/***************************************************************************

 *                                  _   _ ____  _

 *  Project                     ___| | | |  _ \| |

 *                             / __| | | | |_) | |

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) 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.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.

 *

 * SPDX-License-Identifier: curl

 *

 ***************************************************************************/

/*

 * The Alt-Svc: header is defined in RFC 7838:

 * https://datatracker.ietf.org/doc/html/rfc7838

 */

#include "curl_setup.h"

#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_ALTSVC)

#include <curl/curl.h>

#include "urldata.h"

#include "altsvc.h"

#include "curl_get_line.h"

#include "parsedate.h"

#include "sendf.h"

#include "curlx/warnless.h"

#include "fopen.h"

#include "rename.h"

#include "strdup.h"

#include "curlx/inet_pton.h"

#include "curlx/strparse.h"

#include "connect.h"

/* The last 3 #include files should be in this order */

#include "curl_printf.h"

#include "curl_memory.h"

#include "memdebug.h"

#define MAX_ALTSVC_LINE 4095

#define MAX_ALTSVC_DATELEN 256

#define MAX_ALTSVC_HOSTLEN 2048

#define MAX_ALTSVC_ALPNLEN 10

#define H3VERSION "h3"

/* Given the ALPN ID, return the name */

const char *Curl_alpnid2str(enum alpnid id)

{

  switch(id) {

  case ALPN_h1:

    return "h1";

  case ALPN_h2:

    return "h2";

  case ALPN_h3:

    return H3VERSION;

  default:

    return ""; /* bad */

  }

}

static void altsvc_free(struct altsvc *as)

{

  free(as->src.host);

  free(as->dst.host);

  free(as);

}

static struct altsvc *altsvc_createid(const char *srchost,

                                      size_t hlen,

                                      const char *dsthost,

                                      size_t dlen, /* dsthost length */

                                      enum alpnid srcalpnid,

                                      enum alpnid dstalpnid,

                                      size_t srcport,

                                      size_t dstport)

{

  struct altsvc *as = calloc(1, sizeof(struct altsvc));

  if(!as)

    return NULL;

  DEBUGASSERT(hlen);

  DEBUGASSERT(dlen);

  if(!hlen || !dlen)

    /* bad input */

    goto error;

  if((hlen > 2) && srchost[0] == '[') {

    /* IPv6 address, strip off brackets */

    srchost++;

    hlen -= 2;

  }

  else if(srchost[hlen - 1] == '.') {

    /* strip off trailing dot */

    hlen--;

    if(!hlen)

      goto error;

  }

  if((dlen > 2) && dsthost[0] == '[') {

    /* IPv6 address, strip off brackets */

    dsthost++;

    dlen -= 2;

  }

  as->src.host = Curl_memdup0(srchost, hlen);

  if(!as->src.host)

    goto error;

  as->dst.host = Curl_memdup0(dsthost, dlen);

  if(!as->dst.host)

    goto error;

  as->src.alpnid = srcalpnid;

  as->dst.alpnid = dstalpnid;

  as->src.port = (unsigned short)srcport;

  as->dst.port = (unsigned short)dstport;

  return as;

error:

  altsvc_free(as);

  return NULL;

}

static struct altsvc *altsvc_create(struct Curl_str *srchost,

                                    struct Curl_str *dsthost,

                                    struct Curl_str *srcalpn,

                                    struct Curl_str *dstalpn,

                                    size_t srcport,

                                    size_t dstport)

{

  enum alpnid dstalpnid =

    Curl_alpn2alpnid(curlx_str(dstalpn), curlx_strlen(dstalpn));

  enum alpnid srcalpnid =

    Curl_alpn2alpnid(curlx_str(srcalpn), curlx_strlen(srcalpn));

  if(!srcalpnid || !dstalpnid)

    return NULL;

  return altsvc_createid(curlx_str(srchost), curlx_strlen(srchost),

                         curlx_str(dsthost), curlx_strlen(dsthost),

                         srcalpnid, dstalpnid,

                         srcport, dstport);

}

/* only returns SERIOUS errors */

static CURLcode altsvc_add(struct altsvcinfo *asi, const char *line)

{

  /* Example line:

     h2 example.com 443 h3 shiny.example.com 8443 "20191231 10:00:00" 1

   */

  struct Curl_str srchost;

  struct Curl_str dsthost;

  struct Curl_str srcalpn;

  struct Curl_str dstalpn;

  struct Curl_str date;

  curl_off_t srcport;

  curl_off_t dstport;

  curl_off_t persist;

  curl_off_t prio;

  if(curlx_str_word(&line, &srcalpn, MAX_ALTSVC_ALPNLEN) ||

     curlx_str_singlespace(&line) ||

     curlx_str_word(&line, &srchost, MAX_ALTSVC_HOSTLEN) ||

     curlx_str_singlespace(&line) ||

     curlx_str_number(&line, &srcport, 65535) ||

     curlx_str_singlespace(&line) ||

     curlx_str_word(&line, &dstalpn, MAX_ALTSVC_ALPNLEN) ||

     curlx_str_singlespace(&line) ||

     curlx_str_word(&line, &dsthost, MAX_ALTSVC_HOSTLEN) ||

     curlx_str_singlespace(&line) ||

     curlx_str_number(&line, &dstport, 65535) ||

     curlx_str_singlespace(&line) ||

     curlx_str_quotedword(&line, &date, MAX_ALTSVC_DATELEN) ||

     curlx_str_singlespace(&line) ||

     curlx_str_number(&line, &persist, 1) ||

     curlx_str_singlespace(&line) ||

     curlx_str_number(&line, &prio, 0) ||

     curlx_str_newline(&line))

    ;

  else {

    struct altsvc *as;

    char dbuf[MAX_ALTSVC_DATELEN + 1];

    time_t expires;

    /* The date parser works on a null-terminated string. The maximum length

       is upheld by curlx_str_quotedword(). */

    memcpy(dbuf, curlx_str(&date), curlx_strlen(&date));

    dbuf[curlx_strlen(&date)] = 0;

    expires = Curl_getdate_capped(dbuf);

    as = altsvc_create(&srchost, &dsthost, &srcalpn, &dstalpn,

                       (size_t)srcport, (size_t)dstport);

    if(as) {

      as->expires = expires;

      as->prio = 0; /* not supported to just set zero */

      as->persist = persist ? 1 : 0;

      Curl_llist_append(&asi->list, as, &as->node);

    }

  }

  return CURLE_OK;

}

/*

 * Load alt-svc entries from the given file. The text based line-oriented file

 * format is documented here: https://curl.se/docs/alt-svc.html

 *

 * This function only returns error on major problems that prevent alt-svc

 * handling to work completely. It will ignore individual syntactical errors

 * etc.

 */

static CURLcode altsvc_load(struct altsvcinfo *asi, const char *file)

{

  CURLcode result = CURLE_OK;

  FILE *fp;

  /* we need a private copy of the filename so that the altsvc cache file

     name survives an easy handle reset */

  free(asi->filename);

  asi->filename = strdup(file);

  if(!asi->filename)

    return CURLE_OUT_OF_MEMORY;

  fp = fopen(file, FOPEN_READTEXT);

  if(fp) {

    struct dynbuf buf;

    curlx_dyn_init(&buf, MAX_ALTSVC_LINE);

    while(Curl_get_line(&buf, fp)) {

      const char *lineptr = curlx_dyn_ptr(&buf);

      curlx_str_passblanks(&lineptr);

      if(curlx_str_single(&lineptr, '#'))

        altsvc_add(asi, lineptr);

    }

    curlx_dyn_free(&buf); /* free the line buffer */

    fclose(fp);

  }

  return result;

}

/*

 * Write this single altsvc entry to a single output line

 */

static CURLcode altsvc_out(struct altsvc *as, FILE *fp)

{

  struct tm stamp;

  const char *dst6_pre = "";

  const char *dst6_post = "";

  const char *src6_pre = "";

  const char *src6_post = "";

  CURLcode result = Curl_gmtime(as->expires, &stamp);

  if(result)

    return result;

#ifdef USE_IPV6

  else {

    char ipv6_unused[16];

    if(1 == curlx_inet_pton(AF_INET6, as->dst.host, ipv6_unused)) {

      dst6_pre = "[";

      dst6_post = "]";

    }

    if(1 == curlx_inet_pton(AF_INET6, as->src.host, ipv6_unused)) {

      src6_pre = "[";

      src6_post = "]";

    }

  }

#endif

  fprintf(fp,

          "%s %s%s%s %u "

          "%s %s%s%s %u "

          "\"%d%02d%02d "

          "%02d:%02d:%02d\" "

          "%u %u\n",

          Curl_alpnid2str(as->src.alpnid),

          src6_pre, as->src.host, src6_post,

          as->src.port,

          Curl_alpnid2str(as->dst.alpnid),

          dst6_pre, as->dst.host, dst6_post,

          as->dst.port,

          stamp.tm_year + 1900, stamp.tm_mon + 1, stamp.tm_mday,

          stamp.tm_hour, stamp.tm_min, stamp.tm_sec,

          as->persist, as->prio);

  return CURLE_OK;

}

/* ---- library-wide functions below ---- */

/*

 * Curl_altsvc_init() creates a new altsvc cache.

 * It returns the new instance or NULL if something goes wrong.

 */

struct altsvcinfo *Curl_altsvc_init(void)

{

  struct altsvcinfo *asi = calloc(1, sizeof(struct altsvcinfo));

  if(!asi)

    return NULL;

  Curl_llist_init(&asi->list, NULL);

  /* set default behavior */

  asi->flags = CURLALTSVC_H1

#ifdef USE_HTTP2

    | CURLALTSVC_H2

#endif

#ifdef USE_HTTP3

    | CURLALTSVC_H3

#endif

    ;

  return asi;

}

/*

 * Curl_altsvc_load() loads alt-svc from file.

 */

CURLcode Curl_altsvc_load(struct altsvcinfo *asi, const char *file)

{

  DEBUGASSERT(asi);

  return altsvc_load(asi, file);

}

/*

 * Curl_altsvc_ctrl() passes on the external bitmask.

 */

CURLcode Curl_altsvc_ctrl(struct altsvcinfo *asi, const long ctrl)

{

  DEBUGASSERT(asi);

  asi->flags = ctrl;

  return CURLE_OK;

}

/*

 * Curl_altsvc_cleanup() frees an altsvc cache instance and all associated

 * resources.

 */

void Curl_altsvc_cleanup(struct altsvcinfo **altsvcp)

{

  if(*altsvcp) {

    struct Curl_llist_node *e;

    struct Curl_llist_node *n;

    struct altsvcinfo *altsvc = *altsvcp;

    for(e = Curl_llist_head(&altsvc->list); e; e = n) {

      struct altsvc *as = Curl_node_elem(e);

      n = Curl_node_next(e);

      altsvc_free(as);

    }

    free(altsvc->filename);

    free(altsvc);

    *altsvcp = NULL; /* clear the pointer */

  }

}

/*

 * Curl_altsvc_save() writes the altsvc cache to a file.

 */

CURLcode Curl_altsvc_save(struct Curl_easy *data,

                          struct altsvcinfo *altsvc, const char *file)

{

  CURLcode result = CURLE_OK;

  FILE *out;

  char *tempstore = NULL;

  if(!altsvc)

    /* no cache activated */

    return CURLE_OK;

  /* if not new name is given, use the one we stored from the load */

  if(!file && altsvc->filename)

    file = altsvc->filename;

  if((altsvc->flags & CURLALTSVC_READONLYFILE) || !file || !file[0])

    /* marked as read-only, no file or zero length filename */

    return CURLE_OK;

  result = Curl_fopen(data, file, &out, &tempstore);

  if(!result) {

    struct Curl_llist_node *e;

    struct Curl_llist_node *n;

    fputs("# Your alt-svc cache. https://curl.se/docs/alt-svc.html\n"

          "# This file was generated by libcurl! Edit at your own risk.\n",

          out);

    for(e = Curl_llist_head(&altsvc->list); e; e = n) {

      struct altsvc *as = Curl_node_elem(e);

      n = Curl_node_next(e);

      result = altsvc_out(as, out);

      if(result)

        break;

    }

    fclose(out);

    if(!result && tempstore && Curl_rename(tempstore, file))

      result = CURLE_WRITE_ERROR;

    if(result && tempstore)

      unlink(tempstore);

  }

  free(tempstore);

  return result;

}

/* hostcompare() returns true if 'host' matches 'check'. The first host

 * argument may have a trailing dot present that will be ignored.

 */

static bool hostcompare(const char *host, const char *check)

{

  size_t hlen = strlen(host);

  size_t clen = strlen(check);

  if(hlen && (host[hlen - 1] == '.'))

    hlen--;

  if(hlen != clen)

    /* they cannot match if they have different lengths */

    return FALSE;

  return curl_strnequal(host, check, hlen);

}

/* altsvc_flush() removes all alternatives for this source origin from the

   list */

static void altsvc_flush(struct altsvcinfo *asi, enum alpnid srcalpnid,

                         const char *srchost, unsigned short srcport)

{

  struct Curl_llist_node *e;

  struct Curl_llist_node *n;

  for(e = Curl_llist_head(&asi->list); e; e = n) {

    struct altsvc *as = Curl_node_elem(e);

    n = Curl_node_next(e);

    if((srcalpnid == as->src.alpnid) &&

       (srcport == as->src.port) &&

       hostcompare(srchost, as->src.host)) {

      Curl_node_remove(e);

      altsvc_free(as);

    }

  }

}

#if defined(DEBUGBUILD) || defined(UNITTESTS)

/* to play well with debug builds, we can *set* a fixed time this will

   return */

static time_t altsvc_debugtime(void *unused)

{

  const char *timestr = getenv("CURL_TIME");

  (void)unused;

  if(timestr) {

    curl_off_t val;

    curlx_str_number(&timestr, &val, TIME_T_MAX);

    return (time_t)val;

  }

  return time(NULL);

}

#undef time

#define time(x) altsvc_debugtime(x)

#endif

/*

 * Curl_altsvc_parse() takes an incoming alt-svc response header and stores

 * the data correctly in the cache.

 *

 * 'value' points to the header *value*. That is contents to the right of the

 * header name.

 *

 * Currently this function rejects invalid data without returning an error.

 * Invalid hostname, port number will result in the specific alternative

 * being rejected. Unknown protocols are skipped.

 */

CURLcode Curl_altsvc_parse(struct Curl_easy *data,

                           struct altsvcinfo *asi, const char *value,

                           enum alpnid srcalpnid, const char *srchost,

                           unsigned short srcport)

{

  const char *p = value;

  struct altsvc *as;

  unsigned short dstport = srcport; /* the same by default */

  size_t entries = 0;

  struct Curl_str alpn;

  const char *sp;

  time_t maxage = 24 * 3600; /* default is 24 hours */

  bool persist = FALSE;

#ifdef CURL_DISABLE_VERBOSE_STRINGS

  (void)data;

#endif

  DEBUGASSERT(asi);

  /* initial check for "clear" */

  if(!curlx_str_until(&p, &alpn, MAX_ALTSVC_LINE, ';') &&

     !curlx_str_single(&p, ';')) {

    curlx_str_trimblanks(&alpn);

    /* "clear" is a magic keyword */

    if(curlx_str_casecompare(&alpn, "clear")) {

      /* Flush cached alternatives for this source origin */

      altsvc_flush(asi, srcalpnid, srchost, srcport);

      return CURLE_OK;

    }

  }

  p = value;

  if(curlx_str_until(&p, &alpn, MAX_ALTSVC_LINE, '='))

    return CURLE_OK; /* strange line */

  curlx_str_trimblanks(&alpn);

  /* Handle the optional 'ma' and 'persist' flags once first, as they need to

     be known for each alternative service. Unknown flags are skipped. */

  sp = strchr(p, ';');

  if(sp) {

    sp++; /* pass the semicolon */

    for(;;) {

      struct Curl_str name;

      struct Curl_str val;

      const char *vp;

      curl_off_t num;

      bool quoted;

      /* allow some extra whitespaces around name and value */

      if(curlx_str_until(&sp, &name, 20, '=') ||

         curlx_str_single(&sp, '=') ||

         curlx_str_until(&sp, &val, 80, ';'))

        break;

      curlx_str_trimblanks(&name);

      curlx_str_trimblanks(&val);

      /* the value might be quoted */

      vp = curlx_str(&val);

      quoted = (*vp == '\"');

      if(quoted)

        vp++;

      if(!curlx_str_number(&vp, &num, TIME_T_MAX)) {

        if(curlx_str_casecompare(&name, "ma"))

          maxage = (time_t)num;

        else if(curlx_str_casecompare(&name, "persist") && (num == 1))

          persist = TRUE;

      }

      if(quoted && curlx_str_single(&sp, '\"'))

        break;

      if(curlx_str_single(&sp, ';'))

        break;

    }

  }

  do {

    if(!curlx_str_single(&p, '=')) {

      /* [protocol]="[host][:port], [protocol]="[host][:port]" */

      enum alpnid dstalpnid =

        Curl_alpn2alpnid(curlx_str(&alpn), curlx_strlen(&alpn));

      if(!curlx_str_single(&p, '\"')) {

        struct Curl_str dsthost;

        curl_off_t port = 0;

        if(curlx_str_single(&p, ':')) {

          /* hostname starts here */

          if(curlx_str_single(&p, '[')) {

            if(curlx_str_until(&p, &dsthost, MAX_ALTSVC_HOSTLEN, ':')) {

              infof(data, "Bad alt-svc hostname, ignoring.");

              break;

            }

          }

          else {

            /* IPv6 host name */

            if(curlx_str_until(&p, &dsthost, MAX_IPADR_LEN, ']') ||

               curlx_str_single(&p, ']')) {

              infof(data, "Bad alt-svc IPv6 hostname, ignoring.");

              break;

            }

          }

          if(curlx_str_single(&p, ':'))

            break;

        }

        else

          /* no destination name, use source host */

          curlx_str_assign(&dsthost, srchost, strlen(srchost));

        if(curlx_str_number(&p, &port, 0xffff)) {

          infof(data, "Unknown alt-svc port number, ignoring.");

          break;

        }

        dstport = (unsigned short)port;

        if(curlx_str_single(&p, '\"'))

          break;

        if(dstalpnid) {

          if(!entries++)

            /* Flush cached alternatives for this source origin, if any - when

               this is the first entry of the line. */

            altsvc_flush(asi, srcalpnid, srchost, srcport);

          as = altsvc_createid(srchost, strlen(srchost),

                               curlx_str(&dsthost),

                               curlx_strlen(&dsthost),

                               srcalpnid, dstalpnid,

                               srcport, dstport);

          if(as) {

            time_t secs = time(NULL);

            /* The expires time also needs to take the Age: value (if any)

               into account. [See RFC 7838 section 3.1] */

            if(maxage > (TIME_T_MAX - secs))

              as->expires = TIME_T_MAX;

            else

              as->expires = maxage + secs;

            as->persist = persist;

            Curl_llist_append(&asi->list, as, &as->node);

            infof(data, "Added alt-svc: %.*s:%d over %s",

                  (int)curlx_strlen(&dsthost), curlx_str(&dsthost),

                  dstport, Curl_alpnid2str(dstalpnid));

          }

        }

      }

      else

        break;

      /* after the double quote there can be a comma if there is another

         string or a semicolon if no more */

      if(curlx_str_single(&p, ','))

        break;

      /* comma means another alternative is present */

      if(curlx_str_until(&p, &alpn, MAX_ALTSVC_LINE, '='))

        break;

      curlx_str_trimblanks(&alpn);

    }

    else

      break;

  } while(1);

  return CURLE_OK;

}

/*

 * Return TRUE on a match

 */

bool Curl_altsvc_lookup(struct altsvcinfo *asi,

                        enum alpnid srcalpnid, const char *srchost,

                        int srcport,

                        struct altsvc **dstentry,

                        const int versions) /* one or more bits */

{

  struct Curl_llist_node *e;

  struct Curl_llist_node *n;

  time_t now = time(NULL);

  DEBUGASSERT(asi);

  DEBUGASSERT(srchost);

  DEBUGASSERT(dstentry);

  for(e = Curl_llist_head(&asi->list); e; e = n) {

    struct altsvc *as = Curl_node_elem(e);

    n = Curl_node_next(e);

    if(as->expires < now) {

      /* an expired entry, remove */

      Curl_node_remove(e);

      altsvc_free(as);

      continue;

    }

    if((as->src.alpnid == srcalpnid) &&

       hostcompare(srchost, as->src.host) &&

       (as->src.port == srcport) &&

       (versions & (int)as->dst.alpnid)) {

      /* match */

      *dstentry = as;

      return TRUE;

    }

  }

  return FALSE;

}

#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_ALTSVC */