mod_negotiation.c

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/* Given the text of the Content-Languages: line from the var map file,
 * return an array containing the languages of this variant
 */

static array_header *do_languages_line(pool *p, const char **lang_line)
{
    array_header *lang_recs = ap_make_array(p, 2, sizeof(char *));

    if (!lang_line) {
        return lang_recs;
    }

    while (**lang_line) {
        char **new = (char **) ap_push_array(lang_recs);
        *new = ap_get_token(p, lang_line, 0);
        ap_str_tolower(*new);
        if (**lang_line == ',' || **lang_line == ';') {
            ++(*lang_line);
        }
    }

    return lang_recs;
}

/*****************************************************************
 *
 * Handling header lines from clients...
 */

static negotiation_state *parse_accept_headers(request_rec *r)
{
    negotiation_state *new =
        (negotiation_state *) ap_pcalloc(r->pool, sizeof(negotiation_state));
    accept_rec *elts;
    table *hdrs = r->headers_in;
    int i;

    new->pool = r->pool;
    new->r = r;
    new->dir_name = ap_make_dirstr_parent(r->pool, r->filename);

    new->accepts = do_header_line(r->pool, ap_table_get(hdrs, "Accept"));

    /* calculate new->accept_q value */
    if (new->accepts) {
        elts = (accept_rec *) new->accepts->elts;

        for (i = 0; i < new->accepts->nelts; ++i) {
            if (elts[i].quality < 1.0) {
                new->accept_q = 1;
            }
        }
    }

    new->accept_encodings =
        do_header_line(r->pool, ap_table_get(hdrs, "Accept-Encoding"));
    new->accept_langs =
        do_header_line(r->pool, ap_table_get(hdrs, "Accept-Language"));
    new->accept_charsets =
        do_header_line(r->pool, ap_table_get(hdrs, "Accept-Charset"));

    new->avail_vars = ap_make_array(r->pool, 40, sizeof(var_rec));

    return new;
}


static void parse_negotiate_header(request_rec *r, negotiation_state *neg)
{
    const char *negotiate = ap_table_get(r->headers_in, "Negotiate");
    char *tok;
    
    /* First, default to no TCN, no Alternates, and the original Apache
     * negotiation algorithm with fiddles for broken browser configs.
     *
     * To save network bandwidth, we do not configure to send an
     * Alternates header to the user agent by default.  User
     * agents that want an Alternates header for agent-driven
     * negotiation will have to request it by sending an
     * appropriate Negotiate header.
     */
    neg->ua_supports_trans   = 0;
    neg->send_alternates     = 0;
    neg->may_choose          = 1;
    neg->use_rvsa            = 0;
    neg->dont_fiddle_headers = 0;

    if (!negotiate)
        return;

    if (strcmp(negotiate, "trans") == 0) {
        /* Lynx 2.7 and 2.8 send 'negotiate: trans' even though they
         * do not support transparent content negotiation, so for Lynx we
         * ignore the negotiate header when its contents are exactly "trans".
         * If future versions of Lynx ever need to say 'negotiate: trans',
         * they can send the equivalent 'negotiate: trans, trans' instead
         * to avoid triggering the workaround below. 
         */
        const char *ua = ap_table_get(r->headers_in, "User-Agent");

        if (ua && (strncmp(ua, "Lynx", 4) == 0))
            return;
    }

    neg->may_choose = 0;  /* An empty Negotiate would require 300 response */

    while ((tok = ap_get_list_item(neg->pool, &negotiate)) != NULL) {

        if (strcmp(tok, "trans") == 0 ||
            strcmp(tok, "vlist") == 0 ||
            strcmp(tok, "guess-small") == 0 ||
            ap_isdigit(tok[0]) ||
            strcmp(tok, "*") == 0) {

            /* The user agent supports transparent negotiation */
            neg->ua_supports_trans = 1;

            /* Send-alternates could be configurable, but note
             * that it must be 1 if we have 'vlist' in the
             * negotiate header.
             */
            neg->send_alternates = 1;

            if (strcmp(tok, "1.0") == 0) {
                /* we may use the RVSA/1.0 algorithm, configure for it */
                neg->may_choose = 1;
                neg->use_rvsa = 1;
                neg->dont_fiddle_headers = 1;
            }
            else if (tok[0] == '*') {
                /* we may use any variant selection algorithm, configure
                 * to use the Apache algorithm
                 */
                neg->may_choose = 1;
                
                /* We disable header fiddles on the assumption that a
                 * client sending Negotiate knows how to send correct
                 * headers which don't need fiddling.
                 */
                neg->dont_fiddle_headers = 1; 
            }
        }
    }

#ifdef NEG_DEBUG
    fprintf(stderr, "dont_fiddle_headers=%d use_rvsa=%d ua_supports_trans=%d "
            "send_alternates=%d, may_choose=%d\n",
            neg->dont_fiddle_headers, neg->use_rvsa,  
            neg->ua_supports_trans, neg->send_alternates, neg->may_choose);
#endif

}

/* Sometimes clients will give us no Accept info at all; this routine sets
 * up the standard default for that case, and also arranges for us to be
 * willing to run a CGI script if we find one.  (In fact, we set up to
 * dramatically prefer CGI scripts in cases where that's appropriate,
 * e.g., POST or when URI includes query args or extra path info).
 */
static void maybe_add_default_accepts(negotiation_state *neg, 
                                      int prefer_scripts)
{
    accept_rec *new_accept;

    if (!neg->accepts) {
        neg->accepts = ap_make_array(neg->pool, 4, sizeof(accept_rec));

        new_accept = (accept_rec *) ap_push_array(neg->accepts);
        
        new_accept->name = "*/*";
        new_accept->quality = 1.0f;
        new_accept->level = 0.0f;
    }    

    new_accept = (accept_rec *) ap_push_array(neg->accepts);

    new_accept->name = CGI_MAGIC_TYPE;
    if (neg->use_rvsa) {
        new_accept->quality = 0;
    }
    else {
        new_accept->quality = prefer_scripts ? 2.0f : 0.001f;
    }
    new_accept->level = 0.0f;
}

/*****************************************************************
 *
 * Parsing type-map files, in Roy's meta/http format augmented with
 * #-comments.
 */

/* Reading RFC822-style header lines, ignoring #-comments and
 * handling continuations.
 */

enum header_state {
    header_eof, header_seen, header_sep
};

static enum header_state get_header_line(char *buffer, int len, FILE *map)
{
    char *buf_end = buffer + len;
    char *cp;
    int c;

    /* Get a noncommented line */

    do {
        if (fgets(buffer, MAX_STRING_LEN, map) == NULL) {
            return header_eof;
        }
    } while (buffer[0] == '#');

    /* If blank, just return it --- this ends information on this variant */

    for (cp = buffer; (*cp && ap_isspace(*cp)); ++cp) {
        continue;
    }

    if (*cp == '\0') {
        return header_sep;
    }

    /* If non-blank, go looking for header lines, but note that we still
     * have to treat comments specially...
     */

    cp += strlen(cp);

    while ((c = getc(map)) != EOF) {
        if (c == '#') {
            /* Comment line */
            while ((c = getc(map)) != EOF && c != '\n') {
                continue;
            }
        }
        else if (ap_isspace(c)) {
            /* Leading whitespace.  POSSIBLE continuation line
             * Also, possibly blank --- if so, we ungetc() the final newline
             * so that we will pick up the blank line the next time 'round.
             */

            while (c != EOF && c != '\n' && ap_isspace(c)) {
                c = getc(map);
            }

            ungetc(c, map);

            if (c == '\n') {
                return header_seen;     /* Blank line */
            }

            /* Continuation */

            while (cp < buf_end - 2 && (c = getc(map)) != EOF && c != '\n') {
                *cp++ = c;
            }

            *cp++ = '\n';
            *cp = '\0';
        }
        else {

            /* Line beginning with something other than whitespace */

            ungetc(c, map);
            return header_seen;
        }
    }

    return header_seen;
}

/* Stripping out RFC822 comments */

static void strip_paren_comments(char *hdr)
{
    /* Hmmm... is this correct?  In Roy's latest draft, (comments) can nest! */
    /* Nope, it isn't correct.  Fails to handle backslash escape as well.    */

    while (*hdr) {
        if (*hdr == '"') {
            hdr = strchr(hdr, '"');
            if (hdr == NULL) {
                return;
            }
            ++hdr;
        }
        else if (*hdr == '(') {
            while (*hdr && *hdr != ')') {
                *hdr++ = ' ';
            }

            if (*hdr) {
                *hdr++ = ' ';
            }
        }
        else {
            ++hdr;
        }
    }
}

/* Getting to a header body from the header */

static char *lcase_header_name_return_body(char *header, request_rec *r)
{
    char *cp = header;

    for ( ; *cp && *cp != ':' ; ++cp) {
        *cp = ap_tolower(*cp);
    }

    if (!*cp) {
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                      "Syntax error in type map --- no ':': %s", r->filename);
        return NULL;
    }

    do {
        ++cp;
    } while (*cp && ap_isspace(*cp));

    if (!*cp) {
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                      "Syntax error in type map --- no header body: %s",
                      r->filename);
        return NULL;
    }

    return cp;
}

static int read_type_map(negotiation_state *neg, request_rec *rr)
{
    request_rec *r = neg->r;
    FILE *map;
    char buffer[MAX_STRING_LEN];
    enum header_state hstate;
    struct var_rec mime_info;
    int has_content;

    /* We are not using multiviews */
    neg->count_multiviews_variants = 0;

    map = ap_pfopen(neg->pool, rr->filename, "r");
    if (map == NULL) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
                      "cannot access type map file: %s", rr->filename);
        return HTTP_FORBIDDEN;
    }

    clean_var_rec(&mime_info);
    has_content = 0;

    do {
        hstate = get_header_line(buffer, MAX_STRING_LEN, map);

        if (hstate == header_seen) {
            char *body1 = lcase_header_name_return_body(buffer, neg->r);
            const char *body;

            if (body1 == NULL) {
                return SERVER_ERROR;
            }

            strip_paren_comments(body1);
            body = body1;

            if (!strncmp(buffer, "uri:", 4)) {
                mime_info.file_name = ap_get_token(neg->pool, &body, 0);
            }
            else if (!strncmp(buffer, "content-type:", 13)) {
                struct accept_rec accept_info;

                get_entry(neg->pool, &accept_info, body);
                set_mime_fields(&mime_info, &accept_info);
                has_content = 1;
            }
            else if (!strncmp(buffer, "content-length:", 15)) {
                mime_info.bytes = (float)atof(body);
                has_content = 1;
            }
            else if (!strncmp(buffer, "content-language:", 17)) {
                mime_info.content_languages = do_languages_line(neg->pool,
                                                                &body);
                has_content = 1;
            }
            else if (!strncmp(buffer, "content-encoding:", 17)) {
                mime_info.content_encoding = ap_get_token(neg->pool, &body, 0);
                has_content = 1;
            }
            else if (!strncmp(buffer, "description:", 12)) {
                char *desc = ap_pstrdup(neg->pool, body);
                char *cp;