Just so that we notice in the future if another hash function is added
without updating this utility function, make it panic when passed an
unknown handshake hash function. (Which should never happen.)
Change-Id: I60a6fc01669441523d8c44e8fbe7ed435e7f04c8
Reviewed-on: https://go-review.googlesource.com/7646
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Joël Stemmer <stemmertech@gmail.com>
Commit f1d669aee994b28e1afcfe974680565932d25b70 added support for
AES_256_GCM_SHA384 cipher suites as specified in RFC5289. However, it
did not take the arbitrary hash function into account in the TLS client
handshake when using client certificates.
The hashForClientCertificate method always returned SHA256 as its
hashing function, even if it actually used a different one to calculate
its digest. Setting up the connection would eventually fail with the
error "tls: failed to sign handshake with client certificate:
crypto/rsa: input must be hashed message".
Included is an additional test for this specific situation that uses the
SHA384 hash.
Fixes#9808
Change-Id: Iccbf4ab225633471ef897907c208ad31f92855a3
Reviewed-on: https://go-review.googlesource.com/7040
Reviewed-by: Adam Langley <agl@golang.org>
Run-TryBot: Adam Langley <agl@golang.org>
Some servers which misunderstood the point of the CertificateRequest
message send huge reply records. These records are large enough that
they were considered “insane” by the TLS code and rejected.
This change removes the sanity test for record lengths. Although the
maxCiphertext test still remains, just above, which (roughly) enforces
the 16KB protocol limit on record sizes:
https://tools.ietf.org/html/rfc5246#section-6.2.1Fixes#8928.
Change-Id: Idf89a2561b1947325b7ddc2613dc2da638d7d1c9
Reviewed-on: https://go-review.googlesource.com/5690
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Only documentation / comment changes. Update references to
point to golang.org permalinks or go.googlesource.com/go.
References in historical release notes under doc are left as is.
Change-Id: Icfc14e4998723e2c2d48f9877a91c5abef6794ea
Reviewed-on: https://go-review.googlesource.com/4060
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Generalizes PRF calculation for TLS 1.2 to support arbitrary hashes (SHA-384 instead of SHA-256).
Testdata were all updated to correspond with the new cipher suites in the handshake.
Change-Id: I3d9fc48c19d1043899e38255a53c80dc952ee08f
Reviewed-on: https://go-review.googlesource.com/3265
Reviewed-by: Adam Langley <agl@golang.org>
ECDSA is unsafe to use if an entropy source produces predictable
output for the ephemeral nonces. E.g., [Nguyen]. A simple
countermeasure is to hash the secret key, the message, and
entropy together to seed a CSPRNG, from which the ephemeral key
is derived.
Fixes#9452
--
This is a minimalist (in terms of patch size) solution, though
not the most parsimonious in its use of primitives:
- csprng_key = ChopMD-256(SHA2-512(priv.D||entropy||hash))
- reader = AES-256-CTR(k=csprng_key)
This, however, provides at most 128-bit collision-resistance,
so that Adv will have a term related to the number of messages
signed that is significantly worse than plain ECDSA. This does
not seem to be of any practical importance.
ChopMD-256(SHA2-512(x)) is used, rather than SHA2-256(x), for
two sets of reasons:
*Practical:* SHA2-512 has a larger state and 16 more rounds; it
is likely non-generically stronger than SHA2-256. And, AFAIK,
cryptanalysis backs this up. (E.g., [Biryukov] gives a
distinguisher on 47-round SHA2-256 with cost < 2^85.) This is
well below a reasonable security-strength target.
*Theoretical:* [Coron] and [Chang] show that Chop-MD(F(x)) is
indifferentiable from a random oracle for slightly beyond the
birthday barrier. It seems likely that this makes a generic
security proof that this construction remains UF-CMA is
possible in the indifferentiability framework.
--
Many thanks to Payman Mohassel for reviewing this construction;
any mistakes are mine, however. And, as he notes, reusing the
private key in this way means that the generic-group (non-RO)
proof of ECDSA's security given in [Brown] no longer directly
applies.
--
[Brown]: http://www.cacr.math.uwaterloo.ca/techreports/2000/corr2000-54.ps
"Brown. The exact security of ECDSA. 2000"
[Coron]: https://www.cs.nyu.edu/~puniya/papers/merkle.pdf
"Coron et al. Merkle-Damgard revisited. 2005"
[Chang]: 50860436.pdf
"Chang and Nandi. Improved indifferentiability security analysis
of chopMD hash function. 2008"
[Biryukov]: 70730269.pdf
"Biryukov et al. Second-order differential collisions for reduced
SHA-256. 2011"
[Nguyen]: ftp://ftp.di.ens.fr/pub/users/pnguyen/PubECDSA.ps
"Nguyen and Shparlinski. The insecurity of the elliptic curve
digital signature algorithm with partially known nonces. 2003"
New tests:
TestNonceSafety: Check that signatures are safe even with a
broken entropy source.
TestINDCCA: Check that signatures remain non-deterministic
with a functional entropy source.
Updated "golden" KATs in crypto/tls/testdata that use ECDSA suites.
Change-Id: I55337a2fbec2e42a36ce719bd2184793682d678a
Reviewed-on: https://go-review.googlesource.com/3340
Reviewed-by: Adam Langley <agl@golang.org>
There are two methods by which TLS clients signal the renegotiation
extension: either a special cipher suite value or a TLS extension.
It appears that I left debugging code in when I landed support for the
extension because there's a "+ 1" in the switch statement that shouldn't
be there.
The effect of this is very small, but it will break Firefox if
security.ssl.require_safe_negotiation is enabled in about:config.
(Although almost nobody does this.)
This change fixes the original bug and adds a test. Sadly the test is a
little complex because there's no OpenSSL s_client option that mirrors
that behaviour of require_safe_negotiation.
Change-Id: Ia6925c7d9bbc0713e7104228a57d2d61d537c07a
Reviewed-on: https://go-review.googlesource.com/1900
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
SSLv3 (the old minimum) is still supported and can be enabled via the
tls.Config, but this change increases the default minimum version to TLS
1.0. This is now common practice in light of the POODLE[1] attack
against SSLv3's CBC padding format.
[1] https://www.imperialviolet.org/2014/10/14/poodle.htmlFixes#9364.
Change-Id: Ibae6666ee038ceee0cb18c339c393155928c6510
Reviewed-on: https://go-review.googlesource.com/1791
Reviewed-by: Minux Ma <minux@golang.org>
Fix TLS_FALLBACK_SCSV check when comparing the client version to the
default max version. This enables the TLS_FALLBACK_SCSV check by default
in servers that do not explicitly set a max version in the tls config.
Change-Id: I5a51f9da6d71b79bc6c2ba45032be51d0f704b5e
Reviewed-on: https://go-review.googlesource.com/1776
Reviewed-by: Adam Langley <agl@golang.org>
A new attack on CBC padding in SSLv3 was released yesterday[1]. Go only
supports SSLv3 as a server, not as a client. An easy fix is to change
the default minimum version to TLS 1.0 but that seems a little much
this late in the 1.4 process as it may break some things.
Thus this patch adds server support for TLS_FALLBACK_SCSV[2] -- a
mechanism for solving the fallback problem overall. Chrome has
implemented this since February and Google has urged others to do so in
light of yesterday's news.
With this change, clients can indicate that they are doing a fallback
connection and Go servers will be able to correctly reject them.
[1] http://googleonlinesecurity.blogspot.com/2014/10/this-poodle-bites-exploiting-ssl-30.html
[2] https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/157090043
