cookies: leave secure cookies alone

Only allow secure origins to be able to write cookies with the
'secure' flag set. This reduces the risk of non-secure origins
to influence the state of secure origins. This implements IETF
Internet-Draft draft-ietf-httpbis-cookie-alone-01 which updates
RFC6265.

Closes #2956
Reviewed-by: Daniel Stenberg <daniel@haxx.se>

lib/cookie.c

@@ -433,9 +433,10 @@ Curl_cookie_add(struct Curl_easy *data,
                 bool noexpire, /* if TRUE, skip remove_expired() */
                 char *lineptr,   /* first character of the line */
                 const char *domain, /* default domain */
-                const char *path)   /* full path used when this cookie is set,
+                const char *path,   /* full path used when this cookie is set,
                                        used to get default path for the cookie
                                        unless set */
+                bool secure)  /* TRUE if connection is over secure origin */
 {
   struct Cookie *clist;
   struct Cookie *co;
@@ -546,8 +547,20 @@ Curl_cookie_add(struct Curl_easy *data,
           /* this was a "<name>=" with no content, and we must allow
              'secure' and 'httponly' specified this weirdly */
           done = TRUE;
-          if(strcasecompare("secure", name))
-            co->secure = TRUE;
+          /*
+           * secure cookies are only allowed to be set when the connection is
+           * using a secure protocol, or when the cookie is being set by
+           * reading from file
+           */
+          if(strcasecompare("secure", name)) {
+            if(secure || !c->running) {
+              co->secure = TRUE;
+            }
+            else {
+              badcookie = TRUE;
+              break;
+            }
+          }
           else if(strcasecompare("httponly", name))
             co->httponly = TRUE;
           else if(sep)
@@ -831,7 +844,13 @@ Curl_cookie_add(struct Curl_easy *data,
         fields++; /* add a field and fall down to secure */
         /* FALLTHROUGH */
       case 3:
-        co->secure = strcasecompare(ptr, "TRUE")?TRUE:FALSE;
+        co->secure = FALSE;
+        if(strcasecompare(ptr, "TRUE")) {
+          if(secure || c->running)
+            co->secure = TRUE;
+          else
+            badcookie = TRUE;
+        }
         break;
       case 4:
         if(curlx_strtoofft(ptr, NULL, 10, &co->expires))
@@ -929,9 +948,31 @@ Curl_cookie_add(struct Curl_easy *data,
         /* the domains were identical */
 
         if(clist->spath && co->spath) {
-          if(strcasecompare(clist->spath, co->spath)) {
-            replace_old = TRUE;
+          if(clist->secure && !co->secure) {
+            size_t cllen;
+            const char *sep;
+
+            /*
+             * A non-secure cookie may not overlay an existing secure cookie.
+             * For an existing cookie "a" with path "/login", refuse a new
+             * cookie "a" with for example path "/login/en", while the path
+             * "/loginhelper" is ok.
+             */
+
+            sep = strchr(clist->spath + 1, '/');
+
+            if(sep)
+              cllen = sep - clist->spath;
+            else
+              cllen = strlen(clist->spath);
+
+            if(strncasecompare(clist->spath, co->spath, cllen)) {
+              freecookie(co);
+              return NULL;
+            }
           }
+          else if(strcasecompare(clist->spath, co->spath))
+            replace_old = TRUE;
           else
             replace_old = FALSE;
         }
@@ -1103,7 +1144,7 @@ struct CookieInfo *Curl_cookie_init(struct Curl_easy *data,
       while(*lineptr && ISBLANK(*lineptr))
         lineptr++;
 
-      Curl_cookie_add(data, c, headerline, TRUE, lineptr, NULL, NULL);
+      Curl_cookie_add(data, c, headerline, TRUE, lineptr, NULL, NULL, TRUE);
     }
     free(line); /* free the line buffer */
     remove_expired(c); /* run this once, not on every cookie */

lib/cookie.h

@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2018, 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
@@ -85,7 +85,8 @@ struct Curl_easy;
 struct Cookie *Curl_cookie_add(struct Curl_easy *data,
                                struct CookieInfo *, bool header, bool noexpiry,
                                char *lineptr,
-                               const char *domain, const char *path);
+                               const char *domain, const char *path,
+                               bool secure);
 
 struct Cookie *Curl_cookie_getlist(struct CookieInfo *, const char *,
                                    const char *, bool);

lib/http.c

@@ -3873,7 +3873,9 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
                          here, or else use real peer host name. */
                       conn->allocptr.cookiehost?
                       conn->allocptr.cookiehost:conn->host.name,
-                      data->state.up.path);
+                      data->state.up.path,
+                      (conn->handler->protocol&CURLPROTO_HTTPS)?
+                      TRUE:FALSE);
       Curl_share_unlock(data, CURL_LOCK_DATA_COOKIE);
     }
 #endif

lib/setopt.c

@@ -803,12 +803,12 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option,
         if(checkprefix("Set-Cookie:", argptr))
           /* HTTP Header format line */
           Curl_cookie_add(data, data->cookies, TRUE, FALSE, argptr + 11, NULL,
-                          NULL);
+                          NULL, TRUE);
 
         else
           /* Netscape format line */
           Curl_cookie_add(data, data->cookies, FALSE, FALSE, argptr, NULL,
-                          NULL);
+                          NULL, TRUE);
 
         Curl_share_unlock(data, CURL_LOCK_DATA_COOKIE);
         free(argptr);