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| author | Martijn Coenen <maco@google.com> | 2021-04-21 10:44:04 +0200 |
|---|---|---|
| committer | Martijn Coenen <maco@google.com> | 2021-05-25 08:47:37 +0200 |
| commit | 7278a33e1c0cd20fccf4cfd9f49537ccde49c2d0 (patch) | |
| tree | aea2cf10d71b278be9036e78aad0639f5a216f11 /ondevice-signing/KeyConstants.h | |
| parent | 9b885740bff1fdf8a110f19b3530e98360b40b4a (diff) | |
| download | security-7278a33e1c0cd20fccf4cfd9f49537ccde49c2d0.tar.gz | |
On-device signing: verify the public key.
While we can generally trust the key properties of the Keystore key to
be correct, the public key certificate that Keystore returns in
KeyMetadata is simply retrieved from an on-disk database. This allows
an attacker that gets filesystem access to simply modify the public key,
and we will happily accept that (and the artifacts that are signed with
the private key component).
To prevent this, sign the public key itself with another HMAC key that
carries the same boot level as the signing key. This is secure, because
in order to forge such a signature, an attacker would need to create an
HMAC key with the same boot level, which is not possible once early boot
has passed.
Bug: 187862706
Test: TEST_MAPPING
Change-Id: I688fff83f73b1df4e91c3fa03c43df647703d9f8
Diffstat (limited to 'ondevice-signing/KeyConstants.h')
| -rw-r--r-- | ondevice-signing/KeyConstants.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/ondevice-signing/KeyConstants.h b/ondevice-signing/KeyConstants.h index 9e1a5137..ccc9251c 100644 --- a/ondevice-signing/KeyConstants.h +++ b/ondevice-signing/KeyConstants.h @@ -16,3 +16,6 @@ static constexpr int kRsaKeySize = 2048; static constexpr int kRsaKeyExponent = 65537; + +static constexpr int kHmacKeySize = 256; +static constexpr int kHmacMinMacLength = 256; |