Add libtomcrypt and libtommath submodules

These provide e.g. rsa_oaep, which can be used for sw crypto

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

src/lib/CMakeLists.txt

@@ -32,7 +32,6 @@
 ############################################################################
 
 px4_add_git_submodule(TARGET git_matrix PATH "matrix")
-px4_add_git_submodule(TARGET git_monocypher PATH "crypto/monocypher")
 
 add_subdirectory(airspeed)
 add_subdirectory(avoidance)

src/lib/crypto/CMakeLists.txt

@@ -31,6 +31,12 @@
 #
 ############################################################################
 
+if (DEFINED PX4_CRYPTO)
+
+px4_add_git_submodule(TARGET git_monocypher PATH "monocypher")
+px4_add_git_submodule(TARGET git_libtomcrypt PATH "libtomcrypt")
+px4_add_git_submodule(TARGET git_libtommath PATH "libtommath")
+
 px4_add_library(monocypher
 	monocypher/src/monocypher.c
 	monocypher/src/optional/monocypher-ed25519.c
@@ -43,3 +49,54 @@ target_include_directories(monocypher
 
 # There is a one shadow warning in monocypher 3.1.2, ignore it
 target_compile_options(monocypher PRIVATE -Wno-shadow)
+
+
+
+file(GLOB TOMMATH_SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "libtommath/*.c")
+px4_add_library(libtommath
+  ${TOMMATH_SRC}
+)
+
+
+file(GLOB_RECURSE PK_SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "libtomcrypt/src/pk/*.c")
+file(GLOB_RECURSE MATH_SRC RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "libtomcrypt/src/math/*.c")
+
+px4_add_library(libtomcrypt
+libtomcrypt_wrappers.c
+	${PK_SRC}
+	${MATH_SRC}
+	libtomcrypt/src/hashes/sha2/sha256.c
+	libtomcrypt/src/hashes/helper/hash_memory.c
+	libtomcrypt/src/prngs/sprng.c
+	libtomcrypt/src/misc/crypt/crypt_ltc_mp_descriptor.c
+	libtomcrypt/src/misc/crypt/crypt_hash_is_valid.c
+	libtomcrypt/src/misc/crypt/crypt_prng_is_valid.c
+	libtomcrypt/src/misc/zeromem.c
+)
+
+target_include_directories(libtomcrypt
+	PRIVATE
+		${CMAKE_CURRENT_SOURCE_DIR}/libtommath
+        )
+
+target_include_directories(libtomcrypt
+	PUBLIC
+		${CMAKE_CURRENT_SOURCE_DIR}/libtomcrypt/src/headers
+)
+
+# libtomcrypt defines:
+# ARGTYPE=3: No argument checking
+add_definitions(-DARGTYPE=3 -DLTC_EASY -DLTC_NO_TEST -DLTM_DESC -DMP_LOW_MEM)
+
+# link to libtommath and os provided random library
+target_link_libraries(libtomcrypt
+	PRIVATE
+		libtommath
+		px4_random
+)
+
+# Fix for erroneous warning on some compilers:
+# "der_encode_asn1_identifier.c:39:18: error: comparison is always false due to limited range of data type"
+target_compile_options(libtomcrypt PRIVATE -Wno-type-limits)
+
+endif()

src/lib/crypto/libtomcrypt_wrappers.c

@@ -0,0 +1,47 @@
+#include <px4_random.h>
+#include <tomcrypt.h>
+
+struct ltc_hash_descriptor hash_descriptor[] = {
+	{
+		"sha256",
+		0,
+		32,
+		64,
+
+		/* OID */
+		{ 2, 16, 840, 1, 101, 3, 4, 2, 1,  },
+		9,
+
+		&sha256_init,
+		&sha256_process,
+		&sha256_done,
+		&sha256_test,
+		NULL
+	}
+};
+
+struct ltc_prng_descriptor prng_descriptor[] = {
+	{
+		"sprng", 0,
+		&sprng_start,
+		&sprng_add_entropy,
+		&sprng_ready,
+		&sprng_read,
+		&sprng_done,
+		&sprng_export,
+		&sprng_import,
+		&sprng_test
+	}
+};
+
+unsigned long rng_get_bytes(unsigned char *out,
+			    unsigned long outlen,
+			    void (*callback)(void))
+{
+	return px4_get_secure_random((uint8_t *)out, (size_t)outlen);
+}
+
+void libtomcrypt_init(void)
+{
+	ltc_mp = ltm_desc;
+}