urlapi: fix use-after-free bug

Follow-up from 2c20109a9b

Added test 663 to verify.

Reported by OSS-Fuzz
Bug: https://crbug.com/oss-fuzz/17954

Closes #4453

lib/urlapi.c

@@ -64,6 +64,7 @@ struct Curl_URL {
   char *fragment;
 
   char *scratch; /* temporary scratch area */
+  char *temppath; /* temporary path pointer */
   long portnum; /* the numerical version */
 };
 
@@ -82,6 +83,7 @@ static void free_urlhandle(struct Curl_URL *u)
   free(u->query);
   free(u->fragment);
   free(u->scratch);
+  free(u->temppath);
 }
 
 /* move the full contents of one handle onto another and
@@ -858,43 +860,53 @@ static CURLUcode seturl(const char *url, CURLU *u, unsigned int flags)
       return CURLUE_OUT_OF_MEMORY;
     path_alloced = TRUE;
     strcpy_url(newp, path, TRUE); /* consider it relative */
-    path = newp;
+    u->temppath = path = newp;
   }
 
   fragment = strchr(path, '#');
-  if(fragment)
+  if(fragment) {
     *fragment++ = 0;
+    if(fragment[0]) {
+      u->fragment = strdup(fragment);
+      if(!u->fragment)
+        return CURLUE_OUT_OF_MEMORY;
+    }
+  }
 
   query = strchr(path, '?');
-  if(query)
+  if(query) {
     *query++ = 0;
+    /* done even if the query part is a blank string */
+    u->query = strdup(query);
+    if(!u->query)
+      return CURLUE_OUT_OF_MEMORY;
+  }
 
   if(!path[0])
-    /* if there's no path set, unset */
+    /* if there's no path left set, unset */
     path = NULL;
-  else if(!(flags & CURLU_PATH_AS_IS)) {
+  else {
-    /* sanitise paths and remove ../ and ./ sequences according to RFC3986 */
+    if(!(flags & CURLU_PATH_AS_IS)) {
-    char *newp = Curl_dedotdotify(path);
+      /* remove ../ and ./ sequences according to RFC3986 */
-    if(!newp) {
+      char *newp = Curl_dedotdotify(path);
-      if(path_alloced)
+      if(!newp)
-        free(path);
+        return CURLUE_OUT_OF_MEMORY;
-      return CURLUE_OUT_OF_MEMORY;
+
+      if(strcmp(newp, path)) {
+        /* if we got a new version */
+        if(path_alloced)
+          Curl_safefree(u->temppath);
+        u->temppath = path = newp;
+        path_alloced = TRUE;
+      }
+      else
+        free(newp);
     }
 
-    if(strcmp(newp, path)) {
-      /* if we got a new version */
-      if(path_alloced)
-        free(path);
-      path = newp;
-      path_alloced = TRUE;
-    }
-    else
-      free(newp);
-  }
-  if(path) {
     u->path = path_alloced?path:strdup(path);
     if(!u->path)
       return CURLUE_OUT_OF_MEMORY;
+    u->temppath = NULL; /* used now */
   }
 
   if(hostname) {
@@ -926,19 +938,8 @@ static CURLUcode seturl(const char *url, CURLU *u, unsigned int flags)
       return CURLUE_OUT_OF_MEMORY;
   }
 
-  if(query) {
+  Curl_safefree(u->scratch);
-    u->query = strdup(query);
+  Curl_safefree(u->temppath);
-    if(!u->query)
-      return CURLUE_OUT_OF_MEMORY;
-  }
-  if(fragment && fragment[0]) {
-    u->fragment = strdup(fragment);
-    if(!u->fragment)
-      return CURLUE_OUT_OF_MEMORY;
-  }
-
-  free(u->scratch);
-  u->scratch = NULL;
 
   return CURLUE_OK;
 }

tests/data/Makefile.inc

@@ -84,7 +84,7 @@ test626 test627 test628 test629 test630 test631 test632 test633 test634 \
 test635 test636 test637 test638 test639 test640 test641 test642 \
 test643 test644 test645 test646 test647 test648 test649 test650 test651 \
 test652 test653 test654 test655 test656 test658 test659 test660 test661 \
-test662 \
+test662 test663 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
 test709 test710 test711 test712 test713 test714 test715 test716 test717 \

tests/data/test663

@@ -0,0 +1,79 @@
+#
+# This test is crafted to reproduce oss-fuzz bug
+# https://crbug.com/oss-fuzz/17954
+#
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+followlocation
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 302 OK
+Location: http://example.net/there/it/is/../../tes t case=/6630002? yes no
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 0
+
+</data>
+<data2>
+HTTP/1.1 200 OK
+Location: this should be ignored
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 5
+
+body
+</data2>
+<datacheck>
+HTTP/1.1 302 OK
+Location: http://example.net/there/it/is/../../tes t case=/6630002? yes no
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 0
+
+HTTP/1.1 200 OK
+Location: this should be ignored
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Content-Length: 5
+
+body
+</datacheck>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+</server>
+ <name>
+HTTP redirect with dotdots and whitespaces in absolute Location: URL
+ </name>
+ <command>
+http://example.com/please/../gimme/663?foobar#hello -L -x http://%HOSTIP:%HTTPPORT
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+GET http://example.com/gimme/663?foobar HTTP/1.1
+Host: example.com
+Accept: */*
+Proxy-Connection: Keep-Alive
+
+GET http://example.net/there/tes%20t%20case=/6630002?+yes+no HTTP/1.1
+Host: example.net
+Accept: */*
+Proxy-Connection: Keep-Alive
+
+</protocol>
+</verify>
+</testcase>