SHA-384 is not supported but is selected by signature_schemes_for_key()
for keys between 3072 and 7680 bits.
Since this is only called for IKEv2 signature authentication we don't
even provide SHA-1 anymore. We always provide both schemes, though,
which is what pubkey-authenticator does too for RSA.
Older agents apparently just ignore the flags and always return a SHA-1
signature. If that's the case, charon.signature_authentication has to
be disabled.
Because `keylen` is unsigned the subtraction results in an integer
underflow if the key length is < 11 bytes.
This is only a problem when verifying signatures with a public key (for
private keys the plugin enforces a minimum modulus length) and to do so
we usually only use trusted keys. However, the x509 plugin actually
calls issued_by() on a parsed certificate to check if it is self-signed,
which is the reason this issue was found by OSS-Fuzz in the first place.
So, unfortunately, this can be triggered by sending an invalid client
cert to a peer.
Fixes: 5955db5b12 ("gmp: Don't parse PKCS1 v1.5 RSA signatures to verify them")
Fixes: CVE-2018-17540
Instead we generate the expected signature encoding and compare it to the
decrypted value.
Due to the lenient nature of the previous parsing code (minimum padding
length was not enforced, the algorithmIdentifier/OID parser accepts arbitrary
data after OIDs and in the parameters field etc.) it was susceptible to
Daniel Bleichenbacher's low-exponent attack (from 2006!), which allowed
forging signatures for keys that use low public exponents (i.e. e=3).
Since the public exponent is usually set to 0x10001 (65537) since quite a
while, the flaws in the previous code should not have had that much of a
practical impact in recent years.
Fixes: CVE-2018-16151, CVE-2018-16152
Simplifies public key loading and this way unencrypted PKCS#8-encoded
keys can be loaded directly without pkcs8 plugin (code for encrypted
keys could probably later be added, if necessary).
It also simplifies the implementation of private_key_t::get_public_key()
a lot.
Without OID we can't generate an algorithmIdentifier when loading the
key again. And older versions of OpenSSL insist on a public key when
e.g. converting a key to PKCS#8.
Simply unwrapping the ECPrivateKey structure avoids log messages when
parsing other keys in the KEY_ANY case.
Support MD5 in the Botan plugin if supported by Botan.
MD5 is required for RADIUS and obviously EAP-MD5,
and also for non-PKCS#8 encoded, encrypted private keys.
If the certificate is revoked, we immediately returned and the chain was
invalid, however, if we couldn't fetch the CRL that result was not stored
for intermediate CAs and we weren't able to enforce a strict CRL policy
later.
Using such CRLs can be a problem if the clock on the host doing the
revocation check is trailing behind that of the host issuing CRLs in
scenarios where expired certificates are removed from CRLs. As revoked
certificates that expired will then not be part of new CRLs a host with
trailing clock might still accept such a certificate if it is still
valid according to its system clock but is not contained anymore in the
not yet valid CRL.
Depending on the plugins that eventually parse the certificate and CRL,
serials with MSB set (i.e. negative numbers that have a zero byte prefixed
when encoded as ASN.1 INTEGER) might have (x509 plugin) or not have
(openssl plugin) a zero byte prefix when returned by get_serial() or
enumerated from the CRL. Strip them before doing the comparison or
revocation checking might fail if not both credentials are parsed by the
same plugin (which should be rare and only happen if parsing of either
cert or CRL fails with one of the plugins and there is a fallback to the
implementation provided by the other plugin).
Fixes#2509.
Tobias Brunner