[PATCH 2/5] scripts: Add rsatoc tool

[Sascha Hauer <s.hauer@pengutronix.de>]

The rsatoc tool converts rsa public keys into C structs suitable to
compile with barebox. Most of the openssl rsa related stuff has been
taken from the U-Boot mkimage tool.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 scripts/.gitignore |   1 +
 scripts/Makefile   |   3 +
 scripts/rsatoc.c   | 445 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 449 insertions(+)
 create mode 100644 scripts/rsatoc.c

diff --git a/scripts/.gitignore b/scripts/.gitignore
index 45c81bf8f4..76ea271abb 100644
--- a/scripts/.gitignore
+++ b/scripts/.gitignore
@@ -29,3 +29,4 @@ mxs-usb-loader
 omap4_usbboot
 omap3-usb-loader
 mips-relocs
+rsatoc
diff --git a/scripts/Makefile b/scripts/Makefile
index dffab53c73..81d1a501b0 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -10,6 +10,9 @@ hostprogs-y                      += fix_size
 hostprogs-y                      += bareboxenv
 hostprogs-y                      += bareboxcrc32
 hostprogs-y                      += kernel-install
+hostprogs-$(CONFIG_CRYPTO_RSA_BUILTIN_KEYS) += rsatoc
+HOSTCFLAGS_rsatoc = `pkg-config --cflags openssl`
+HOSTLDLIBS_rsatoc = `pkg-config --libs openssl`
 hostprogs-$(CONFIG_IMD)          += bareboximd
 hostprogs-$(CONFIG_KALLSYMS)     += kallsyms
 hostprogs-$(CONFIG_MIPS)         += mips-relocs
diff --git a/scripts/rsatoc.c b/scripts/rsatoc.c
new file mode 100644
index 0000000000..f853691908
--- /dev/null
+++ b/scripts/rsatoc.c
@@ -0,0 +1,445 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * rsatoc - utility to convert an RSA key to a C struct
+ *
+ * This tool converts an RSA key given as file or PKCS#11
+ * URI to a C struct suitable to compile with barebox.
+ */
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <openssl/bn.h>
+#include <openssl/rsa.h>
+#include <openssl/pem.h>
+#include <openssl/err.h>
+#include <openssl/ssl.h>
+#include <openssl/evp.h>
+#include <openssl/engine.h>
+
+static int rsa_err(const char *msg)
+{
+	unsigned long sslErr = ERR_get_error();
+
+	fprintf(stderr, "%s", msg);
+	fprintf(stderr, ": %s\n",
+		ERR_error_string(sslErr, 0));
+
+	return -1;
+}
+
+/**
+ * rsa_pem_get_pub_key() - read a public key from a .crt file
+ *
+ * @keydir:	Directory containins the key
+ * @name	Name of key file (will have a .crt extension)
+ * @rsap	Returns RSA object, or NULL on failure
+ * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
+ */
+static int rsa_pem_get_pub_key(const char *path, RSA **rsap)
+{
+	EVP_PKEY *key;
+	X509 *cert;
+	RSA *rsa;
+	FILE *f;
+	int ret;
+
+	*rsap = NULL;
+	f = fopen(path, "r");
+	if (!f) {
+		fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
+			path, strerror(errno));
+		return -EACCES;
+	}
+
+	/* Read the certificate */
+	cert = NULL;
+	if (!PEM_read_X509(f, &cert, NULL, NULL)) {
+		rsa_err("Couldn't read certificate");
+		ret = -EINVAL;
+		goto err_cert;
+	}
+
+	/* Get the public key from the certificate. */
+	key = X509_get_pubkey(cert);
+	if (!key) {
+		rsa_err("Couldn't read public key\n");
+		ret = -EINVAL;
+		goto err_pubkey;
+	}
+
+	/* Convert to a RSA_style key. */
+	rsa = EVP_PKEY_get1_RSA(key);
+	if (!rsa) {
+		rsa_err("Couldn't convert to a RSA style key");
+		ret = -EINVAL;
+		goto err_rsa;
+	}
+	fclose(f);
+	EVP_PKEY_free(key);
+	X509_free(cert);
+	*rsap = rsa;
+
+	return 0;
+
+err_rsa:
+	EVP_PKEY_free(key);
+err_pubkey:
+	X509_free(cert);
+err_cert:
+	fclose(f);
+	return ret;
+}
+
+/**
+ * rsa_engine_get_pub_key() - read a public key from given engine
+ *
+ * @keydir:	Key prefix
+ * @name	Name of key
+ * @engine	Engine to use
+ * @rsap	Returns RSA object, or NULL on failure
+ * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
+ */
+static int rsa_engine_get_pub_key(const char *key_id,
+				  ENGINE *engine, RSA **rsap)
+{
+	EVP_PKEY *key;
+	RSA *rsa;
+	int ret;
+
+	*rsap = NULL;
+
+	key = ENGINE_load_public_key(engine, key_id, NULL, NULL);
+	if (!key)
+		return rsa_err("Failure loading public key from engine");
+
+	/* Convert to a RSA_style key. */
+	rsa = EVP_PKEY_get1_RSA(key);
+	if (!rsa) {
+		rsa_err("Couldn't convert to a RSA style key");
+		ret = -EINVAL;
+		goto err_rsa;
+	}
+
+	EVP_PKEY_free(key);
+	*rsap = rsa;
+
+	return 0;
+
+err_rsa:
+	EVP_PKEY_free(key);
+	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;
+	const BIGNUM *key_e;
+	uint64_t te;
+
+	ret = -EINVAL;
+	bn_te = NULL;
+
+	if (!e)
+		goto cleanup;
+
+	RSA_get0_key(key, NULL, &key_e, NULL);
+	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, uint64_t *exponent, uint32_t *n0_invp,
+		   BIGNUM **modulusp, BIGNUM **r_squaredp)
+{
+	BIGNUM *big1, *big2, *big32, *big2_32;
+	BIGNUM *n, *r, *r_squared, *tmp;
+	const BIGNUM *key_n;
+	BN_CTX *bn_ctx = BN_CTX_new();
+	int ret = 0;
+
+	/* Initialize BIGNUMs */
+	big1 = BN_new();
+	big2 = BN_new();
+	big32 = BN_new();
+	r = BN_new();
+	r_squared = BN_new();
+	tmp = BN_new();
+	big2_32 = BN_new();
+	n = BN_new();
+	if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
+	    !n) {
+		fprintf(stderr, "Out of memory (bignum)\n");
+		return -ENOMEM;
+	}
+
+	if (0 != rsa_get_exponent(key, exponent))
+		ret = -1;
+
+	RSA_get0_key(key, &key_n, NULL, NULL);
+	if (!BN_copy(n, key_n) || !BN_set_word(big1, 1L) ||
+	    !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
+		ret = -1;
+
+	/* big2_32 = 2^32 */
+	if (!BN_exp(big2_32, big2, big32, bn_ctx))
+		ret = -1;
+
+	/* Calculate n0_inv = -1 / n[0] mod 2^32 */
+	if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
+	    !BN_sub(tmp, big2_32, tmp))
+		ret = -1;
+	*n0_invp = BN_get_word(tmp);
+
+	/* Calculate R = 2^(# of key bits) */
+	if (!BN_set_word(tmp, BN_num_bits(n)) ||
+	    !BN_exp(r, big2, tmp, bn_ctx))
+		ret = -1;
+
+	/* Calculate r_squared = R^2 mod n */
+	if (!BN_copy(r_squared, r) ||
+	    !BN_mul(tmp, r_squared, r, bn_ctx) ||
+	    !BN_mod(r_squared, tmp, n, bn_ctx))
+		ret = -1;
+
+	*modulusp = n;
+	*r_squaredp = r_squared;
+
+	BN_free(big1);
+	BN_free(big2);
+	BN_free(big32);
+	BN_free(r);
+	BN_free(tmp);
+	BN_free(big2_32);
+	if (ret) {
+		fprintf(stderr, "Bignum operations failed\n");
+		return -ENOMEM;
+	}
+
+	return ret;
+}
+
+static int rsa_engine_init(ENGINE **pe)
+{
+	ENGINE *e;
+	int ret;
+
+	ENGINE_load_builtin_engines();
+
+	e = ENGINE_by_id("pkcs11");
+	if (!e) {
+		fprintf(stderr, "Engine isn't available\n");
+		ret = -1;
+		goto err_engine_by_id;
+	}
+
+	if (!ENGINE_init(e)) {
+		fprintf(stderr, "Couldn't initialize engine\n");
+		ret = -1;
+		goto err_engine_init;
+	}
+
+	if (!ENGINE_set_default_RSA(e)) {
+		fprintf(stderr, "Couldn't set engine as default for RSA\n");
+		ret = -1;
+		goto err_set_rsa;
+	}
+
+	*pe = e;
+
+	return 0;
+
+err_set_rsa:
+	ENGINE_finish(e);
+err_engine_init:
+	ENGINE_free(e);
+err_engine_by_id:
+#if OPENSSL_VERSION_NUMBER < 0x10100000L || \
+	(defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x02070000fL)
+	ENGINE_cleanup();
+#endif
+	return ret;
+}
+
+static int print_bignum(BIGNUM *num, int num_bits)
+{
+	BIGNUM *tmp, *big2, *big32, *big2_32;
+	BN_CTX *ctx;
+	int i;
+
+	tmp = BN_new();
+	big2 = BN_new();
+	big32 = BN_new();
+	big2_32 = BN_new();
+
+	/*
+	 * Note: This code assumes that all of the above succeed, or all fail.
+	 * In practice memory allocations generally do not fail (unless the
+	 * process is killed), so it does not seem worth handling each of these
+	 * as a separate case. Technicaly this could leak memory on failure,
+	 * but a) it won't happen in practice, and b) it doesn't matter as we
+	 * will immediately exit with a failure code.
+	 */
+	if (!tmp || !big2 || !big32 || !big2_32) {
+		fprintf(stderr, "Out of memory (bignum)\n");
+		return -ENOMEM;
+	}
+	ctx = BN_CTX_new();
+	if (!tmp) {
+		fprintf(stderr, "Out of memory (bignum context)\n");
+		return -ENOMEM;
+	}
+	BN_set_word(big2, 2L);
+	BN_set_word(big32, 32L);
+	BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
+
+	for (i = 0; i < num_bits / 32; i++) {
+		BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
+		if (i % 4)
+			printf(" ");
+		else
+			printf("\n\t");
+		printf("0x%08lx,", BN_get_word(tmp));
+		BN_rshift(num, num, 32); /*  N = N/B */
+	}
+
+	BN_free(tmp);
+	BN_free(big2);
+	BN_free(big32);
+	BN_free(big2_32);
+
+	return 0;
+}
+
+static int gen_key(const char *keyname, const char *path)
+{
+	BIGNUM *modulus, *r_squared;
+	uint64_t exponent;
+	uint32_t n0_inv;
+	int ret;
+	int bits;
+	RSA *rsa;
+	ENGINE *e = NULL;
+	char *tmp, *key_name_c;
+
+	tmp = key_name_c = strdup(keyname);
+
+	while (*tmp) {
+		if (*tmp == '-')
+			*tmp = '_';
+		tmp++;
+	}
+
+	if (!strncmp(path, "__ENV__", 7)) {
+		const char *var = getenv(path + 7);
+		if (!var) {
+			fprintf(stderr,
+				"environment variable \"%s\" is empty\n", path + 7);
+			exit(1);
+		}
+		path = var;
+	}
+
+	if (!strncmp(path, "pkcs11:", 7)) {
+		ret = rsa_engine_init(&e);
+		if (ret)
+			exit(1);
+		ret = rsa_engine_get_pub_key(path, e, &rsa);
+		if (ret)
+			exit(1);
+	} else {
+		ret = rsa_pem_get_pub_key(path, &rsa);
+		if (ret)
+			exit(1);
+	}
+
+	ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
+	if (ret)
+		return ret;
+
+	bits = BN_num_bits(modulus);
+
+	printf("\nstatic uint32_t %s_modulus[] = {", key_name_c);
+	print_bignum(modulus, bits);
+	printf("\n};\n\n");
+
+	printf("static uint32_t %s_rr[] = {", key_name_c);
+	print_bignum(r_squared, bits);
+	printf("\n};\n\n");
+
+	printf("static struct rsa_public_key %s = {\n", key_name_c);
+	printf("\t.len = %d,\n", bits / 32);
+	printf("\t.n0inv = 0x%0x,\n", n0_inv);
+	printf("\t.modulus = %s_modulus,\n", key_name_c);
+	printf("\t.rr = %s_rr,\n", key_name_c);
+	printf("\t.exponent = 0x%0lx,\n", exponent);
+	printf("\t.key_name_hint = \"%s\",\n", keyname);
+	printf("};\n\n");
+
+	printf("struct rsa_public_key *%sp __attribute__((section(\".rsa_keys.rodata.%s\"))) = &%s;\n",
+	       key_name_c, key_name_c, key_name_c);
+
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	char *path, *keyname;
+	int i;
+
+	if (argc < 2) {
+		fprintf(stderr, "Usage: %s <key_name_hint>:<crt> ...\n", argv[0]);
+		exit(1);
+	}
+
+	for (i = 1; i < argc; i++) {
+		keyname = argv[i];
+
+		path = strchr(keyname, ':');
+		if (!path) {
+			fprintf(stderr,
+				"keys must be given as <key_name_hint>:<crt>\n");
+			exit(1);
+		}
+
+		*path = 0;
+		path++;
+
+		gen_key(keyname, path);
+	}
+
+	exit(0);
+}
-- 
2.23.0


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