Clarify what MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH and
MBEDTLS_ERR_PK_SIG_LEN_MISMATCH mean. Add comments to highlight that
this indicates that a valid signature is present, unlike other error
codes. See
https://github.com/ARMmbed/mbedtls/pull/1149#discussion_r178130705
The relevant ASN.1 definitions for a PKCS#8 encoded Elliptic Curve key are:
PrivateKeyInfo ::= SEQUENCE {
version Version,
privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
privateKey PrivateKey,
attributes [0] IMPLICIT Attributes OPTIONAL
}
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL
}
ECParameters ::= CHOICE {
namedCurve OBJECT IDENTIFIER
-- implicitCurve NULL
-- specifiedCurve SpecifiedECDomain
}
ECPrivateKey ::= SEQUENCE {
version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
privateKey OCTET STRING,
parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
publicKey [1] BIT STRING OPTIONAL
}
Because of the two optional fields, there are 4 possible variants that need to
be parsed: no optional fields, only parameters, only public key, and both
optional fields. Previously mbedTLS was unable to parse keys with "only
parameters". Also, only "only public key" was tested. There was a test for "no
optional fields", but it was labelled incorrectly as SEC.1 and not run because
of a great renaming mixup.
Initializing arrays using non-constant expressions is not permitted in
C89, and was causing errors when compiling with Metrowerks CodeWarrior
(for classic MacOS) in C89 mode. Clang also produces a warning when
compiling with '-Wc99-extensions':
test/benchmark.c:670:42: warning: initializer for aggregate is not a compile-time constant [-Wc99-extensions]
const unsigned char *dhm_P[] = { dhm_P_2048, dhm_P_3072 };
^~~~~~~~~~
test/benchmark.c:674:42: warning: initializer for aggregate is not a compile-time constant [-Wc99-extensions]
const unsigned char *dhm_G[] = { dhm_G_2048, dhm_G_3072 };
^~~~~~~~~~
Declaring the arrays as 'static' makes them constant expressions.
fixes#1353
