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redirect: escape the URL being redirected to. #106

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redirect: escape the URL being redirected to. #106

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67 changes: 42 additions & 25 deletions darkhttpd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,7 @@ static const char *default_mimetype = octet_stream;
static void poll_recv_request(struct connection *conn);
static void poll_send_header(struct connection *conn);
static void poll_send_reply(struct connection *conn);
static void urlencode(const char *src, char *dest);

/* close() that dies on error. */
static void xclose(const int fd) {
Expand Down Expand Up @@ -473,6 +474,8 @@ static struct apbuf *make_apbuf(void) {
return buf;
}

static void append_escaped(struct apbuf *dst, const char *src);

/* Append s (of length len) to buf. */
static void appendl(struct apbuf *buf, const char *s, const size_t len) {
size_t need = buf->length + len;
Expand Down Expand Up @@ -1728,24 +1731,30 @@ static void default_reply(struct connection *conn,
static void redirect(struct connection *conn, const char *format, ...)
__printflike(2, 3);
static void redirect(struct connection *conn, const char *format, ...) {
char *where, date[DATE_LEN];
char* where;
char date[DATE_LEN];
struct apbuf* reply;
va_list va;

va_start(va, format);
xvasprintf(&where, format, va);
va_end(va);

/* Only really need to calculate the date once. */
rfc1123_date(date, now);

conn->reply_length = xasprintf(&(conn->reply),
"<!DOCTYPE html><html><head><title>301 Moved Permanently</title></head><body>\n"
"<h1>Moved Permanently</h1>\n"
"Moved to: <a href=\"%s\">%s</a>\n" /* where x 2 */
"<hr>\n"
"%s" /* generated on */
"</body></html>\n",
where, where, generated_on(date));
reply = make_apbuf();
append(reply, "<!DOCTYPE html><html><head>"
"<title>301 Moved Permanently</title></head><body>\n"
"<h1>Moved Permanently</h1>\n"
"Moved to: <a href=\"");
append(reply, where);
append(reply, "\">");
append_escaped(reply, where);
append(reply, "</a>\n<hr>\n");
append(reply, generated_on(date));
append(reply, "</body></html>\n");
conn->reply = reply->str;
conn->reply_length = reply->length;
free(reply);

conn->header_length = xasprintf(&(conn->header),
"HTTP/1.1 301 Moved Permanently\r\n"
Expand Down Expand Up @@ -1833,7 +1842,10 @@ static void redirect_https(struct connection *conn) {
return;
}

redirect(conn, "https://%s%s", host, url);
char* encoded_url = xmalloc(strlen(url) * 3 + 1);
urlencode(url, encoded_url);
redirect(conn, "https://%s%s", host, encoded_url);
free(encoded_url);
free(host);
free(url);
}
Expand Down Expand Up @@ -2078,21 +2090,23 @@ static void cleanup_sorted_dirlist(struct dlent **list, const ssize_t size) {
}
}

/* Is this an unreserved character according to
* https://tools.ietf.org/html/rfc3986#section-2.3
*/
static int is_unreserved(const unsigned char c) {
if (c >= 'a' && c <= 'z') return 1;
if (c >= 'A' && c <= 'Z') return 1;
if (c >= '0' && c <= '9') return 1;
static int needs_encoding(char c) {
/* Is this an unreserved character according to
* https://tools.ietf.org/html/rfc3986#section-2.3
*/
if (c >= 'a' && c <= 'z') return 0;
if (c >= 'A' && c <= 'Z') return 0;
if (c >= '0' && c <= '9') return 0;
switch (c) {
case '-':
case '.':
case '_':
case '~':
return 1;
/* Also allow '/' */
case '/':
return 0;
}
return 0;
return 1;
}

/* Encode string to be an RFC3986-compliant URL part.
Expand All @@ -2103,13 +2117,13 @@ static void urlencode(const char *src, char *dest) {
int i, j;

for (i = j = 0; src[i] != '\0'; i++) {
if (!is_unreserved((unsigned char)src[i])) {
if (needs_encoding(src[i])) {
dest[j++] = '%';
dest[j++] = hex[(src[i] >> 4) & 0xF];
dest[j++] = hex[ src[i] & 0xF];
}
else
} else {
dest[j++] = src[i];
}
}
dest[j] = '\0';
}
Expand Down Expand Up @@ -2326,7 +2340,10 @@ static void process_get(struct connection *conn) {
forward_to = forward_all_url;
}
if (forward_to) {
redirect(conn, "%s%s", forward_to, decoded_url);
char* encoded_url = xmalloc(strlen(decoded_url) * 3 + 1);
urlencode(decoded_url, encoded_url);
redirect(conn, "%s%s", forward_to, encoded_url);
free(encoded_url);
free(decoded_url);
return;
}
Expand Down
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