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Implement generalised RSA public exponents for verified boot

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Remove the verified boot limitation that only allows a single
RSA public exponent of 65537 (F4).  This change allows use with
existing PKI infrastructure and has been tested with HSM-based
PKI.

Change the configuration OF tree format to store the RSA public
exponent as a 64 bit integer and implement backward compatibility
for verified boot configuration trees without this extra field.

Parameterise vboot_test.sh to test different public exponents.

Mathematics and other hard work by Andrew Bott.

Tested with the following public exponents: 3, 5, 17, 257, 39981,
50457, 65537 and 4294967297.

Signed-off-by: Andrew Bott <Andrew.Bott@ipaccess.com>
Signed-off-by: Andrew Wishart <Andrew.Wishart@ipaccess.com>
Signed-off-by: Neil Piercy <Neil.Piercy@ipaccess.com>
Signed-off-by: Michael van der Westhuizen <michael@smart-africa.com>
Cc: Simon Glass <sjg@chromium.org>
This commit is contained in:
Michael van der Westhuizen
2014-07-02 10:17:26 +02:00
committed by Tom Rini
parent 53022c3113
commit e0f2f15534
5 changed files with 158 additions and 10 deletions
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60
lib/rsa/rsa-sign.c
View File

@@ -260,11 +260,58 @@ err_priv:
return ret;
}
/*
* rsa_get_exponent(): - Get the public exponent from an RSA key
*/
static int rsa_get_exponent(RSA *key, uint64_t *e)
{
int ret;
BIGNUM *bn_te;
uint64_t te;
ret = -EINVAL;
bn_te = NULL;
if (!e)
goto cleanup;
if (BN_num_bits(key->e) > 64)
goto cleanup;
*e = BN_get_word(key->e);
if (BN_num_bits(key->e) < 33) {
ret = 0;
goto cleanup;
}
bn_te = BN_dup(key->e);
if (!bn_te)
goto cleanup;
if (!BN_rshift(bn_te, bn_te, 32))
goto cleanup;
if (!BN_mask_bits(bn_te, 32))
goto cleanup;
te = BN_get_word(bn_te);
te <<= 32;
*e |= te;
ret = 0;
cleanup:
if (bn_te)
BN_free(bn_te);
return ret;
}
/*
* rsa_get_params(): - Get the important parameters of an RSA public key
*/
int rsa_get_params(RSA *key, uint32_t *n0_invp, BIGNUM **modulusp,
BIGNUM **r_squaredp)
int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
BIGNUM **modulusp, BIGNUM **r_squaredp)
{
BIGNUM *big1, *big2, *big32, *big2_32;
BIGNUM *n, *r, *r_squared, *tmp;
@@ -286,6 +333,9 @@ int rsa_get_params(RSA *key, uint32_t *n0_invp, BIGNUM **modulusp,
return -ENOMEM;
}
if (0 != rsa_get_exponent(key, exponent))
ret = -1;
if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
!BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
ret = -1;
@@ -386,6 +436,7 @@ static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
{
BIGNUM *modulus, *r_squared;
uint64_t exponent;
uint32_t n0_inv;
int parent, node;
char name[100];
@@ -397,7 +448,7 @@ int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
ret = rsa_get_pub_key(info->keydir, info->keyname, &rsa);
if (ret)
return ret;
ret = rsa_get_params(rsa, &n0_inv, &modulus, &r_squared);
ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
if (ret)
return ret;
bits = BN_num_bits(modulus);
@@ -441,6 +492,9 @@ int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
if (!ret)
ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
if (!ret) {
ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
}
if (!ret) {
ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
bits);