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How will be cipher selected when client is running on version TLS 1.3 and server is running on TLS 1.2?

The 9 lives of Bleichenbacher's CAT, it puts another scratch againWhat is the 'Version Incompatibility" Problem in TLS 1.1/1.2 and 1.0?Is what i'm trying to do safe?What does the TLS 1.2 client finished message contain?Can the TLS 1.3 PSK-DHE handshake be turned into a PAKE?What is the format of the TLS extension field?Is TLS 1.2 compression methods in client_hello a mandatory field?How is the TLS 1.2 sequence number generated?In a TLS 1.3 connection, how do the client and server choose a mutual cipher suite?Which 'info' and 'salt' parameters to use in HKDF for TLS 1.3?Why Static RSA and Diffie-Hellman cipher suites have been removed in TLS 1.3?

3

1

$begingroup$

How will be cipher selected when a client is running on version TLS 1.3 and server is running on TLS 1.2?

The cipher list provided by TLS 1.3 client will be different than the version supported on the TLS 1.2 server.

encryption tls key-derivation

share|improve this question

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Note: Downgrade can be very dangerous. See The 9 lives of Bleichenbacher's CAT, it puts another scratch again
  $endgroup$
  – kelalaka
  Apr 21 at 17:18
  

  
  
  
  

add a comment | 

3

1

$begingroup$

How will be cipher selected when a client is running on version TLS 1.3 and server is running on TLS 1.2?

The cipher list provided by TLS 1.3 client will be different than the version supported on the TLS 1.2 server.

encryption tls key-derivation

share|improve this question

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Note: Downgrade can be very dangerous. See The 9 lives of Bleichenbacher's CAT, it puts another scratch again
  $endgroup$
  – kelalaka
  Apr 21 at 17:18
  

  
  
  
  

add a comment | 

$begingroup$

How will be cipher selected when a client is running on version TLS 1.3 and server is running on TLS 1.2?

The cipher list provided by TLS 1.3 client will be different than the version supported on the TLS 1.2 server.

encryption tls key-derivation

share|improve this question

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

$endgroup$

share|improve this question

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

share|improve this question

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

edited Apr 23 at 9:04

Maarten Bodewes♦

56.3k679197

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

asked Apr 21 at 13:59

rakesh sharmarakesh sharma

262

1 Answer
1

active

oldest

votes

4

$begingroup$

If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake will fail. Otherwise the cipher will be selected as it is usually done with TLS 1.2: the client shows which ciphers it supports in the ClientHello and the server will pick the one which a) is supported by the server and b) fits the type of certificate of the server (i.e. authentication RSA or ECDSA). If there is no common cipher the handshake will fail.

share|improve this answer

edited Apr 21 at 20:25

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  As we know the cipher list of TLS1.3 is completely different then TlS1.2 and below version. Here my question is, if server supports tls1.2 and below version, how the cipher will be selected from the cipher list available in client hello of TLS1.3 version(where cipher list available in tls1.3 is different then tls1.2)
  $endgroup$
  – rakesh sharma
  Apr 21 at 19:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma This might lead to the two lists having no entries in common, hence connection failure
  $endgroup$
  – Hagen von Eitzen
  Apr 21 at 19:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma: If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake fails. If the client supports also older ciphers and TLS 1.2 and there is cipher overlap with the server then the server can pick a shared cipher, otherwise it will fail.
  $endgroup$
  – Steffen Ullrich
  Apr 21 at 20:27
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @SteffenUllrich Thanks for your reply, Actually in one openssl Library(1.1.*), the cipher list provided by client was only having the ciphers supported in tls1.3 though client was supporting all the version(i confirmed it by checking the supported_version extension ) so i thought if this is the case then it will never work if server supports the version below tls_1.3 because of no common ciphers and will break everything. i have not observed the same in the latest openssl library(1.1.1b) , it includes all the previous ciphers in cipher list along with new ciphers.
  $endgroup$
  – rakesh sharma
  Apr 22 at 10:05
  

  
  
  
  

add a comment | 

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4

$begingroup$

If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake will fail. Otherwise the cipher will be selected as it is usually done with TLS 1.2: the client shows which ciphers it supports in the ClientHello and the server will pick the one which a) is supported by the server and b) fits the type of certificate of the server (i.e. authentication RSA or ECDSA). If there is no common cipher the handshake will fail.

share|improve this answer

edited Apr 21 at 20:25

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  As we know the cipher list of TLS1.3 is completely different then TlS1.2 and below version. Here my question is, if server supports tls1.2 and below version, how the cipher will be selected from the cipher list available in client hello of TLS1.3 version(where cipher list available in tls1.3 is different then tls1.2)
  $endgroup$
  – rakesh sharma
  Apr 21 at 19:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma This might lead to the two lists having no entries in common, hence connection failure
  $endgroup$
  – Hagen von Eitzen
  Apr 21 at 19:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma: If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake fails. If the client supports also older ciphers and TLS 1.2 and there is cipher overlap with the server then the server can pick a shared cipher, otherwise it will fail.
  $endgroup$
  – Steffen Ullrich
  Apr 21 at 20:27
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @SteffenUllrich Thanks for your reply, Actually in one openssl Library(1.1.*), the cipher list provided by client was only having the ciphers supported in tls1.3 though client was supporting all the version(i confirmed it by checking the supported_version extension ) so i thought if this is the case then it will never work if server supports the version below tls_1.3 because of no common ciphers and will break everything. i have not observed the same in the latest openssl library(1.1.1b) , it includes all the previous ciphers in cipher list along with new ciphers.
  $endgroup$
  – rakesh sharma
  Apr 22 at 10:05
  

  
  
  
  

add a comment | 

4

$begingroup$

If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake will fail. Otherwise the cipher will be selected as it is usually done with TLS 1.2: the client shows which ciphers it supports in the ClientHello and the server will pick the one which a) is supported by the server and b) fits the type of certificate of the server (i.e. authentication RSA or ECDSA). If there is no common cipher the handshake will fail.

share|improve this answer

edited Apr 21 at 20:25

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  As we know the cipher list of TLS1.3 is completely different then TlS1.2 and below version. Here my question is, if server supports tls1.2 and below version, how the cipher will be selected from the cipher list available in client hello of TLS1.3 version(where cipher list available in tls1.3 is different then tls1.2)
  $endgroup$
  – rakesh sharma
  Apr 21 at 19:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma This might lead to the two lists having no entries in common, hence connection failure
  $endgroup$
  – Hagen von Eitzen
  Apr 21 at 19:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @rakeshsharma: If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake fails. If the client supports also older ciphers and TLS 1.2 and there is cipher overlap with the server then the server can pick a shared cipher, otherwise it will fail.
  $endgroup$
  – Steffen Ullrich
  Apr 21 at 20:27
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @SteffenUllrich Thanks for your reply, Actually in one openssl Library(1.1.*), the cipher list provided by client was only having the ciphers supported in tls1.3 though client was supporting all the version(i confirmed it by checking the supported_version extension ) so i thought if this is the case then it will never work if server supports the version below tls_1.3 because of no common ciphers and will break everything. i have not observed the same in the latest openssl library(1.1.1b) , it includes all the previous ciphers in cipher list along with new ciphers.
  $endgroup$
  – rakesh sharma
  Apr 22 at 10:05
  

  
  
  
  

add a comment | 

$begingroup$

If the client is only supporting TLS 1.3 or only TLS 1.3 ciphers the SSL handshake will fail. Otherwise the cipher will be selected as it is usually done with TLS 1.2: the client shows which ciphers it supports in the ClientHello and the server will pick the one which a) is supported by the server and b) fits the type of certificate of the server (i.e. authentication RSA or ECDSA). If there is no common cipher the handshake will fail.

share|improve this answer

edited Apr 21 at 20:25

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

$endgroup$

share|improve this answer

edited Apr 21 at 20:25

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136

answered Apr 21 at 15:58

Steffen UllrichSteffen Ullrich

76136