Blob nonce;          /* The nonce */
  const char *zLogin;  /* The user login name */
  const char *zPw;     /* The user password */
  Blob pw;             /* The nonce with user password appended */
  Blob sig;            /* The signature field */

  blob_zero(pLogin);
  if( g.urlUser==0 || fossil_strcmp(g.urlUser, "anonymous")==0 ){
     return;  /* If no login card for users "nobody" and "anonymous" */
  }
  if( g.urlIsSsh ){
     return;  /* If no login card for SSH: */
  }
  blob_zero(&nonce);
  blob_zero(&pw);
  sha1sum_blob(pPayload, &nonce);
  blob_copy(&pw, &nonce);
  zLogin = g.urlUser;
  if( g.urlPasswd ){
    zPw = g.urlPasswd;
  }else if( g.cgiOutput ){
    /* Password failure while doing a sync from the web interface */
    cgi_printf("*** incorrect or missing password for user %h\n", zLogin);
    zPw = 0;
  }else{
    /* Password failure while doing a sync from the command-line interface */
    url_prompt_for_password();
    zPw = g.urlPasswd;
  }

  /* The login card wants the SHA1 hash of the password, so convert the
  ** password to its SHA1 hash it it isn't already a SHA1 hash.
  */
  /* fossil_print("\nzPw=[%s]\n", zPw); // TESTING ONLY */
  if( zPw && zPw[0] ) zPw = sha1_shared_secret(zPw, zLogin, 0);

** the complete payload (including the login card) already compressed.
*/
static void http_build_header(Blob *pPayload, Blob *pHdr){
  int i;
  const char *zSep;

  blob_zero(pHdr);
  i = strlen(g.urlPath);
  if( i>0 && g.urlPath[i-1]=='/' ){
    zSep = "";
  }else{
    zSep = "/";
  }
  blob_appendf(pHdr, "POST %s%sxfer/xfer HTTP/1.0\r\n", g.urlPath, zSep);
  if( g.urlProxyAuth ){
    blob_appendf(pHdr, "Proxy-Authorization: %s\r\n", g.urlProxyAuth);
  }
  if( g.zHttpAuth && g.zHttpAuth[0] ){
    const char *zCredentials = g.zHttpAuth;
    char *zEncoded = encode64(zCredentials, -1);
    blob_appendf(pHdr, "Authorization: Basic %s\r\n", zEncoded);
    fossil_free(zEncoded);
  }
  blob_appendf(pHdr, "Host: %s\r\n", g.urlHostname);
  blob_appendf(pHdr, "User-Agent: %s\r\n", get_user_agent());
  if( g.urlIsSsh ) blob_appendf(pHdr, "X-Fossil-Transport: SSH\r\n");
  if( g.fHttpTrace ){
    blob_appendf(pHdr, "Content-Type: application/x-fossil-debug\r\n");
  }else{
    blob_appendf(pHdr, "Content-Type: application/x-fossil\r\n");
  }
  blob_appendf(pHdr, "Content-Length: %d\r\n\r\n", blob_size(pPayload));
}

/*
** Prompt to save HTTP Basic Authorization information
*/
static int save_httpauth_prompt(void){
  Blob x;
  char c;
  if( (g.urlFlags & URL_REMEMBER)==0 ) return 0;
  prompt_user("Remember Basic Authorization credentials (Y/n)? ", &x);
  c = blob_str(&x)[0];
  blob_reset(&x);
  return ( c!='n' && c!='N' );
}

/*
** Get the HTTP Basic Authorization credentials from the user 
** when 401 is received.
*/
char *prompt_for_httpauth_creds(void){
  Blob x;
  char *zUser;
  char *zPw;
  char *zPrompt;
  char *zHttpAuth = 0;
  if( !isatty(fileno(stdin)) ) return 0;
  zPrompt = mprintf("\n%s authorization required by\n%s\n",
    g.urlIsHttps==1 ? "Encrypted HTTPS" : "Unencrypted HTTP", g.urlCanonical);
  fossil_print(zPrompt);
  free(zPrompt);
  if ( g.urlUser && g.urlPasswd && use_fossil_creds_for_httpauth_prompt() ){
    zHttpAuth = mprintf("%s:%s", g.urlUser, g.urlPasswd);
  }else{
    prompt_user("Basic Authorization user: ", &x);
    zUser = mprintf("%b", &x);
    zPrompt = mprintf("HTTP password for %b: ", &x);
    blob_reset(&x);
    prompt_for_password(zPrompt, &x, 1);
    zPw = mprintf("%b", &x);

  int rc = 0;           /* Result code */
  int iHttpVersion;     /* Which version of HTTP protocol server uses */
  char *zLine;          /* A single line of the reply header */
  int i;                /* Loop counter */
  int isError = 0;      /* True if the reply is an error message */
  int isCompressed = 1; /* True if the reply is compressed */

  if( transport_open(GLOBAL_URL()) ){
    fossil_warning(transport_errmsg(GLOBAL_URL()));
    return 1;
  }

  /* Construct the login card and prepare the complete payload */
  blob_zero(&login);
  if( useLogin ) http_build_login_card(pSend, &login);
  if( g.fHttpTrace ){

    transport_log(out);
    free(zOutFile);
  }

  /*
  ** Send the request to the server.
  */
  transport_send(GLOBAL_URL(), &hdr);
  transport_send(GLOBAL_URL(), &payload);
  blob_reset(&hdr);
  blob_reset(&payload);
  transport_flip(GLOBAL_URL());
  
  /*
  ** Read and interpret the server reply
  */
  closeConnection = 1;
  iLength = -1;
  while( (zLine = transport_receive_line(GLOBAL_URL()))!=0 && zLine[0]!=0 ){
    /* printf("[%s]\n", zLine); fflush(stdout); */
    if( fossil_strnicmp(zLine, "http/1.", 7)==0 ){
      if( sscanf(zLine, "HTTP/1.%d %d", &iHttpVersion, &rc)!=2 ) goto write_err;
      if( rc==401 ){
        if( fSeenHttpAuth++ < MAX_HTTP_AUTH ){
          if( g.zHttpAuth ){
            if( g.zHttpAuth ) free(g.zHttpAuth);
          }
          g.zHttpAuth = prompt_for_httpauth_creds();
          transport_close(GLOBAL_URL());
          return http_exchange(pSend, pReply, useLogin, maxRedirect);
        }
      }
      if( rc!=200 && rc!=302 ){
        int ii;
        for(ii=7; zLine[ii] && zLine[ii]!=' '; ii++){}
        while( zLine[ii]==' ' ) ii++;
        fossil_warning("server says: %s", &zLine[ii]);
        goto write_err;
      }
      if( iHttpVersion==0 ){
        closeConnection = 1;
      }else{
        closeConnection = 0;
      }
    }else if( g.urlIsSsh && fossil_strnicmp(zLine, "status:", 7)==0 ){
      if( sscanf(zLine, "Status: %d", &rc)!=1 ) goto write_err;
      if( rc!=200 && rc!=302 ){
        int ii;
        for(ii=7; zLine[ii] && zLine[ii]!=' '; ii++){}
        while( zLine[ii]==' ' ) ii++;
        fossil_warning("server says: %s", &zLine[ii]);
        goto write_err;

         zLine[j] = 0;
      }
      fossil_print("redirect to %s\n", &zLine[i]);
      url_parse(&zLine[i], 0);
      fSeenHttpAuth = 0;
      if( g.zHttpAuth ) free(g.zHttpAuth);
      g.zHttpAuth = get_httpauth();
      transport_close(GLOBAL_URL());
      return http_exchange(pSend, pReply, useLogin, maxRedirect);
    }else if( fossil_strnicmp(zLine, "content-type: ", 14)==0 ){
      if( fossil_strnicmp(&zLine[14], "application/x-fossil-debug", -1)==0 ){
        isCompressed = 0;
      }else if( fossil_strnicmp(&zLine[14], 
                          "application/x-fossil-uncompressed", -1)==0 ){
        isCompressed = 0;

  }

  /*
  ** Extract the reply payload that follows the header
  */
  blob_zero(pReply);
  blob_resize(pReply, iLength);
  iLength = transport_receive(GLOBAL_URL(), blob_buffer(pReply), iLength);
  blob_resize(pReply, iLength);
  if( isError ){
    char *z;
    int i, j;
    z = blob_str(pReply);
    for(i=j=0; z[i]; i++, j++){
      if( z[i]=='<' ){

  **
  ** FIXME:  There is some bug in the lower layers that prevents the
  ** connection from remaining open.  The easiest fix for now is to
  ** simply close and restart the connection for each round-trip.
  **
  ** For SSH we will leave the connection open.
  */
  if( ! g.urlIsSsh ) closeConnection = 1; /* FIX ME */
  if( closeConnection ){
    transport_close(GLOBAL_URL());
  }else{
    transport_rewind(GLOBAL_URL());
  }
  return 0;

  /* 
  ** Jump to here if an error is seen.
  */
write_err:
  transport_close(GLOBAL_URL());
  return 1;  
}