url: handle arbitrary-length username and password before '@'

libcurl quietly truncates usernames, passwords, and options from
before an '@' sign in a URL to 255 (= MAX_CURL_PASSWORD_LENGTH - 1)
characters to fit in fixed-size buffers on the stack.  Allocate a
buffer large enough to fit the parsed fields on the fly instead to
support longer passwords.

After this change, there are no more uses of MAX_CURL_OPTIONS_LENGTH
left, so stop defining that constant while at it.  The hardcoded max
username and password length constants, on the other hand, are still
used in HTTP proxy credential handling (which this patch doesn't
touch).

Reported-by: Colby Ranger

lib/url.c

@@ -144,7 +144,8 @@ static void signalPipeClose(struct curl_llist *pipeline, bool pipe_broke);
 static CURLcode do_init(struct connectdata *conn);
 static CURLcode parse_url_login(struct SessionHandle *data,
                                 struct connectdata *conn,
-                                char *user, char *passwd, char *options);
+                                char **userptr, char **passwdptr,
+                                char **optionsptr);
 static CURLcode parse_login_details(const char *login, const size_t len,
                                     char **userptr, char **passwdptr,
                                     char **optionsptr);
@@ -3687,7 +3688,8 @@ static CURLcode findprotocol(struct SessionHandle *data,
 static CURLcode parseurlandfillconn(struct SessionHandle *data,
                                     struct connectdata *conn,
                                     bool *prot_missing,
-                                    char *user, char *passwd, char *options)
+                                    char **userp, char **passwdp,
+                                    char **optionsp)
 {
   char *at;
   char *fragment;
@@ -3931,7 +3933,7 @@ static CURLcode parseurlandfillconn(struct SessionHandle *data,
    * Parse the login details from the URL and strip them out of
    * the host name
    */
-  result = parse_url_login(data, conn, user, passwd, options);
+  result = parse_url_login(data, conn, userp, passwdp, optionsp);
   if(result != CURLE_OK)
     return result;
 
@@ -4439,7 +4441,7 @@ static CURLcode parse_proxy_auth(struct SessionHandle *data,
  */
 static CURLcode parse_url_login(struct SessionHandle *data,
                                 struct connectdata *conn,
-                                char *user, char *passwd, char *options)
+                                char **user, char **passwd, char **options)
 {
   CURLcode result = CURLE_OK;
   char *userp = NULL;
@@ -4456,9 +4458,9 @@ static CURLcode parse_url_login(struct SessionHandle *data,
   char *ptr = strchr(conn->host.name, '@');
   char *login = conn->host.name;
 
-  user[0] = 0;   /* to make everything well-defined */
-  passwd[0] = 0;
-  options[0] = 0;
+  DEBUGASSERT(!**user);
+  DEBUGASSERT(!**passwd);
+  DEBUGASSERT(!**options);
 
   if(!ptr)
     goto out;
@@ -4497,10 +4499,8 @@ static CURLcode parse_url_login(struct SessionHandle *data,
       goto out;
     }
 
-    if(strlen(newname) < MAX_CURL_USER_LENGTH)
-      strcpy(user, newname);
-
-    free(newname);
+    free(*user);
+    *user = newname;
   }
 
   if(passwdp) {
@@ -4511,10 +4511,8 @@ static CURLcode parse_url_login(struct SessionHandle *data,
       goto out;
     }
 
-    if(strlen(newpasswd) < MAX_CURL_PASSWORD_LENGTH)
-      strcpy(passwd, newpasswd);
-
-    free(newpasswd);
+    free(*passwd);
+    *passwd = newpasswd;
   }
 
   if(optionsp) {
@@ -4525,12 +4523,11 @@ static CURLcode parse_url_login(struct SessionHandle *data,
       goto out;
     }
 
-    if(strlen(newoptions) < MAX_CURL_OPTIONS_LENGTH)
-      strcpy(options, newoptions);
-
-    free(newoptions);
+    free(*options);
+    *options = newoptions;
   }
 
+
   out:
 
   Curl_safefree(userp);
@@ -5128,16 +5125,16 @@ static CURLcode create_conn(struct SessionHandle *data,
   conn->host.name = conn->host.rawalloc;
   conn->host.name[0] = 0;
 
-  user = malloc(MAX_CURL_USER_LENGTH);
-  passwd = malloc(MAX_CURL_PASSWORD_LENGTH);
-  options = malloc(MAX_CURL_OPTIONS_LENGTH);
+  user = strdup("");
+  passwd = strdup("");
+  options = strdup("");
   if(!user || !passwd || !options) {
     result = CURLE_OUT_OF_MEMORY;
     goto out;
   }
 
-  result = parseurlandfillconn(data, conn, &prot_missing, user, passwd,
-                               options);
+  result = parseurlandfillconn(data, conn, &prot_missing, &user, &passwd,
+                               &options);
   if(result != CURLE_OK)
     goto out;
 

lib/urldata.h

@@ -1152,7 +1152,6 @@ typedef enum {
  * Session-data MUST be put in the connectdata struct and here.  */
 #define MAX_CURL_USER_LENGTH 256
 #define MAX_CURL_PASSWORD_LENGTH 256
-#define MAX_CURL_OPTIONS_LENGTH 256
 
 struct auth {
   unsigned long want;  /* Bitmask set to the authentication methods wanted by