escape: make the URL decode able to reject only %00 bytes

... or all "control codes" or nothing.

Assisted-by: Nicolas Sterchele

lib/curl_path.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -42,7 +42,7 @@ CURLcode Curl_getworkingpath(struct connectdata *conn,
   size_t working_path_len;
   CURLcode result =
     Curl_urldecode(data, data->state.up.path, 0, &working_path,
-                   &working_path_len, FALSE);
+                   &working_path_len, REJECT_ZERO);
   if(result)
     return result;
 

lib/dict.c

@@ -99,7 +99,8 @@ static char *unescape_word(struct Curl_easy *data, const char *inputbuff)
   char *dictp;
   size_t len;
 
-  CURLcode result = Curl_urldecode(data, inputbuff, 0, &newp, &len, FALSE);
+  CURLcode result = Curl_urldecode(data, inputbuff, 0, &newp, &len,
+                                   REJECT_NADA);
   if(!newp || result)
     return NULL;
 

lib/escape.c

@@ -123,19 +123,26 @@ char *curl_easy_escape(struct Curl_easy *data, const char *string,
 /*
  * Curl_urldecode() URL decodes the given string.
  *
- * Optionally detects control characters (byte codes lower than 32) in the
- * data and rejects such data.
- *
  * Returns a pointer to a malloced string in *ostring with length given in
  * *olen. If length == 0, the length is assumed to be strlen(string).
  *
  * 'data' can be set to NULL but then this function can't convert network
  * data to host for non-ascii.
+ *
+ * ctrl options:
+ * - REJECT_NADA: accept everything
+ * - REJECT_CTRL: rejects control characters (byte codes lower than 32) in
+ *                the data
+ * - REJECT_ZERO: rejects decoded zero bytes
+ *
+ * The values for the enum starts at 2, to make the assert detect legacy
+ * invokes that used TRUE/FALSE (0 and 1).
  */
+
 CURLcode Curl_urldecode(struct Curl_easy *data,
                         const char *string, size_t length,
                         char **ostring, size_t *olen,
-                        bool reject_ctrl)
+                        enum urlreject ctrl)
 {
   size_t alloc;
   char *ns;
@@ -144,6 +151,7 @@ CURLcode Curl_urldecode(struct Curl_easy *data,
   CURLcode result = CURLE_OK;
 
   DEBUGASSERT(string);
+  DEBUGASSERT(ctrl >= REJECT_NADA); /* crash on TRUE/FALSE */
 
   alloc = (length?length:strlen(string)) + 1;
   ns = malloc(alloc);
@@ -179,7 +187,8 @@ CURLcode Curl_urldecode(struct Curl_easy *data,
       alloc -= 2;
     }
 
-    if(reject_ctrl && (in < 0x20)) {
+    if(((ctrl == REJECT_CTRL) && (in < 0x20)) ||
+       ((ctrl == REJECT_ZERO) && (in == 0))) {
       free(ns);
       return CURLE_URL_MALFORMAT;
     }
@@ -213,7 +222,7 @@ char *curl_easy_unescape(struct Curl_easy *data, const char *string,
     size_t inputlen = length;
     size_t outputlen;
     CURLcode res = Curl_urldecode(data, string, inputlen, &str, &outputlen,
-                                  FALSE);
+                                  REJECT_NADA);
     if(res)
       return NULL;
 

lib/escape.h

@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -25,9 +25,16 @@
  * allocated string or NULL if an error occurred.  */
 
 bool Curl_isunreserved(unsigned char in);
+
+enum urlreject {
+  REJECT_NADA = 2,
+  REJECT_CTRL,
+  REJECT_ZERO
+};
+
 CURLcode Curl_urldecode(struct Curl_easy *data,
                         const char *string, size_t length,
                         char **ostring, size_t *olen,
-                        bool reject_crlf);
+                        enum urlreject ctrl);
 
 #endif /* HEADER_CURL_ESCAPE_H */

lib/file.c

@@ -144,7 +144,7 @@ static CURLcode file_connect(struct connectdata *conn, bool *done)
   size_t real_path_len;
 
   CURLcode result = Curl_urldecode(data, data->state.up.path, 0, &real_path,
-                                   &real_path_len, FALSE);
+                                   &real_path_len, REJECT_ZERO);
   if(result)
     return result;
 

lib/ftp.c

@@ -1452,7 +1452,7 @@ static CURLcode ftp_state_list(struct connectdata *conn)
     /* url-decode before evaluation: e.g. paths starting/ending with %2f */
     const char *slashPos = NULL;
     char *rawPath = NULL;
-    result = Curl_urldecode(data, ftp->path, 0, &rawPath, NULL, TRUE);
+    result = Curl_urldecode(data, ftp->path, 0, &rawPath, NULL, REJECT_CTRL);
     if(result)
       return result;
 
@@ -3194,7 +3194,8 @@ static CURLcode ftp_done(struct connectdata *conn, CURLcode status,
 
   if(!result)
     /* get the url-decoded "raw" path */
-    result = Curl_urldecode(data, ftp->path, 0, &rawPath, &pathLen, TRUE);
+    result = Curl_urldecode(data, ftp->path, 0, &rawPath, &pathLen,
+                            REJECT_CTRL);
   if(result) {
     /* We can limp along anyway (and should try to since we may already be in
      * the error path) */
@@ -4110,7 +4111,7 @@ CURLcode ftp_parse_url_path(struct connectdata *conn)
   ftpc->cwdfail = FALSE;
 
   /* url-decode ftp path before further evaluation */
-  result = Curl_urldecode(data, ftp->path, 0, &rawPath, &pathLen, TRUE);
+  result = Curl_urldecode(data, ftp->path, 0, &rawPath, &pathLen, REJECT_CTRL);
   if(result)
     return result;
 

lib/gopher.c

@@ -116,7 +116,7 @@ static CURLcode gopher_do(struct connectdata *conn, bool *done)
     newp += 2;
 
     /* ... and finally unescape */
-    result = Curl_urldecode(data, newp, 0, &sel, &len, FALSE);
+    result = Curl_urldecode(data, newp, 0, &sel, &len, REJECT_ZERO);
     free(gopherpath);
     if(result)
       return result;

lib/imap.c

@@ -1957,7 +1957,7 @@ static CURLcode imap_parse_url_path(struct connectdata *conn)
       end--;
 
     result = Curl_urldecode(data, begin, end - begin, &imap->mailbox, NULL,
-                            TRUE);
+                            REJECT_CTRL);
     if(result)
       return result;
   }
@@ -1979,7 +1979,8 @@ static CURLcode imap_parse_url_path(struct connectdata *conn)
       return CURLE_URL_MALFORMAT;
 
     /* Decode the name parameter */
-    result = Curl_urldecode(data, begin, ptr - begin, &name, NULL, TRUE);
+    result = Curl_urldecode(data, begin, ptr - begin, &name, NULL,
+                            REJECT_CTRL);
     if(result)
       return result;
 
@@ -1989,7 +1990,8 @@ static CURLcode imap_parse_url_path(struct connectdata *conn)
       ptr++;
 
     /* Decode the value parameter */
-    result = Curl_urldecode(data, begin, ptr - begin, &value, &valuelen, TRUE);
+    result = Curl_urldecode(data, begin, ptr - begin, &value, &valuelen,
+                            REJECT_CTRL);
     if(result) {
       free(name);
       return result;
@@ -2077,7 +2079,7 @@ static CURLcode imap_parse_custom_request(struct connectdata *conn)
 
   if(custom) {
     /* URL decode the custom request */
-    result = Curl_urldecode(data, custom, 0, &imap->custom, NULL, TRUE);
+    result = Curl_urldecode(data, custom, 0, &imap->custom, NULL, REJECT_CTRL);
 
     /* Extract the parameters if specified */
     if(!result) {

lib/ldap.c

@@ -883,7 +883,7 @@ static int _ldap_url_parse2(const struct connectdata *conn, LDAPURLDesc *ludp)
     LDAP_TRACE(("DN '%s'\n", dn));
 
     /* Unescape the DN */
-    result = Curl_urldecode(conn->data, dn, 0, &unescaped, NULL, FALSE);
+    result = Curl_urldecode(conn->data, dn, 0, &unescaped, NULL, REJECT_ZERO);
     if(result) {
       rc = LDAP_NO_MEMORY;
 
@@ -949,7 +949,7 @@ static int _ldap_url_parse2(const struct connectdata *conn, LDAPURLDesc *ludp)
 
       /* Unescape the attribute */
       result = Curl_urldecode(conn->data, attributes[i], 0, &unescaped, NULL,
-                              FALSE);
+                              REJECT_ZERO);
       if(result) {
         free(attributes);
 
@@ -1018,7 +1018,8 @@ static int _ldap_url_parse2(const struct connectdata *conn, LDAPURLDesc *ludp)
     LDAP_TRACE(("filter '%s'\n", filter));
 
     /* Unescape the filter */
-    result = Curl_urldecode(conn->data, filter, 0, &unescaped, NULL, FALSE);
+    result = Curl_urldecode(conn->data, filter, 0, &unescaped, NULL,
+                            REJECT_ZERO);
     if(result) {
       rc = LDAP_NO_MEMORY;
 

lib/mqtt.c

@@ -211,7 +211,8 @@ static CURLcode mqtt_get_topic(struct connectdata *conn,
   char *path = conn->data->state.up.path;
 
   if(strlen(path) > 1) {
-    result = Curl_urldecode(conn->data, path + 1, 0, topic, topiclen, FALSE);
+    result = Curl_urldecode(conn->data, path + 1, 0, topic, topiclen,
+                            REJECT_NADA);
   }
   else {
     failf(conn->data, "Error: No topic specified.");

lib/pop3.c

@@ -1390,7 +1390,7 @@ static CURLcode pop3_parse_url_path(struct connectdata *conn)
   const char *path = &data->state.up.path[1]; /* skip leading path */
 
   /* URL decode the path for the message ID */
-  return Curl_urldecode(data, path, 0, &pop3->id, NULL, TRUE);
+  return Curl_urldecode(data, path, 0, &pop3->id, NULL, REJECT_CTRL);
 }
 
 /***********************************************************************
@@ -1408,7 +1408,7 @@ static CURLcode pop3_parse_custom_request(struct connectdata *conn)
 
   /* URL decode the custom request */
   if(custom)
-    result = Curl_urldecode(data, custom, 0, &pop3->custom, NULL, TRUE);
+    result = Curl_urldecode(data, custom, 0, &pop3->custom, NULL, REJECT_CTRL);
 
   return result;
 }

lib/smb.c

@@ -6,7 +6,7 @@
  *                             \___|\___/|_| \_\_____|
  *
  * Copyright (C) 2014, Bill Nagel <wnagel@tycoint.com>, Exacq Technologies
- * Copyright (C) 2016-2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 2016-2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -964,7 +964,7 @@ static CURLcode smb_parse_url_path(struct connectdata *conn)
 
   /* URL decode the path */
   CURLcode result = Curl_urldecode(data, data->state.up.path, 0, &path, NULL,
-                                   TRUE);
+                                   REJECT_CTRL);
   if(result)
     return result;
 

lib/smtp.c

@@ -1689,7 +1689,8 @@ static CURLcode smtp_parse_url_path(struct connectdata *conn)
   }
 
   /* URL decode the path and use it as the domain in our EHLO */
-  return Curl_urldecode(conn->data, path, 0, &smtpc->domain, NULL, TRUE);
+  return Curl_urldecode(conn->data, path, 0, &smtpc->domain, NULL,
+                        REJECT_CTRL);
 }
 
 /***********************************************************************
@@ -1707,7 +1708,7 @@ static CURLcode smtp_parse_custom_request(struct connectdata *conn)
 
   /* URL decode the custom request */
   if(custom)
-    result = Curl_urldecode(data, custom, 0, &smtp->custom, NULL, TRUE);
+    result = Curl_urldecode(data, custom, 0, &smtp->custom, NULL, REJECT_CTRL);
 
   return result;
 }

lib/tftp.c

@@ -487,7 +487,7 @@ static CURLcode tftp_send_first(struct tftp_state_data *state,
        file name so we skip the always-present first letter of the path
        string. */
     result = Curl_urldecode(data, &state->conn->data->state.up.path[1], 0,
-                            &filename, NULL, FALSE);
+                            &filename, NULL, REJECT_ZERO);
     if(result)
       return result;
 

lib/url.c

@@ -2373,10 +2373,10 @@ static CURLcode parse_proxy_auth(struct Curl_easy *data,
 
   if(proxyuser)
     result = Curl_urldecode(data, proxyuser, 0, &conn->http_proxy.user, NULL,
-                            FALSE);
+                            REJECT_ZERO);
   if(!result && proxypasswd)
     result = Curl_urldecode(data, proxypasswd, 0, &conn->http_proxy.passwd,
-                            NULL, FALSE);
+                            NULL, REJECT_ZERO);
   return result;
 }
 

lib/urlapi.c

@@ -1185,7 +1185,10 @@ CURLUcode curl_url_get(CURLU *u, CURLUPart what,
     if(urldecode) {
       char *decoded;
       size_t dlen;
-      CURLcode res = Curl_urldecode(NULL, *part, 0, &decoded, &dlen, TRUE);
+      /* this unconditional rejection of control bytes is documented
+         API behavior */
+      CURLcode res = Curl_urldecode(NULL, *part, 0, &decoded, &dlen,
+                                    REJECT_CTRL);
       free(*part);
       if(res) {
         *part = NULL;