target = "https://tools.ietf.org/rfc/rfc8446#7.5"

# 7.5.  Exporters
#
# [RFC5705] defines keying material exporters for TLS in terms of the
# TLS pseudorandom function (PRF).  This document replaces the PRF with
# HKDF, thus requiring a new construction.  The exporter interface
# remains the same.
# 
# The exporter value is computed as:
# 
# TLS-Exporter(label, context_value, key_length) =
#     HKDF-Expand-Label(Derive-Secret(Secret, label, ""),
#                       "exporter", Hash(context_value), key_length)
# 
# Where Secret is either the early_exporter_master_secret or the
# exporter_master_secret.  Implementations MUST use the
# exporter_master_secret unless explicitly specified by the
# application.  The early_exporter_master_secret is defined for use in
# settings where an exporter is needed for 0-RTT data.  A separate
# interface for the early exporter is RECOMMENDED; this avoids the
# exporter user accidentally using an early exporter when a regular one
# is desired or vice versa.
# 
# If no context is provided, the context_value is zero length.
# Consequently, providing no context computes the same value as
# providing an empty context.  This is a change from previous versions
# of TLS where an empty context produced a different output than an
# absent context.  As of this document's publication, no allocated
# exporter label is used both with and without a context.  Future
# specifications MUST NOT define a use of exporters that permit both an
# empty context and no context with the same label.  New uses of
# exporters SHOULD provide a context in all exporter computations,
# though the value could be empty.
# 
# Requirements for the format of exporter labels are defined in
# Section 4 of [RFC5705].

[[spec]]
level = "MUST"
quote = '''
Implementations MUST use the
exporter_master_secret unless explicitly specified by the
application.
'''

[[spec]]
level = "SHOULD"
quote = '''
A separate
interface for the early exporter is RECOMMENDED; this avoids the
exporter user accidentally using an early exporter when a regular one
is desired or vice versa.
'''

[[spec]]
level = "MUST"
quote = '''
Future
specifications MUST NOT define a use of exporters that permit both an
empty context and no context with the same label.
'''

[[spec]]
level = "SHOULD"
quote = '''
New uses of
exporters SHOULD provide a context in all exporter computations,
though the value could be empty.
'''