Indy odd/strang behavior with TLS version

Question

I sometimes get TLSv1 even when I set the version explicit to TLSv1.2.

I get this exception:

First chance exception at $75D917D2. Exception class EIdOSSLConnectError with message 'Error connecting with SSL. EOF was observed that violates the protocol'.

My Delphi version: Embarcadero® RAD Studio 10 Seattle Version 23.0.21418.4207

I am on Windows 10: Microsoft Windows [Version 10.0.17134.345]

My Indy Version: 10.6.2.5311 - That's what's coming with Seattle

This is a trace when it works:

This is a trace when it does NOT work:

As you can see it is TLSv1. Why?

I had a look at following questions: Using Indy 10 IdHTTP with TLS 1.2 EIdOSSLConnectError Error connecting with SSL - EOF was observed

Here is my example code:

procedure TOpenWeatherFr.SetIcon(const IconCode: String);
var
  HTTPS: TSSLHTTP;
  MS : TMemoryStream;
  PNG: TPngImage;
  URL: string;
begin
  HTTPS := TSSLHTTP.Create(nil);
  MS := TMemoryStream.Create;
  PNG := TPngImage.Create;
  URL := 'https://openweathermap.org/img/w/' + IconCode + '.png';
  try
    (HTTPS.IOHandler as TIdSSLIOHandlerSocketOpenSSL).SSLOptions.SSLVersions := [sslvTLSv1_2];
    HTTPS.Get(URL, MS);
    MS.Seek(0, soFromBeginning);
    PNG.LoadFromStream(MS);
    Image1.Picture.Assign(PNG);
  finally
    HTTPS.Free;
    PNG.Free;
    MS.Free;
  end;
  Image1.Visible := true;
end;

For the sake of completeness here is the code of TSSLHTTP. The purpose is an old Indy version without SNI Support.

unit SSLHTTP;

interface

uses
  Classes, IdHTTP, IdSSLOpenSSLHeaders, IdCTypes;

type
  TSSLHTTP = class(TIdHTTP)
  private
    procedure OnStatusInfoEx(ASender: TObject; const AsslSocket: PSSL; const AWhere, Aret: TIdC_INT; const AType, AMsg: String);
  public
    constructor Create(AOwner: TComponent);
  end;

implementation

uses
  IdSSLOpenSSL;

{ TSSLHTTP }

constructor TSSLHTTP.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  IOHandler := TIdSSLIOHandlerSocketOpenSSL.Create(self);
  (IOHandler as TIdSSLIOHandlerSocketOpenSSL).OnStatusInfoEx := OnStatusInfoEx;
end;

procedure TSSLHTTP.OnStatusInfoEx(ASender: TObject; const AsslSocket: PSSL;
  const AWhere, Aret: TIdC_INT; const AType, AMsg: String);
begin
  SSL_set_tlsext_host_name(AsslSocket, Request.Host);
end;

end.

Where is my mistake? What am I doing wrong? This is the URL of the image I download: https://openweathermap.org/img/w/04d.png

EDIT: Adding paylod as hex dumb

Working payload - Client Hello:

0000   16 03 01 01 49 01 00 01 45 03 03 8b 3d e5 54 59
0010   f8 59 44 82 f7 14 92 45 50 e1 a3 86 68 3a c2 94
0020   76 be ea 8b 54 98 f3 27 69 50 af 00 00 94 c0 30
0030   c0 2c c0 28 c0 24 c0 14 c0 0a 00 a3 00 9f 00 6b
0040   00 6a 00 39 00 38 c0 32 c0 2e c0 2a c0 26 c0 0f
0050   c0 05 00 9d 00 3d 00 35 00 88 00 87 00 84 c0 2f
0060   c0 2b c0 27 c0 23 c0 13 c0 09 00 a2 00 9e 00 67
0070   00 40 00 33 00 32 c0 31 c0 2d c0 29 c0 25 c0 0e
0080   c0 04 00 9c 00 3c 00 2f 00 9a 00 99 00 45 00 44
0090   00 96 00 41 00 07 c0 11 c0 07 c0 0c c0 02 00 05
00a0   00 04 c0 12 c0 08 00 16 00 13 c0 0d c0 03 00 0a
00b0   00 15 00 12 00 09 00 14 00 11 00 08 00 06 00 03
00c0   00 ff 01 00 00 88 00 00 00 17 00 15 00 00 12 6f
00d0   70 65 6e 77 65 61 74 68 65 72 6d 61 70 2e 6f 72
00e0   67 00 0b 00 04 03 00 01 02 00 0a 00 34 00 32 00
00f0   0e 00 0d 00 19 00 0b 00 0c 00 18 00 09 00 0a 00
0100   16 00 17 00 08 00 06 00 07 00 14 00 15 00 04 00
0110   05 00 12 00 13 00 01 00 02 00 03 00 0f 00 10 00
0120   11 00 23 00 00 00 0d 00 20 00 1e 06 01 06 02 06
0130   03 05 01 05 02 05 03 04 01 04 02 04 03 03 01 03
0140   02 03 03 02 01 02 02 02 03 00 0f 00 01 01

Not working payload - Client hello:

0000   16 03 01 01 49 01 00 01 45 03 03 f6 7b de 81 5d
0010   76 74 a7 31 99 36 8d 17 4c 07 5e 73 5d f7 b8 a1
0020   4f 06 5e 91 e5 f0 4b 37 0d 65 e7 00 00 94 c0 30
0030   c0 2c c0 28 c0 24 c0 14 c0 0a 00 a3 00 9f 00 6b
0040   00 6a 00 39 00 38 c0 32 c0 2e c0 2a c0 26 c0 0f
0050   c0 05 00 9d 00 3d 00 35 00 88 00 87 00 84 c0 2f
0060   c0 2b c0 27 c0 23 c0 13 c0 09 00 a2 00 9e 00 67
0070   00 40 00 33 00 32 c0 31 c0 2d c0 29 c0 25 c0 0e
0080   c0 04 00 9c 00 3c 00 2f 00 9a 00 99 00 45 00 44
0090   00 96 00 41 00 07 c0 11 c0 07 c0 0c c0 02 00 05
00a0   00 04 c0 12 c0 08 00 16 00 13 c0 0d c0 03 00 0a
00b0   00 15 00 12 00 09 00 14 00 11 00 08 00 06 00 03
00c0   00 ff 01 00 00 88 00 00 00 17 00 15 00 00 12 6f
00d0   70 65 6e 77 65 61 74 68 65 72 6d 61 70 2e 6f 72
00e0   67 00 0b 00 04 03 00 01 02 00 0a 00 34 00 32 00
00f0   0e 00 0d 00 19 00 0b 00 0c 00 18 00 09 00 0a 00
0100   16 00 17 00 08 00 06 00 07 00 14 00 15 00 04 00
0110   05 00 12 00 13 00 01 00 02 00 03 00 0f 00 10 00
0120   11 00 23 00 00 00 0d 00 20 00 1e 06 01 06 02 06
0130   03 05 01 05 02 05 03 04 01 04 02 04 03 03 01 03
0140   02 03 03 02 01 02 02 02 03 00 0f 00 01 01

Look again more closely, both screenshots you provided show TLS v1.2 client requests, not TLS v1.0 (look at the `Version` inside the `Handshake Protocol`, not in the `Record Layer`). And you should upgrade to the latest Indy 10 version (currently 10.6.2.5485), [it supports SNI on the client side](https://www.indyproject.org/2016/01/10/client-side-sni-support-added-to-tidssliohandlersocketopenssl/) (and has for almost 3 years now), so you don't need your `TSSLHTTP` class anymore — Remy Lebeau, Nov 09 '18 at 17:42
You are right. If an upgrade would be that simple in our selfmade framework. Back to topic: Why do I get the exception in 2 or 3 out of 10 of the requests? — complete_stranger, Nov 09 '18 at 20:26
The code you showed is fine. You will just have to analyze the TLS client hellos more deeply (your screenshots don't expand everything) for differences between working and non-working cases. "EOF was observed" means the server closed the connection on its end before the TLS handshake was finished, which means the server most likely didn't like something in the hellos, and chose not to send a TLS alert explaining why before closing the connection. If you can't find any differences, then there is likely a problem on the server side that you won't be able to do anything about on your client side. — Remy Lebeau, Nov 09 '18 at 21:09
Thank you for confirming my code is fine. I can not find any non-obvious changes at all except the 32 random bytes. I am curious as to why wireshark misinterprets the protocol. If wiresharks shows TLSv1 I have the issue. I added the payload to my question. — complete_stranger, Nov 11 '18 at 15:05
16 03 01 01 49 01 00 01 45 03 03 || > 16 = Dont know > 03 01 = TLS v1.0 > 01 49 = Length = 329 > 00 = Dont know > 01 45 = Length = 325 > 03 03 = TLS v1.2 || It's the same on both as you can see on the screenshots — complete_stranger, Nov 11 '18 at 15:11
it is not misinterpreting anything. The outer layer record begins in TLS v1.0 format, with an inner version of 1.2 to indicate the client supports a higher version. If the server also supports 1.2, it can upgrade the remainder of the handshake to that version. — Remy Lebeau, Nov 11 '18 at 17:57
Okay, now I am lost and stuck. There is no difference in the payload. My code is fine. Everytime wireshark shows TLSv1 it doesn't work. So it is a server issue? — complete_stranger, Nov 11 '18 at 22:55

Indy odd/strang behavior with TLS version

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