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Support for micro-ecc (WIP) #228

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6cf43c0
dtls.c: add check for valid handshake message type when version is 1.0.
boaks Sep 29, 2023
0f1be30
dtls_debug.h: explicitly cast macro parameter to size_t.
boaks Dec 7, 2023
ff73600
dtls-server.c: check for left cli-arguments.
boaks Jan 17, 2024
44eddf4
dtls-client.c: accept options after arguments.
boaks Jan 18, 2024
b306f27
dtls-client.c: apply option for local port.
boaks Jan 18, 2024
9232271
Add client dtls connection ID.
boaks Nov 18, 2021
0580b36
dtls-client.c: add support_cid option.
boaks Jan 24, 2023
4c39d5c
dtls.c: Handle DTLS1.3 ClientHello when calculating cookie
mrdeep1 Feb 6, 2024
3ce86c2
[Documentation] Update Doxyfile.in to version 1.9.8
obgm Feb 14, 2024
86b6765
Makefile.in: Remove SUB_OBJS rule to preserve CPPFLAGS
obgm Feb 14, 2024
121cad5
configure.ac: Set flags for uECC if ECC support is enabled
obgm Feb 15, 2024
61763fe
dtls.c: Initialize PRNG function for micro-ecc
obgm Feb 15, 2024
f972a67
[Tests] Remove unit tests for internal ECC implementation
obgm Feb 16, 2024
8014f05
crypto.c: Replace ECC functions with micro-ecc
obgm Feb 15, 2024
f8204f2
[ECC] Add micro-ecc as submodule
obgm Feb 15, 2024
0e068ec
Makefile.in: Add in micro-ecc dependencies
obgm Feb 16, 2024
3dc62b1
crypto.[hc]: Use micro-ecc for ECC support
obgm Feb 16, 2024
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3 changes: 3 additions & 0 deletions .gitmodules
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
[submodule "ext/micro-ecc"]
path = ext/micro-ecc
url = https://github.com/kmackay/micro-ecc.git
14 changes: 8 additions & 6 deletions Makefile.in
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Original file line number Diff line number Diff line change
Expand Up @@ -47,14 +47,16 @@ HEADERS:=dtls.h hmac.h dtls_debug.h dtls_config.h uthash.h numeric.h crypto.h gl
netq.h alert.h utlist.h dtls_prng.h peer.h state.h dtls_time.h session.h \
tinydtls.h dtls_mutex.h
PKG_CONFIG_FILES:=tinydtls.pc
__micro_ecc_path:=ext/micro-ecc
MICRO_ECC_FILES:=$(addprefix $(__micro_ecc_path)/, uECC.h uECC.c uECC_vli.h types.h) $(wildcard $(__micro_ecc_path)/*.inc)
CFLAGS:=-Wall -pedantic -std=c99 -DSHA2_USE_INTTYPES_H @CFLAGS@ \
@WARNING_CFLAGS@ $(EXTRA_CFLAGS)
CPPFLAGS:=@CPPFLAGS@ -DDTLS_CHECK_CONTENTTYPE -I$(top_srcdir)
SUBDIRS:=tests tests/unit-tests doc platform-specific sha2 aes ecc
SUBDIRS:=tests tests/unit-tests doc platform-specific sha2 aes
DISTSUBDIRS:=$(SUBDIRS)
DISTDIR=$(top_builddir)/$(package)
FILES:=Makefile.in configure configure.ac dtls_config.h.in \
Makefile.tinydtls $(SOURCES) $(HEADERS)
Makefile.tinydtls tinydtls.pc.in ar-lib $(SOURCES) $(HEADERS) $(MICRO_ECC_FILES)
LIB:=libtinydtls
LIBS:=$(LIB).a
ifeq ("@ENABLE_SHARED@", "1")
Expand Down Expand Up @@ -87,9 +89,6 @@ dirs: $(SUBDIRS)

dtls_prng.o:: $(wildcard platform-specific/dtls_prng_*.c)

$(SUB_OBJECTS)::
$(MAKE) -C $(@D) $(@F)

$(LIB).so: $(OBJECTS)
$(LINK.c) $(LDFLAGS) -shared $^ -o $@

Expand All @@ -104,6 +103,9 @@ clean:
done
endif # WITH_CONTIKI

# Override several warnings for uECC.o
ext/micro-ecc/uECC.o:: CFLAGS+=-Wno-pedantic -Wno-unused-parameter -Wno-missing-prototypes -Wno-missing-declarations

doc:
$(MAKE) -C doc

Expand All @@ -113,7 +115,7 @@ distclean: clean

dist: $(FILES) $(DISTSUBDIRS)
test -d $(DISTDIR) || mkdir $(DISTDIR)
cp $(FILES) $(DISTDIR)
cp --parents $(FILES) $(DISTDIR)
for dir in $(DISTSUBDIRS); do \
$(MAKE) -C $$dir dist; \
done
Expand Down
19 changes: 15 additions & 4 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,13 @@ AC_ARG_WITH(ecc,
[AS_HELP_STRING([--without-ecc],[disable support for TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8])],
[],
[AC_DEFINE(DTLS_ECC, 1, [Define to 1 if building with ECC support.])
OPT_OBJS="${OPT_OBJS} ecc/ecc.o"
OPT_OBJS="${OPT_OBJS} ext/micro-ecc/uECC.o"
dnl remove all ECC except for secp256r1
AC_DEFINE([uECC_SUPPORTS_secp160r1], [0], [Define to 1 if building with uECC curve secp160r1])
AC_DEFINE([uECC_SUPPORTS_secp192r1], [0], [Define to 1 if building with uECC curve secp192r1])
AC_DEFINE([uECC_SUPPORTS_secp224r1], [0], [Define to 1 if building with uECC curve secp224r1])
AC_DEFINE([uECC_SUPPORTS_secp256r1], [1], [Define to 1 if building with uECC curve secp256r1])
AC_DEFINE([uECC_SUPPORTS_secp256k1], [0], [Define to 1 if building with uECC curve secp256k1])
DTLS_ECC=1])

AC_ARG_WITH(psk,
Expand Down Expand Up @@ -116,7 +122,13 @@ AC_SUBST(NDEBUG)
AC_SUBST(DTLS_ECC)
AC_SUBST(DTLS_PSK)
AC_SUBST(ENABLE_SHARED)
AC_SUBST(AR)
AC_SUBST(AC)

AC_SUBST(uECC_SUPPORTS_secp160r1)
AC_SUBST(uECC_SUPPORTS_secp192r1)
AC_SUBST(uECC_SUPPORTS_secp224r1)
AC_SUBST(uECC_SUPPORTS_secp256r1)
AC_SUBST(uECC_SUPPORTS_secp256k1)

# Checks for header files.
AC_CHECK_HEADERS([assert.h arpa/inet.h fcntl.h inttypes.h netdb.h netinet/in.h stddef.h stdint.h stdlib.h string.h strings.h sys/param.h sys/socket.h unistd.h])
Expand Down Expand Up @@ -148,6 +160,5 @@ AC_CONFIG_FILES([Makefile
platform-specific/Makefile
tinydtls.pc
sha2/Makefile
aes/Makefile
ecc/Makefile])
aes/Makefile])
AC_OUTPUT
204 changes: 155 additions & 49 deletions crypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,14 +24,17 @@
#else
#define assert(x)
#endif
#include <inttypes.h>

#include "global.h"
#include "dtls_debug.h"
#include "numeric.h"
#include "dtls.h"
#include "crypto.h"
#include "ccm.h"
#include "ecc/ecc.h"
#ifdef DTLS_ECC
#include "ext/micro-ecc/uECC.h"
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"ext/micro-ecc" is part of the include path, maybe it's simpler to use "uECC.h"?

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@mrdeep1 mrdeep1 Feb 26, 2024 •
edited
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It is my preference to always include the package information path in the #include statement, to prevent name clashes (unlikely with uECC.h, but with possible with names like global.h etc.).

So, I would recommend that the include path includes ext/, and use #include <micro-ecc/uECC.h>.

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The pain is, that "micro-ecc/uECC.c" uses:

#include "uECC.h"
#include "uECC_vli.h"

and "micro-ecc/uECC_vli.h" uses:

#include "uECC.h"
#include "types.h"

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Anything that is getting built external to micro-ecc will need the equivalent of "micro-ecc/uECC.h" to get at the function definitions. For the actual micro-ecc code compilation, I assume that it is done in the micro-ecc/ directory, in which case just "uECCH.h" without a path is fine.

If you declare #include "" , the compiler first searches in current directory of source file and if not found,
continues to search in any included -I directories and then the default include directories.

If you declare #include <> , the compiler searches directly in any included -I directories and then the default
include directories.

$ cpp -v shows the include search directory order.

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OK. I've checked it and at least the cmake build doesn't need to extend the include path with "ext/micro-ecc".

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"ext/micro-ecc" is part of the include path,

I mixed it up, it's only part of "FILES".

#endif /* DTLS_ECC */
#include "dtls_prng.h"
#include "netq.h"

Expand Down Expand Up @@ -356,6 +359,10 @@ dtls_psk_pre_master_secret(unsigned char *key, size_t keylen,
#endif /* DTLS_PSK */

#ifdef DTLS_ECC
#ifdef uECC_SUPPORTS_secp256r1
const dtls_ecdh_curve default_curve = TLS_EXT_ELLIPTIC_CURVES_SECP256R1;
#endif /* uECC_SUPPORTS_secp256r1 */

static void dtls_ec_key_to_uint32(const unsigned char *key, size_t key_size,
uint32_t *result) {
int i;
Expand Down Expand Up @@ -432,69 +439,148 @@ int dtls_ec_key_asn1_from_uint32(const uint32_t *key, size_t key_size,
return key_size + 2;
}

static int get_uecc_curve(dtls_ecdh_curve curve, uECC_Curve *result) {
struct {
dtls_ecdh_curve curve;
uECC_Curve uecc_curve;
} known_curves[] = {
#if uECC_SUPPORTS_secp256r1
{ TLS_EXT_ELLIPTIC_CURVES_SECP256R1, uECC_secp256r1() },
#endif /* uECC_SUPPORTS_secp256r1 */
};
unsigned int index;

for (index = 0; index < sizeof(known_curves)/sizeof(known_curves[0]); index++) {
if (known_curves[index].curve == curve) {
*result = known_curves[index].uecc_curve;
return 1;
}
}
return 0;
}

int dtls_ecdh_pre_master_secret2(const unsigned char *priv_key,
const unsigned char *pub_key,
size_t key_size,
dtls_ecdh_curve curve,
unsigned char *result,
size_t result_len) {
uECC_Curve uecc_curve;
if (!get_uecc_curve(curve, &uecc_curve)) {
dtls_warn("curve %" PRIu16 " not supported\n", curve);
return -1;
}

if (result_len < key_size) {
return -1;
}

if (!uECC_valid_public_key(pub_key, uecc_curve)) {
dtls_warn("invalid public key\n");
}

if (!uECC_shared_secret(pub_key, priv_key, result, uecc_curve)) {
dtls_warn("cannot generate ECDH shared secret\n");
return 0;
}

return key_size;
}

int dtls_ecdh_pre_master_secret(unsigned char *priv_key,
unsigned char *pub_key_x,
unsigned char *pub_key_y,
size_t key_size,
unsigned char *result,
size_t result_len) {
uint32_t priv[8];
uint32_t pub_x[8];
uint32_t pub_y[8];
uint32_t result_x[8];
uint32_t result_y[8];
const dtls_ecdh_curve curve = default_curve;
uint8_t pub_key[2 * DTLS_EC_KEY_SIZE];

assert(key_size == sizeof(priv));
if (result_len < key_size) {
return -1;
}

dtls_ec_key_to_uint32(priv_key, key_size, priv);
dtls_ec_key_to_uint32(pub_key_x, key_size, pub_x);
dtls_ec_key_to_uint32(pub_key_y, key_size, pub_y);

ecc_ecdh(pub_x, pub_y, priv, result_x, result_y);

dtls_ec_key_from_uint32(result_x, key_size, result);
return key_size;
memcpy(pub_key, pub_key_x, DTLS_EC_KEY_SIZE);
memcpy(pub_key + DTLS_EC_KEY_SIZE, pub_key_y, DTLS_EC_KEY_SIZE);
return dtls_ecdh_pre_master_secret2(priv_key, pub_key, key_size, curve,
result, result_len);
}

void
dtls_ecdsa_generate_key(unsigned char *priv_key,
unsigned char *pub_key_x,
unsigned char *pub_key_y,
size_t key_size) {
uint32_t priv[8];
uint32_t pub_x[8];
uint32_t pub_y[8];
const dtls_ecdh_curve curve = default_curve;
uint8_t pub_key[2 * DTLS_EC_KEY_SIZE];

int res = dtls_ecdsa_generate_key2(priv_key, pub_key, key_size, curve);
if (res > 0) {
memcpy(pub_key_x, pub_key, res);
memcpy(pub_key_y, pub_key + res, res);
}
}

do {
dtls_prng((unsigned char *)priv, key_size);
} while (!ecc_is_valid_key(priv));
int
dtls_ecdsa_generate_key2(unsigned char *priv_key,
unsigned char *pub_key,
size_t key_size,
dtls_ecdh_curve curve) {
uECC_Curve uecc_curve;
if (!get_uecc_curve(curve, &uecc_curve)) {
dtls_warn("curve %" PRIu16 " not supported\n", curve);
return -1;
}

ecc_gen_pub_key(priv, pub_x, pub_y);
assert(key_size >= (unsigned int)uECC_curve_private_key_size(uecc_curve));
assert(2 * key_size >= (unsigned int)uECC_curve_public_key_size(uecc_curve));

dtls_ec_key_from_uint32(priv, key_size, priv_key);
dtls_ec_key_from_uint32(pub_x, key_size, pub_key_x);
dtls_ec_key_from_uint32(pub_y, key_size, pub_key_y);
if (!uECC_make_key(pub_key, priv_key, uecc_curve)
|| !uECC_valid_public_key(pub_key, uecc_curve)) {
dtls_crit("cannot generate ECC key pair\n");
return 0;
}
return uECC_curve_private_key_size(uecc_curve);
}

/* rfc4492#section-5.4 */
void
dtls_ecdsa_create_sig_hash(const unsigned char *priv_key, size_t key_size,
const unsigned char *sign_hash, size_t sign_hash_size,
uint32_t point_r[9], uint32_t point_s[9]) {
int ret;
uint32_t priv[8];
uint32_t hash[8];
uint32_t randv[8];

dtls_ec_key_to_uint32(priv_key, key_size, priv);
dtls_ec_key_to_uint32(sign_hash, sign_hash_size, hash);
do {
dtls_prng((unsigned char *)randv, key_size);
ret = ecc_ecdsa_sign(priv, hash, randv, point_r, point_s);
} while (ret);
const dtls_ecdh_curve curve = default_curve;
dtls_ecdsa_create_sig_hash2(priv_key, key_size,
sign_hash, sign_hash_size,
curve, point_r, point_s);

}

int
dtls_ecdsa_create_sig_hash2(const unsigned char *priv_key, size_t key_size,
const unsigned char *sign_hash, size_t sign_hash_size,
dtls_ecdh_curve curve,
uint32_t point_r[9], uint32_t point_s[9]) {
uint8_t sign[2 * DTLS_EC_KEY_SIZE];
uECC_Curve uecc_curve;
int curve_size;
if (!get_uecc_curve(curve, &uecc_curve)) {
dtls_warn("curve %" PRIu16 " not supported\n", curve);
return -1;
}

curve_size = uECC_curve_private_key_size(uecc_curve);

assert(key_size >= (unsigned int)curve_size);
assert(sign_hash_size >= (unsigned int)curve_size);
assert(sizeof(sign) >= 2 * (unsigned int)curve_size);
if (!uECC_sign(priv_key, sign_hash, sign_hash_size, sign, uecc_curve)) {
dtls_warn("cannot create signature\n");
return -1;
}

dtls_ec_key_to_uint32(sign, curve_size, point_r);
dtls_ec_key_to_uint32(sign + curve_size, curve_size, point_s);
return 2 * curve_size;
}

void
Expand Down Expand Up @@ -522,19 +608,39 @@ dtls_ecdsa_verify_sig_hash(const unsigned char *pub_key_x,
const unsigned char *pub_key_y, size_t key_size,
const unsigned char *sign_hash, size_t sign_hash_size,
unsigned char *result_r, unsigned char *result_s) {
uint32_t pub_x[8];
uint32_t pub_y[8];
uint32_t hash[8];
uint32_t point_r[8];
uint32_t point_s[8];

dtls_ec_key_to_uint32(pub_key_x, key_size, pub_x);
dtls_ec_key_to_uint32(pub_key_y, key_size, pub_y);
dtls_ec_key_to_uint32(result_r, key_size, point_r);
dtls_ec_key_to_uint32(result_s, key_size, point_s);
dtls_ec_key_to_uint32(sign_hash, sign_hash_size, hash);

return ecc_ecdsa_validate(pub_x, pub_y, hash, point_r, point_s);
const dtls_ecdh_curve curve = default_curve;
uint8_t pub_key[2 * DTLS_EC_KEY_SIZE];
memcpy(pub_key, pub_key_x, key_size);
memcpy(pub_key + key_size, pub_key_y, key_size);
return dtls_ecdsa_verify_sig_hash2(pub_key, key_size,
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I guess, the size of pub_key isn't that of the passed in key_size.

sign_hash, sign_hash_size,
curve,
result_r, result_s);
}

int
dtls_ecdsa_verify_sig_hash2(const unsigned char *pub_key, size_t key_size,
const unsigned char *sign_hash, size_t sign_hash_size,
dtls_ecdh_curve curve,
unsigned char *result_r, unsigned char *result_s) {
uint8_t sign[2 * DTLS_EC_KEY_SIZE];
uECC_Curve uecc_curve;
int curve_size;
if (!get_uecc_curve(curve, &uecc_curve)) {
dtls_warn("curve %" PRIu16 " not supported\n", curve);
return -1;
}
(void)result_r;
(void)result_s;

curve_size = uECC_curve_public_key_size(uecc_curve);

assert(key_size == (unsigned int)curve_size);
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That fires on my interop test. Adding

dtls_warn("%d != %d\n", (int) key_size, curve_size);

I get

Feb 26 16:46:45 WARN 32 != 64
tinydtls-server: crypto.c:638: dtls_ecdsa_verify_sig_hash2: Assertion `key_size == (unsigned int)curve_size' failed.

AFAIK, the key-size is passed in as sizeof(config->keyx.ecdsa.other_pub_x) in dtls.c, line 2589

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Beside the assert, the first interop-tests with Californium are successful.
Great!

assert(sizeof(sign) >= (unsigned int)curve_size);

/* clear sign to avoid maybe-unitialized warning */
memset(sign, 0, sizeof(sign));
return uECC_verify(pub_key, sign_hash, sign_hash_size, sign, uecc_curve);
}

int
Expand Down
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