WIP cryptographic design

9 files changed, 292 insertions, 6 deletions

diff --git a/controller/fw/Makefile b/controller/fw/Makefile
index a7d690a..c678963 100644
--- a/controller/fw/Makefile
+++ b/controller/fw/Makefile
@@ -60,6 +60,10 @@ DSSS_FILTER_ORDER		?= 12
 
 PAYLOAD_DATA_BIT		?= 64
 TRANSMISSION_SYMBOLS	?= 32
+PRESIG_STORE_SIZE		?= 3
+
+PRESIG_KEYFILE			?= presig_test_key.private
+PRESIG_DBFILE			?= presig_test_db.sqlite3
 
 CC			:= $(PREFIX)gcc
 CXX			:= $(PREFIX)g++
@@ -90,7 +94,7 @@ MUSL_DIR_ABS		:= $(abspath $(MUSL_DIR))
 COMMON_CFLAGS		+= -I$(OPENCM3_DIR_ABS)/include -Imspdebug/util -Imspdebug/drivers -Ilevmarq
 COMMON_CFLAGS		+= -I$(CMSIS_DIR_ABS)/CMSIS/DSP/Include -I$(CMSIS_DIR_ABS)/CMSIS/Core/Include 
 CFLAGS				+= -I$(abspath musl_include_shims)
-COMMON_CFLAGS		+= -I$(BUILDDIR) -Isrc
+COMMON_CFLAGS		+= -I$(BUILDDIR) -Isrc -Itinyaes
 
 COMMON_CFLAGS	+= -Os -std=gnu11 -g -DSTM32F4
 CFLAGS			+= -mthumb -mcpu=cortex-m4 -mfloat-abi=hard -mfpu=fpv4-sp-d16
@@ -107,6 +111,7 @@ COMMON_CFLAGS	+= -DDSSS_WAVELET_WIDTH=$(DSSS_WAVELET_WIDTH)
 COMMON_CFLAGS	+= -DDSSS_WAVELET_LUT_SIZE=$(DSSS_WAVELET_LUT_SIZE)
 COMMON_CFLAGS	+= -DPAYLOAD_DATA_BIT=$(PAYLOAD_DATA_BIT)
 COMMON_CFLAGS	+= -DTRANSMISSION_SYMBOLS=$(TRANSMISSION_SYMBOLS)
+COMMON_CFLAGS	+= -DPRESIG_STORE_SIZE=$(PRESIG_STORE_SIZE)
 
 # for musl
 CFLAGS			+= -Dhidden=
@@ -154,6 +159,14 @@ $(BUILDDIR)/generated/dsss_cwt_wavelet.c: | $(BUILDDIR)/generated
 $(BUILDDIR)/generated/dsss_butter_filter.h: | $(BUILDDIR)/generated
 	$(PYTHON3) tools/butter_filter_gen.py -m dsss_filter $(DSSS_FILTER_FC) $(FMEAS_SAMPLING_RATE) $(DSSS_FILTER_ORDER) > $@
 
+.PRECIOUS: $(BUILDDIR)/generated/crypto_presig_data.c
+$(BUILDDIR)/generated/crypto_presig_data.c: $(PRESIG_KEYFILE) tools/presig_gen.py | $(BUILDDIR)/generated
+	$(PYTHON3) tools/presig_gen.py $(PRESIG_KEYFILE) $(PRESIG_DBFILE) > $@
+
+.PRECIOUS: $(PRESIG_KEYFILE)
+$(PRESIG_KEYFILE):
+	$(PYTHON3) tools/presig_gen.py -g $@
+
 $(BUILDDIR)/generated: ; mkdir -p $@
 
 OBJS := $(addprefix $(BUILDDIR)/,$(C_SOURCES:.c=.o) $(CXX_SOURCES:.cpp=.o))
@@ -180,6 +193,11 @@ $(BUILDDIR)/tools/dsss_demod_test: tools/dsss_demod_test.c src/dsss_demod.c $(BU
 	mkdir -p $(@D)
 	$(HOST_CC) $(COMMON_CFLAGS) $(SIM_CFLAGS) -o $@ $^
 
+tools: $(BUILDDIR)/tools/crypto_test
+$(BUILDDIR)/tools/crypto_test: tools/crypto_test.c src/crypto.c tinyaes/aes.c $(BUILDDIR)/generated/crypto_presig_data.c
+	mkdir -p $(@D)
+	$(HOST_CC) $(COMMON_CFLAGS) $(SIM_CFLAGS) -lsodium -o $@ $^
+
 $(BUILDDIR)/src/%.o: src/%.c
 	mkdir -p $(@D)
 	$(CC) $(COMMON_CFLAGS) $(CFLAGS) $(INT_CFLAGS) -o $@ -c $<
diff --git a/controller/fw/src/crypto.c b/controller/fw/src/crypto.c
new file mode 100644
index 0000000..73ad783
--- /dev/null
+++ b/controller/fw/src/crypto.c
@@ -0,0 +1,48 @@
+
+#include <unistd.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <aes.h>
+
+#include "crypto.h"
+#include "simulation.h"
+
+void debug_hexdump(const char *name, uint8_t *buf, size_t len);
+void debug_hexdump(const char *name, uint8_t *buf, size_t len) {
+    DEBUG_PRINTN("%20s: ", name);
+    for (size_t i=0; i<len;) {
+        for (size_t j=0; j<8 && i<len; i++, j++)
+            DEBUG_PRINTN("%02x ", buf[i]);
+        DEBUG_PRINTN(" ");
+    }
+    DEBUG_PRINTN("\n");
+}
+
+int oob_message_received(uint8_t msg[static OOB_TRIGGER_LEN]) {
+    struct AES_ctx ctx;
+    uint8_t buf[crypto_sign_BYTES];
+
+    for (size_t serial=0; serial<PRESIG_STORE_SIZE; serial++) {
+        for (size_t dom=0; dom<_TRIGGER_DOMAIN_COUNT; dom++) {
+
+            DEBUG_PRINT("Trying domain %zd serial %zd", dom, serial);
+            debug_hexdump("oob_presig_iv", oob_presig_iv, sizeof(oob_presig_iv));
+
+            memcpy(buf, presig_store[dom][serial], crypto_sign_BYTES);
+            debug_hexdump("presig", buf, sizeof(buf));
+            AES_init_ctx_iv(&ctx, msg, oob_presig_iv);
+            AES_CBC_decrypt_buffer(&ctx, buf, crypto_sign_BYTES);
+            debug_hexdump("decrypted", buf, sizeof(buf));
+
+            if (!crypto_sign_verify_detached(buf, presig_messages[dom][serial], PRESIG_MSG_LEN, oob_trigger_pubkey)) {
+                oob_trigger_activated(dom, presig_first_serial + serial);
+                return 1;
+            }
+            DEBUG_PRINTN("\n");
+        }
+    }
+
+    return 0;
+}
diff --git a/controller/fw/src/crypto.h b/controller/fw/src/crypto.h
new file mode 100644
index 0000000..61a0da8
--- /dev/null
+++ b/controller/fw/src/crypto.h
@@ -0,0 +1,33 @@
+#ifndef __CRYPTO_H__
+#define __CRYPTO_H__
+
+#include <stdint.h>
+
+#include <sodium.h>
+
+
+#define OOB_TRIGGER_LEN 16
+#define PRESIG_MSG_LEN 16
+
+
+enum trigger_domain {
+    TRIGGER_DOMAIN_ALL,
+    TRIGGER_DOMAIN_VENDOR,
+    TRIGGER_DOMAIN_SERIES,
+    TRIGGER_DOMAIN_COUNTRY,
+    TRIGGER_DOMAIN_REGION,
+    _TRIGGER_DOMAIN_COUNT
+};
+
+extern uint8_t presig_store[_TRIGGER_DOMAIN_COUNT][PRESIG_STORE_SIZE][crypto_sign_BYTES];
+extern uint8_t oob_trigger_pubkey[crypto_sign_PUBLICKEYBYTES];
+extern uint8_t presig_messages[_TRIGGER_DOMAIN_COUNT][PRESIG_STORE_SIZE][PRESIG_MSG_LEN];
+extern uint8_t oob_presig_iv[16];
+extern int presig_first_serial;
+
+
+extern void oob_trigger_activated(enum trigger_domain domain, int serial);
+
+int oob_message_received(uint8_t msg[static OOB_TRIGGER_LEN]);
+
+#endif /* __CRYPTO_H__ */
diff --git a/controller/fw/src/dsss_demod.c b/controller/fw/src/dsss_demod.c
index 97cc039..c5a2070 100644
--- a/controller/fw/src/dsss_demod.c
+++ b/controller/fw/src/dsss_demod.c
@@ -248,7 +248,6 @@ void group_received(struct dsss_demod_state *st) {
 
     /* If we found empty entries, replace one by a new decoding starting at this group */
     if (empty_idx >= 0) {
-        DEBUG_PRINT("Writing to %zd", empty_idx);
         assert(0 <= empty_idx && empty_idx < DSSS_MATCHER_CACHE_SIZE);
         st->matcher_cache[empty_idx].last_phase = group_phase;
         st->matcher_cache[empty_idx].candidate_score = base_score;
@@ -261,7 +260,6 @@ void group_received(struct dsss_demod_state *st) {
 
     /* If the weakest decoding in cache is weaker than a new decoding starting here, replace it */
     } else if (min_score < base_score && min_idx >= 0) {
-        DEBUG_PRINT("Writing to %zd", min_idx);
         assert(0 <= min_idx && min_idx < DSSS_MATCHER_CACHE_SIZE);
         st->matcher_cache[min_idx].last_phase = group_phase;
         st->matcher_cache[min_idx].candidate_score = base_score;
diff --git a/controller/fw/src/dsss_demod.h b/controller/fw/src/dsss_demod.h
index e7e5cf9..98cf590 100644
--- a/controller/fw/src/dsss_demod.h
+++ b/controller/fw/src/dsss_demod.h
@@ -63,7 +63,7 @@ struct dsss_demod_state {
 };
 
 
-extern void handle_dsss_received(uint8_t data[TRANSMISSION_SYMBOLS]);
+extern void handle_dsss_received(uint8_t data[static TRANSMISSION_SYMBOLS]);
 
 void dsss_demod_init(struct dsss_demod_state *st);
 void dsss_demod_step(struct dsss_demod_state *st, float new_value, uint64_t ts);
diff --git a/controller/fw/tools/crypto_test.c b/controller/fw/tools/crypto_test.c
new file mode 100644
index 0000000..8552117
--- /dev/null
+++ b/controller/fw/tools/crypto_test.c
@@ -0,0 +1,46 @@
+
+#include <stdint.h>
+#include <math.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/fcntl.h>
+
+#include "crypto.h"
+
+void oob_trigger_activated(enum trigger_domain domain, int serial) {
+    printf("oob_trigger_activated(%d, %d)\n", domain, serial);
+    fflush(stdout);
+}
+
+void print_usage() {
+    fprintf(stderr, "Usage: crypto_test [auth_key_hex]\n");
+}
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        fprintf(stderr, "Error: Invalid arguments.\n");
+        print_usage();
+        return 1;
+    }
+
+    uint8_t auth_key[16];
+
+    for (size_t i=0; argv[1][i+0] != '\0' && argv[1][i+1] != '\0'; i+= 2) {
+        char buf[3] = { argv[1][i+0], argv[1][i+1], 0};
+        char *endptr;
+        auth_key[i/2] = strtoul(buf, &endptr, 16);
+        if (!endptr || *endptr != '\0') {
+            fprintf(stderr, "Invalid authkey\n");
+            return 1;
+        }
+    }
+
+    printf("rc=%d\n", oob_message_received(auth_key));
+
+    return 0;
+}
diff --git a/controller/fw/tools/dsss_demod_test.c b/controller/fw/tools/dsss_demod_test.c
index d09ce87..64fd889 100644
--- a/controller/fw/tools/dsss_demod_test.c
+++ b/controller/fw/tools/dsss_demod_test.c
@@ -12,7 +12,7 @@
 
 #include "dsss_demod.h"
 
-void handle_dsss_received(uint8_t data[TRANSMISSION_SYMBOLS]) {
+void handle_dsss_received(uint8_t data[static TRANSMISSION_SYMBOLS]) {
     printf("data sequence received: [ ");
     for (size_t i=0; i<TRANSMISSION_SYMBOLS; i++) {
         printf("%+3d", ((data[i]&1) ? 1 : -1) * (data[i]>>1));
diff --git a/controller/fw/tools/presig_gen.py b/controller/fw/tools/presig_gen.py
new file mode 100644
index 0000000..2d97391
--- /dev/null
+++ b/controller/fw/tools/presig_gen.py
@@ -0,0 +1,143 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import textwrap
+import uuid
+import hashlib
+import binascii
+import sqlite3
+import time
+
+import nacl.signing
+import nacl.encoding
+
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.backends import default_backend
+
+
+PRESIG_VERSION = '000.001'
+
+def format_hex(data, indent=4, wrap=True):
+    indent = ' '*indent
+    par = ', '.join(f'0x{b:02x}' for b in data)
+    par = textwrap.fill(par, width=120,
+        initial_indent=indent, subsequent_indent=indent,
+        replace_whitespace=False, drop_whitespace=False)
+    if wrap:
+        return f'{{\n{par}\n}}'
+    return par
+
+def domain_string(domain_name, value, serial):
+    return f'smart reset domain string v{PRESIG_VERSION}: domain:{domain_name}={value}@{serial}'
+
+if __name__ == '__main__':
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('keyfile', help='Key file to use')
+    parser.add_argument('presig_db', nargs='?', help='sqlite3 dbfile for generated presig authorization keys')
+    parser.add_argument('-g', '--generate', action='store_true', help='Generate signing keypair')
+    parser.add_argument('-v', '--vendor', type=str, default='Darthenschmidt Cyberei und Verschleierungstechnik GmbH', help='Vendor name for vendor domain')
+    parser.add_argument('-s', '--series', type=str, default='Frobnicator v0.23.7', help='Series identifier for series domain')
+    parser.add_argument('-r', '--region', type=str, default='Neuland', help='Region name for region domain')
+    parser.add_argument('-c', '--country', type=str, default='Germany', help='Country name for country domain')
+    parser.add_argument('-p', '--start-serial', type=int, default=0, help='First presig serial number to use')
+    parser.add_argument('-n', '--presig-count', type=int, default=3, help='Number of presigs to generate')
+    parser.add_argument('-i', '--iv', type=str, default='safety reset oob presig iv', help='IV for presig generation')
+    args = parser.parse_args()
+
+    if args.generate:
+        if os.path.exists(args.keyfile):
+            print("Error: keyfile already exists. We won't overwrite it. Instead please remove it manually.",
+                    file=sys.stderr)
+            sys.exit(1)
+        signing_key = nacl.signing.SigningKey.generate()
+        with open(args.keyfile, 'wb') as f:
+            f.write(signing_key.encode(encoder=nacl.encoding.Base64Encoder))
+            f.write(b'\n')
+        sys.exit(0)
+
+    with open(args.keyfile, 'r') as f:
+        signing_key = nacl.signing.SigningKey(f.read().strip(), encoder=nacl.encoding.Base64Encoder)
+        pubkey_bytes = signing_key.verify_key.encode(encoder=nacl.encoding.RawEncoder)
+        pubkey_hash = hashlib.sha512(pubkey_bytes).digest()[:16]
+
+    if not args.presig_db:
+        print('The presig_db parameter is required.', file=sys.stderr)
+        sys.exit(1)
+
+    db = sqlite3.connect(args.presig_db)
+    db.execute('CREATE TABLE IF NOT EXISTS presig_authkey (timestamp, pubkey_hash, bundle_id, presig_ver, domain, value, serial, authkey)')
+
+    bundle_id = uuid.uuid4().bytes
+
+    print('#include <stdint.h>')
+    print('#include <assert.h>')
+    print()
+    print('#include "crypto.h"')
+    print()
+
+    print(f'/* bundle id {binascii.hexlify(bundle_id).decode()} */')
+    print(f'uint8_t presig_bundle_id[16] = {format_hex(bundle_id)};')
+    print(f'int presig_first_serial = {args.start_serial};')
+    print()
+
+    print(f'uint8_t oob_trigger_pubkey[crypto_sign_PUBLICKEYBYTES] = {format_hex(pubkey_bytes)};')
+    print()
+
+    print('uint8_t presig_messages[_TRIGGER_DOMAIN_COUNT][PRESIG_STORE_SIZE][PRESIG_MSG_LEN] = {')
+    device_domains = {
+            'all': 'all',
+            'country': args.country,
+            'region': args.region,
+            'vendor': args.vendor,
+            'series': args.series
+            }
+    presigs = { dom: [] for dom in device_domains }
+    for dom, val in device_domains.items():
+        print('    {')
+        for i in range(args.presig_count):
+            serial = args.start_serial + i
+            ds = domain_string(dom, val, serial)
+            ds_hash = hashlib.sha512(ds.encode()).digest()[:16]
+            presigs[dom].append((ds_hash, val, serial))
+            print(f'        {{ /* "{ds}" */')
+            print(format_hex(ds_hash, indent=8, wrap=False))
+            print(f'        }},')
+        print('    },')
+    print('};')
+    print()
+
+    presig_iv = hashlib.sha512(args.iv.encode()).digest()[:16]
+    print(f'uint8_t oob_presig_iv[16] = {{ /* sha512("{args.iv}")[:16] */')
+    print(format_hex(presig_iv, wrap=False))
+    print(f'}};')
+    print()
+
+
+    print('uint8_t presig_store[_TRIGGER_DOMAIN_COUNT][PRESIG_STORE_SIZE][crypto_sign_BYTES] = {')
+    for dom, hashes in presigs.items():
+        print(f'    {{ /* domain {dom} */')
+
+        for ds_hash, val, serial in hashes:
+            authkey = os.urandom(16)
+            cipher = Cipher(algorithms.AES(authkey), modes.CTR(presig_iv), backend=default_backend())
+            enc = cipher.encryptor()
+            ciphertext = enc.update(ds_hash)
+            assert len(enc.finalize()) == 0
+
+            with db:
+                db.execute('INSERT INTO presig_authkey VALUES (?, ?, ?, ?, ?, ?, ?, ?)',
+                        (int(time.time()*1000), pubkey_hash, binascii.hexlify(bundle_id).decode(), PRESIG_VERSION, dom,
+            print(format_hex(ciphertext, indent=8, wrap=False))
+            print(f'        }},')
+
+        print(f'    }},')
+    print(f'}};')
+
+    print()
+    print('static inline void __hack_asserts_only(void) {')
+    print(f'    static_assert(_TRIGGER_DOMAIN_COUNT == {len(presigs)});')
+    print(f'    static_assert(PRESIG_STORE_SIZE == {args.presig_count});')
+    print('}')
+    print()
diff --git a/lab-windows/cryptography_experiments.ipynb b/lab-windows/cryptography_experiments.ipynb
index abf571e..c7c046a 100644
--- a/lab-windows/cryptography_experiments.ipynb
+++ b/lab-windows/cryptography_experiments.ipynb
@@ -122,7 +122,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.8.1"
+   "version": "3.8.2"
   }
  },
  "nbformat": 4,