summaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
Diffstat (limited to 'lib')
-rw-r--r--lib/rsa/rsa-sign.c60
-rw-r--r--lib/rsa/rsa-verify.c93
2 files changed, 145 insertions, 8 deletions
diff --git a/lib/rsa/rsa-sign.c b/lib/rsa/rsa-sign.c
index 83f5e87..f4d4338 100644
--- a/lib/rsa/rsa-sign.c
+++ b/lib/rsa/rsa-sign.c
@@ -261,10 +261,57 @@ err_priv:
}
/*
+ * 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);
@@ -442,6 +493,9 @@ int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
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);
}
diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
index bcb9063..c5bcdb6 100644
--- a/lib/rsa/rsa-verify.c
+++ b/lib/rsa/rsa-verify.c
@@ -26,6 +26,9 @@
#define get_unaligned_be32(a) fdt32_to_cpu(*(uint32_t *)a)
#define put_unaligned_be32(a, b) (*(uint32_t *)(b) = cpu_to_fdt32(a))
+/* Default public exponent for backward compatibility */
+#define RSA_DEFAULT_PUBEXP 65537
+
/**
* subtract_modulus() - subtract modulus from the given value
*
@@ -123,6 +126,48 @@ static void montgomery_mul(const struct rsa_public_key *key,
}
/**
+ * num_pub_exponent_bits() - Number of bits in the public exponent
+ *
+ * @key: RSA key
+ * @num_bits: Storage for the number of public exponent bits
+ */
+static int num_public_exponent_bits(const struct rsa_public_key *key,
+ int *num_bits)
+{
+ uint64_t exponent;
+ int exponent_bits;
+ const uint max_bits = (sizeof(exponent) * 8);
+
+ exponent = key->exponent;
+ exponent_bits = 0;
+
+ if (!exponent) {
+ *num_bits = exponent_bits;
+ return 0;
+ }
+
+ for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits)
+ if (!(exponent >>= 1)) {
+ *num_bits = exponent_bits;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+/**
+ * is_public_exponent_bit_set() - Check if a bit in the public exponent is set
+ *
+ * @key: RSA key
+ * @pos: The bit position to check
+ */
+static int is_public_exponent_bit_set(const struct rsa_public_key *key,
+ int pos)
+{
+ return key->exponent & (1ULL << pos);
+}
+
+/**
* pow_mod() - in-place public exponentiation
*
* @key: RSA key
@@ -132,6 +177,7 @@ static int pow_mod(const struct rsa_public_key *key, uint32_t *inout)
{
uint32_t *result, *ptr;
uint i;
+ int j, k;
/* Sanity check for stack size - key->len is in 32-bit words */
if (key->len > RSA_MAX_KEY_BITS / 32) {
@@ -141,18 +187,48 @@ static int pow_mod(const struct rsa_public_key *key, uint32_t *inout)
}
uint32_t val[key->len], acc[key->len], tmp[key->len];
+ uint32_t a_scaled[key->len];
result = tmp; /* Re-use location. */
/* Convert from big endian byte array to little endian word array. */
for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--)
val[i] = get_unaligned_be32(ptr);
- montgomery_mul(key, acc, val, key->rr); /* axx = a * RR / R mod M */
- for (i = 0; i < 16; i += 2) {
- montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod M */
- montgomery_mul(key, acc, tmp, tmp); /* acc = tmp^2 / R mod M */
+ if (0 != num_public_exponent_bits(key, &k))
+ return -EINVAL;
+
+ if (k < 2) {
+ debug("Public exponent is too short (%d bits, minimum 2)\n",
+ k);
+ return -EINVAL;
}
- montgomery_mul(key, result, acc, val); /* result = XX * a / R mod M */
+
+ if (!is_public_exponent_bit_set(key, 0)) {
+ debug("LSB of RSA public exponent must be set.\n");
+ return -EINVAL;
+ }
+
+ /* the bit at e[k-1] is 1 by definition, so start with: C := M */
+ montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */
+ /* retain scaled version for intermediate use */
+ memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0]));
+
+ for (j = k - 2; j > 0; --j) {
+ montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
+
+ if (is_public_exponent_bit_set(key, j)) {
+ /* acc = tmp * val / R mod n */
+ montgomery_mul(key, acc, tmp, a_scaled);
+ } else {
+ /* e[j] == 0, copy tmp back to acc for next operation */
+ memcpy(acc, tmp, key->len * sizeof(acc[0]));
+ }
+ }
+
+ /* the bit at e[0] is always 1 */
+ montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */
+ montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */
+ memcpy(result, acc, key->len * sizeof(result[0]));
/* Make sure result < mod; result is at most 1x mod too large. */
if (greater_equal_modulus(key, result))
@@ -229,6 +305,8 @@ static int rsa_verify_with_keynode(struct image_sign_info *info,
const void *blob = info->fdt_blob;
struct rsa_public_key key;
const void *modulus, *rr;
+ const uint64_t *public_exponent;
+ int length;
int ret;
if (node < 0) {
@@ -241,6 +319,11 @@ static int rsa_verify_with_keynode(struct image_sign_info *info,
}
key.len = fdtdec_get_int(blob, node, "rsa,num-bits", 0);
key.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0);
+ public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length);
+ if (!public_exponent || length < sizeof(*public_exponent))
+ key.exponent = RSA_DEFAULT_PUBEXP;
+ else
+ key.exponent = fdt64_to_cpu(*public_exponent);
modulus = fdt_getprop(blob, node, "rsa,modulus", NULL);
rr = fdt_getprop(blob, node, "rsa,r-squared", NULL);
if (!key.len || !modulus || !rr) {
generated by cgit v1.1 at 2024-12-02 00:35:58 +0000