[PATCH v4 0/6] Add support for ECDSA image signing (with test)

classic Classic list List threaded Threaded
7 messages Options
Reply | Threaded
Open this post in threaded view
|

[PATCH v4 0/6] Add support for ECDSA image signing (with test)

Alexandru Gagniuc-2
## Purpose and intent

The purpose of this series is to enable ECDSA as an alternative to RSA
for FIT signing. As new chips have built-in support for ECDSA verified
boot, it makes sense to stick to one signing algorithm, instead of
resorting to RSA for u-boot images.

The focus of this series is signing an existing FIT image:

        mkimage -F some-existing.fit --signing-key some/key.pem

Signing while assembling a FIT is not a tested use case.
       
# Implementation

## Code organization

Unlike the RSA path, which mixes host and firmware code in the same,
source files, this series keeps a very clear distinction.
ecdsa-libcrypto.c is intended to be used for host code and only for
host code. There is more opportunity for code reuse this way.

## Signing

There is one major difference from the RSA path. The 'key-name-hint'
property is ignored in the ECDSA path. There are two reasons:
  (1) The intent of 'key-name-hint' is not clear
  (2) Initial implementation is much easier to review
 
There is an intentional side-effect. The RSA path takes 'key-name-hint'
to decide which key file to read from disk. In the context of "which
fdt node describes my signing key", this makes sense. On the other
hand, 'key-name-hint' is also used as the basename of where the key is
on the filesystem. This leads to some funny search paths, such as

        "some/dir/(null).key"
       
So I am using the -K option to mkimage as the _full_ path to the key
file. It doesn't have to be named .key, it doesn't have to be named
.crt, and it doesn't have to exist in a particular directory (as is
the case for the RSA path). I understand and recognize that this
discrepancy must be resolved, but resolving it right now would make
the initial implementation much harder and longer.


# Testing

test/py/tests/test_fit_ecdsa.py is implemented withe the goal to check
that the signing is done correctly, and that the signature is encoded
in the proper raw format. Verification is done with pyCryptodomex, so
this test will catch both coding errors and openssl bugs. This is the
only scope of testing proposed here.


# Things not yet resolved:
 - is mkimage '-k' supposed to be a directory or file path
I'm hoping I can postpone answering this question pending further discussion.

Changes since v3:
 - Don't use 'log_msg_ret()', as it's not available host-side

Changes since v1 and v2:
 - Added lots of function comments
 - Replaced hardcoded error numbers with more meaningful errno numbers
 - Changed some error paths to use 'return log_msg_ret'

Alexandru Gagniuc (6):
  lib: Rename rsa-checksum.c to hash-checksum.c
  lib/rsa: Make fdt_add_bignum() available outside of RSA code
  lib: Add support for ECDSA image signing
  doc: signature.txt: Document devicetree format for ECDSA keys
  test/py: Add pycryptodomex to list of required pakages
  test/py: ecdsa: Add test for mkimage ECDSA signing

 common/image-fit-sig.c                        |   2 +-
 common/image-sig.c                            |  13 +-
 doc/uImage.FIT/signature.txt                  |   7 +-
 include/image.h                               |   5 +-
 include/u-boot/ecdsa.h                        |  94 ++++++
 include/u-boot/fdt-libcrypto.h                |  27 ++
 .../{rsa-checksum.h => hash-checksum.h}       |   0
 lib/Makefile                                  |   1 +
 lib/crypto/pkcs7_verify.c                     |   2 +-
 lib/crypto/x509_public_key.c                  |   2 +-
 lib/ecdsa/ecdsa-libcrypto.c                   | 306 ++++++++++++++++++
 lib/fdt-libcrypto.c                           |  72 +++++
 lib/{rsa/rsa-checksum.c => hash-checksum.c}   |   3 +-
 lib/rsa/Makefile                              |   2 +-
 lib/rsa/rsa-sign.c                            |  65 +---
 test/py/requirements.txt                      |   1 +
 test/py/tests/test_fit_ecdsa.py               | 111 +++++++
 tools/Makefile                                |   7 +-
 18 files changed, 645 insertions(+), 75 deletions(-)
 create mode 100644 include/u-boot/ecdsa.h
 create mode 100644 include/u-boot/fdt-libcrypto.h
 rename include/u-boot/{rsa-checksum.h => hash-checksum.h} (100%)
 create mode 100644 lib/ecdsa/ecdsa-libcrypto.c
 create mode 100644 lib/fdt-libcrypto.c
 rename lib/{rsa/rsa-checksum.c => hash-checksum.c} (96%)
 create mode 100644 test/py/tests/test_fit_ecdsa.py

--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 1/6] lib: Rename rsa-checksum.c to hash-checksum.c

Alexandru Gagniuc-2
rsa-checksum.c sontains the hash_calculate() implementations. Despite
the "rsa-" file prefix, this function is useful for other algorithms.

To prevent confusion, move this file to lib/crypto, and rename it to
hash-checksum.c, to give it a more "generic" feel.

Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 common/image-fit-sig.c                             | 2 +-
 common/image-sig.c                                 | 2 +-
 include/image.h                                    | 2 +-
 include/u-boot/{rsa-checksum.h => hash-checksum.h} | 0
 lib/Makefile                                       | 1 +
 lib/crypto/pkcs7_verify.c                          | 2 +-
 lib/crypto/x509_public_key.c                       | 2 +-
 lib/{rsa/rsa-checksum.c => hash-checksum.c}        | 3 ++-
 lib/rsa/Makefile                                   | 2 +-
 tools/Makefile                                     | 3 ++-
 10 files changed, 11 insertions(+), 8 deletions(-)
 rename include/u-boot/{rsa-checksum.h => hash-checksum.h} (100%)
 rename lib/{rsa/rsa-checksum.c => hash-checksum.c} (96%)

diff --git a/common/image-fit-sig.c b/common/image-fit-sig.c
index 5401d9411b..7fcbb47235 100644
--- a/common/image-fit-sig.c
+++ b/common/image-fit-sig.c
@@ -15,7 +15,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #include <fdt_region.h>
 #include <image.h>
 #include <u-boot/rsa.h>
-#include <u-boot/rsa-checksum.h>
+#include <u-boot/hash-checksum.h>
 
 #define IMAGE_MAX_HASHED_NODES 100
 
diff --git a/common/image-sig.c b/common/image-sig.c
index f3c209ae8b..21dafe6b91 100644
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -16,7 +16,7 @@ DECLARE_GLOBAL_DATA_PTR;
 #endif /* !USE_HOSTCC*/
 #include <image.h>
 #include <u-boot/rsa.h>
-#include <u-boot/rsa-checksum.h>
+#include <u-boot/hash-checksum.h>
 
 #define IMAGE_MAX_HASHED_NODES 100
 
diff --git a/include/image.h b/include/image.h
index 41473dbb9c..a55b11b3ae 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1258,7 +1258,7 @@ struct image_region {
 };
 
 #if IMAGE_ENABLE_VERIFY
-# include <u-boot/rsa-checksum.h>
+# include <u-boot/hash-checksum.h>
 #endif
 struct checksum_algo {
  const char *name;
diff --git a/include/u-boot/rsa-checksum.h b/include/u-boot/hash-checksum.h
similarity index 100%
rename from include/u-boot/rsa-checksum.h
rename to include/u-boot/hash-checksum.h
diff --git a/lib/Makefile b/lib/Makefile
index 851a80ef3b..cf64188ba5 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -60,6 +60,7 @@ endif
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpi/
 obj-$(CONFIG_$(SPL_)MD5) += md5.o
 obj-$(CONFIG_$(SPL_)RSA) += rsa/
+obj-$(CONFIG_FIT_SIGNATURE) += hash-checksum.o
 obj-$(CONFIG_SHA1) += sha1.o
 obj-$(CONFIG_SHA256) += sha256.o
 obj-$(CONFIG_SHA512_ALGO) += sha512.o
diff --git a/lib/crypto/pkcs7_verify.c b/lib/crypto/pkcs7_verify.c
index 320ba49f79..3c411f651f 100644
--- a/lib/crypto/pkcs7_verify.c
+++ b/lib/crypto/pkcs7_verify.c
@@ -15,7 +15,7 @@
 #include <linux/bitops.h>
 #include <linux/compat.h>
 #include <linux/asn1.h>
-#include <u-boot/rsa-checksum.h>
+#include <u-boot/hash-checksum.h>
 #include <crypto/public_key.h>
 #include <crypto/pkcs7_parser.h>
 #else
diff --git a/lib/crypto/x509_public_key.c b/lib/crypto/x509_public_key.c
index 91810a8640..d557ab27ae 100644
--- a/lib/crypto/x509_public_key.c
+++ b/lib/crypto/x509_public_key.c
@@ -19,7 +19,7 @@
 #include <linux/kernel.h>
 #ifdef __UBOOT__
 #include <crypto/x509_parser.h>
-#include <u-boot/rsa-checksum.h>
+#include <u-boot/hash-checksum.h>
 #else
 #include <linux/slab.h>
 #include <keys/asymmetric-subtype.h>
diff --git a/lib/rsa/rsa-checksum.c b/lib/hash-checksum.c
similarity index 96%
rename from lib/rsa/rsa-checksum.c
rename to lib/hash-checksum.c
index e60debb7df..d732ecc38f 100644
--- a/lib/rsa/rsa-checksum.c
+++ b/lib/hash-checksum.c
@@ -13,7 +13,8 @@
 #else
 #include "fdt_host.h"
 #endif
-#include <u-boot/rsa.h>
+#include <hash.h>
+#include <image.h>
 
 int hash_calculate(const char *name,
     const struct image_region region[],
diff --git a/lib/rsa/Makefile b/lib/rsa/Makefile
index 8b75d41f04..c9ac72c1e2 100644
--- a/lib/rsa/Makefile
+++ b/lib/rsa/Makefile
@@ -5,6 +5,6 @@
 # (C) Copyright 2000-2007
 # Wolfgang Denk, DENX Software Engineering, [hidden email].
 
-obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY) += rsa-verify.o rsa-checksum.o
+obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY) += rsa-verify.o
 obj-$(CONFIG_$(SPL_TPL_)RSA_VERIFY_WITH_PKEY) += rsa-keyprop.o
 obj-$(CONFIG_RSA_SOFTWARE_EXP) += rsa-mod-exp.o
diff --git a/tools/Makefile b/tools/Makefile
index 253a6b9706..b1595ad814 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -67,7 +67,7 @@ LIBFDT_OBJS := $(addprefix libfdt/, fdt.o fdt_ro.o fdt_wip.o fdt_sw.o fdt_rw.o \
  fdt_strerror.o fdt_empty_tree.o fdt_addresses.o fdt_overlay.o)
 
 RSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/rsa/, \
- rsa-sign.o rsa-verify.o rsa-checksum.o \
+ rsa-sign.o rsa-verify.o \
  rsa-mod-exp.o)
 
 AES_OBJS-$(CONFIG_FIT_CIPHER) := $(addprefix lib/aes/, \
@@ -105,6 +105,7 @@ dumpimage-mkimage-objs := aisimage.o \
  $(ROCKCHIP_OBS) \
  socfpgaimage.o \
  lib/crc16.o \
+ lib/hash-checksum.o \
  lib/sha1.o \
  lib/sha256.o \
  lib/sha512.o \
--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 2/6] lib/rsa: Make fdt_add_bignum() available outside of RSA code

Alexandru Gagniuc-2
In reply to this post by Alexandru Gagniuc-2
fdt_add_bignum() is useful for algorithms other than just RSA. To
allow its use for ECDSA, move it to a common file under lib/.

The new file is suffixed with '-libcrypto' because it has a direct
dependency on openssl. This is due to the use of the "BIGNUM *" type.

Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 include/u-boot/fdt-libcrypto.h | 27 +++++++++++++
 lib/fdt-libcrypto.c            | 72 ++++++++++++++++++++++++++++++++++
 lib/rsa/rsa-sign.c             | 65 +-----------------------------
 tools/Makefile                 |  1 +
 4 files changed, 101 insertions(+), 64 deletions(-)
 create mode 100644 include/u-boot/fdt-libcrypto.h
 create mode 100644 lib/fdt-libcrypto.c

diff --git a/include/u-boot/fdt-libcrypto.h b/include/u-boot/fdt-libcrypto.h
new file mode 100644
index 0000000000..5142f37039
--- /dev/null
+++ b/include/u-boot/fdt-libcrypto.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2020, Alexandru Gagniuc <[hidden email]>
+ * Copyright (c) 2013, Google Inc.
+ */
+
+#ifndef _FDT_LIBCRYPTO_H
+#define _FDT_LIBCRYPTO_H
+
+#include <openssl/bn.h>
+
+/**
+ * fdt_add_bignum() - Write a libcrypto BIGNUM as an FDT property
+ *
+ * Convert a libcrypto BIGNUM * into a big endian array of integers.
+ *
+ * @blob: FDT blob to modify
+ * @noffset: Offset of the FDT node
+ * @prop_name: What to call the property in the FDT
+ * @num: pointer to a libcrypto big number
+ * @num_bits: How big is 'num' in bits?
+ * @return 0 if all good all working, -ve on horror
+ */
+int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
+   BIGNUM *num, int num_bits);
+
+#endif /* _FDT_LIBCRYPTO_H */
diff --git a/lib/fdt-libcrypto.c b/lib/fdt-libcrypto.c
new file mode 100644
index 0000000000..ecb0344c8f
--- /dev/null
+++ b/lib/fdt-libcrypto.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2020, Alexandru Gagniuc <[hidden email]>
+ * Copyright (c) 2013, Google Inc.
+ */
+
+#include <libfdt.h>
+#include <u-boot/fdt-libcrypto.h>
+
+int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
+   BIGNUM *num, int num_bits)
+{
+ int nwords = num_bits / 32;
+ int size;
+ uint32_t *buf, *ptr;
+ BIGNUM *tmp, *big2, *big32, *big2_32;
+ BN_CTX *ctx;
+ int ret;
+
+ 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 (!ctx) {
+ 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 */
+
+ size = nwords * sizeof(uint32_t);
+ buf = malloc(size);
+ if (!buf) {
+ fprintf(stderr, "Out of memory (%d bytes)\n", size);
+ return -ENOMEM;
+ }
+
+ /* Write out modulus as big endian array of integers */
+ for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
+ BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
+ *ptr = cpu_to_fdt32(BN_get_word(tmp));
+ BN_rshift(num, num, 32); /*  N = N/B */
+ }
+
+ /*
+ * We try signing with successively increasing size values, so this
+ * might fail several times
+ */
+ ret = fdt_setprop(blob, noffset, prop_name, buf, size);
+ free(buf);
+ BN_free(tmp);
+ BN_free(big2);
+ BN_free(big32);
+ BN_free(big2_32);
+
+ return ret ? -FDT_ERR_NOSPACE : 0;
+}
diff --git a/lib/rsa/rsa-sign.c b/lib/rsa/rsa-sign.c
index 1f0d81bd7a..557c690a6d 100644
--- a/lib/rsa/rsa-sign.c
+++ b/lib/rsa/rsa-sign.c
@@ -9,6 +9,7 @@
 #include <string.h>
 #include <image.h>
 #include <time.h>
+#include <u-boot/fdt-libcrypto.h>
 #include <openssl/bn.h>
 #include <openssl/rsa.h>
 #include <openssl/pem.h>
@@ -680,70 +681,6 @@ int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
  return ret;
 }
 
-static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
-  BIGNUM *num, int num_bits)
-{
- int nwords = num_bits / 32;
- int size;
- uint32_t *buf, *ptr;
- BIGNUM *tmp, *big2, *big32, *big2_32;
- BN_CTX *ctx;
- int ret;
-
- 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 (!ctx) {
- 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 */
-
- size = nwords * sizeof(uint32_t);
- buf = malloc(size);
- if (!buf) {
- fprintf(stderr, "Out of memory (%d bytes)\n", size);
- return -ENOMEM;
- }
-
- /* Write out modulus as big endian array of integers */
- for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
- BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
- *ptr = cpu_to_fdt32(BN_get_word(tmp));
- BN_rshift(num, num, 32); /*  N = N/B */
- }
-
- /*
- * We try signing with successively increasing size values, so this
- * might fail several times
- */
- ret = fdt_setprop(blob, noffset, prop_name, buf, size);
- free(buf);
- BN_free(tmp);
- BN_free(big2);
- BN_free(big32);
- BN_free(big2_32);
-
- return ret ? -FDT_ERR_NOSPACE : 0;
-}
-
 int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
 {
  BIGNUM *modulus, *r_squared;
diff --git a/tools/Makefile b/tools/Makefile
index b1595ad814..af7698fd01 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -106,6 +106,7 @@ dumpimage-mkimage-objs := aisimage.o \
  socfpgaimage.o \
  lib/crc16.o \
  lib/hash-checksum.o \
+ lib/fdt-libcrypto.o \
  lib/sha1.o \
  lib/sha256.o \
  lib/sha512.o \
--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 3/6] lib: Add support for ECDSA image signing

Alexandru Gagniuc-2
In reply to this post by Alexandru Gagniuc-2
mkimage supports rsa2048, and rsa4096 signatures. With newer silicon
now supporting hardware-accelerated ECDSA, it makes sense to expand
signing support to elliptic curves.

Implement host-side ECDSA signing and verification with libcrypto.
Device-side implementation of signature verification is beyond the
scope of this patch.

Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 common/image-sig.c          |  11 +-
 include/image.h             |   3 +
 include/u-boot/ecdsa.h      |  94 +++++++++++
 lib/ecdsa/ecdsa-libcrypto.c | 306 ++++++++++++++++++++++++++++++++++++
 tools/Makefile              |   3 +
 5 files changed, 415 insertions(+), 2 deletions(-)
 create mode 100644 include/u-boot/ecdsa.h
 create mode 100644 lib/ecdsa/ecdsa-libcrypto.c

diff --git a/common/image-sig.c b/common/image-sig.c
index 21dafe6b91..4b7d01f6c2 100644
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -15,6 +15,7 @@
 DECLARE_GLOBAL_DATA_PTR;
 #endif /* !USE_HOSTCC*/
 #include <image.h>
+#include <u-boot/ecdsa.h>
 #include <u-boot/rsa.h>
 #include <u-boot/hash-checksum.h>
 
@@ -82,8 +83,14 @@ struct crypto_algo crypto_algos[] = {
  .sign = rsa_sign,
  .add_verify_data = rsa_add_verify_data,
  .verify = rsa_verify,
- }
-
+ },
+ {
+ .name = "ecdsa256",
+ .key_len = ECDSA256_BYTES,
+ .sign = ecdsa_sign,
+ .add_verify_data = ecdsa_add_verify_data,
+ .verify = ecdsa_verify,
+ },
 };
 
 struct padding_algo padding_algos[] = {
diff --git a/include/image.h b/include/image.h
index a55b11b3ae..6628173dca 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1199,16 +1199,19 @@ int calculate_hash(const void *data, int data_len, const char *algo,
 # if defined(CONFIG_FIT_SIGNATURE)
 #  define IMAGE_ENABLE_SIGN 1
 #  define IMAGE_ENABLE_VERIFY 1
+#  define IMAGE_ENABLE_VERIFY_ECDSA 1
 #  define FIT_IMAGE_ENABLE_VERIFY 1
 #  include <openssl/evp.h>
 # else
 #  define IMAGE_ENABLE_SIGN 0
 #  define IMAGE_ENABLE_VERIFY 0
+# define IMAGE_ENABLE_VERIFY_ECDSA 0
 #  define FIT_IMAGE_ENABLE_VERIFY 0
 # endif
 #else
 # define IMAGE_ENABLE_SIGN 0
 # define IMAGE_ENABLE_VERIFY CONFIG_IS_ENABLED(RSA_VERIFY)
+# define IMAGE_ENABLE_VERIFY_ECDSA 0
 # define FIT_IMAGE_ENABLE_VERIFY CONFIG_IS_ENABLED(FIT_SIGNATURE)
 #endif
 
diff --git a/include/u-boot/ecdsa.h b/include/u-boot/ecdsa.h
new file mode 100644
index 0000000000..979690d966
--- /dev/null
+++ b/include/u-boot/ecdsa.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2020, Alexandru Gagniuc <[hidden email]>.
+ */
+
+#ifndef _ECDSA_H
+#define _ECDSA_H
+
+#include <errno.h>
+#include <image.h>
+#include <linux/kconfig.h>
+
+/**
+ * crypto_algo API impementation for ECDSA;
+ * @see "struct crypto_algo"
+ * @{
+ */
+#if IMAGE_ENABLE_SIGN
+/**
+ * sign() - calculate and return signature for given input data
+ *
+ * @info: Specifies key and FIT information
+ * @data: Pointer to the input data
+ * @data_len: Data length
+ * @sigp: Set to an allocated buffer holding the signature
+ * @sig_len: Set to length of the calculated hash
+ *
+ * This computes input data signature according to selected algorithm.
+ * Resulting signature value is placed in an allocated buffer, the
+ * pointer is returned as *sigp. The length of the calculated
+ * signature is returned via the sig_len pointer argument. The caller
+ * should free *sigp.
+ *
+ * @return: 0, on success, -ve on error
+ */
+int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
+       int region_count, uint8_t **sigp, uint *sig_len);
+
+/**
+ * add_verify_data() - Add verification information to FDT
+ *
+ * Add public key information to the FDT node, suitable for
+ * verification at run-time. The information added depends on the
+ * algorithm being used. I just copypasted this from rsa.h.
+ *
+ * @info: Specifies key and FIT information
+ * @keydest: Destination FDT blob for public key data
+ * @return: 0, on success, -ENOSPC if the keydest FDT blob ran out of space,
+ * other -ve value on error
+ */
+int ecdsa_add_verify_data(struct image_sign_info *info, void *keydest);
+#else
+static inline
+int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
+       int region_count, uint8_t **sigp, uint *sig_len)
+{
+ return -ENXIO;
+}
+
+static inline
+int ecdsa_add_verify_data(struct image_sign_info *info, void *keydest)
+{
+ return -ENXIO;
+}
+#endif
+
+#if IMAGE_ENABLE_VERIFY_ECDSA
+/**
+ * verify() - Verify a signature against some data
+ *
+ * @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 ecdsa_verify(struct image_sign_info *info,
+ const struct image_region region[], int region_count,
+ uint8_t *sig, uint sig_len);
+#else
+static inline
+int ecdsa_verify(struct image_sign_info *info,
+ const struct image_region region[], int region_count,
+ uint8_t *sig, uint sig_len)
+{
+ return -ENXIO;
+}
+#endif
+/** @} */
+
+#define ECDSA256_BYTES (256 / 8)
+
+#endif
diff --git a/lib/ecdsa/ecdsa-libcrypto.c b/lib/ecdsa/ecdsa-libcrypto.c
new file mode 100644
index 0000000000..322880963f
--- /dev/null
+++ b/lib/ecdsa/ecdsa-libcrypto.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * ECDSA image signing implementation using libcrypto backend
+ *
+ * The signature is a binary representation of the (R, S) points, padded to the
+ * key size. The signature will be (2 * key_size_bits) / 8 bytes.
+ *
+ * Deviations from behavior of RSA equivalent:
+ *  - Verification uses private key. This is not technically required, but a
+ *    limitation on how clumsy the openssl API is to use.
+ *  - Handling of keys and key paths:
+ *    - The '-K' key directory option must contain path to the key file,
+ *      instead of the key directory.
+ *    - No assumptions are made about the file extension of the key
+ *    - The 'key-name-hint' property is only used for naming devicetree nodes,
+ *      but is not used for looking up keys on the filesystem.
+ *
+ * Copyright (c) 2020,2021, Alexandru Gagniuc <[hidden email]>
+ */
+
+#include <u-boot/ecdsa.h>
+#include <u-boot/fdt-libcrypto.h>
+#include <openssl/ssl.h>
+#include <openssl/ec.h>
+#include <openssl/bn.h>
+
+/* Image signing context for openssl-libcrypto */
+struct signer {
+ EVP_PKEY *evp_key; /* Pointer to EVP_PKEY object */
+ EC_KEY *ecdsa_key; /* Pointer to EC_KEY object */
+ void *hash; /* Pointer to hash used for verification */
+ void *signature; /* Pointer to output signature. Do not free()!*/
+};
+
+static int alloc_ctx(struct signer *ctx, const struct image_sign_info *info)
+{
+ memset(ctx, 0, sizeof(*ctx));
+
+ if (!OPENSSL_init_ssl(0, NULL)) {
+ fprintf(stderr, "Failure to init SSL library\n");
+ return -1;
+ }
+
+ ctx->hash = malloc(info->checksum->checksum_len);
+ ctx->signature = malloc(info->crypto->key_len * 2);
+
+ if (!ctx->hash || !ctx->signature)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static void free_ctx(struct signer *ctx)
+{
+ if (ctx->ecdsa_key)
+ EC_KEY_free(ctx->ecdsa_key);
+
+ if (ctx->evp_key)
+ EVP_PKEY_free(ctx->evp_key);
+
+ if (ctx->hash)
+ free(ctx->hash);
+}
+
+/*
+ * Convert an ECDSA signature to raw format
+ *
+ * openssl DER-encodes 'binary' signatures. We want the signature in a raw
+ * (R, S) point pair. So we have to dance a bit.
+ */
+static void ecdsa_sig_encode_raw(void *buf, const ECDSA_SIG *sig, size_t order)
+{
+ int point_bytes = order;
+ const BIGNUM *r, *s;
+ uintptr_t s_buf;
+
+ ECDSA_SIG_get0(sig, &r, &s);
+ s_buf = (uintptr_t)buf + point_bytes;
+ BN_bn2binpad(r, buf, point_bytes);
+ BN_bn2binpad(s, (void *)s_buf, point_bytes);
+}
+
+/* Get a signature from a raw encoding */
+static ECDSA_SIG *ecdsa_sig_from_raw(void *buf, size_t order)
+{
+ int point_bytes = order;
+ uintptr_t s_buf;
+ ECDSA_SIG *sig;
+ BIGNUM *r, *s;
+
+ sig = ECDSA_SIG_new();
+ if (!sig)
+ return NULL;
+
+ s_buf = (uintptr_t)buf + point_bytes;
+ r = BN_bin2bn(buf, point_bytes, NULL);
+ s = BN_bin2bn((void *)s_buf, point_bytes, NULL);
+ ECDSA_SIG_set0(sig, r, s);
+
+ return sig;
+}
+
+/* ECDSA key size in bytes */
+static size_t ecdsa_key_size_bytes(const EC_KEY *key)
+{
+ const EC_GROUP *group;
+
+ group = EC_KEY_get0_group(key);
+ return EC_GROUP_order_bits(group) / 8;
+}
+
+static int read_key(struct signer *ctx, const char *key_name)
+{
+ FILE *f = fopen(key_name, "r");
+
+ if (!f) {
+ fprintf(stderr, "Can not get key file '%s'\n", key_name);
+ return -ENOENT;
+ }
+
+ ctx->evp_key = PEM_read_PrivateKey(f, NULL, NULL, NULL);
+ fclose(f);
+ if (!ctx->evp_key) {
+ fprintf(stderr, "Can not read key from '%s'\n", key_name);
+ return -EIO;
+ }
+
+ if (EVP_PKEY_id(ctx->evp_key) != EVP_PKEY_EC) {
+ fprintf(stderr, "'%s' is not an ECDSA key\n", key_name);
+ return -EINVAL;
+ }
+
+ ctx->ecdsa_key = EVP_PKEY_get1_EC_KEY(ctx->evp_key);
+ if (!ctx->ecdsa_key)
+ fprintf(stderr, "Can not extract ECDSA key\n");
+
+ return (ctx->ecdsa_key) ? 0 : -EINVAL;
+}
+
+/* Prepare a 'signer' context that's ready to sign and verify. */
+static int prepare_ctx(struct signer *ctx, const struct image_sign_info *info)
+{
+ const char *kname = info->keydir;
+ int key_len_bytes, ret;
+
+ ret = alloc_ctx(ctx, info);
+ if (ret)
+ return ret;
+
+ ret = read_key(ctx, kname);
+ if (ret)
+ return ret;
+
+ key_len_bytes = ecdsa_key_size_bytes(ctx->ecdsa_key);
+ if (key_len_bytes != info->crypto->key_len) {
+ fprintf(stderr, "Expected a %u-bit key, got %u-bit key\n",
+ info->crypto->key_len * 8, key_len_bytes * 8);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int do_sign(struct signer *ctx, struct image_sign_info *info,
+   const struct image_region region[], int region_count)
+{
+ const struct checksum_algo *algo = info->checksum;
+ ECDSA_SIG *sig;
+
+ algo->calculate(algo->name, region, region_count, ctx->hash);
+ sig = ECDSA_do_sign(ctx->hash, algo->checksum_len, ctx->ecdsa_key);
+
+ ecdsa_sig_encode_raw(ctx->signature, sig, info->crypto->key_len);
+
+ return 0;
+}
+
+static int ecdsa_check_signature(struct signer *ctx, struct image_sign_info *info)
+{
+ ECDSA_SIG *sig;
+ int okay;
+
+ sig = ecdsa_sig_from_raw(ctx->signature, info->crypto->key_len);
+ if (!sig)
+ return -ENOMEM;
+
+ okay = ECDSA_do_verify(ctx->hash, info->checksum->checksum_len,
+       sig, ctx->ecdsa_key);
+ if (!okay)
+ fprintf(stderr, "WARNING: Signature is fake news!\n");
+
+ ECDSA_SIG_free(sig);
+ return !okay;
+}
+
+static int do_verify(struct signer *ctx, struct image_sign_info *info,
+     const struct image_region region[], int region_count,
+     uint8_t *raw_sig, uint sig_len)
+{
+ const struct checksum_algo *algo = info->checksum;
+
+ if (sig_len != info->crypto->key_len * 2) {
+ fprintf(stderr, "Signature has wrong length\n");
+ return -EINVAL;
+ }
+
+ memcpy(ctx->signature, raw_sig, sig_len);
+ algo->calculate(algo->name, region, region_count, ctx->hash);
+
+ return ecdsa_check_signature(ctx, info);
+}
+
+int ecdsa_sign(struct image_sign_info *info, const struct image_region region[],
+       int region_count, uint8_t **sigp, uint *sig_len)
+{
+ struct signer ctx;
+ int ret;
+
+ ret = prepare_ctx(&ctx, info);
+ if (ret >= 0) {
+ do_sign(&ctx, info, region, region_count);
+ *sigp = ctx.signature;
+ *sig_len = info->crypto->key_len * 2;
+
+ ret = ecdsa_check_signature(&ctx, info);
+ }
+
+ free_ctx(&ctx);
+ return ret;
+}
+
+int ecdsa_verify(struct image_sign_info *info,
+ const struct image_region region[], int region_count,
+ uint8_t *sig, uint sig_len)
+{
+ struct signer ctx;
+ int ret;
+
+ ret = prepare_ctx(&ctx, info);
+ if (ret >= 0)
+ ret = do_verify(&ctx, info, region, region_count, sig, sig_len);
+
+ free_ctx(&ctx);
+ return ret;
+}
+
+static int do_add(struct signer *ctx, void *fdt, const char *key_node_name)
+{
+ int signature_node, key_node, ret, key_bits;
+ const char *curve_name;
+ const EC_GROUP *group;
+ const EC_POINT *point;
+ BIGNUM *x, *y;
+
+ signature_node = fdt_subnode_offset(fdt, 0, FIT_SIG_NODENAME);
+ if (signature_node < 0) {
+ fprintf(stderr, "Could not find 'signature node: %s\n",
+ fdt_strerror(signature_node));
+ return signature_node;
+ }
+
+ key_node = fdt_add_subnode(fdt, signature_node, key_node_name);
+ if (key_node < 0) {
+ fprintf(stderr, "Could not create '%s' node: %s\n",
+ key_node_name, fdt_strerror(key_node));
+ return key_node;
+ }
+
+ group = EC_KEY_get0_group(ctx->ecdsa_key);
+ key_bits = EC_GROUP_order_bits(group);
+ curve_name = OBJ_nid2sn(EC_GROUP_get_curve_name(group));
+ /* Let 'x' and 'y' memory leak by not BN_free()'ing them. */
+ x = BN_new();
+ y = BN_new();
+ point = EC_KEY_get0_public_key(ctx->ecdsa_key);
+ EC_POINT_get_affine_coordinates(group, point, x, y, NULL);
+
+ ret = fdt_setprop_string(fdt, key_node, "ecdsa,curve", curve_name);
+ if (ret < 0)
+ return ret;
+
+ ret = fdt_add_bignum(fdt, key_node, "ecdsa,x-point", x, key_bits);
+ if (ret < 0)
+ return ret;
+
+ ret = fdt_add_bignum(fdt, key_node, "ecdsa,y-point", y, key_bits);
+ if (ret < 0)
+ return ret;
+
+ return 0;
+}
+
+int ecdsa_add_verify_data(struct image_sign_info *info, void *fdt)
+{
+ const char *fdt_key_name;
+ struct signer ctx;
+ int ret;
+
+ fdt_key_name = info->keyname ? info->keyname : "default-key";
+ ret = prepare_ctx(&ctx, info);
+ if (ret >= 0)
+ do_add(&ctx, fdt, fdt_key_name);
+
+ free_ctx(&ctx);
+ return ret;
+}
diff --git a/tools/Makefile b/tools/Makefile
index af7698fd01..a4f7b7e80c 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -70,6 +70,8 @@ RSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/rsa/, \
  rsa-sign.o rsa-verify.o \
  rsa-mod-exp.o)
 
+ECDSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/ecdsa/, ecdsa-libcrypto.o)
+
 AES_OBJS-$(CONFIG_FIT_CIPHER) := $(addprefix lib/aes/, \
  aes-encrypt.o aes-decrypt.o)
 
@@ -119,6 +121,7 @@ dumpimage-mkimage-objs := aisimage.o \
  gpimage.o \
  gpimage-common.o \
  mtk_image.o \
+ $(ECDSA_OBJS-y) \
  $(RSA_OBJS-y) \
  $(AES_OBJS-y)
 
--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 4/6] doc: signature.txt: Document devicetree format for ECDSA keys

Alexandru Gagniuc-2
In reply to this post by Alexandru Gagniuc-2
Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 doc/uImage.FIT/signature.txt | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/doc/uImage.FIT/signature.txt b/doc/uImage.FIT/signature.txt
index a3455889ed..0139295d33 100644
--- a/doc/uImage.FIT/signature.txt
+++ b/doc/uImage.FIT/signature.txt
@@ -142,7 +142,7 @@ public key in U-Boot's control FDT (using CONFIG_OF_CONTROL).
 Public keys should be stored as sub-nodes in a /signature node. Required
 properties are:
 
-- algo: Algorithm name (e.g. "sha1,rsa2048")
+- algo: Algorithm name (e.g. "sha1,rsa2048" or "sha256,ecdsa256")
 
 Optional properties are:
 
@@ -167,6 +167,11 @@ For RSA the following are mandatory:
 - rsa,r-squared: (2^num-bits)^2 as a big-endian multi-word integer
 - rsa,n0-inverse: -1 / modulus[0] mod 2^32
 
+For ECDSA the following are mandatory:
+- ecdsa,curve: Name of ECDSA curve (e.g. "prime256v1")
+- ecdsa,x-point: Public key X coordinate as a big-endian multi-word integer
+- ecdsa,y-point: Public key Y coordinate as a big-endian multi-word integer
+
 These parameters can be added to a binary device tree using parameter -K of the
 mkimage command::
 
--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 5/6] test/py: Add pycryptodomex to list of required pakages

Alexandru Gagniuc-2
In reply to this post by Alexandru Gagniuc-2
We wish to use pycryptodomex to verify code paths involving ECDSA
signatures. Add it to requirements.txt so that they get picked up
automatically .gitlab and .azure tasks

Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 test/py/requirements.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test/py/requirements.txt b/test/py/requirements.txt
index cf251186f4..5a25a9d5d5 100644
--- a/test/py/requirements.txt
+++ b/test/py/requirements.txt
@@ -10,6 +10,7 @@ packaging==19.2
 pbr==5.4.3
 pluggy==0.13.0
 py==1.8.0
+pycryptodomex==3.9.8
 pyparsing==2.4.2
 pytest==5.2.1
 python-mimeparse==1.6.0
--
2.26.2

Reply | Threaded
Open this post in threaded view
|

[PATCH v4 6/6] test/py: ecdsa: Add test for mkimage ECDSA signing

Alexandru Gagniuc-2
In reply to this post by Alexandru Gagniuc-2
Add a test to make sure that the ECDSA signatures generated by
mkimage can be verified successfully. pyCryptodomex was chosen as the
crypto library because it integrates much better with python code.
Using openssl would have been unnecessarily painful.

Signed-off-by: Alexandru Gagniuc <[hidden email]>
---
 test/py/tests/test_fit_ecdsa.py | 111 ++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 test/py/tests/test_fit_ecdsa.py

diff --git a/test/py/tests/test_fit_ecdsa.py b/test/py/tests/test_fit_ecdsa.py
new file mode 100644
index 0000000000..6cadb0cbb5
--- /dev/null
+++ b/test/py/tests/test_fit_ecdsa.py
@@ -0,0 +1,111 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2020,2021 Alexandru Gagniuc <[hidden email]>
+
+"""
+Test ECDSA signing of FIT images
+
+This test uses mkimage to sign an existing FIT image with an ECDSA key. The
+signature is then extracted, and verified against pyCryptodome.
+This test doesn't run the sandbox. It only checks the host tool 'mkimage'
+"""
+
+import pytest
+import u_boot_utils as util
+from Cryptodome.Hash import SHA256
+from Cryptodome.PublicKey import ECC
+from Cryptodome.Signature import DSS
+
+class SignableFitImage(object):
+    """ Helper to manipulate a FIT image on disk """
+    def __init__(self, cons, file_name):
+        self.fit = file_name
+        self.cons = cons
+        self.signable_nodes = set()
+
+    def __fdt_list(self, path):
+        return util.run_and_log(self.cons, f'fdtget -l {self.fit} {path}')
+
+    def __fdt_set(self, node, **prop_value):
+        for prop, value in prop_value.items():
+            util.run_and_log(self.cons, f'fdtput -ts {self.fit} {node} {prop} {value}')
+
+    def __fdt_get_binary(self, node, prop):
+        numbers = util.run_and_log(self.cons, f'fdtget -tbi {self.fit} {node} {prop}')
+
+        bignum = bytearray()
+        for little_num in numbers.split():
+            bignum.append(int(little_num))
+
+        return bignum
+
+    def find_signable_image_nodes(self):
+        for node in self.__fdt_list('/images').split():
+            image = f'/images/{node}'
+            if 'signature' in self.__fdt_list(image):
+                self.signable_nodes.add(image)
+
+        return self.signable_nodes
+
+    def change_signature_algo_to_ecdsa(self):
+        for image in self.signable_nodes:
+            self.__fdt_set(f'{image}/signature', algo='sha256,ecdsa256')
+
+    def sign(self, mkimage, key_file):
+        util.run_and_log(self.cons, [mkimage, '-F', self.fit, f'-k{key_file}'])
+
+    def check_signatures(self, key):
+        for image in self.signable_nodes:
+            raw_sig = self.__fdt_get_binary(f'{image}/signature', 'value')
+            raw_bin = self.__fdt_get_binary(image, 'data')
+
+            sha = SHA256.new(raw_bin)
+            verifier = DSS.new(key, 'fips-186-3')
+            verifier.verify(sha, bytes(raw_sig))
+
+
+@pytest.mark.buildconfigspec('fit_signature')
+@pytest.mark.requiredtool('dtc')
+@pytest.mark.requiredtool('fdtget')
+@pytest.mark.requiredtool('fdtput')
+def test_fit_ecdsa(u_boot_console):
+    """ Test that signatures generated by mkimage are legible. """
+    def generate_ecdsa_key():
+        return ECC.generate(curve='prime256v1')
+
+    def assemble_fit_image(dest_fit, its, destdir):
+        dtc_args = f'-I dts -O dtb -i {destdir}'
+        util.run_and_log(cons, [mkimage, '-D', dtc_args, '-f', its, dest_fit])
+
+    def dtc(dts):
+        dtb = dts.replace('.dts', '.dtb')
+        util.run_and_log(cons, f'dtc {datadir}/{dts} -O dtb -o {tempdir}/{dtb}')
+
+    cons = u_boot_console
+    mkimage = cons.config.build_dir + '/tools/mkimage'
+    datadir = cons.config.source_dir + '/test/py/tests/vboot/'
+    tempdir = cons.config.result_dir
+    key_file = f'{tempdir}/ecdsa-test-key.pem'
+    fit_file = f'{tempdir}/test.fit'
+    dtc('sandbox-kernel.dts')
+
+    key = generate_ecdsa_key()
+
+    # Create a fake kernel image -- zeroes will do just fine
+    with open(f'{tempdir}/test-kernel.bin', 'w') as fd:
+        fd.write(500 * chr(0))
+
+    # invokations of mkimage expect to read the key from disk
+    with open(key_file, 'w') as f:
+        f.write(key.export_key(format='PEM'))
+
+    assemble_fit_image(fit_file, f'{datadir}/sign-images-sha256.its', tempdir)
+
+    fit = SignableFitImage(cons, fit_file)
+    nodes = fit.find_signable_image_nodes()
+    if len(nodes) == 0:
+        raise ValueError('FIT image has no "/image" nodes with "signature"')
+
+    fit.change_signature_algo_to_ecdsa()
+    fit.sign(mkimage, key_file)
+    fit.check_signatures(key)
--
2.26.2