Create sample key material for symmetric keys
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/scripts/mbedtls_dev/crypto_knowledge.py b/scripts/mbedtls_dev/crypto_knowledge.py
index eea7962..2e0fa2f 100644
--- a/scripts/mbedtls_dev/crypto_knowledge.py
+++ b/scripts/mbedtls_dev/crypto_knowledge.py
@@ -85,3 +85,29 @@
assert self.params is not None
return self.ECC_KEY_SIZES[self.params[0]]
return self.KEY_TYPE_SIZES[self.private_type]
+
+ # "48657265006973206b6579a064617461"
+ DATA_BLOCK = b'Here\000is key\240data'
+ def key_material(self, bits: int) -> bytes:
+ """Return a byte string containing suitable key material with the given bit length.
+
+ Use the PSA export representation. The resulting byte string is one that
+ can be obtained with the following code:
+ ```
+ psa_set_key_type(&attributes, `self.expression`);
+ psa_set_key_bits(&attributes, `bits`);
+ psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_EXPORT);
+ psa_generate_key(&attributes, &id);
+ psa_export_key(id, `material`, ...);
+ ```
+ """
+ if bits % 8 != 0:
+ raise ValueError('Non-integer number of bytes: {} bits'.format(bits))
+ length = bits // 8
+ if self.name == 'PSA_KEY_TYPE_DES':
+ # "644573206b457901644573206b457902644573206b457904"
+ des3 = b'dEs kEy\001dEs kEy\002dEs kEy\004'
+ return des3[:length]
+ # TODO: ECC, RSA
+ return b''.join([self.DATA_BLOCK] * (length // len(self.DATA_BLOCK)) +
+ [self.DATA_BLOCK[:length % len(self.DATA_BLOCK)]])
