lib: rsa: generate additional parameters for public key
In the current implementation of FIT_SIGNATURE, five parameters for
a RSA public key are required while only two of them are essential.
(See rsa-mod-exp.h and uImage.FIT/signature.txt)
This is a result of considering relatively limited computer power
and resources on embedded systems, while such a assumption may not
be quite practical for other use cases.
In this patch, added is a function, rsa_gen_key_prop(), which will
generate additional parameters for other uses, in particular
UEFI secure boot, on the fly.
Note: the current code uses some "big number" routines from BearSSL
for the calculation.
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/include/u-boot/rsa-mod-exp.h b/include/u-boot/rsa-mod-exp.h
index 8a428c4..1da8af1 100644
--- a/include/u-boot/rsa-mod-exp.h
+++ b/include/u-boot/rsa-mod-exp.h
@@ -27,6 +27,29 @@
};
/**
+ * rsa_gen_key_prop() - Generate key properties of RSA public key
+ * @key: Specifies key data in DER format
+ * @keylen: Length of @key
+ * @prop: Generated key property
+ *
+ * This function takes a blob of encoded RSA public key data in DER
+ * format, parse it and generate all the relevant properties
+ * in key_prop structure.
+ * Return a pointer to struct key_prop in @prop on success.
+ *
+ * Return: 0 on success, negative on error
+ */
+int rsa_gen_key_prop(const void *key, uint32_t keylen, struct key_prop **proc);
+
+/**
+ * rsa_free_key_prop() - Free key properties
+ * @prop: Pointer to struct key_prop
+ *
+ * This function frees all the memories allocated by rsa_gen_key_prop().
+ */
+void rsa_free_key_prop(struct key_prop *prop);
+
+/**
* rsa_mod_exp_sw() - Perform RSA Modular Exponentiation in sw
*
* Operation: out[] = sig ^ exponent % modulus