest_config_rec *) ap_get_module_config(r->per_dir_config,
                                            &digest_module);
    digest_header_rec *response = ap_pcalloc(r->pool, sizeof(digest_header_rec));
    conn_rec *c = r->connection;
    char *a1;
    int res;
    if ((res = get_digest_rec(r, response)))
        return res;
    if (!sec->pwfile)
        return DECLINED;
    if (!(a1 = get_hash(r, c->user, sec->pwfile))) {
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                    "user %s not found: %s", c->user, r->uri);
        ap_note_digest_auth_failure(r);
        return AUTH_REQUIRED;
    }
    if (strcmp(response->digest, find_digest(r, response, a1))) {
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                    "user %s: password mismatch: %s", c->user, r->uri);
        ap_note_digest_auth_failure(r);
        return AUTH_REQUIRED;
    }
    return OK;
}
/* Checking ID */
static int digest_check_auth(request_rec *r)
{
    char *user = r->connection->user;
    int m = r->method_number;
    int method_restricted = 0;
    register int x;
    const char *t;
    char *w;
    const array_header *reqs_arr;
    require_line *reqs;
    if (!(t = ap_auth_type(r)) || strcasecmp(t, "Digest"))
        return DECLINED;
    reqs_arr = ap_requires(r);
    /* If there is no "requires" directive, 
     * then any user will do.
     */
    if (!reqs_arr)
        return OK;
    reqs = (require_line *) reqs_arr->elts;
    for (x = 0; x < reqs_arr->nelts; x++) {
        if (!(reqs[x].method_mask & (1 << m)))
            continue;
        method_restricted = 1;
        t = reqs[x].requirement;
        w = ap_getword_white(r->pool, &t);
        if (!strcmp(w, "valid-user"))
            return OK;
        else if (!strcmp(w, "user")) {
            while (t[0]) {
                w = ap_getword_conf(r->pool, &t);
                if (!strcmp(user, w))
                    return OK;
            }
        }
        else
            return DECLINED;
    }
    if (!method_restricted)
        return OK;
    ap_note_digest_auth_failure(r);
    return AUTH_REQUIRED;
}
module MODULE_VAR_EXPORT digest_module =
{
    STANDARD_MODULE_STUFF,
    NULL,                       /* initializer */
    create_digest_dir_config,   /* dir config creater */
    NULL,                       /* dir merger --- default is to override */
    NULL,                       /* server config */
    NULL,                       /* merge server config */
    digest_cmds,                /* command table */
    NULL,                       /* handlers */
    NULL,                       /* filename translation */
    authenticate_digest_user,   /* check_user_id */
    digest_check_auth,          /* check auth */
    NULL,                       /* check access */
    NULL,                       /* type_checker */
    NULL,                       /* fixups */
    NULL,                       /* logger */
    NULL,                       /* header parser */
    NULL,                       /* child_init */
    NULL,                       /* child_exit */
    NULL                        /* post read-request */
};