The following errata report has been submitted for RFC5751,
"Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message
Specification".
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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=5751&eid=10000
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Type: Technical
Reported by: Derek Edson <Derek(_dot_)Edson(_at_)sss(_dot_)co(_dot_)nz>
Section: 3.4.3.2
Original Text
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The micalg parameter allows for one-pass processing when the
signature is being verified. The value of the micalg parameter is
dependent on the message digest algorithm(s) used in the calculation
of the Message Integrity Check. If multiple message digest
algorithms are used, they MUST be separated by commas per [MIME-
SECURE]. The values to be placed in the micalg parameter SHOULD be
from the following:
Algorithm Value Used
MD5 md5
SHA-1 sha-1
SHA-224 sha-224
SHA-256 sha-256
SHA-384 sha-384
SHA-512 sha-512
Any other (defined separately in algorithm profile or "unknown"
if not defined)
(Historical note: some early implementations of S/MIME emitted and
expected "rsa-md5", "rsa-sha1", and "sha1" for the micalg parameter.)
Receiving agents SHOULD be able to recover gracefully from a micalg
parameter value that they do not recognize. Future names for this
parameter will be consistent with the IANA "Hash Function Textual
Names" registry.
Corrected Text
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Notes
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This revision creates a backward compatibility issue with S/MIME v2, S/MIME v3
and S/MIME v3.1 agents. In each of the previous (obsoleted) standards, they
all refer to the micalg for SHA-1 as "sha1" and not "sha-1".
The historical note should mean that v3.2 agents will recognize "sha1" as
emitted by earlier implementations, but these implementations are unlikely to
recognize the micalg value of "sha-1" emitted by a v3.2 agent.
All previous standards state that receiving agents SHOULD be able to handle
this situation gracefully, but when these agents fail to recognize a micalg
value, they can no longer perform a "one-pass processing". Given that this
parameter is "required", the most likely implication is that they will fail to
verify the signature.
To ensure interoperability with clients supporting previous versions, the
micalg for SHA-1 MUST remain as "sha1", and receiving agents SHOULD also accept
"sha-1".
The micalg parameters values have always been defined as "SHOULD", but for
interoperability they should be declared as "MUST".
Instructions:
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RFC5751 (draft-ietf-smime-3851bis-11)
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Title : Secure/Multipurpose Internet Mail Extensions (S/MIME)
Version 3.2 Message Specification
Publication Date : January 2010
Author(s) : B. Ramsdell, S. Turner
Category : PROPOSED STANDARD
Source : S/MIME Mail Security
Area : Security
Stream : IETF
Verifying Party : IESG
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