Re: [openssl-users] Explicit IV in TLS 1.1+

[Curt Johansson]

Hi Matt, 
I had an error in my PRF that is new for TLS 1.2. Now it works. 
Thanks for pointing me in the right directionand THANK YOU all for 
devoting time to this important project. 

Best regards
Curt 


> On 15 Feb 2018, at 12:12 , Matt Caswell  wrote:
> 
> 
> 
> On 15/02/18 03:52, Curt Johansson wrote:
>> Hi Matt, thanks for your prompt answer. The testclient is using
>> openssl-1.0.2m and my previous assumption that the IV was derived
>> from the key_block as in TLS 1.0 was wrong. It seems that when
>> initialising the cipher with the IV is ignored when the crypto is AES
>> and the first 16 bytes of the encrypted payload is used as IV (as per
>> TLS spec). This is a Java issue and has nothing to do with OpenSSL
>> but assuming this is correct behaviour (I'll have to dig in to that)
>> I use the same logic (in this respect) for TLS1.1 and TLS1.2
>> assuming that the client also does which it obviously does not.
>> 
>> Below is the logging from my server handling two authentications (the
>> Finished message that is the first encrypted). The first (TLS1.1)
>> succeeds and the second (1.2) fails. You can see that the decrypted
>> text is correctly padded in the first case (TLS 1.1) indicating that
>> the decryption succeeded but the second (1.2) decrypted buffer does
>> not. The "Finished" message for this (AES; SHA) mac- and block size
>> should be padded with 11 bytes which the first is. Also as seen I use
>> the same provider and algoritm in the two cases, actually I handle
>> the decryption in the same way for the two TLS-levels
>> 
>> 
>> Also added the wireshark output for the two authentications where
>> I've verified that the logged encrypted data really is whats coming
>> in on the line.
>> 
>> 
>> Basically when selecting 1.1 in the client everything works as
>> expected but selecting 1.2 the prepended IV is not correct as far as
>> I understand. The testclient vendor says they are using OpenSLL for
>> TLS handling so I expect that they're not fiddling with any IV bytes
>> at all. Given the version 1.0.2m, can this be explained?
> 
> My best guess is that the calculated client write key is probably
> incorrect on the server side (which probably implies either the master
> or pre-master secret is wrong). You might need to instrument OpenSSL to
> dump out the internal secrets at various points and compare them with
> your calculations on the server to verify that they are the same.
> 
> Matt
> 
>> 
>> 
>> Best Curt
>> 
>> 
>> 
>> 
>> 
>> TLS 1.1
>> 
>> 04:09:40.295 Cipher provider: SunJCE 04:09:40.295 Cipher algoritm:
>> AES/CBC/NoPadding 04:09:40.295 IV from key_block used in cipher init:
>> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 04:09:40.295
>> Encrypted: [f5, 21, 77, 27, f7, bf, 31, 1f, b9, 74, 14, 50, be, 5f,
>> 66, 21, 1b, 4e, b, 33, 78, 3b, b8, 31, a3, 7c, c2, 93, f6, ec, a, 8f,
>> c4, 28, 71, cb, 82, b4, 12, c2, 6b, 56, f2, 9e, c8, b0, 2b, 64, 7c,
>> 89, ef, bb, 68, 6b, 73, 6b, 80, 3a, 1b, 7, 33, 4e, 36, 6b] 
>> 04:09:40.296 Decrypted: [a6, c7, bc, 87, 7, 2, 85, c, c3, c7, 91, 73,
>> b3, 85, 19, 21, 14, 0, 0, c, 1, 6f, 1e, 4e, 97, d0, c4, 10, a9, 35,
>> 37, bc, 2a, 87, 79, 78, 4c, 4, 88, a1, fd, 35, 42, 26, 56, 51, b3,
>> 36, d, 3b, be, 4a, b, b, b, b, b, b, b, b, b, b, b, b]
>> 
>> TLS 1.2 04:09:47.779 Cipher provider: SunJCE 04:09:47.779 Cipher
>> algoritm: AES/CBC/NoPadding 04:09:47.779 IV from key_block used in
>> cipher init: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 
>> 04:09:47.779 Encrypted: [80, 83, 98, 6b, 55, 98, 73, b4, f6, 22, 2d,
>> 88, b, 4d, af, 6f, 2d, d6, 1e, 9, 1d, b1, 94, f4, 49, 20, 15, d2, a0,
>> a0, 35, c5, 95, 3d, d3, 35, fd, 92, ef, a6, 0, 7d, 49, 3, 70, 5e, 5a,
>> 57, e3, f9, 89, 3f, 83, 11, cf, 82, 4e, a3, 87, 6e, 9e, 97, 9c, 7c] 
>> 04:09:47.779 Decrypted: [f1, 4e, b3, 18, 26, d7, ae, 12, bf, 5d, fe,
>> 2a, 18, a1, 6f, 19, 60, 73, 26, c8, 74, 7c, c6, a6, a1, 65, d3, ad,
>> 45, f9, e3, 42, aa, e0, bd, 1d, a0, 18, b3, f3, 94, 28, 4e, 2a, ca,
>> 24, 25, 70, 7c, a9, f6, 19, 17, f5, ef, ee, b, 30, 2f, ec, 4d, b3,
>> 9c, 8b]
>> 
>> 
>> 
>>> On 14 Feb 2018, at 0:26 , Matt Caswell  wrote:
>>> 
>>> 
>>> 
>>> On 13/02/18 22:02, Curt Johansson wrote:
 Hi all,
 
 I'm developing support for TLS 1.1 and 1.2 in a radius-server
 that until now only handles TLS 1.0. I'm testing with a testtool
 that the vendor says is using OpenSSL to implement the TLS
 support. It all seems to work except for the following:
 
 When all key exchange messages are sent from the server and back
 from the client the client sends the "Finished" message which is
 the first encrypted with the negotiated symmetric cipher suite. I
 use AES-128 in block mode and according to the spec (RFC4346 for
 TLS 1.1) the IV is prepended to the encrypted message (containing
 the payload, MAC and padding). The message size i right and when
 (in the server) I use the first 16 bytes of the message received
 

Re: [openssl-users] Explicit IV in TLS 1.1+

[Matt Caswell]

On 15/02/18 03:52, Curt Johansson wrote:
> Hi Matt, thanks for your prompt answer. The testclient is using
> openssl-1.0.2m and my previous assumption that the IV was derived
> from the key_block as in TLS 1.0 was wrong. It seems that when
> initialising the cipher with the IV is ignored when the crypto is AES
> and the first 16 bytes of the encrypted payload is used as IV (as per
> TLS spec). This is a Java issue and has nothing to do with OpenSSL
> but assuming this is correct behaviour (I'll have to dig in to that)
> I use the same logic (in this respect) for TLS1.1 and TLS1.2
> assuming that the client also does which it obviously does not.
> 
> Below is the logging from my server handling two authentications (the
> Finished message that is the first encrypted). The first (TLS1.1)
> succeeds and the second (1.2) fails. You can see that the decrypted
> text is correctly padded in the first case (TLS 1.1) indicating that
> the decryption succeeded but the second (1.2) decrypted buffer does
> not. The "Finished" message for this (AES; SHA) mac- and block size
> should be padded with 11 bytes which the first is. Also as seen I use
> the same provider and algoritm in the two cases, actually I handle
> the decryption in the same way for the two TLS-levels
> 
> 
> Also added the wireshark output for the two authentications where
> I've verified that the logged encrypted data really is whats coming
> in on the line.
> 
> 
> Basically when selecting 1.1 in the client everything works as
> expected but selecting 1.2 the prepended IV is not correct as far as
> I understand. The testclient vendor says they are using OpenSLL for
> TLS handling so I expect that they're not fiddling with any IV bytes
> at all. Given the version 1.0.2m, can this be explained?

My best guess is that the calculated client write key is probably
incorrect on the server side (which probably implies either the master
or pre-master secret is wrong). You might need to instrument OpenSSL to
dump out the internal secrets at various points and compare them with
your calculations on the server to verify that they are the same.

Matt

> 
> 
> Best Curt
> 
> 
> 
> 
> 
> TLS 1.1
> 
> 04:09:40.295 Cipher provider: SunJCE 04:09:40.295 Cipher algoritm:
> AES/CBC/NoPadding 04:09:40.295 IV from key_block used in cipher init:
> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 04:09:40.295
> Encrypted: [f5, 21, 77, 27, f7, bf, 31, 1f, b9, 74, 14, 50, be, 5f,
> 66, 21, 1b, 4e, b, 33, 78, 3b, b8, 31, a3, 7c, c2, 93, f6, ec, a, 8f,
> c4, 28, 71, cb, 82, b4, 12, c2, 6b, 56, f2, 9e, c8, b0, 2b, 64, 7c,
> 89, ef, bb, 68, 6b, 73, 6b, 80, 3a, 1b, 7, 33, 4e, 36, 6b] 
> 04:09:40.296 Decrypted: [a6, c7, bc, 87, 7, 2, 85, c, c3, c7, 91, 73,
> b3, 85, 19, 21, 14, 0, 0, c, 1, 6f, 1e, 4e, 97, d0, c4, 10, a9, 35,
> 37, bc, 2a, 87, 79, 78, 4c, 4, 88, a1, fd, 35, 42, 26, 56, 51, b3,
> 36, d, 3b, be, 4a, b, b, b, b, b, b, b, b, b, b, b, b]
> 
> TLS 1.2 04:09:47.779 Cipher provider: SunJCE 04:09:47.779 Cipher
> algoritm: AES/CBC/NoPadding 04:09:47.779 IV from key_block used in
> cipher init: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 
> 04:09:47.779 Encrypted: [80, 83, 98, 6b, 55, 98, 73, b4, f6, 22, 2d,
> 88, b, 4d, af, 6f, 2d, d6, 1e, 9, 1d, b1, 94, f4, 49, 20, 15, d2, a0,
> a0, 35, c5, 95, 3d, d3, 35, fd, 92, ef, a6, 0, 7d, 49, 3, 70, 5e, 5a,
> 57, e3, f9, 89, 3f, 83, 11, cf, 82, 4e, a3, 87, 6e, 9e, 97, 9c, 7c] 
> 04:09:47.779 Decrypted: [f1, 4e, b3, 18, 26, d7, ae, 12, bf, 5d, fe,
> 2a, 18, a1, 6f, 19, 60, 73, 26, c8, 74, 7c, c6, a6, a1, 65, d3, ad,
> 45, f9, e3, 42, aa, e0, bd, 1d, a0, 18, b3, f3, 94, 28, 4e, 2a, ca,
> 24, 25, 70, 7c, a9, f6, 19, 17, f5, ef, ee, b, 30, 2f, ec, 4d, b3,
> 9c, 8b]
> 
> 
> 
>> On 14 Feb 2018, at 0:26 , Matt Caswell  wrote:
>> 
>> 
>> 
>> On 13/02/18 22:02, Curt Johansson wrote:
>>> Hi all,
>>> 
>>> I'm developing support for TLS 1.1 and 1.2 in a radius-server
>>> that until now only handles TLS 1.0. I'm testing with a testtool
>>> that the vendor says is using OpenSSL to implement the TLS
>>> support. It all seems to work except for the following:
>>> 
>>> When all key exchange messages are sent from the server and back
>>> from the client the client sends the "Finished" message which is
>>> the first encrypted with the negotiated symmetric cipher suite. I
>>> use AES-128 in block mode and according to the spec (RFC4346 for
>>> TLS 1.1) the IV is prepended to the encrypted message (containing
>>> the payload, MAC and padding). The message size i right and when
>>> (in the server) I use the first 16 bytes of the message received
>>> from the client as IV the decryption fails but when I use the
>>> mechanism from TLS 1.0 to pick up the IV from the key_block the
>>> decryption is successful. I understand that this is one way to
>>> generate the IV that I suppose you use which is fine but 
>>> shouldn't this 16 byte vector be prepended, unecrypted, to the
>>> encrypted data that is sent to the server? In TLS 1.2 there 

Re: [openssl-users] Explicit IV in TLS 1.1+

[Curt Johansson]

Hi Matt, thanks for your prompt answer. The testclient is using openssl-1.0.2m 
and my previous assumption that the IV was derived from the key_block as in TLS 
1.0 was wrong. 
It seems that when initialising the cipher with the IV is ignored when the 
crypto is AES and the first 16 bytes of the encrypted payload is used as IV (as 
per TLS spec). This is a Java issue 
and has nothing to do with OpenSSL but assuming this is correct behaviour (I'll 
have to dig in to that) I use the same logic (in this respect) for TLS1.1 and 
TLS1.2  assuming that
the client also does which it obviously does not. 

Below is the logging from my server handling two authentications (the Finished 
message that is the first encrypted). The first (TLS1.1) succeeds and the 
second (1.2) fails. You can see that the decrypted text is correctly padded in 
the first case (TLS 1.1) indicating that the decryption succeeded but the 
second (1.2) decrypted buffer does not. The "Finished" message for this (AES; 
SHA) mac- and block size should be padded with 11 bytes which the first is. 
Also as seen I use the same provider and algoritm in the two cases, actually I 
handle the decryption in the same way for the two TLS-levels


Also added the wireshark output for the two authentications where I've verified 
that the logged encrypted data really is whats coming in on the line. 


Basically when selecting 1.1 in the client everything works as expected but 
selecting 1.2 the prepended IV is not correct as far as I understand. The 
testclient vendor says they are using
OpenSLL for TLS handling so I expect that they're not fiddling with any IV 
bytes at all. Given the version 1.0.2m, can this be explained? 


Best 
Curt 



TLS11-TLS12.pcapng
Description: Binary data


TLS 1.1
 
04:09:40.295 Cipher provider: SunJCE
04:09:40.295 Cipher algoritm: AES/CBC/NoPadding
04:09:40.295 IV from key_block used in cipher init: [0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0]
04:09:40.295 Encrypted: [f5, 21, 77, 27, f7, bf, 31, 1f, b9, 74, 14, 50, be, 
5f, 66, 21, 1b, 4e, b, 33, 78, 3b, b8, 31, a3, 7c, c2, 93, f6, ec, a, 8f, c4, 
28, 71, cb, 82, b4, 12, c2, 6b, 56, f2, 9e, c8, b0, 2b, 64, 7c, 89, ef, bb, 68, 
6b, 73, 6b, 80, 3a, 1b, 7, 33, 4e, 36, 6b]
04:09:40.296 Decrypted: [a6, c7, bc, 87, 7, 2, 85, c, c3, c7, 91, 73, b3, 85, 
19, 21, 14, 0, 0, c, 1, 6f, 1e, 4e, 97, d0, c4, 10, a9, 35, 37, bc, 2a, 87, 79, 
78, 4c, 4, 88, a1, fd, 35, 42, 26, 56, 51, b3, 36, d, 3b, be, 4a, b, b, b, b, 
b, b, b, b, b, b, b, b]

TLS 1.2
04:09:47.779 Cipher provider: SunJCE
04:09:47.779 Cipher algoritm: AES/CBC/NoPadding
04:09:47.779 IV from key_block used in cipher init: [0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0]
04:09:47.779 Encrypted: [80, 83, 98, 6b, 55, 98, 73, b4, f6, 22, 2d, 88, b, 4d, 
af, 6f, 2d, d6, 1e, 9, 1d, b1, 94, f4, 49, 20, 15, d2, a0, a0, 35, c5, 95, 3d, 
d3, 35, fd, 92, ef, a6, 0, 7d, 49, 3, 70, 5e, 5a, 57, e3, f9, 89, 3f, 83, 11, 
cf, 82, 4e, a3, 87, 6e, 9e, 97, 9c, 7c]
04:09:47.779 Decrypted: [f1, 4e, b3, 18, 26, d7, ae, 12, bf, 5d, fe, 2a, 18, 
a1, 6f, 19, 60, 73, 26, c8, 74, 7c, c6, a6, a1, 65, d3, ad, 45, f9, e3, 42, aa, 
e0, bd, 1d, a0, 18, b3, f3, 94, 28, 4e, 2a, ca, 24, 25, 70, 7c, a9, f6, 19, 17, 
f5, ef, ee, b, 30, 2f, ec, 4d, b3, 9c, 8b]



> On 14 Feb 2018, at 0:26 , Matt Caswell  wrote:
> 
> 
> 
> On 13/02/18 22:02, Curt Johansson wrote:
>> Hi all, 
>> 
>> I'm developing support for TLS 1.1 and 1.2 in a radius-server that until now 
>> only handles TLS 1.0. I'm testing with a testtool that the vendor says is
>> using OpenSSL to implement the TLS support. It all seems to work except for 
>> the following: 
>> 
>> When all key exchange messages are sent from the server and back from the 
>> client the client sends the "Finished" message which 
>> is the first encrypted with the negotiated symmetric cipher suite. I use 
>> AES-128 in block mode and according to the spec (RFC4346 for TLS 1.1) 
>> the IV is prepended to the encrypted message (containing the payload, MAC 
>> and padding). The message size i right and when (in the server) I use the 
>> first 16 bytes 
>> of the message received from the client as IV the decryption fails but when 
>> I use the mechanism from TLS 1.0 to pick up the IV from 
>> the key_block the decryption is successful. I understand that this is one 
>> way to generate the IV that I suppose you use which is fine but 
>> shouldn't this 16 byte vector be prepended, unecrypted, to the encrypted 
>> data that is sent to the server? In TLS 1.2 there is not IV material 
>> generated 
>> at all in the key_block so in that case I don't even know where to find it. 
>> 
>> The simple question is, shouldn't the first 16 bytes (assuming AES) of the 
>> message (after the 5 byte header) be the unencrypted IV to be used in the 
>> decryption of the rest of the message?
> 
> Yes, assuming you have negotiated an AES CBC ciphersuite in TLSv1.1 or
> TLSv1.2, then that is what happens. You don't say what version of

Re: [openssl-users] Explicit IV in TLS 1.1+

[Matt Caswell]

On 13/02/18 22:02, Curt Johansson wrote:
> Hi all, 
> 
> I'm developing support for TLS 1.1 and 1.2 in a radius-server that until now 
> only handles TLS 1.0. I'm testing with a testtool that the vendor says is
> using OpenSSL to implement the TLS support. It all seems to work except for 
> the following: 
> 
> When all key exchange messages are sent from the server and back from the 
> client the client sends the "Finished" message which 
> is the first encrypted with the negotiated symmetric cipher suite. I use 
> AES-128 in block mode and according to the spec (RFC4346 for TLS 1.1) 
> the IV is prepended to the encrypted message (containing the payload, MAC and 
> padding). The message size i right and when (in the server) I use the first 
> 16 bytes 
> of the message received from the client as IV the decryption fails but when I 
> use the mechanism from TLS 1.0 to pick up the IV from 
> the key_block the decryption is successful. I understand that this is one way 
> to generate the IV that I suppose you use which is fine but 
> shouldn't this 16 byte vector be prepended, unecrypted, to the encrypted data 
> that is sent to the server? In TLS 1.2 there is not IV material generated 
> at all in the key_block so in that case I don't even know where to find it. 
> 
> The simple question is, shouldn't the first 16 bytes (assuming AES) of the 
> message (after the 5 byte header) be the unencrypted IV to be used in the 
> decryption of the rest of the message?

Yes, assuming you have negotiated an AES CBC ciphersuite in TLSv1.1 or
TLSv1.2, then that is what happens. You don't say what version of
OpenSSL you are using. Here is the code that does it for 1.1.1 (i.e.
master branch):

https://github.com/openssl/openssl/blob/master/ssl/record/ssl3_record.c#L954

As can be seen on line 969 we just fill the IV with random bytes.

Perhaps you could provide a wireshark trace of the handshake which might
provide some enlightenment as to what is happening.

Matt


> 
> I tried to dig in to the OpenSSL source but it's far too long ago I did some 
> serious C coding so I hope someone with a working knowledge can enlighten me. 
> I might have
> misunderstood the spec but in that case I would be grateful if someone could 
> clarify this specific part of it. 
> 
> TIA 
> Curt Johansson
> 
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[openssl-users] Explicit IV in TLS 1.1+

[Curt Johansson]

Hi all, 

I'm developing support for TLS 1.1 and 1.2 in a radius-server that until now 
only handles TLS 1.0. I'm testing with a testtool that the vendor says is
using OpenSSL to implement the TLS support. It all seems to work except for the 
following: 

When all key exchange messages are sent from the server and back from the 
client the client sends the "Finished" message which 
is the first encrypted with the negotiated symmetric cipher suite. I use 
AES-128 in block mode and according to the spec (RFC4346 for TLS 1.1) 
the IV is prepended to the encrypted message (containing the payload, MAC and 
padding). The message size i right and when (in the server) I use the first 16 
bytes 
of the message received from the client as IV the decryption fails but when I 
use the mechanism from TLS 1.0 to pick up the IV from 
the key_block the decryption is successful. I understand that this is one way 
to generate the IV that I suppose you use which is fine but 
shouldn't this 16 byte vector be prepended, unecrypted, to the encrypted data 
that is sent to the server? In TLS 1.2 there is not IV material generated 
at all in the key_block so in that case I don't even know where to find it. 

The simple question is, shouldn't the first 16 bytes (assuming AES) of the 
message (after the 5 byte header) be the unencrypted IV to be used in the 
decryption of the rest of the message? 

I tried to dig in to the OpenSSL source but it's far too long ago I did some 
serious C coding so I hope someone with a working knowledge can enlighten me. I 
might have
misunderstood the spec but in that case I would be grateful if someone could 
clarify this specific part of it. 

TIA 
Curt Johansson
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To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users