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

 *                                  _   _ ____  _

 *  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 "strcase.h"

#include "parsedate.h"

#include "sendf.h"

#include "warnless.h"

#include "fopen.h"

#include "rename.h"

#include "strdup.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"

#define MAX_ALTSVC_LINE 4095

#define MAX_ALTSVC_DATELENSTR "64"

#define MAX_ALTSVC_DATELEN 64

#define MAX_ALTSVC_HOSTLENSTR "512"

#define MAX_ALTSVC_HOSTLEN 512

#define MAX_ALTSVC_ALPNLENSTR "10"

#define MAX_ALTSVC_ALPNLEN 10

#define H3VERSION "h3"

static enum alpnid alpn2alpnid(char *name)

{

  if(strcasecompare(name, "h1"))

    return ALPN_h1;

  if(strcasecompare(name, "h2"))

    return ALPN_h2;

  if(strcasecompare(name, H3VERSION))

    return ALPN_h3;

  return ALPN_none; /* unknown, probably rubbish input */

}

/* 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,

                                      const char *dsthost,

                                      enum alpnid srcalpnid,

                                      enum alpnid dstalpnid,

                                      unsigned int srcport,

                                      unsigned int dstport)

{

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

  size_t hlen;

  size_t dlen;

  if(!as)

    return NULL;

  hlen = strlen(srchost);

  dlen = strlen(dsthost);

  DEBUGASSERT(hlen);

  DEBUGASSERT(dlen);

  if(!hlen || !dlen) {

    /* bad input */

    free(as);

    return NULL;

  }

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

    /* IPv6 address, strip off brackets */

    srchost++;

    hlen -= 2;

  }

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

    /* strip off trailing dot */

    hlen--;

  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 = curlx_ultous(srcport);

  as->dst.port = curlx_ultous(dstport);

  return as;

error:

  altsvc_free(as);

  return NULL;

}

static struct altsvc *altsvc_create(char *srchost,

                                    char *dsthost,

                                    char *srcalpn,

                                    char *dstalpn,

                                    unsigned int srcport,

                                    unsigned int dstport)

{

  enum alpnid dstalpnid = alpn2alpnid(dstalpn);

  enum alpnid srcalpnid = alpn2alpnid(srcalpn);

  if(!srcalpnid || !dstalpnid)

    return NULL;

  return altsvc_createid(srchost, dsthost, srcalpnid, dstalpnid,

                         srcport, dstport);

}

/* only returns SERIOUS errors */

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

{

  /* Example line:

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

   */

  char srchost[MAX_ALTSVC_HOSTLEN + 1];

  char dsthost[MAX_ALTSVC_HOSTLEN + 1];

  char srcalpn[MAX_ALTSVC_ALPNLEN + 1];

  char dstalpn[MAX_ALTSVC_ALPNLEN + 1];

  char date[MAX_ALTSVC_DATELEN + 1];

  unsigned int srcport;

  unsigned int dstport;

  unsigned int prio;

  unsigned int persist;

  int rc;

  rc = sscanf(line,

              "%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "

              "%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "

              "\"%" MAX_ALTSVC_DATELENSTR "[^\"]\" %u %u",

              srcalpn, srchost, &srcport,

              dstalpn, dsthost, &dstport,

              date, &persist, &prio);

  if(9 == rc) {

    struct altsvc *as;

    time_t expires = Curl_getdate_capped(date);

    as = altsvc_create(srchost, dsthost, srcalpn, dstalpn, srcport, dstport);

    if(as) {

      as->expires = expires;

      as->prio = prio;

      as->persist = persist ? 1 : 0;

      Curl_llist_insert_next(&asi->list, asi->list.tail, 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 file name 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;

    Curl_dyn_init(&buf, MAX_ALTSVC_LINE);

    while(Curl_get_line(&buf, fp)) {

      char *lineptr = Curl_dyn_ptr(&buf);

      while(*lineptr && ISBLANK(*lineptr))

        lineptr++;

      if(*lineptr == '#')

        /* skip commented lines */

        continue;

      altsvc_add(asi, lineptr);

    }

    Curl_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 ENABLE_IPV6

  else {

    char ipv6_unused[16];

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

      dst6_pre = "[";

      dst6_post = "]";

    }

    if(1 == Curl_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 %d\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 ENABLE_QUIC

    | CURLALTSVC_H3

#endif

    ;

  return asi;

}

/*

 * Curl_altsvc_load() loads alt-svc from file.

 */

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

{

  CURLcode result;

  DEBUGASSERT(asi);

  result = altsvc_load(asi, file);

  return result;

}

/*

 * 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)

{

  struct Curl_llist_element *e;

  struct Curl_llist_element *n;

  if(*altsvcp) {

    struct altsvcinfo *altsvc = *altsvcp;

    for(e = altsvc->list.head; e; e = n) {

      struct altsvc *as = e->ptr;

      n = e->next;

      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)

{

  struct Curl_llist_element *e;

  struct Curl_llist_element *n;

  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 file name */

    return CURLE_OK;

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

  if(!result) {

    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 = altsvc->list.head; e; e = n) {

      struct altsvc *as = e->ptr;

      n = e->next;

      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;

}

static CURLcode getalnum(const char **ptr, char *alpnbuf, size_t buflen)

{

  size_t len;

  const char *protop;

  const char *p = *ptr;

  while(*p && ISBLANK(*p))

    p++;

  protop = p;

  while(*p && !ISBLANK(*p) && (*p != ';') && (*p != '='))

    p++;

  len = p - protop;

  *ptr = p;

  if(!len || (len >= buflen))

    return CURLE_BAD_FUNCTION_ARGUMENT;

  memcpy(alpnbuf, protop, len);

  alpnbuf[len] = 0;

  return CURLE_OK;

}

/* 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 can't match if they have different lengths */

    return FALSE;

  return strncasecompare(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_element *e;

  struct Curl_llist_element *n;

  for(e = asi->list.head; e; e = n) {

    struct altsvc *as = e->ptr;

    n = e->next;

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

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

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

      Curl_llist_remove(&asi->list, e, NULL);

      altsvc_free(as);

    }

  }

}

#ifdef DEBUGBUILD

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

   return */

static time_t altsvc_debugtime(void *unused)

{

  char *timestr = getenv("CURL_TIME");

  (void)unused;

  if(timestr) {

    unsigned long val = strtol(timestr, NULL, 10);

    return (time_t)val;

  }

  return time(NULL);

}

#undef time

#define time(x) altsvc_debugtime(x)

#endif

#define ISNEWLINE(x) (((x) == '\n') || (x) == '\r')

/*

 * 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's contents to the right of the

 * header name.

 *

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

 * Invalid host name, 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;

  size_t len;

  char namebuf[MAX_ALTSVC_HOSTLEN] = "";

  char alpnbuf[MAX_ALTSVC_ALPNLEN] = "";

  struct altsvc *as;

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

  CURLcode result = getalnum(&p, alpnbuf, sizeof(alpnbuf));

  size_t entries = 0;

#ifdef CURL_DISABLE_VERBOSE_STRINGS

  (void)data;

#endif

  if(result) {

    infof(data, "Excessive alt-svc header, ignoring.");

    return CURLE_OK;

  }

  DEBUGASSERT(asi);

  /* "clear" is a magic keyword */

  if(strcasecompare(alpnbuf, "clear")) {

    /* Flush cached alternatives for this source origin */

    altsvc_flush(asi, srcalpnid, srchost, srcport);

    return CURLE_OK;

  }

  do {

    if(*p == '=') {

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

      enum alpnid dstalpnid = alpn2alpnid(alpnbuf); /* the same by default */

      p++;

      if(*p == '\"') {

        const char *dsthost = "";

        const char *value_ptr;

        char option[32];

        unsigned long num;

        char *end_ptr;

        bool quoted = FALSE;

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

        bool persist = FALSE;

        bool valid = TRUE;

        p++;

        if(*p != ':') {

          /* host name starts here */

          const char *hostp = p;

          if(*p == '[') {

            /* pass all valid IPv6 letters - does not handle zone id */

            len = strspn(++p, "0123456789abcdefABCDEF:.");

            if(p[len] != ']')

              /* invalid host syntax, bail out */

              break;

            /* we store the IPv6 numerical address *with* brackets */

            len += 2;

            p = &p[len-1];

          }

          else {

            while(*p && (ISALNUM(*p) || (*p == '.') || (*p == '-')))

              p++;

            len = p - hostp;

          }

          if(!len || (len >= MAX_ALTSVC_HOSTLEN)) {

            infof(data, "Excessive alt-svc host name, ignoring.");

            valid = FALSE;

          }

          else {

            memcpy(namebuf, hostp, len);

            namebuf[len] = 0;

            dsthost = namebuf;

          }

        }

        else {

          /* no destination name, use source host */

          dsthost = srchost;

        }

        if(*p == ':') {

          unsigned long port = 0;

          p++;

          if(ISDIGIT(*p))

            /* a port number */

            port = strtoul(p, &end_ptr, 10);

          else

            end_ptr = (char *)p; /* not left uninitialized */

          if(!port || port > USHRT_MAX || end_ptr == p || *end_ptr != '\"') {

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

            valid = FALSE;

          }

          else {

            dstport = curlx_ultous(port);

            p = end_ptr;

          }

        }

        if(*p++ != '\"')

          break;

        /* Handle the optional 'ma' and 'persist' flags. Unknown flags

           are skipped. */

        for(;;) {

          while(ISBLANK(*p))

            p++;

          if(*p != ';')

            break;

          p++; /* pass the semicolon */

          if(!*p || ISNEWLINE(*p))

            break;

          result = getalnum(&p, option, sizeof(option));

          if(result) {

            /* skip option if name is too long */

            option[0] = '\0';

          }

          while(*p && ISBLANK(*p))

            p++;

          if(*p != '=')

            return CURLE_OK;

          p++;

          while(*p && ISBLANK(*p))

            p++;

          if(!*p)

            return CURLE_OK;

          if(*p == '\"') {

            /* quoted value */

            p++;

            quoted = TRUE;

          }

          value_ptr = p;

          if(quoted) {

            while(*p && *p != '\"')

              p++;

            if(!*p++)

              return CURLE_OK;

          }

          else {

            while(*p && !ISBLANK(*p) && *p!= ';' && *p != ',')

              p++;

          }

          num = strtoul(value_ptr, &end_ptr, 10);

          if((end_ptr != value_ptr) && (num < ULONG_MAX)) {

            if(strcasecompare("ma", option))

              maxage = num;

            else if(strcasecompare("persist", option) && (num == 1))

              persist = TRUE;

          }

        }

        if(dstalpnid && valid) {

          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, dsthost,

                               srcalpnid, dstalpnid,

                               srcport, dstport);

          if(as) {

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

               account. [See RFC 7838 section 3.1] */

            as->expires = maxage + time(NULL);

            as->persist = persist;

            Curl_llist_insert_next(&asi->list, asi->list.tail, as, &as->node);

            infof(data, "Added alt-svc: %s:%d over %s", dsthost, dstport,

                  Curl_alpnid2str(dstalpnid));

          }

        }

      }

      else

        break;

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

         string or a semicolon if no more */

      if(*p == ',') {

        /* comma means another alternative is presented */

        p++;

        result = getalnum(&p, alpnbuf, sizeof(alpnbuf));

        if(result)

          break;

      }

    }

    else

      break;

  } while(*p && (*p != ';') && (*p != '\n') && (*p != '\r'));

  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_element *e;

  struct Curl_llist_element *n;

  time_t now = time(NULL);

  DEBUGASSERT(asi);

  DEBUGASSERT(srchost);

  DEBUGASSERT(dstentry);

  for(e = asi->list.head; e; e = n) {

    struct altsvc *as = e->ptr;

    n = e->next;

    if(as->expires < now) {

      /* an expired entry, remove */

      Curl_llist_remove(&asi->list, e, NULL);

      altsvc_free(as);

      continue;

    }

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

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

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

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

      /* match */

      *dstentry = as;

      return TRUE;

    }

  }

  return FALSE;

}

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