target = "https://tools.ietf.org/rfc/rfc7627#5.3"

# 5.3.  Client and Server Behavior: Abbreviated Handshake
#
# The client SHOULD NOT offer an abbreviated handshake to resume a
# session that does not use an extended master secret.  Instead, it
# SHOULD offer a full handshake.
# 
# If the client chooses to offer an abbreviated handshake even for such
# sessions in order to support legacy insecure resumption, then the
# current connection is not protected by the mechanisms in this
# document.  So, the client should follow the guidelines in Section 5.4
# 
# to avoid dangerous usage scenarios.  In particular, renegotiation is
# no longer secure on this connection, even if the client and server
# support the renegotiation indication extension [RFC5746].
# 
# When offering an abbreviated handshake, the client MUST send the
# "extended_master_secret" extension in its ClientHello.
# 
# If a server receives a ClientHello for an abbreviated handshake
# offering to resume a known previous session, it behaves as follows:
# 
# o  If the original session did not use the "extended_master_secret"
#    extension but the new ClientHello contains the extension, then the
#    server MUST NOT perform the abbreviated handshake.  Instead, it
#    SHOULD continue with a full handshake (as described in
#    Section 5.2) to negotiate a new session.
# 
# o  If the original session used the "extended_master_secret"
#    extension but the new ClientHello does not contain it, the server
#    MUST abort the abbreviated handshake.
# 
# o  If neither the original session nor the new ClientHello uses the
#    extension, the server SHOULD abort the handshake.  If it continues
#    with an abbreviated handshake in order to support legacy insecure
#    resumption, the connection is no longer protected by the
#    mechanisms in this document, and the server should follow the
#    guidelines in Section 5.4.
# 
# o  If the new ClientHello contains the extension and the server
#    chooses to continue the handshake, then the server MUST include
#    the "extended_master_secret" extension in its ServerHello message.
# 
# If a client receives a ServerHello that accepts an abbreviated
# handshake, it behaves as follows:
# 
# o  If the original session did not use the "extended_master_secret"
#    extension but the new ServerHello contains the extension, the
#    client MUST abort the handshake.
# 
# o  If the original session used the extension but the new ServerHello
#    does not contain the extension, the client MUST abort the
#    handshake.
# 
# If the client and server continue the abbreviated handshake, they
# derive the connection keys for the new session as usual from the
# master secret of the original session.

[[spec]]
level = "SHOULD"
quote = '''
The client SHOULD NOT offer an abbreviated handshake to resume a
session that does not use an extended master secret.
'''

[[spec]]
level = "SHOULD"
quote = '''
Instead, it
SHOULD offer a full handshake.
'''

[[spec]]
level = "MUST"
quote = '''
When offering an abbreviated handshake, the client MUST send the
"extended_master_secret" extension in its ClientHello.
'''

[[spec]]
level = "MUST"
quote = '''
o  If the original session did not use the "extended_master_secret"
extension but the new ClientHello contains the extension, then the
server MUST NOT perform the abbreviated handshake.
'''

[[spec]]
level = "SHOULD"
quote = '''
Instead, it
SHOULD continue with a full handshake (as described in
Section 5.2) to negotiate a new session.
'''

[[spec]]
level = "MUST"
quote = '''
o  If the original session used the "extended_master_secret"
extension but the new ClientHello does not contain it, the server
MUST abort the abbreviated handshake.
'''

[[spec]]
level = "SHOULD"
quote = '''
o  If neither the original session nor the new ClientHello uses the
extension, the server SHOULD abort the handshake.
'''

[[spec]]
level = "MUST"
quote = '''
o  If the new ClientHello contains the extension and the server
chooses to continue the handshake, then the server MUST include
the "extended_master_secret" extension in its ServerHello message.
'''

[[spec]]
level = "MUST"
quote = '''
o  If the original session did not use the "extended_master_secret"
extension but the new ServerHello contains the extension, the
client MUST abort the handshake.
'''

[[spec]]
level = "MUST"
quote = '''
o  If the original session used the extension but the new ServerHello
does not contain the extension, the client MUST abort the
handshake.
'''