[PATCH 2/3] crypto: add RSA support
Marc Kleine-Budde
mkl at pengutronix.de
Tue Jan 5 00:11:02 PST 2016
From: Sascha Hauer <s.hauer at pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl at pengutronix.de>
---
crypto/Kconfig | 3 +
crypto/Makefile | 1 +
crypto/rsa.c | 420 ++++++++++++++++++++++++++++++++++++++++++++
include/asm-generic/errno.h | 5 +
include/rsa.h | 54 ++++++
5 files changed, 483 insertions(+)
create mode 100644 crypto/rsa.c
create mode 100644 include/rsa.h
diff --git a/crypto/Kconfig b/crypto/Kconfig
index 41145a312d8e..ca6f03a1edd1 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -87,6 +87,9 @@ config CRYPTO_PBKDF2
select DIGEST_SHA1_GENERIC
bool
+config CRYPTO_RSA
+ bool
+
config CRYPTO_KEYSTORE
bool "Keystore"
help
diff --git a/crypto/Makefile b/crypto/Makefile
index c6d17787ca4e..b4fb3d8da01f 100644
--- a/crypto/Makefile
+++ b/crypto/Makefile
@@ -11,4 +11,5 @@ obj-$(CONFIG_DIGEST_SHA384_GENERIC) += sha4.o
obj-$(CONFIG_DIGEST_SHA512_GENERIC) += sha4.o
obj-$(CONFIG_CRYPTO_PBKDF2) += pbkdf2.o
+obj-$(CONFIG_CRYPTO_RSA) += rsa.o
obj-$(CONFIG_CRYPTO_KEYSTORE) += keystore.o
diff --git a/crypto/rsa.c b/crypto/rsa.c
new file mode 100644
index 000000000000..3caee3ce7525
--- /dev/null
+++ b/crypto/rsa.c
@@ -0,0 +1,420 @@
+/*
+ * Copyright (c) 2013, Google Inc.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <common.h>
+#include <malloc.h>
+#include <of.h>
+#include <digest.h>
+#include <asm/types.h>
+#include <asm/byteorder.h>
+#include <errno.h>
+#include <rsa.h>
+#include <asm/types.h>
+#include <asm/unaligned.h>
+
+#define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby)))
+
+#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
+
+/* This is the minimum/maximum key size we support, in bits */
+#define RSA_MIN_KEY_BITS 1024
+#define RSA_MAX_KEY_BITS 4096
+
+/**
+ * subtract_modulus() - subtract modulus from the given value
+ *
+ * @key: Key containing modulus to subtract
+ * @num: Number to subtract modulus from, as little endian word array
+ */
+static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[])
+{
+ int64_t acc = 0;
+ uint i;
+
+ for (i = 0; i < key->len; i++) {
+ acc += (uint64_t)num[i] - key->modulus[i];
+ num[i] = (uint32_t)acc;
+ acc >>= 32;
+ }
+}
+
+/**
+ * greater_equal_modulus() - check if a value is >= modulus
+ *
+ * @key: Key containing modulus to check
+ * @num: Number to check against modulus, as little endian word array
+ * @return 0 if num < modulus, 1 if num >= modulus
+ */
+static int greater_equal_modulus(const struct rsa_public_key *key,
+ uint32_t num[])
+{
+ int i;
+
+ for (i = (int)key->len - 1; i >= 0; i--) {
+ if (num[i] < key->modulus[i])
+ return 0;
+ if (num[i] > key->modulus[i])
+ return 1;
+ }
+
+ return 1; /* equal */
+}
+
+/**
+ * montgomery_mul_add_step() - Perform montgomery multiply-add step
+ *
+ * Operation: montgomery result[] += a * b[] / n0inv % modulus
+ *
+ * @key: RSA key
+ * @result: Place to put result, as little endian word array
+ * @a: Multiplier
+ * @b: Multiplicand, as little endian word array
+ */
+static void montgomery_mul_add_step(const struct rsa_public_key *key,
+ uint32_t result[], const uint32_t a, const uint32_t b[])
+{
+ uint64_t acc_a, acc_b;
+ uint32_t d0;
+ uint i;
+
+ acc_a = (uint64_t)a * b[0] + result[0];
+ d0 = (uint32_t)acc_a * key->n0inv;
+ acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a;
+ for (i = 1; i < key->len; i++) {
+ acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i];
+ acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] +
+ (uint32_t)acc_a;
+ result[i - 1] = (uint32_t)acc_b;
+ }
+
+ acc_a = (acc_a >> 32) + (acc_b >> 32);
+
+ result[i - 1] = (uint32_t)acc_a;
+
+ if (acc_a >> 32)
+ subtract_modulus(key, result);
+}
+
+/**
+ * montgomery_mul() - Perform montgomery mutitply
+ *
+ * Operation: montgomery result[] = a[] * b[] / n0inv % modulus
+ *
+ * @key: RSA key
+ * @result: Place to put result, as little endian word array
+ * @a: Multiplier, as little endian word array
+ * @b: Multiplicand, as little endian word array
+ */
+static void montgomery_mul(const struct rsa_public_key *key,
+ uint32_t result[], uint32_t a[], const uint32_t b[])
+{
+ uint i;
+
+ for (i = 0; i < key->len; ++i)
+ result[i] = 0;
+ for (i = 0; i < key->len; ++i)
+ montgomery_mul_add_step(key, result, a[i], b);
+}
+
+/**
+ * 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
+ * @inout: Big-endian word array containing value and result
+ */
+static int pow_mod(const struct rsa_public_key *key, void *__inout)
+{
+ uint32_t *inout = __inout;
+ uint32_t *result, *ptr;
+ uint i;
+ int j, k;
+ uint32_t val[RSA_MAX_KEY_BITS / 32], acc[RSA_MAX_KEY_BITS / 32], tmp[RSA_MAX_KEY_BITS / 32];
+ uint32_t a_scaled[RSA_MAX_KEY_BITS / 32];
+
+ /* Sanity check for stack size - key->len is in 32-bit words */
+ if (key->len > RSA_MAX_KEY_BITS / 32) {
+ debug("RSA key words %u exceeds maximum %d\n", key->len,
+ RSA_MAX_KEY_BITS / 32);
+ return -EINVAL;
+ }
+
+ 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);
+
+ 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;
+ }
+
+ 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))
+ subtract_modulus(key, result);
+
+ /* Convert to bigendian byte array */
+ for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++)
+ put_unaligned_be32(result[i], ptr);
+ return 0;
+}
+
+/*
+ * Hash algorithm OIDs plus ASN.1 DER wrappings [RFC4880 sec 5.2.2].
+ */
+static const u8 RSA_digest_info_MD5[] = {
+ 0x30, 0x20, 0x30, 0x0C, 0x06, 0x08,
+ 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* OID */
+ 0x05, 0x00, 0x04, 0x10
+};
+
+static const u8 RSA_digest_info_SHA1[] = {
+ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
+ 0x2B, 0x0E, 0x03, 0x02, 0x1A,
+ 0x05, 0x00, 0x04, 0x14
+};
+
+static const u8 RSA_digest_info_RIPE_MD_160[] = {
+ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
+ 0x2B, 0x24, 0x03, 0x02, 0x01,
+ 0x05, 0x00, 0x04, 0x14
+};
+
+static const u8 RSA_digest_info_SHA224[] = {
+ 0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
+ 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
+ 0x05, 0x00, 0x04, 0x1C
+};
+
+static const u8 RSA_digest_info_SHA256[] = {
+ 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
+ 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
+ 0x05, 0x00, 0x04, 0x20
+};
+
+static const u8 RSA_digest_info_SHA384[] = {
+ 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
+ 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
+ 0x05, 0x00, 0x04, 0x30
+};
+
+static const u8 RSA_digest_info_SHA512[] = {
+ 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
+ 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
+ 0x05, 0x00, 0x04, 0x40
+};
+
+static const struct {
+ const u8 *data;
+ size_t size;
+} RSA_ASN1_templates[] = {
+#define _(X) { RSA_digest_info_##X, sizeof(RSA_digest_info_##X) }
+ [HASH_ALGO_MD5] = _(MD5),
+ [HASH_ALGO_SHA1] = _(SHA1),
+ [HASH_ALGO_RIPE_MD_160] = _(RIPE_MD_160),
+ [HASH_ALGO_SHA256] = _(SHA256),
+ [HASH_ALGO_SHA384] = _(SHA384),
+ [HASH_ALGO_SHA512] = _(SHA512),
+ [HASH_ALGO_SHA224] = _(SHA224),
+#undef _
+};
+
+int rsa_verify(const struct rsa_public_key *key, const uint8_t *sig,
+ const uint32_t sig_len, const uint8_t *hash,
+ enum hash_algo algo)
+{
+ int ret = 0;
+ uint8_t buf[RSA_MAX_SIG_BITS / 8];
+ int i;
+ unsigned PS_end, T_offset;
+ const u8 *asn1_template = RSA_ASN1_templates[algo].data;
+ size_t asn1_size = RSA_ASN1_templates[algo].size;
+ struct digest *d = digest_alloc_by_algo(algo);
+
+ if (!d)
+ return -EOPNOTSUPP;
+
+ if (sig_len != (key->len * sizeof(uint32_t))) {
+ debug("Signature is of incorrect length %d, should be %d\n", sig_len,
+ key->len * sizeof(uint32_t));
+ ret = -EINVAL;
+ goto out_free_digest;
+ }
+
+ /* Sanity check for stack size */
+ if (sig_len > RSA_MAX_SIG_BITS / 8) {
+ debug("Signature length %u exceeds maximum %d\n", sig_len,
+ RSA_MAX_SIG_BITS / 8);
+ ret = -EINVAL;
+ goto out_free_digest;
+ }
+
+ memcpy(buf, sig, sig_len);
+
+ ret = pow_mod(key, buf);
+ if (ret)
+ goto out_free_digest;
+
+ T_offset = sig_len - (asn1_size + digest_length(d));
+
+ PS_end = T_offset - 1;
+ if (buf[PS_end] != 0x00) {
+ pr_err(" = -EBADMSG [EM[T-1] == %02u]", buf[PS_end]);
+ ret = -EBADMSG;
+ goto out_free_digest;
+ }
+
+ for (i = 2; i < PS_end; i++) {
+ if (buf[i] != 0xff) {
+ pr_err(" = -EBADMSG [EM[PS%x] == %02u]", i - 2, buf[i]);
+ ret = -EBADMSG;
+ goto out_free_digest;
+ }
+ }
+
+ if (memcmp(asn1_template, buf + T_offset, asn1_size) != 0) {
+ pr_err(" = -EBADMSG [EM[T] ASN.1 mismatch]");
+ ret = -EBADMSG;
+ goto out_free_digest;
+ }
+
+ if (memcmp(hash, buf + T_offset + asn1_size, digest_length(d)) != 0) {
+ pr_err(" = -EKEYREJECTED [EM[T] hash mismatch]");
+ ret = -EKEYREJECTED;
+ goto out_free_digest;
+ }
+
+ out_free_digest:
+ digest_free(d);
+
+ return ret;
+}
+
+static void rsa_convert_big_endian(uint32_t *dst, const uint32_t *src, int len)
+{
+ int i;
+
+ for (i = 0; i < len; i++)
+ dst[i] = fdt32_to_cpu(src[len - 1 - i]);
+}
+
+int rsa_of_read_key(struct device_node *node, struct rsa_public_key *key)
+{
+ const void *modulus, *rr;
+ const uint64_t *public_exponent;
+ int length;
+
+ of_property_read_u32(node, "rsa,num-bits", &key->len);
+ of_property_read_u32(node, "rsa,n0-inverse", &key->n0inv);
+
+ public_exponent = of_get_property(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 = of_get_property(node, "rsa,modulus", NULL);
+ rr = of_get_property(node, "rsa,r-squared", NULL);
+
+ if (!key->len || !modulus || !rr) {
+ debug("%s: Missing RSA key info", __func__);
+ return -EFAULT;
+ }
+
+ /* Sanity check for stack size */
+ if (key->len > RSA_MAX_KEY_BITS || key->len < RSA_MIN_KEY_BITS) {
+ debug("RSA key bits %u outside allowed range %d..%d\n",
+ key->len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS);
+ return -EFAULT;
+ }
+
+ key->len /= sizeof(uint32_t) * 8;
+
+ key->modulus = xzalloc(RSA_MAX_KEY_BITS / 8);
+ key->rr = xzalloc(RSA_MAX_KEY_BITS / 8);
+
+ rsa_convert_big_endian(key->modulus, modulus, key->len);
+ rsa_convert_big_endian(key->rr, rr, key->len);
+
+ return 0;
+}
diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index 6072f7b605bb..7d99a9537050 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h
@@ -126,6 +126,11 @@
#define ENOMEDIUM 123 /* No medium found */
#define EMEDIUMTYPE 124 /* Wrong medium type */
+#define ECANCELED 125 /* Operation Canceled */
+#define ENOKEY 126 /* Required key not available */
+#define EKEYEXPIRED 127 /* Key has expired */
+#define EKEYREVOKED 128 /* Key has been revoked */
+#define EKEYREJECTED 129 /* Key was rejected by service */
/* Should never be seen by user programs */
#define ERESTARTSYS 512
diff --git a/include/rsa.h b/include/rsa.h
new file mode 100644
index 000000000000..feb8c3120023
--- /dev/null
+++ b/include/rsa.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2013, Google Inc.
+ *
+ * (C) Copyright 2008 Semihalf
+ *
+ * (C) Copyright 2000-2006
+ * Wolfgang Denk, DENX Software Engineering, wd at denx.de.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#ifndef _RSA_H
+#define _RSA_H
+
+#include <errno.h>
+#include <digest.h>
+
+/**
+ * struct rsa_public_key - holder for a public key
+ *
+ * An RSA public key consists of a modulus (typically called N), the inverse
+ * and R^2, where R is 2^(# key bits).
+ */
+
+struct rsa_public_key {
+ uint len; /* len of modulus[] in number of uint32_t */
+ uint32_t n0inv; /* -1 / modulus[0] mod 2^32 */
+ uint32_t *modulus; /* modulus as little endian array */
+ uint32_t *rr; /* R^2 as little endian array */
+ uint64_t exponent; /* public exponent */
+};
+
+/**
+ * rsa_verify() - Verify a signature against some data
+ *
+ * Verify a RSA PKCS1.5 signature against an expected hash.
+ *
+ * @info: Specifies key and FIT information
+ * @data: Pointer to the input data
+ * @data_len: Data length
+ * @sig: Signature
+ * @sig_len: Number of bytes in signature
+ * @return 0 if verified, -ve on error
+ */
+int rsa_verify(const struct rsa_public_key *key, const uint8_t *sig,
+ const uint32_t sig_len, const uint8_t *hash,
+ enum hash_algo algo);
+
+/* This is the maximum signature length that we support, in bits */
+#define RSA_MAX_SIG_BITS 4096
+
+int rsa_of_read_key(struct device_node *node, struct rsa_public_key *key);
+
+#endif
--
2.6.2
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