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Best way forward for CVE-2021-22876/curl?



Hello,

[CCing the Security team in case they have some ideas or suggestions
for CVE-2021-22876/curl]

Whilst triaging and looking thoroughly for this CVE, affecting curl, I
noticed that the upstream patch uses elements like CURLU,
CURLUPART_{URL,FRAGMENT,USER,PASSWORD}. This comes from the URL API
which seems to be missing in both, stretch and jessie.

There seem to be two plausible options at this point:

1. Given that this CVE has been assigned low severity by upstream, we
could perhaps mark this as no-dsa or ignored, with an appropriate
comment; or

2. Backport the entire URL API (patch for that is attached; is
intrusive) and then apply the fix for CVE-2021-22876 (patch attached)
on top of that. Whilst this option makes sense, but backporting the
entire URL API could have an unforeseen effect (or chances of
potential regressions) and in any case, looks somewhat intrusive.

So for now, I've added curl to dla-needed and ela-needed but if we
decide to mark this as no-dsa or ignored, we could simply drop this
from there as this is the only CVE that needs working on.

Let me know what y'all think.


- u
Description: backport url api support
Origin: backported from 7.68.0-1ubuntu2.4 in Ubuntu 20.04 LTS.

--- a/include/curl/Makefile.am
+++ b/include/curl/Makefile.am
@@ -21,7 +21,7 @@
 ###########################################################################
 pkginclude_HEADERS = \
 	curl.h curlver.h easy.h mprintf.h stdcheaders.h multi.h \
-	typecheck-gcc.h curlbuild.h curlrules.h
+	typecheck-gcc.h curlbuild.h curlrules.h urlapi.h
 
 pkgincludedir= $(includedir)/curl
 
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -2394,6 +2394,7 @@ CURL_EXTERN CURLcode curl_easy_pause(CUR
   stuff before they can be included! */
 #include "easy.h" /* nothing in curl is fun without the easy stuff */
 #include "multi.h"
+#include "urlapi.h"
 
 /* the typechecker doesn't work in C++ (yet) */
 #if defined(__GNUC__) && defined(__GNUC_MINOR__) && \
--- /dev/null
+++ b/include/curl/urlapi.h
@@ -0,0 +1,125 @@
+#ifndef CURLINC_URLAPI_H
+#define CURLINC_URLAPI_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2018 - 2019, 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
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl.h"
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+/* the error codes for the URL API */
+typedef enum {
+  CURLUE_OK,
+  CURLUE_BAD_HANDLE,          /* 1 */
+  CURLUE_BAD_PARTPOINTER,     /* 2 */
+  CURLUE_MALFORMED_INPUT,     /* 3 */
+  CURLUE_BAD_PORT_NUMBER,     /* 4 */
+  CURLUE_UNSUPPORTED_SCHEME,  /* 5 */
+  CURLUE_URLDECODE,           /* 6 */
+  CURLUE_OUT_OF_MEMORY,       /* 7 */
+  CURLUE_USER_NOT_ALLOWED,    /* 8 */
+  CURLUE_UNKNOWN_PART,        /* 9 */
+  CURLUE_NO_SCHEME,           /* 10 */
+  CURLUE_NO_USER,             /* 11 */
+  CURLUE_NO_PASSWORD,         /* 12 */
+  CURLUE_NO_OPTIONS,          /* 13 */
+  CURLUE_NO_HOST,             /* 14 */
+  CURLUE_NO_PORT,             /* 15 */
+  CURLUE_NO_QUERY,            /* 16 */
+  CURLUE_NO_FRAGMENT          /* 17 */
+} CURLUcode;
+
+typedef enum {
+  CURLUPART_URL,
+  CURLUPART_SCHEME,
+  CURLUPART_USER,
+  CURLUPART_PASSWORD,
+  CURLUPART_OPTIONS,
+  CURLUPART_HOST,
+  CURLUPART_PORT,
+  CURLUPART_PATH,
+  CURLUPART_QUERY,
+  CURLUPART_FRAGMENT,
+  CURLUPART_ZONEID /* added in 7.65.0 */
+} CURLUPart;
+
+#define CURLU_DEFAULT_PORT (1<<0)       /* return default port number */
+#define CURLU_NO_DEFAULT_PORT (1<<1)    /* act as if no port number was set,
+                                           if the port number matches the
+                                           default for the scheme */
+#define CURLU_DEFAULT_SCHEME (1<<2)     /* return default scheme if
+                                           missing */
+#define CURLU_NON_SUPPORT_SCHEME (1<<3) /* allow non-supported scheme */
+#define CURLU_PATH_AS_IS (1<<4)         /* leave dot sequences */
+#define CURLU_DISALLOW_USER (1<<5)      /* no user+password allowed */
+#define CURLU_URLDECODE (1<<6)          /* URL decode on get */
+#define CURLU_URLENCODE (1<<7)          /* URL encode on set */
+#define CURLU_APPENDQUERY (1<<8)        /* append a form style part */
+#define CURLU_GUESS_SCHEME (1<<9)       /* legacy curl-style guessing */
+#define CURLU_NO_AUTHORITY (1<<10)      /* Allow empty authority when the
+                                           scheme is unknown. */
+
+typedef struct Curl_URL CURLU;
+
+/*
+ * curl_url() creates a new CURLU handle and returns a pointer to it.
+ * Must be freed with curl_url_cleanup().
+ */
+CURL_EXTERN CURLU *curl_url(void);
+
+/*
+ * curl_url_cleanup() frees the CURLU handle and related resources used for
+ * the URL parsing. It will not free strings previously returned with the URL
+ * API.
+ */
+CURL_EXTERN void curl_url_cleanup(CURLU *handle);
+
+/*
+ * curl_url_dup() duplicates a CURLU handle and returns a new copy. The new
+ * handle must also be freed with curl_url_cleanup().
+ */
+CURL_EXTERN CURLU *curl_url_dup(CURLU *in);
+
+/*
+ * curl_url_get() extracts a specific part of the URL from a CURLU
+ * handle. Returns error code. The returned pointer MUST be freed with
+ * curl_free() afterwards.
+ */
+CURL_EXTERN CURLUcode curl_url_get(CURLU *handle, CURLUPart what,
+                                   char **part, unsigned int flags);
+
+/*
+ * curl_url_set() sets a specific part of the URL in a CURLU handle. Returns
+ * error code. The passed in string will be copied. Passing a NULL instead of
+ * a part string, clears that part.
+ */
+CURL_EXTERN CURLUcode curl_url_set(CURLU *handle, CURLUPart what,
+                                   const char *part, unsigned int flags);
+
+
+#ifdef __cplusplus
+} /* end of extern "C" */
+#endif
+
+#endif /* CURLINC_URLAPI_H */
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@@ -48,7 +48,7 @@ LIB_CFILES = file.c timeval.c base64.c h
   curl_ntlm_core.c curl_ntlm_msgs.c curl_sasl.c curl_multibyte.c        \
   hostcheck.c conncache.c pipeline.c dotdot.c x509asn1.c                \
   http2.c curl_sasl_sspi.c smb.c curl_sasl_gssapi.c curl_endian.c       \
-  curl_des.c
+  curl_des.c urlapi.c
 
 LIB_HFILES = arpa_telnet.h netrc.h file.h timeval.h hostip.h progress.h \
   formdata.h cookie.h http.h sendf.h ftp.h url.h dict.h if2ip.h         \
@@ -67,7 +67,7 @@ LIB_HFILES = arpa_telnet.h netrc.h file.
   curl_ntlm_msgs.h curl_sasl.h curl_multibyte.h hostcheck.h             \
   conncache.h curl_setup_once.h multihandle.h setup-vms.h pipeline.h    \
   dotdot.h x509asn1.h http2.h sigpipe.h smb.h curl_endian.h curl_des.h  \
-  curl_printf.h
+  curl_printf.h urlapi-int.h
 
 LIB_RCFILES = libcurl.rc
 
--- /dev/null
+++ b/lib/urlapi-int.h
@@ -0,0 +1,34 @@
+#ifndef HEADER_CURL_URLAPI_INT_H
+#define HEADER_CURL_URLAPI_INT_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, 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
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+/* scheme is not URL encoded, the longest libcurl supported ones are... */
+#define MAX_SCHEME_LEN 40
+
+bool Curl_is_absolute_url(const char *url, char *scheme, size_t buflen);
+
+#ifdef DEBUGBUILD
+CURLUcode Curl_parse_port(struct Curl_URL *u, char *hostname);
+#endif
+
+#endif /* HEADER_CURL_URLAPI_INT_H */
--- /dev/null
+++ b/lib/urlapi.c
@@ -0,0 +1,1479 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, 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
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#include "urldata.h"
+#include "urlapi-int.h"
+#include "rawstr.h"
+#include "dotdot.h"
+#include "url.h"
+#include "escape.h"
+#include "inet_pton.h"
+
+/* The last 3 #include files should be in this order */
+#include "curl_printf.h"
+#include "curl_memory.h"
+#include "memdebug.h"
+
+  /* MSDOS/Windows style drive prefix, eg c: in c:foo */
+#define STARTS_WITH_DRIVE_PREFIX(str) \
+  ((('a' <= str[0] && str[0] <= 'z') || \
+    ('A' <= str[0] && str[0] <= 'Z')) && \
+   (str[1] == ':'))
+
+  /* MSDOS/Windows style drive prefix, optionally with
+   * a '|' instead of ':', followed by a slash or NUL */
+#define STARTS_WITH_URL_DRIVE_PREFIX(str) \
+  ((('a' <= (str)[0] && (str)[0] <= 'z') || \
+    ('A' <= (str)[0] && (str)[0] <= 'Z')) && \
+   ((str)[1] == ':' || (str)[1] == '|') && \
+   ((str)[2] == '/' || (str)[2] == '\\' || (str)[2] == 0))
+
+/* Internal representation of CURLU. Point to URL-encoded strings. */
+struct Curl_URL {
+  char *scheme;
+  char *user;
+  char *password;
+  char *options; /* IMAP only? */
+  char *host;
+  char *zoneid; /* for numerical IPv6 addresses */
+  char *port;
+  char *path;
+  char *query;
+  char *fragment;
+
+  char *scratch; /* temporary scratch area */
+  char *temppath; /* temporary path pointer */
+  long portnum; /* the numerical version */
+};
+
+#define DEFAULT_SCHEME "https"
+
+static void free_urlhandle(struct Curl_URL *u)
+{
+  free(u->scheme);
+  free(u->user);
+  free(u->password);
+  free(u->options);
+  free(u->host);
+  free(u->zoneid);
+  free(u->port);
+  free(u->path);
+  free(u->query);
+  free(u->fragment);
+  free(u->scratch);
+  free(u->temppath);
+}
+
+/* move the full contents of one handle onto another and
+   free the original */
+static void mv_urlhandle(struct Curl_URL *from,
+                         struct Curl_URL *to)
+{
+  free_urlhandle(to);
+  *to = *from;
+  free(from);
+}
+
+/*
+ * Find the separator at the end of the host name, or the '?' in cases like
+ * http://www.url.com?id=2380
+ */
+static const char *find_host_sep(const char *url)
+{
+  const char *sep;
+  const char *query;
+
+  /* Find the start of the hostname */
+  sep = strstr(url, "//");
+  if(!sep)
+    sep = url;
+  else
+    sep += 2;
+
+  query = strchr(sep, '?');
+  sep = strchr(sep, '/');
+
+  if(!sep)
+    sep = url + strlen(url);
+
+  if(!query)
+    query = url + strlen(url);
+
+  return sep < query ? sep : query;
+}
+
+/*
+ * Decide in an encoding-independent manner whether a character in an
+ * URL must be escaped. The same criterion must be used in strlen_url()
+ * and strcpy_url().
+ */
+static bool urlchar_needs_escaping(int c)
+{
+    return !(ISCNTRL(c) || ISSPACE(c) || ISGRAPH(c));
+}
+
+/*
+ * strlen_url() returns the length of the given URL if the spaces within the
+ * URL were properly URL encoded.
+ * URL encoding should be skipped for host names, otherwise IDN resolution
+ * will fail.
+ */
+static size_t strlen_url(const char *url, bool relative)
+{
+  const unsigned char *ptr;
+  size_t newlen = 0;
+  bool left = TRUE; /* left side of the ? */
+  const unsigned char *host_sep = (const unsigned char *) url;
+
+  if(!relative)
+    host_sep = (const unsigned char *) find_host_sep(url);
+
+  for(ptr = (unsigned char *)url; *ptr; ptr++) {
+
+    if(ptr < host_sep) {
+      ++newlen;
+      continue;
+    }
+
+    switch(*ptr) {
+    case '?':
+      left = FALSE;
+      /* FALLTHROUGH */
+    default:
+      if(urlchar_needs_escaping(*ptr))
+        newlen += 2;
+      newlen++;
+      break;
+    case ' ':
+      if(left)
+        newlen += 3;
+      else
+        newlen++;
+      break;
+    }
+  }
+  return newlen;
+}
+
+/* strcpy_url() copies a url to a output buffer and URL-encodes the spaces in
+ * the source URL accordingly.
+ * URL encoding should be skipped for host names, otherwise IDN resolution
+ * will fail.
+ */
+static void strcpy_url(char *output, const char *url, bool relative)
+{
+  /* we must add this with whitespace-replacing */
+  bool left = TRUE;
+  const unsigned char *iptr;
+  char *optr = output;
+  const unsigned char *host_sep = (const unsigned char *) url;
+
+  if(!relative)
+    host_sep = (const unsigned char *) find_host_sep(url);
+
+  for(iptr = (unsigned char *)url;    /* read from here */
+      *iptr;         /* until zero byte */
+      iptr++) {
+
+    if(iptr < host_sep) {
+      *optr++ = *iptr;
+      continue;
+    }
+
+    switch(*iptr) {
+    case '?':
+      left = FALSE;
+      /* FALLTHROUGH */
+    default:
+      if(urlchar_needs_escaping(*iptr)) {
+        snprintf(optr, 4, "%%%02x", *iptr);
+        optr += 3;
+      }
+      else
+        *optr++=*iptr;
+      break;
+    case ' ':
+      if(left) {
+        *optr++='%'; /* add a '%' */
+        *optr++='2'; /* add a '2' */
+        *optr++='0'; /* add a '0' */
+      }
+      else
+        *optr++='+'; /* add a '+' here */
+      break;
+    }
+  }
+  *optr = 0; /* zero terminate output buffer */
+
+}
+
+/*
+ * Returns true if the given URL is absolute (as opposed to relative) within
+ * the buffer size. Returns the scheme in the buffer if TRUE and 'buf' is
+ * non-NULL.
+ */
+bool Curl_is_absolute_url(const char *url, char *buf, size_t buflen)
+{
+  size_t i;
+#ifdef WIN32
+  if(STARTS_WITH_DRIVE_PREFIX(url))
+    return FALSE;
+#endif
+  for(i = 0; i < buflen && url[i]; ++i) {
+    char s = url[i];
+    if((s == ':') && (url[i + 1] == '/')) {
+      if(buf)
+        buf[i] = 0;
+      return TRUE;
+    }
+    /* RFC 3986 3.1 explains:
+      scheme      = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
+    */
+    else if(ISALNUM(s) || (s == '+') || (s == '-') || (s == '.') ) {
+      if(buf)
+        buf[i] = (char)TOLOWER(s);
+    }
+    else
+      break;
+  }
+  return FALSE;
+}
+
+/*
+ * Concatenate a relative URL to a base URL making it absolute.
+ * URL-encodes any spaces.
+ * The returned pointer must be freed by the caller unless NULL
+ * (returns NULL on out of memory).
+ */
+static char *concat_url(const char *base, const char *relurl)
+{
+  /***
+   TRY to append this new path to the old URL
+   to the right of the host part. Oh crap, this is doomed to cause
+   problems in the future...
+  */
+  char *newest;
+  char *protsep;
+  char *pathsep;
+  size_t newlen;
+  bool host_changed = FALSE;
+
+  const char *useurl = relurl;
+  size_t urllen;
+
+  /* we must make our own copy of the URL to play with, as it may
+     point to read-only data */
+  char *url_clone = strdup(base);
+
+  if(!url_clone)
+    return NULL; /* skip out of this NOW */
+
+  /* protsep points to the start of the host name */
+  protsep = strstr(url_clone, "//");
+  if(!protsep)
+    protsep = url_clone;
+  else
+    protsep += 2; /* pass the slashes */
+
+  if('/' != relurl[0]) {
+    int level = 0;
+
+    /* First we need to find out if there's a ?-letter in the URL,
+       and cut it and the right-side of that off */
+    pathsep = strchr(protsep, '?');
+    if(pathsep)
+      *pathsep = 0;
+
+    /* we have a relative path to append to the last slash if there's one
+       available, or if the new URL is just a query string (starts with a
+       '?')  we append the new one at the end of the entire currently worked
+       out URL */
+    if(useurl[0] != '?') {
+      pathsep = strrchr(protsep, '/');
+      if(pathsep)
+        *pathsep = 0;
+    }
+
+    /* Check if there's any slash after the host name, and if so, remember
+       that position instead */
+    pathsep = strchr(protsep, '/');
+    if(pathsep)
+      protsep = pathsep + 1;
+    else
+      protsep = NULL;
+
+    /* now deal with one "./" or any amount of "../" in the newurl
+       and act accordingly */
+
+    if((useurl[0] == '.') && (useurl[1] == '/'))
+      useurl += 2; /* just skip the "./" */
+
+    while((useurl[0] == '.') &&
+          (useurl[1] == '.') &&
+          (useurl[2] == '/')) {
+      level++;
+      useurl += 3; /* pass the "../" */
+    }
+
+    if(protsep) {
+      while(level--) {
+        /* cut off one more level from the right of the original URL */
+        pathsep = strrchr(protsep, '/');
+        if(pathsep)
+          *pathsep = 0;
+        else {
+          *protsep = 0;
+          break;
+        }
+      }
+    }
+  }
+  else {
+    /* We got a new absolute path for this server */
+
+    if(relurl[1] == '/') {
+      /* the new URL starts with //, just keep the protocol part from the
+         original one */
+      *protsep = 0;
+      useurl = &relurl[2]; /* we keep the slashes from the original, so we
+                              skip the new ones */
+      host_changed = TRUE;
+    }
+    else {
+      /* cut off the original URL from the first slash, or deal with URLs
+         without slash */
+      pathsep = strchr(protsep, '/');
+      if(pathsep) {
+        /* When people use badly formatted URLs, such as
+           "http://www.url.com?dir=/home/daniel"; we must not use the first
+           slash, if there's a ?-letter before it! */
+        char *sep = strchr(protsep, '?');
+        if(sep && (sep < pathsep))
+          pathsep = sep;
+        *pathsep = 0;
+      }
+      else {
+        /* There was no slash. Now, since we might be operating on a badly
+           formatted URL, such as "http://www.url.com?id=2380"; which doesn't
+           use a slash separator as it is supposed to, we need to check for a
+           ?-letter as well! */
+        pathsep = strchr(protsep, '?');
+        if(pathsep)
+          *pathsep = 0;
+      }
+    }
+  }
+
+  /* If the new part contains a space, this is a mighty stupid redirect
+     but we still make an effort to do "right". To the left of a '?'
+     letter we replace each space with %20 while it is replaced with '+'
+     on the right side of the '?' letter.
+  */
+  newlen = strlen_url(useurl, !host_changed);
+
+  urllen = strlen(url_clone);
+
+  newest = malloc(urllen + 1 + /* possible slash */
+                  newlen + 1 /* zero byte */);
+
+  if(!newest) {
+    free(url_clone); /* don't leak this */
+    return NULL;
+  }
+
+  /* copy over the root url part */
+  memcpy(newest, url_clone, urllen);
+
+  /* check if we need to append a slash */
+  if(('/' == useurl[0]) || (protsep && !*protsep) || ('?' == useurl[0]))
+    ;
+  else
+    newest[urllen++]='/';
+
+  /* then append the new piece on the right side */
+  strcpy_url(&newest[urllen], useurl, !host_changed);
+
+  free(url_clone);
+
+  return newest;
+}
+
+/*
+ * parse_hostname_login()
+ *
+ * Parse the login details (user name, password and options) from the URL and
+ * strip them out of the host name
+ *
+ */
+static CURLUcode parse_hostname_login(struct Curl_URL *u,
+                                      const struct Curl_handler *h,
+                                      char **hostname,
+                                      unsigned int flags)
+{
+  CURLUcode result = CURLUE_OK;
+  CURLcode ccode;
+  char *userp = NULL;
+  char *passwdp = NULL;
+  char *optionsp = NULL;
+
+  /* At this point, we're hoping all the other special cases have
+   * been taken care of, so conn->host.name is at most
+   *    [user[:password][;options]]@]hostname
+   *
+   * We need somewhere to put the embedded details, so do that first.
+   */
+
+  char *ptr = strchr(*hostname, '@');
+  char *login = *hostname;
+
+  if(!ptr)
+    goto out;
+
+  /* We will now try to extract the
+   * possible login information in a string like:
+   * ftp://user:password@ftp.my.site:8021/README */
+  *hostname = ++ptr;
+
+  /* We could use the login information in the URL so extract it. Only parse
+     options if the handler says we should. Note that 'h' might be NULL! */
+  ccode = Curl_parse_login_details(login, ptr - login - 1,
+                                   &userp, &passwdp, &optionsp);
+  if(ccode) {
+    result = CURLUE_MALFORMED_INPUT;
+    goto out;
+  }
+
+  if(userp) {
+    if(flags & CURLU_DISALLOW_USER) {
+      /* Option DISALLOW_USER is set and url contains username. */
+      result = CURLUE_USER_NOT_ALLOWED;
+      goto out;
+    }
+
+    u->user = userp;
+  }
+
+  if(passwdp)
+    u->password = passwdp;
+
+  if(optionsp)
+    u->options = optionsp;
+
+  return CURLUE_OK;
+  out:
+
+  free(userp);
+  free(passwdp);
+  free(optionsp);
+
+  return result;
+}
+
+CURLUcode Curl_parse_port(struct Curl_URL *u, char *hostname)
+{
+  char *portptr = NULL;
+  char endbracket;
+  int len;
+
+  /*
+   * Find the end of an IPv6 address, either on the ']' ending bracket or
+   * a percent-encoded zone index.
+   */
+  if(1 == sscanf(hostname, "[%*45[0123456789abcdefABCDEF:.]%c%n",
+                 &endbracket, &len)) {
+    if(']' == endbracket)
+      portptr = &hostname[len];
+    else if('%' == endbracket) {
+      int zonelen = len;
+      if(1 == sscanf(hostname + zonelen, "%*[^]]%c%n", &endbracket, &len)) {
+        if(']' != endbracket)
+          return CURLUE_MALFORMED_INPUT;
+        portptr = &hostname[--zonelen + len + 1];
+      }
+      else
+        return CURLUE_MALFORMED_INPUT;
+    }
+    else
+      return CURLUE_MALFORMED_INPUT;
+
+    /* this is a RFC2732-style specified IP-address */
+    if(portptr && *portptr) {
+      if(*portptr != ':')
+        return CURLUE_MALFORMED_INPUT;
+    }
+    else
+      portptr = NULL;
+  }
+  else
+    portptr = strchr(hostname, ':');
+
+  if(portptr) {
+    char *rest;
+    long port;
+    char portbuf[7];
+
+    /* Browser behavior adaptation. If there's a colon with no digits after,
+       just cut off the name there which makes us ignore the colon and just
+       use the default port. Firefox, Chrome and Safari all do that. */
+    if(!portptr[1]) {
+      *portptr = '\0';
+      return CURLUE_OK;
+    }
+
+    if(!ISDIGIT(portptr[1]))
+      return CURLUE_BAD_PORT_NUMBER;
+
+    port = strtol(portptr + 1, &rest, 10);  /* Port number must be decimal */
+
+    if((port <= 0) || (port > 0xffff))
+      /* Single unix standard says port numbers are 16 bits long, but we don't
+         treat port zero as OK. */
+      return CURLUE_BAD_PORT_NUMBER;
+
+    if(rest[0])
+      return CURLUE_BAD_PORT_NUMBER;
+
+    *portptr++ = '\0'; /* cut off the name there */
+    *rest = 0;
+    /* generate a new port number string to get rid of leading zeroes etc */
+    snprintf(portbuf, sizeof(portbuf), "%ld", port);
+    u->portnum = port;
+    u->port = strdup(portbuf);
+    if(!u->port)
+      return CURLUE_OUT_OF_MEMORY;
+  }
+
+  return CURLUE_OK;
+}
+
+/* scan for byte values < 31 or 127 */
+static CURLUcode junkscan(char *part)
+{
+  if(part) {
+    static const char badbytes[]={
+      /* */ 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+      0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+      0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+      0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+      0x7f,
+      0x00 /* zero terminate */
+    };
+    size_t n = strlen(part);
+    size_t nfine = strcspn(part, badbytes);
+    if(nfine != n)
+      /* since we don't know which part is scanned, return a generic error
+         code */
+      return CURLUE_MALFORMED_INPUT;
+  }
+  return CURLUE_OK;
+}
+
+static CURLUcode hostname_check(struct Curl_URL *u, char *hostname)
+{
+  size_t len;
+  size_t hlen = strlen(hostname);
+
+  if(hostname[0] == '[') {
+#ifdef ENABLE_IPV6
+    char dest[16]; /* fits a binary IPv6 address */
+#endif
+    const char *l = "0123456789abcdefABCDEF:.";
+    if(hlen < 5) /* '[::1]' is the shortest possible valid string */
+      return CURLUE_MALFORMED_INPUT;
+    hostname++;
+    hlen -= 2;
+
+    if(hostname[hlen] != ']')
+      return CURLUE_MALFORMED_INPUT;
+
+    /* only valid letters are ok */
+    len = strspn(hostname, l);
+    if(hlen != len) {
+      hlen = len;
+      if(hostname[len] == '%') {
+        /* this could now be '%[zone id]' */
+        char zoneid[16];
+        int i = 0;
+        char *h = &hostname[len + 1];
+        /* pass '25' if present and is a url encoded percent sign */
+        if(!strncmp(h, "25", 2) && h[2] && (h[2] != ']'))
+          h += 2;
+        while(*h && (*h != ']') && (i < 15))
+          zoneid[i++] = *h++;
+        if(!i || (']' != *h))
+          return CURLUE_MALFORMED_INPUT;
+        zoneid[i] = 0;
+        u->zoneid = strdup(zoneid);
+        if(!u->zoneid)
+          return CURLUE_OUT_OF_MEMORY;
+        hostname[len] = ']'; /* insert end bracket */
+        hostname[len + 1] = 0; /* terminate the hostname */
+      }
+      else
+        return CURLUE_MALFORMED_INPUT;
+      /* hostname is fine */
+    }
+#ifdef ENABLE_IPV6
+    hostname[hlen] = 0; /* end the address there */
+    if(1 != Curl_inet_pton(AF_INET6, hostname, dest))
+      return CURLUE_MALFORMED_INPUT;
+    hostname[hlen] = ']'; /* restore ending bracket */
+#endif
+  }
+  else {
+    /* letters from the second string is not ok */
+    len = strcspn(hostname, " ");
+    if(hlen != len)
+      /* hostname with bad content */
+      return CURLUE_MALFORMED_INPUT;
+  }
+  if(!hostname[0])
+    return CURLUE_NO_HOST;
+  return CURLUE_OK;
+}
+
+
+#define HOSTNAME_END(x) (((x) == '/') || ((x) == '?') || ((x) == '#'))
+#define CURL_MAX_INPUT_LENGTH 8000000
+
+static CURLUcode seturl(const char *url, CURLU *u, unsigned int flags)
+{
+  char *path;
+  bool path_alloced = FALSE;
+  char *hostname;
+  char *query = NULL;
+  char *fragment = NULL;
+  CURLUcode result;
+  bool url_has_scheme = FALSE;
+  char schemebuf[MAX_SCHEME_LEN + 1];
+  char *schemep = NULL;
+  size_t schemelen = 0;
+  size_t urllen;
+  const struct Curl_handler *h = NULL;
+
+  if(!url)
+    return CURLUE_MALFORMED_INPUT;
+
+  /*************************************************************
+   * Parse the URL.
+   ************************************************************/
+  /* allocate scratch area */
+  urllen = strlen(url);
+  if(urllen > CURL_MAX_INPUT_LENGTH)
+    /* excessive input length */
+    return CURLUE_MALFORMED_INPUT;
+
+  path = u->scratch = malloc(urllen * 2 + 2);
+  if(!path)
+    return CURLUE_OUT_OF_MEMORY;
+
+  hostname = &path[urllen + 1];
+  hostname[0] = 0;
+
+  if(Curl_is_absolute_url(url, schemebuf, sizeof(schemebuf))) {
+    url_has_scheme = TRUE;
+    schemelen = strlen(schemebuf);
+  }
+
+  /* handle the file: scheme */
+  if(url_has_scheme && Curl_raw_equal(schemebuf, "file")) {
+    /* path has been allocated large enough to hold this */
+    strcpy(path, &url[5]);
+
+    hostname = NULL; /* no host for file: URLs */
+    u->scheme = strdup("file");
+    if(!u->scheme)
+      return CURLUE_OUT_OF_MEMORY;
+
+    /* Extra handling URLs with an authority component (i.e. that start with
+     * "file://")
+     *
+     * We allow omitted hostname (e.g. file:/<path>) -- valid according to
+     * RFC 8089, but not the (current) WHAT-WG URL spec.
+     */
+    if(path[0] == '/' && path[1] == '/') {
+      /* swallow the two slashes */
+      char *ptr = &path[2];
+
+      /*
+       * According to RFC 8089, a file: URL can be reliably dereferenced if:
+       *
+       *  o it has no/blank hostname, or
+       *
+       *  o the hostname matches "localhost" (case-insensitively), or
+       *
+       *  o the hostname is a FQDN that resolves to this machine.
+       *
+       * For brevity, we only consider URLs with empty, "localhost", or
+       * "127.0.0.1" hostnames as local.
+       *
+       * Additionally, there is an exception for URLs with a Windows drive
+       * letter in the authority (which was accidentally omitted from RFC 8089
+       * Appendix E, but believe me, it was meant to be there. --MK)
+       */
+      if(ptr[0] != '/' && !STARTS_WITH_URL_DRIVE_PREFIX(ptr)) {
+        /* the URL includes a host name, it must match "localhost" or
+           "127.0.0.1" to be valid */
+        if(!checkprefix("localhost/", ptr) &&
+           !checkprefix("127.0.0.1/", ptr)) {
+          /* Invalid file://hostname/, expected localhost or 127.0.0.1 or
+             none */
+          return CURLUE_MALFORMED_INPUT;
+        }
+        ptr += 9; /* now points to the slash after the host */
+      }
+
+      path = ptr;
+    }
+
+#if !defined(MSDOS) && !defined(WIN32) && !defined(__CYGWIN__)
+    /* Don't allow Windows drive letters when not in Windows.
+     * This catches both "file:/c:" and "file:c:" */
+    if(('/' == path[0] && STARTS_WITH_URL_DRIVE_PREFIX(&path[1])) ||
+       STARTS_WITH_URL_DRIVE_PREFIX(path)) {
+      /* File drive letters are only accepted in MSDOS/Windows */
+      return CURLUE_MALFORMED_INPUT;
+    }
+#else
+    /* If the path starts with a slash and a drive letter, ditch the slash */
+    if('/' == path[0] && STARTS_WITH_URL_DRIVE_PREFIX(&path[1])) {
+      /* This cannot be done with strcpy, as the memory chunks overlap! */
+      memmove(path, &path[1], strlen(&path[1]) + 1);
+    }
+#endif
+
+  }
+  else {
+    /* clear path */
+    const char *p;
+    const char *hostp;
+    size_t len;
+    path[0] = 0;
+
+    if(url_has_scheme) {
+      int i = 0;
+      p = &url[schemelen + 1];
+      while(p && (*p == '/') && (i < 4)) {
+        p++;
+        i++;
+      }
+      if((i < 1) || (i>3))
+        /* less than one or more than three slashes */
+        return CURLUE_MALFORMED_INPUT;
+
+      schemep = schemebuf;
+      if(!Curl_builtin_scheme(schemep) &&
+         !(flags & CURLU_NON_SUPPORT_SCHEME))
+        return CURLUE_UNSUPPORTED_SCHEME;
+
+      if(junkscan(schemep))
+        return CURLUE_MALFORMED_INPUT;
+
+    }
+    else {
+      /* no scheme! */
+
+      if(!(flags & (CURLU_DEFAULT_SCHEME|CURLU_GUESS_SCHEME)))
+        return CURLUE_MALFORMED_INPUT;
+      if(flags & CURLU_DEFAULT_SCHEME)
+        schemep = (char *) DEFAULT_SCHEME;
+
+      /*
+       * The URL was badly formatted, let's try without scheme specified.
+       */
+      p = url;
+    }
+    hostp = p; /* host name starts here */
+
+    while(*p && !HOSTNAME_END(*p)) /* find end of host name */
+      p++;
+
+    len = p - hostp;
+    if(len) {
+      memcpy(hostname, hostp, len);
+      hostname[len] = 0;
+    }
+    else {
+      if(!(flags & CURLU_NO_AUTHORITY))
+        return CURLUE_MALFORMED_INPUT;
+    }
+
+    if((flags & CURLU_GUESS_SCHEME) && !schemep) {
+      /* legacy curl-style guess based on host name */
+      if(checkprefix("ftp.", hostname))
+        schemep = (char *)"ftp";
+      else if(checkprefix("dict.", hostname))
+        schemep = (char *)"dict";
+      else if(checkprefix("ldap.", hostname))
+        schemep = (char *)"ldap";
+      else if(checkprefix("imap.", hostname))
+        schemep = (char *)"imap";
+      else if(checkprefix("smtp.", hostname))
+        schemep = (char *)"smtp";
+      else if(checkprefix("pop3.", hostname))
+        schemep = (char *)"pop3";
+      else
+        schemep = (char *)"http";
+    }
+
+    len = strlen(p);
+    memcpy(path, p, len);
+    path[len] = 0;
+
+    u->scheme = strdup(schemep);
+    if(!u->scheme)
+      return CURLUE_OUT_OF_MEMORY;
+  }
+
+  /* if this is a known scheme, get some details */
+  h = Curl_builtin_scheme(u->scheme);
+
+  if(junkscan(path))
+    return CURLUE_MALFORMED_INPUT;
+
+  if((flags & CURLU_URLENCODE) && path[0]) {
+    /* worst case output length is 3x the original! */
+    char *newp = malloc(strlen(path) * 3);
+    if(!newp)
+      return CURLUE_OUT_OF_MEMORY;
+    path_alloced = TRUE;
+    strcpy_url(newp, path, TRUE); /* consider it relative */
+    u->temppath = path = newp;
+  }
+
+  fragment = strchr(path, '#');
+  if(fragment) {
+    *fragment++ = 0;
+    if(fragment[0]) {
+      u->fragment = strdup(fragment);
+      if(!u->fragment)
+        return CURLUE_OUT_OF_MEMORY;
+    }
+  }
+
+  query = strchr(path, '?');
+  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 left set, unset */
+    path = NULL;
+  else {
+    if(!(flags & CURLU_PATH_AS_IS)) {
+      /* remove ../ and ./ sequences according to RFC3986 */
+      char *newp = Curl_dedotdotify(path);
+      if(!newp)
+        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);
+    }
+
+    u->path = path_alloced?path:strdup(path);
+    if(!u->path)
+      return CURLUE_OUT_OF_MEMORY;
+    u->temppath = NULL; /* used now */
+  }
+
+  if(hostname) {
+    /*
+     * Parse the login details and strip them out of the host name.
+     */
+    if(junkscan(hostname))
+      return CURLUE_MALFORMED_INPUT;
+
+    result = parse_hostname_login(u, h, &hostname, flags);
+    if(result)
+      return result;
+
+    result = Curl_parse_port(u, hostname);
+    if(result)
+      return result;
+
+    if(0 == strlen(hostname) && (flags & CURLU_NO_AUTHORITY)) {
+      /* Skip hostname check, it's allowed to be empty. */
+    }
+    else {
+      result = hostname_check(u, hostname);
+      if(result)
+        return result;
+    }
+
+    u->host = strdup(hostname);
+    if(!u->host)
+      return CURLUE_OUT_OF_MEMORY;
+  }
+
+  Curl_safefree(u->scratch);
+  Curl_safefree(u->temppath);
+
+  return CURLUE_OK;
+}
+
+/*
+ * Parse the URL and set the relevant members of the Curl_URL struct.
+ */
+static CURLUcode parseurl(const char *url, CURLU *u, unsigned int flags)
+{
+  CURLUcode result = seturl(url, u, flags);
+  if(result) {
+    free_urlhandle(u);
+    memset(u, 0, sizeof(struct Curl_URL));
+  }
+  return result;
+}
+
+/*
+ */
+CURLU *curl_url(void)
+{
+  return calloc(sizeof(struct Curl_URL), 1);
+}
+
+void curl_url_cleanup(CURLU *u)
+{
+  if(u) {
+    free_urlhandle(u);
+    free(u);
+  }
+}
+
+#define DUP(dest, src, name)         \
+  if(src->name) {                    \
+    dest->name = strdup(src->name);  \
+    if(!dest->name)                  \
+      goto fail;                     \
+  }
+
+CURLU *curl_url_dup(CURLU *in)
+{
+  struct Curl_URL *u = calloc(sizeof(struct Curl_URL), 1);
+  if(u) {
+    DUP(u, in, scheme);
+    DUP(u, in, user);
+    DUP(u, in, password);
+    DUP(u, in, options);
+    DUP(u, in, host);
+    DUP(u, in, port);
+    DUP(u, in, path);
+    DUP(u, in, query);
+    DUP(u, in, fragment);
+    u->portnum = in->portnum;
+  }
+  return u;
+  fail:
+  curl_url_cleanup(u);
+  return NULL;
+}
+
+CURLUcode curl_url_get(CURLU *u, CURLUPart what,
+                       char **part, unsigned int flags)
+{
+  char *ptr;
+  CURLUcode ifmissing = CURLUE_UNKNOWN_PART;
+  char portbuf[7];
+  bool urldecode = (flags & CURLU_URLDECODE)?1:0;
+  bool plusdecode = FALSE;
+  (void)flags;
+  if(!u)
+    return CURLUE_BAD_HANDLE;
+  if(!part)
+    return CURLUE_BAD_PARTPOINTER;
+  *part = NULL;
+
+  switch(what) {
+  case CURLUPART_SCHEME:
+    ptr = u->scheme;
+    ifmissing = CURLUE_NO_SCHEME;
+    urldecode = FALSE; /* never for schemes */
+    break;
+  case CURLUPART_USER:
+    ptr = u->user;
+    ifmissing = CURLUE_NO_USER;
+    break;
+  case CURLUPART_PASSWORD:
+    ptr = u->password;
+    ifmissing = CURLUE_NO_PASSWORD;
+    break;
+  case CURLUPART_OPTIONS:
+    ptr = u->options;
+    ifmissing = CURLUE_NO_OPTIONS;
+    break;
+  case CURLUPART_HOST:
+    ptr = u->host;
+    ifmissing = CURLUE_NO_HOST;
+    break;
+  case CURLUPART_ZONEID:
+    ptr = u->zoneid;
+    break;
+  case CURLUPART_PORT:
+    ptr = u->port;
+    ifmissing = CURLUE_NO_PORT;
+    urldecode = FALSE; /* never for port */
+    if(!ptr && (flags & CURLU_DEFAULT_PORT) && u->scheme) {
+      /* there's no stored port number, but asked to deliver
+         a default one for the scheme */
+      const struct Curl_handler *h =
+        Curl_builtin_scheme(u->scheme);
+      if(h) {
+        snprintf(portbuf, sizeof(portbuf), "%ld", h->defport);
+        ptr = portbuf;
+      }
+    }
+    else if(ptr && u->scheme) {
+      /* there is a stored port number, but ask to inhibit if
+         it matches the default one for the scheme */
+      const struct Curl_handler *h =
+        Curl_builtin_scheme(u->scheme);
+      if(h && (h->defport == u->portnum) &&
+         (flags & CURLU_NO_DEFAULT_PORT))
+        ptr = NULL;
+    }
+    break;
+  case CURLUPART_PATH:
+    ptr = u->path;
+    if(!ptr) {
+      ptr = u->path = strdup("/");
+      if(!u->path)
+        return CURLUE_OUT_OF_MEMORY;
+    }
+    break;
+  case CURLUPART_QUERY:
+    ptr = u->query;
+    ifmissing = CURLUE_NO_QUERY;
+    plusdecode = urldecode;
+    break;
+  case CURLUPART_FRAGMENT:
+    ptr = u->fragment;
+    ifmissing = CURLUE_NO_FRAGMENT;
+    break;
+  case CURLUPART_URL: {
+    char *url;
+    char *scheme;
+    char *options = u->options;
+    char *port = u->port;
+    char *allochost = NULL;
+    if(u->scheme && Curl_raw_equal("file", u->scheme)) {
+      url = aprintf("file://%s%s%s",
+                    u->path,
+                    u->fragment? "#": "",
+                    u->fragment? u->fragment : "");
+    }
+    else if(!u->host)
+      return CURLUE_NO_HOST;
+    else {
+      const struct Curl_handler *h = NULL;
+      if(u->scheme)
+        scheme = u->scheme;
+      else if(flags & CURLU_DEFAULT_SCHEME)
+        scheme = (char *) DEFAULT_SCHEME;
+      else
+        return CURLUE_NO_SCHEME;
+
+      h = Curl_builtin_scheme(scheme);
+      if(!port && (flags & CURLU_DEFAULT_PORT)) {
+        /* there's no stored port number, but asked to deliver
+           a default one for the scheme */
+        if(h) {
+          snprintf(portbuf, sizeof(portbuf), "%ld", h->defport);
+          port = portbuf;
+        }
+      }
+      else if(port) {
+        /* there is a stored port number, but asked to inhibit if it matches
+           the default one for the scheme */
+        if(h && (h->defport == u->portnum) &&
+           (flags & CURLU_NO_DEFAULT_PORT))
+          port = NULL;
+      }
+
+      if((u->host[0] == '[') && u->zoneid) {
+        /* make it '[ host %25 zoneid ]' */
+        size_t hostlen = strlen(u->host);
+        size_t alen = hostlen + 3 + strlen(u->zoneid) + 1;
+        allochost = malloc(alen);
+        if(!allochost)
+          return CURLUE_OUT_OF_MEMORY;
+        memcpy(allochost, u->host, hostlen - 1);
+        snprintf(&allochost[hostlen - 1], alen - hostlen + 1,
+                  "%%25%s]", u->zoneid);
+      }
+
+      url = aprintf("%s://%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
+                    scheme,
+                    u->user ? u->user : "",
+                    u->password ? ":": "",
+                    u->password ? u->password : "",
+                    options ? ";" : "",
+                    options ? options : "",
+                    (u->user || u->password || options) ? "@": "",
+                    allochost ? allochost : u->host,
+                    port ? ":": "",
+                    port ? port : "",
+                    (u->path && (u->path[0] != '/')) ? "/": "",
+                    u->path ? u->path : "/",
+                    (u->query && u->query[0]) ? "?": "",
+                    (u->query && u->query[0]) ? u->query : "",
+                    u->fragment? "#": "",
+                    u->fragment? u->fragment : "");
+      free(allochost);
+    }
+    if(!url)
+      return CURLUE_OUT_OF_MEMORY;
+    *part = url;
+    return CURLUE_OK;
+  }
+  default:
+    ptr = NULL;
+    break;
+  }
+  if(ptr) {
+    *part = strdup(ptr);
+    if(!*part)
+      return CURLUE_OUT_OF_MEMORY;
+    if(plusdecode) {
+      /* convert + to space */
+      char *plus;
+      for(plus = *part; *plus; ++plus) {
+        if(*plus == '+')
+          *plus = ' ';
+      }
+    }
+    if(urldecode) {
+      char *decoded;
+      size_t dlen;
+      CURLcode res = Curl_urldecode(NULL, *part, 0, &decoded, &dlen, TRUE);
+      free(*part);
+      if(res) {
+        *part = NULL;
+        return CURLUE_URLDECODE;
+      }
+      *part = decoded;
+    }
+    return CURLUE_OK;
+  }
+  else
+    return ifmissing;
+}
+
+CURLUcode curl_url_set(CURLU *u, CURLUPart what,
+                       const char *part, unsigned int flags)
+{
+  char **storep = NULL;
+  long port = 0;
+  bool urlencode = (flags & CURLU_URLENCODE)? 1 : 0;
+  bool plusencode = FALSE;
+  bool urlskipslash = FALSE;
+  bool appendquery = FALSE;
+  bool equalsencode = FALSE;
+
+  if(!u)
+    return CURLUE_BAD_HANDLE;
+  if(!part) {
+    /* setting a part to NULL clears it */
+    switch(what) {
+    case CURLUPART_URL:
+      break;
+    case CURLUPART_SCHEME:
+      storep = &u->scheme;
+      break;
+    case CURLUPART_USER:
+      storep = &u->user;
+      break;
+    case CURLUPART_PASSWORD:
+      storep = &u->password;
+      break;
+    case CURLUPART_OPTIONS:
+      storep = &u->options;
+      break;
+    case CURLUPART_HOST:
+      storep = &u->host;
+      break;
+    case CURLUPART_ZONEID:
+      storep = &u->zoneid;
+      break;
+    case CURLUPART_PORT:
+      u->portnum = 0;
+      storep = &u->port;
+      break;
+    case CURLUPART_PATH:
+      storep = &u->path;
+      break;
+    case CURLUPART_QUERY:
+      storep = &u->query;
+      break;
+    case CURLUPART_FRAGMENT:
+      storep = &u->fragment;
+      break;
+    default:
+      return CURLUE_UNKNOWN_PART;
+    }
+    if(storep && *storep) {
+      free(*storep);
+      *storep = NULL;
+    }
+    return CURLUE_OK;
+  }
+
+  switch(what) {
+  case CURLUPART_SCHEME:
+    if(strlen(part) > MAX_SCHEME_LEN)
+      /* too long */
+      return CURLUE_MALFORMED_INPUT;
+    if(!(flags & CURLU_NON_SUPPORT_SCHEME) &&
+       /* verify that it is a fine scheme */
+       !Curl_builtin_scheme(part))
+      return CURLUE_UNSUPPORTED_SCHEME;
+    storep = &u->scheme;
+    urlencode = FALSE; /* never */
+    break;
+  case CURLUPART_USER:
+    storep = &u->user;
+    break;
+  case CURLUPART_PASSWORD:
+    storep = &u->password;
+    break;
+  case CURLUPART_OPTIONS:
+    storep = &u->options;
+    break;
+  case CURLUPART_HOST:
+    storep = &u->host;
+    free(u->zoneid);
+    u->zoneid = NULL;
+    break;
+  case CURLUPART_ZONEID:
+    storep = &u->zoneid;
+    break;
+  case CURLUPART_PORT:
+  {
+    char *endp;
+    urlencode = FALSE; /* never */
+    port = strtol(part, &endp, 10);  /* Port number must be decimal */
+    if((port <= 0) || (port > 0xffff))
+      return CURLUE_BAD_PORT_NUMBER;
+    if(*endp)
+      /* weirdly provided number, not good! */
+      return CURLUE_MALFORMED_INPUT;
+    storep = &u->port;
+  }
+  break;
+  case CURLUPART_PATH:
+    urlskipslash = TRUE;
+    storep = &u->path;
+    break;
+  case CURLUPART_QUERY:
+    plusencode = urlencode;
+    appendquery = (flags & CURLU_APPENDQUERY)?1:0;
+    equalsencode = appendquery;
+    storep = &u->query;
+    break;
+  case CURLUPART_FRAGMENT:
+    storep = &u->fragment;
+    break;
+  case CURLUPART_URL: {
+    /*
+     * Allow a new URL to replace the existing (if any) contents.
+     *
+     * If the existing contents is enough for a URL, allow a relative URL to
+     * replace it.
+     */
+    CURLUcode result;
+    char *oldurl;
+    char *redired_url;
+    CURLU *handle2;
+
+    if(Curl_is_absolute_url(part, NULL, MAX_SCHEME_LEN + 1)) {
+      handle2 = curl_url();
+      if(!handle2)
+        return CURLUE_OUT_OF_MEMORY;
+      result = parseurl(part, handle2, flags);
+      if(!result)
+        mv_urlhandle(handle2, u);
+      else
+        curl_url_cleanup(handle2);
+      return result;
+    }
+    /* extract the full "old" URL to do the redirect on */
+    result = curl_url_get(u, CURLUPART_URL, &oldurl, flags);
+    if(result) {
+      /* couldn't get the old URL, just use the new! */
+      handle2 = curl_url();
+      if(!handle2)
+        return CURLUE_OUT_OF_MEMORY;
+      result = parseurl(part, handle2, flags);
+      if(!result)
+        mv_urlhandle(handle2, u);
+      else
+        curl_url_cleanup(handle2);
+      return result;
+    }
+
+    /* apply the relative part to create a new URL */
+    redired_url = concat_url(oldurl, part);
+    free(oldurl);
+    if(!redired_url)
+      return CURLUE_OUT_OF_MEMORY;
+
+    /* now parse the new URL */
+    handle2 = curl_url();
+    if(!handle2) {
+      free(redired_url);
+      return CURLUE_OUT_OF_MEMORY;
+    }
+    result = parseurl(redired_url, handle2, flags);
+    free(redired_url);
+    if(!result)
+      mv_urlhandle(handle2, u);
+    else
+      curl_url_cleanup(handle2);
+    return result;
+  }
+  default:
+    return CURLUE_UNKNOWN_PART;
+  }
+  DEBUGASSERT(storep);
+  {
+    const char *newp = part;
+    size_t nalloc = strlen(part);
+
+    if(nalloc > CURL_MAX_INPUT_LENGTH)
+      /* excessive input length */
+      return CURLUE_MALFORMED_INPUT;
+
+    if(urlencode) {
+      const unsigned char *i;
+      char *o;
+      bool free_part = FALSE;
+      char *enc = malloc(nalloc * 3 + 1); /* for worst case! */
+      if(!enc)
+        return CURLUE_OUT_OF_MEMORY;
+      if(plusencode) {
+        /* space to plus */
+        i = (const unsigned char *)part;
+        for(o = enc; *i; ++o, ++i)
+          *o = (*i == ' ') ? '+' : *i;
+        *o = 0; /* zero terminate */
+        part = strdup(enc);
+        if(!part) {
+          free(enc);
+          return CURLUE_OUT_OF_MEMORY;
+        }
+        free_part = TRUE;
+      }
+      for(i = (const unsigned char *)part, o = enc; *i; i++) {
+        if(Curl_isunreserved(*i) ||
+           ((*i == '/') && urlskipslash) ||
+           ((*i == '=') && equalsencode) ||
+           ((*i == '+') && plusencode)) {
+          if((*i == '=') && equalsencode)
+            /* only skip the first equals sign */
+            equalsencode = FALSE;
+          *o = *i;
+          o++;
+        }
+        else {
+          snprintf(o, 4, "%%%02x", *i);
+          o += 3;
+        }
+      }
+      *o = 0; /* zero terminate */
+      newp = enc;
+      if(free_part)
+        free((char *)part);
+    }
+    else {
+      char *p;
+      newp = strdup(part);
+      if(!newp)
+        return CURLUE_OUT_OF_MEMORY;
+      p = (char *)newp;
+      while(*p) {
+        /* make sure percent encoded are lower case */
+        if((*p == '%') && ISXDIGIT(p[1]) && ISXDIGIT(p[2]) &&
+           (ISUPPER(p[1]) || ISUPPER(p[2]))) {
+          p[1] = (char)TOLOWER(p[1]);
+          p[2] = (char)TOLOWER(p[2]);
+          p += 3;
+        }
+        else
+          p++;
+      }
+    }
+
+    if(appendquery) {
+      /* Append the string onto the old query. Add a '&' separator if none is
+         present at the end of the exsting query already */
+      size_t querylen = u->query ? strlen(u->query) : 0;
+      bool addamperand = querylen && (u->query[querylen -1] != '&');
+      if(querylen) {
+        size_t newplen = strlen(newp);
+        char *p = malloc(querylen + addamperand + newplen + 1);
+        if(!p) {
+          free((char *)newp);
+          return CURLUE_OUT_OF_MEMORY;
+        }
+        strcpy(p, u->query); /* original query */
+        if(addamperand)
+          p[querylen] = '&'; /* ampersand */
+        strcpy(&p[querylen + addamperand], newp); /* new suffix */
+        free((char *)newp);
+        free(*storep);
+        *storep = p;
+        return CURLUE_OK;
+      }
+    }
+
+    if(what == CURLUPART_HOST) {
+      if(0 == strlen(newp) && (flags & CURLU_NO_AUTHORITY)) {
+        /* Skip hostname check, it's allowed to be empty. */
+      }
+      else {
+        if(hostname_check(u, (char *)newp)) {
+          free((char *)newp);
+          return CURLUE_MALFORMED_INPUT;
+        }
+      }
+    }
+
+    free(*storep);
+    *storep = (char *)newp;
+  }
+  /* set after the string, to make it not assigned if the allocation above
+     fails */
+  if(port)
+    u->portnum = port;
+  return CURLUE_OK;
+}
--- a/lib/curl_setup_once.h
+++ b/lib/curl_setup_once.h
@@ -288,6 +288,7 @@ struct timeval {
 #define ISPRINT(x)  (isprint((int)  ((unsigned char)x)))
 #define ISUPPER(x)  (isupper((int)  ((unsigned char)x)))
 #define ISLOWER(x)  (islower((int)  ((unsigned char)x)))
+#define ISCNTRL(x)  (iscntrl((int)  ((unsigned char)x)))
 #define ISASCII(x)  (isascii((int)  ((unsigned char)x)))
 
 #define ISBLANK(x)  (int)((((unsigned char)x) == ' ') || \
--- a/lib/url.c
+++ b/lib/url.c
@@ -148,9 +148,6 @@ static CURLcode parse_url_login(struct S
                                 struct connectdata *conn,
                                 char **userptr, char **passwdptr,
                                 char **optionsptr);
-static CURLcode parse_login_details(const char *login, const size_t len,
-                                    char **userptr, char **passwdptr,
-                                    char **optionsptr);
 /*
  * Protocol table.
  */
@@ -325,7 +322,7 @@ static CURLcode setstropt_userpwd(char *
   /* Parse the login details if specified. It not then we treat NULL as a hint
      to clear the existing data */
   if(option) {
-    result = parse_login_details(option, strlen(option),
+    result = Curl_parse_login_details(option, strlen(option),
                                  (userp ? &user : NULL),
                                  (passwdp ? &passwd : NULL),
                                  NULL);
@@ -3954,30 +3951,37 @@ static struct connectdata *allocate_conn
   return NULL;
 }
 
-static CURLcode findprotocol(struct SessionHandle *data,
-                             struct connectdata *conn,
-                             const char *protostr)
+/* returns the handler if the given scheme is built-in */
+const struct Curl_handler *Curl_builtin_scheme(const char *scheme)
 {
   const struct Curl_handler * const *pp;
   const struct Curl_handler *p;
-
-  /* Scan protocol handler table and match against 'protostr' to set a few
-     variables based on the URL. Now that the handler may be changed later
-     when the protocol specific setup function is called. */
-  for(pp = protocols; (p = *pp) != NULL; pp++) {
-    if(Curl_raw_equal(p->scheme, protostr)) {
+  /* Scan protocol handler table and match against 'scheme'. The handler may
+     be changed later when the protocol specific setup function is called. */
+  for(pp = protocols; (p = *pp) != NULL; pp++)
+    if(Curl_raw_equal(p->scheme, scheme))
       /* Protocol found in table. Check if allowed */
-      if(!(data->set.allowed_protocols & p->protocol))
-        /* nope, get out */
-        break;
+      return p;
+  return NULL; /* not found */
+}
 
-      /* it is allowed for "normal" request, now do an extra check if this is
-         the result of a redirect */
-      if(data->state.this_is_a_follow &&
-         !(data->set.redir_protocols & p->protocol))
-        /* nope, get out */
-        break;
 
+static CURLcode findprotocol(struct SessionHandle *data,
+                             struct connectdata *conn,
+                             const char *protostr)
+{
+  const struct Curl_handler *p = Curl_builtin_scheme(protostr);
+
+  if(p && /* Protocol found in table. Check if allowed */
+     (data->set.allowed_protocols & p->protocol)) {
+
+    /* it is allowed for "normal" request, now do an extra check if this is
+       the result of a redirect */
+    if(data->state.this_is_a_follow &&
+       !(data->set.redir_protocols & p->protocol))
+      /* nope, get out */
+      ;
+    else {
       /* Perform setup complement if some. */
       conn->handler = conn->given = p;
 
@@ -4644,7 +4648,7 @@ static CURLcode parse_proxy(struct Sessi
     char *proxyuser = NULL;
     char *proxypasswd = NULL;
     CURLcode result =
-      parse_login_details(proxyptr, atsign - proxyptr,
+      Curl_parse_login_details(proxyptr, atsign - proxyptr,
                           &proxyuser, &proxypasswd, NULL);
     if(!result) {
       /* found user and password, rip them out.  note that we are
@@ -4855,7 +4859,7 @@ static CURLcode parse_url_login(struct S
     goto out;
 
   /* We could use the login information in the URL so extract it */
-  result = parse_login_details(login, ptr - login - 1,
+  result = Curl_parse_login_details(login, ptr - login - 1,
                                &userp, &passwdp, &optionsp);
   if(result)
     goto out;
@@ -4913,7 +4917,7 @@ static CURLcode parse_url_login(struct S
 }
 
 /*
- * parse_login_details()
+ * Curl_parse_login_details()
  *
  * This is used to parse a login string for user name, password and options in
  * the following formats:
@@ -4941,9 +4945,9 @@ static CURLcode parse_url_login(struct S
  *
  * Returns CURLE_OK on success.
  */
-static CURLcode parse_login_details(const char *login, const size_t len,
-                                    char **userp, char **passwdp,
-                                    char **optionsp)
+CURLcode Curl_parse_login_details(const char *login, const size_t len,
+                                  char **userp, char **passwdp,
+                                  char **optionsp)
 {
   CURLcode result = CURLE_OK;
   char *ubuf = NULL;
--- a/lib/url.h
+++ b/lib/url.h
@@ -54,6 +54,9 @@ int Curl_protocol_getsock(struct connect
 int Curl_doing_getsock(struct connectdata *conn,
                        curl_socket_t *socks,
                        int numsocks);
+CURLcode Curl_parse_login_details(const char *login, const size_t len,
+                                  char **userptr, char **passwdptr,
+                                  char **optionsptr);
 
 bool Curl_isPipeliningEnabled(const struct SessionHandle *handle);
 CURLcode Curl_addHandleToPipeline(struct SessionHandle *handle,
@@ -67,6 +70,8 @@ void Curl_getoff_all_pipelines(struct Se
 
 void Curl_close_connections(struct SessionHandle *data);
 
+const struct Curl_handler *Curl_builtin_scheme(const char *scheme);
+
 #define CURL_DEFAULT_PROXY_PORT 1080 /* default proxy port unless specified */
 #define CURL_DEFAULT_SOCKS5_GSSAPI_SERVICE "rcmd" /* default socks5 gssapi
                                                      service */
--- a/lib/escape.c
+++ b/lib/escape.c
@@ -41,7 +41,7 @@
    its behavior is altered by the current locale.
    See http://tools.ietf.org/html/rfc3986#section-2.3
 */
-static bool Curl_isunreserved(unsigned char in)
+bool Curl_isunreserved(unsigned char in)
 {
   switch (in) {
     case '0': case '1': case '2': case '3': case '4':
--- a/lib/escape.h
+++ b/lib/escape.h
@@ -24,6 +24,7 @@
 /* Escape and unescape URL encoding in strings. The functions return a new
  * allocated string or NULL if an error occurred.  */
 
+bool Curl_isunreserved(unsigned char in);
 CURLcode Curl_urldecode(struct SessionHandle *data,
                         const char *string, size_t length,
                         char **ostring, size_t *olen,
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -643,6 +643,35 @@ CURLSSLBACKEND_QSOSSL           7.34.0
 CURLSSLBACKEND_SCHANNEL         7.34.0
 CURLSSLOPT_ALLOW_BEAST          7.25.0
 CURLSSLOPT_NO_REVOKE            7.44.0
+CURLUE_BAD_HANDLE               7.62.0
+CURLUE_BAD_PARTPOINTER          7.62.0
+CURLUE_BAD_PORT_NUMBER          7.62.0
+CURLUE_MALFORMED_INPUT          7.62.0
+CURLUE_NO_FRAGMENT              7.62.0
+CURLUE_NO_HOST                  7.62.0
+CURLUE_NO_OPTIONS               7.62.0
+CURLUE_NO_PASSWORD              7.62.0
+CURLUE_NO_PORT                  7.62.0
+CURLUE_NO_QUERY                 7.62.0
+CURLUE_NO_SCHEME                7.62.0
+CURLUE_NO_USER                  7.62.0
+CURLUE_OK                       7.62.0
+CURLUE_OUT_OF_MEMORY            7.62.0
+CURLUE_UNKNOWN_PART             7.62.0
+CURLUE_UNSUPPORTED_SCHEME       7.62.0
+CURLUE_URLDECODE                7.62.0
+CURLUE_USER_NOT_ALLOWED         7.62.0
+CURLUPART_FRAGMENT              7.62.0
+CURLUPART_HOST                  7.62.0
+CURLUPART_OPTIONS               7.62.0
+CURLUPART_PASSWORD              7.62.0
+CURLUPART_PATH                  7.62.0
+CURLUPART_PORT                  7.62.0
+CURLUPART_QUERY                 7.62.0
+CURLUPART_SCHEME                7.62.0
+CURLUPART_URL                   7.62.0
+CURLUPART_USER                  7.62.0
+CURLUPART_ZONEID                7.65.0
 CURLUSESSL_ALL                  7.17.0
 CURLUSESSL_CONTROL              7.17.0
 CURLUSESSL_NONE                 7.17.0
Backport of:

From 3dec1183be112e587f89edc059c1c11cf8fdc0ae Mon Sep 17 00:00:00 2001
From: Viktor Szakats <commit@vsz.me>
Date: Tue, 23 Feb 2021 14:54:46 +0100
Subject: [PATCH] transfer: strip credentials from the auto-referer header
 field

Added test 2081 to verify.

CVE-2021-22876

Bug: https://curl.se/docs/CVE-2021-22876.html
---
 lib/transfer.c          | 25 ++++++++++++++--
 tests/data/Makefile.inc |  2 +-
 tests/data/test2081     | 66 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+), 3 deletions(-)
 create mode 100644 tests/data/test2081

--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -1665,6 +1665,7 @@ CURLcode Curl_follow(struct SessionHandl
 
   /* Location: redirect */
   bool disallowport = FALSE;
+  CURLUcode uc;
 
   if(type == FOLLOW_REDIR) {
     if((data->set.maxredirs != -1) &&
@@ -1679,6 +1680,9 @@ CURLcode Curl_follow(struct SessionHandl
     data->set.followlocation++; /* count location-followers */
 
     if(data->set.http_auto_referer) {
+        CURLU *u;
+        char *referer;
+
       /* We are asked to automatically set the previous URL as the referer
          when we get the next URL. We pick the ->url field, which may or may
          not be 100% correct */
@@ -1688,9 +1692,27 @@ CURLcode Curl_follow(struct SessionHandl
         data->change.referer_alloc = FALSE;
       }
 
-      data->change.referer = strdup(data->change.url);
-      if(!data->change.referer)
+      /* Make a copy of the URL without crenditals and fragment */
+      u = curl_url();
+      if(!u)
+        return CURLE_OUT_OF_MEMORY;
+
+      uc = curl_url_set(u, CURLUPART_URL, data->change.url, 0);
+      if(!uc)
+        uc = curl_url_set(u, CURLUPART_FRAGMENT, NULL, 0);
+      if(!uc)
+        uc = curl_url_set(u, CURLUPART_USER, NULL, 0);
+      if(!uc)
+        uc = curl_url_set(u, CURLUPART_PASSWORD, NULL, 0);
+      if(!uc)
+        uc = curl_url_get(u, CURLUPART_URL, &referer, 0);
+
+      curl_url_cleanup(u);
+
+      if(uc || referer == NULL)
         return CURLE_OUT_OF_MEMORY;
+
+      data->change.referer = referer;
       data->change.referer_alloc = TRUE; /* yes, free this later */
     }
   }

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