feat(crypto): improve trezor-crypto fuzzer, add new dictionary extraction program

Introduce fuzzing harnesses for zkp* functions and adapt some differential fuzzing
Additional documentation and minor cleanup
Add temporary workaround for clang-14 and more explicit Makefile behavior

crypto/Makefile

@@ -2,10 +2,14 @@ ifeq ($(FUZZER),1)
 CC       ?= clang
 LD       ?= $(CC)
 SANFLAGS += -fsanitize=fuzzer
-CFLAGS   += -fsanitize-ignorelist=fuzzer/sanitizer_ignorelist.txt
 
-# this works around clang optimization issues in relation with -fsanitize=undefined
+# TODO gcc as well as older clang versions <= 12 do not support this feature
+$(info "info: using -fsanitize-ignorelist")
+SANFLAGS   += -fsanitize-ignorelist=fuzzer/sanitizer_ignorelist.txt
+
 # TODO is there a better solution, for example by disabling a specific optimization technique?
+# there is a clang optimization issue in relation with the blake2 code at -fsanitize=undefined
+$(warning "warning: disable optimization on blake2 code as workaround")
 blake2b.o: OPTFLAGS += -O0
 blake2s.o: OPTFLAGS += -O0
 
@@ -56,6 +60,12 @@ ZKP_CFLAGS = \
 ZKP_PATH = ../vendor/secp256k1-zkp
 CFLAGS += -DSECP256K1_CONTEXT_SIZE=208
 
+# TODO remove this workaround once possible
+ifeq ($(CC),clang-14)
+$(warning "warning: suppress clang-14 compiler warning for secp256k1-zkp code")
+ZKP_CFLAGS += -Wno-bitwise-instead-of-logical
+endif
+
 VALGRIND ?= 1
 ifeq ($(VALGRIND),1)
 CFLAGS += -DVALGRIND

crypto/fuzzer/README.md

@@ -47,6 +47,9 @@ To be determined:
 * `-fstack-protector-strong` or `-fstack-protector-all`
 * `-m32` to closer evaluate the 32 bit behavior
     * this requires 32bit build support for gcc-multilib, libc and others
+    * adjust Makefile to `CFLAGS += -DSECP256K1_CONTEXT_SIZE=192`
+* `-DSHA2_UNROLL_TRANSFORM` SHA2 optimization flags
+* `-fsanitize-coverage=edge,trace-cmp,trace-div,indirect-calls,trace-gep,no-prune` to add program counter granularity
 
 ## Operation
 

crypto/fuzzer/extract_fuzzer_dictionary.py

@@ -0,0 +1,389 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+This experimental program is designed to extract a subset of interesting test
+case snippets from the trezor-crypto test directory and output them as a
+standard fuzzer dictionary file.
+
+The program is built on quick-and-dirty regex matching that is known to be
+incorrect for parsing code files, but is considered "good enough" for this
+specific purpose.
+Note that there are target-specific configurations and internal filter settings.
+"""
+
+import argparse
+import binascii
+import glob
+import re
+
+# re2 is considered for future use
+# it requires a system installation and the google-re2 python package
+# import re2
+
+
+# Expected target format for strings in code:
+# Most strings are defined in the general form "example"
+# There are a few test vectors in crypto/tests/wycheproof/javascript/EcUtil.js
+# with 'example' style string definitions, these are ignored for now
+
+TARGET_DIR = "../tests"
+
+# intentionally excluded file types that currently do not provide enough value:
+# *.js, *.md, *.sh, *.html and others from the wycheproof subdirectory
+
+targeted_filetypes_multiline_classA = ("*.c", "*.h", "*.py")
+# Java files have different multiline strings that are handled differently
+targeted_filetypes_multiline_classB = ("*.java",)
+targeted_filetypes_multiline = (
+    targeted_filetypes_multiline_classA + targeted_filetypes_multiline_classB
+)
+
+# files without multiline string content
+# Note: consider switching to actual JSON parsing?
+# Note: the wycheproof repository has a number of test cases for other
+# cryptography such as DSA and RSA which are currently less interesting for the
+# fuzzer dictionary and therefore excluded
+targeted_filetypes_singleline = (
+    "aes*.json",
+    "ecdh*.json",
+    "ecdsa*.json",
+    "x25519*.json",
+    "chacha20*.json",
+    "kw*.json",
+)
+
+verbose = False
+
+# patterns to extract
+# singleline:
+# "4a1e76f133afb"
+# 0xAF8BBDFE8CDD5 and 0x0488b21e
+# m/0'/2147483647'/1'/2147483646'/2' in test_check.c via m/[\d'/]+
+#
+# multiline:
+# "fffc" \n "99"
+# "dpubZ9169K" \n "bTYbcY"
+# "\x65\xf9" \\n  "\xa0\x6a"
+# { 0x086d8bd5, 0x1018f82f, \n 0xc55ece} , see rg "0x([a-zA-Z0-9])+"
+
+# patterns to ignore
+# lines with print statements
+# lines with exceptions
+# comments and other metadata in the testvector JSON files
+# filenames
+# import statements and other package names
+
+# patterns to investigate further
+# public keys with the form BEGIN PUBLIC KEY
+# TODO "abc" + "def" string concatenation on the same line without newline
+# strings in comments
+
+# TODO briefly describe the desired dictionary export file format and its quirks
+
+# match everything in quotes that doesn't have an internal quote character and
+# at least one internal character
+regex_string_general_definition = r"\"[^\"]+\""
+regex_string_general = re.compile(regex_string_general_definition)
+# the capturing group ignores prefix and suffix outside of the quotes
+# Note that this is prone to matching the last line of a C-style multiline string,
+# which is addressed via extra state handling during the file processing
+regex_oneline_string = re.compile(
+    r"(" + regex_string_general_definition + r")\s*[\,\)]+"
+)
+# ignore lines that have a "+" character preceding a string
+regex_oneline_string_java_ignore1 = re.compile(r"^\s*\+\s*\"")
+
+regex_hex_character_segment_inner_definition = "[0-9a-fA-F]+"
+regex_hex_character_input_complete = re.compile(
+    '^"' + regex_hex_character_segment_inner_definition + '"$'
+)
+regex_hex_character_input_inner = re.compile(
+    regex_hex_character_segment_inner_definition
+)
+# most constants are preceded by a space, but some have a "(" "[" or "{" before them
+regex_hex_constant_singleline = re.compile(r"(?<=\(|\[|\{| )0x[a-fA-F0-9]+")
+
+regex_c_style_multiline = re.compile(r"(?:\".+\"\s*\n\s*)+(?:\".+\")", re.MULTILINE)
+regex_c_intermediary_content = re.compile(r"\"\s*\n\s*\"", re.MULTILINE)
+# TODO how to prevent matching in the middle of a multi-line string concatenation?
+# negative lookbehind for "+" is not possible generically and
+# (?<!\+ ) and similar patterns are too static
+
+regex_java_style_multiline = re.compile(
+    r"(?:\".+\"\s*\n\s*\+\s*)+(?:\".+\")", re.MULTILINE
+)
+regex_java_intermediary_content = re.compile(r"\"\s*\n\s*\+\s*\"", re.MULTILINE)
+
+regex_text_newline = re.compile(r"\\n")
+
+# primitive regex that catches most filenames in the data set
+regex_filename_heuristic = re.compile(r"\.[a-zA-Z]+")
+
+counter_hex_content = 0
+counter_wycheproof_hex_reconstruction = 0
+
+# TODO add '"curve"' to capture algorithm names?
+allowlist_keywords_json = (
+    '"uncompressed"',
+    '"wx"',
+    '"wy"',
+    '"msg"',
+    '"sig"',
+    '"key"',
+    '"iv"',
+    '"ct"',
+    '"aad"',
+    '"tag"',
+    '"public"',
+    '"private"',
+    '"shared"',
+    '"padding"',
+    '"x"',
+    '"d"',
+)
+
+# TODO the "keyPem" entry is only a workaround for an encoding issue
+ignore_keywords_java = (
+    "println(",
+    "Exception(",
+    '"keyPem"',
+)
+ignore_keywords_c = ("printf(",)
+
+
+def ignore_single_line_json(data):
+    """return True if the input should be ignored"""
+    # ignore everything that is not matched by the allowlist
+    for keyword in allowlist_keywords_json:
+        if data.find(keyword) > -1:
+            return False
+    return True
+
+
+def ignore_single_line_java(data):
+    """return True if the input should be ignored"""
+    for keyword in ignore_keywords_java:
+        if data.find(keyword) > -1:
+            return True
+    return False
+
+
+def ignore_single_line_c(data):
+    """return True if the input should be ignored"""
+    for keyword in ignore_keywords_c:
+        if data.find(keyword) > -1:
+            return True
+    return False
+
+
+def ignore_general(data):
+    """return True if the input should be ignored"""
+    if regex_filename_heuristic.search(data):
+        return True
+    return False
+
+
+def encode_strings_for_dictionary(data):
+    """
+    Assumes that inputs are already in string quotes
+
+    Handles dictionary-specific encoding steps
+    """
+    # libfuzzer does not like "\n" string patterns in dictionary files, replace
+    # it with an encoded newline
+    data = regex_text_newline.sub("\\\\x0a", data)
+    return data
+
+
+def detect_and_convert_hex(data):
+    """
+    Convert hex strings
+
+    Directly pass through non-hex content
+    """
+    global counter_hex_content
+    global counter_wycheproof_hex_reconstruction
+    match_result1 = regex_hex_character_input_complete.search(data)
+    if match_result1:
+
+        match_result2 = regex_hex_character_input_inner.search(match_result1.string)
+        isolated_substring = match_result2.group(0)
+        if len(isolated_substring) % 2 == 1:
+            # Note: the test cases in the wycheproof testvector JSON files have
+            # a custom binary hex format to represent keys
+            # among other things, this results in hex strings with an uneven
+            # number of characters
+            # see tests/wycheproof/java/com/google/security/wycheproof/JsonUtil.java
+            # specifically the asBigInteger() function for more information
+            if isolated_substring[0] >= "0" and isolated_substring[0] <= "7":
+                isolated_substring = "0" + isolated_substring
+            else:
+                isolated_substring = "f" + isolated_substring
+            counter_wycheproof_hex_reconstruction += 1
+
+        converted_result = ""
+        try:
+            # test error-free conversion to binary
+            binascii.unhexlify(isolated_substring)
+            hex_with_c_style_formatting = ""
+            pos = 0
+            while pos < len(isolated_substring) - 1:
+                hex_with_c_style_formatting += "\\x" + isolated_substring[pos : pos + 2]
+                pos += 2
+
+            converted_result = '"%s"' % hex_with_c_style_formatting
+        # TODO binascii.Incomplete exception also relevant?
+        except binascii.Error:
+            # default to the original input
+            return data
+        counter_hex_content += 1
+        return converted_result
+    return data
+
+
+def search_files_recursively(directory, filetype_glob):
+    """returns glob search results"""
+    target_files = []
+    print_verbose("searching in %s" % directory)
+    for filetype in filetype_glob:
+        print_verbose("searching for %s" % filetype)
+        target_files.extend(glob.glob(f"{directory}/**/{filetype}", recursive=True))
+    return target_files
+
+
+def print_verbose(text):
+    """print wrapper"""
+    if verbose:
+        print(text)
+
+
+def recursive_dictionary_extraction(directory):
+    """handle the central extraction logic"""
+    # TODO split this function up into subfunctions
+    global counter_hex_content
+    # handle as a set structure to de-duplicate results automatically
+    candidate_lines = set()
+
+    target_files = search_files_recursively(directory, targeted_filetypes_singleline)
+    for filepath in target_files:
+        per_file_result_counter = 0
+        with open(filepath) as _file:
+            print_verbose("processing %s" % filepath)
+            for _, line in enumerate(_file.readlines()):
+                if ignore_single_line_json(line):
+                    continue
+                results = regex_oneline_string.findall(line)
+                for result in results:
+                    candidate_lines.add(result)
+                    per_file_result_counter += 1
+            if per_file_result_counter > 0:
+                print_verbose("results: %d" % per_file_result_counter)
+
+    print_verbose("number of candidate entries: %d" % len(candidate_lines))
+
+    target_files = search_files_recursively(directory, targeted_filetypes_multiline)
+    for filepath in target_files:
+        per_file_result_counter = 0
+        with open(filepath) as _file:
+            last_line_was_multiline_string = False
+            print_verbose("processing %s for single-line strings" % filepath)
+            for _, line in enumerate(_file.readlines()):
+                if ignore_single_line_java(line):
+                    last_line_was_multiline_string = False
+                    continue
+                if ignore_single_line_c(line):
+                    last_line_was_multiline_string = False
+                    continue
+                if regex_oneline_string_java_ignore1.search(line):
+                    last_line_was_multiline_string = True
+                    if regex_oneline_string.search(line):
+                        # the Java multiline string apparently ends on this line
+                        last_line_was_multiline_string = False
+                    continue
+
+                result_general_string = regex_string_general.search(line)
+                if result_general_string:
+                    # at least one general string is matched, see if it is
+                    # a single-line string
+                    results = regex_oneline_string.findall(line)
+                    for result in results:
+                        if not last_line_was_multiline_string:
+                            candidate_lines.add(result)
+                            per_file_result_counter += 1
+                        last_line_was_multiline_string = False
+                    if len(results) == 0:
+                        last_line_was_multiline_string = True
+                else:
+                    last_line_was_multiline_string = False
+
+                # TODO split this into a separate loop?
+                results = regex_hex_constant_singleline.findall(line)
+                for result in results:
+                    # remove the "0x" prefix, add quotes
+                    candidate_lines.add('"%s"' % result[2:])
+                    per_file_result_counter += 1
+
+            if per_file_result_counter > 0:
+                print_verbose("results: %d" % per_file_result_counter)
+
+    target_files = search_files_recursively(
+        directory, targeted_filetypes_multiline_classA
+    )
+
+    for filepath in target_files:
+        with open(filepath) as _file:
+            print_verbose("processing %s for C-style multi-line strings" % filepath)
+            filecontent = _file.read()
+            multiline_results = regex_c_style_multiline.findall(filecontent)
+            if len(multiline_results) > 0:
+                print_verbose("results: %d" % len(multiline_results))
+            for result in multiline_results:
+                cleanup = regex_c_intermediary_content.sub("", result)
+                candidate_lines.add(cleanup)
+
+    target_files = search_files_recursively(
+        directory, targeted_filetypes_multiline_classB
+    )
+
+    for filepath in target_files:
+        with open(filepath) as _file:
+            print_verbose("processing %s for Java-style multi-line strings" % filepath)
+            filecontent = _file.read()
+            multiline_results = regex_java_style_multiline.findall(filecontent)
+            if len(multiline_results) > 0:
+                print_verbose("results: %d" % len(multiline_results))
+            for result in multiline_results:
+                cleanup = regex_java_intermediary_content.sub("", result)
+                candidate_lines.add(cleanup)
+
+    return candidate_lines
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("dictionary_output_file", help="output file", type=str)
+    parser.add_argument("--verbose", action="store_true", help="verbose stdout output")
+
+    args = parser.parse_args()
+    verbose = args.verbose
+
+    collected_candidate_lines = recursive_dictionary_extraction(TARGET_DIR)
+    sorted_candidate_lines = sorted(collected_candidate_lines)
+    result_lines = []
+    for candidate_line in sorted_candidate_lines:
+        if ignore_general(candidate_line):
+            continue
+        result_lines.append(
+            encode_strings_for_dictionary(detect_and_convert_hex(candidate_line))
+        )
+
+    print_verbose("counter_hex_content: %d" % counter_hex_content)
+    print_verbose(
+        "counter_wycheproof_hex_reconstruction: %d"
+        % counter_wycheproof_hex_reconstruction
+    )
+    print_verbose("overall deduplicated entries: %d" % len(sorted_candidate_lines))
+
+    with open(args.dictionary_output_file, "w") as _file:
+        for result_line in result_lines:
+            _file.write("%s\n" % result_line)

crypto/fuzzer/extract_fuzzer_dictionary.sh

@@ -2,19 +2,28 @@
 
 # usage: script.sh target-dictionary-filename
 
-# this script searches for interesting strings in the source code and converts
+# This script searches for interesting strings in the source code and converts
 # them into a standard fuzzer dictionary file.
+#
+# Note that this script is phased out in favor of the more sophisticated
+# extract_fuzzer_dictionary.py program
 
+# TODO known issues: the end result has some duplicates in it
 
 TARGET_DIR=../tests
 OUTPUT_FILE=${1:-fuzzer_crypto_tests_strings_dictionary1.txt}
 
-# empty file
+multiline_string_search() {
+  # TODO the `find` regex behavior is Linux-specific
+  find $TARGET_DIR -type f -regextype posix-extended -regex '.*\.(c|h|py|json|java|js)' | xargs cat | perl -p0e 's/"\s*\n\s*\"//smg'
+}
+
+# ensure empty file
 echo -n "" > $OUTPUT_FILE
 
 # strip multiline strings and extract them
 # exclude some hex strings, but allow hex strings with mixed capitalization (Ethereum, rskip60)
-find $TARGET_DIR -type f | xargs cat | perl -p0e 's/"\s*\n\s*\"//smg' | grep -P -o  "\"[\w ]+\"" | grep -v -P "\"(([0-9a-f][0-9a-f])+|([0-9A-F][0-9A-F])+)\"" | sort | uniq | while read -r line ; do
+multiline_string_search | grep -P -o  "\"[\w ]+\"" | grep -v -P "\"(([0-9a-f][0-9a-f])+|([0-9A-F][0-9A-F])+)\"" | sort | uniq | while read -r line ; do
   echo "$line" >> $OUTPUT_FILE
 done
 
@@ -26,7 +35,7 @@ done
 # find each file, cat it, concatenate multiline strings, look for hex strings in quotes
 # note that this returns multiple megabyte of result strings due to the large amount
 # of test cases in the wycheproof project subfolder
-find $TARGET_DIR -type f | xargs cat | perl -p0e 's/"\s*\n\s*\"//smg' | grep -P -o "\"([0-9a-fA-F][0-9a-fA-F])+\"" | grep -P -o "([0-9a-fA-F][0-9a-fA-F])+" | sort | uniq | while read -r line ; do
+multiline_string_search | grep -P -o "\"([0-9a-fA-F][0-9a-fA-F])+\"" | grep -P -o "([0-9a-fA-F][0-9a-fA-F])+" | sort | uniq | while read -r line ; do
   # turn ascii hex strings AA into \xaa for the fuzzer format and add quotes
   # extra backslash escape due to the bash nesting
   escaped_hex=`echo $line | sed -e 's/../\\\\x&/g'`
@@ -35,7 +44,6 @@ done
 
 # search and reassemble BIP39 test seeds that span multiple lines
 # find each file, cat it, concatenate multiline strings, look for BIP39 seed combinations with reasonable length
-find $TARGET_DIR -type f | xargs cat | perl -p0e 's/"\s*\n\s*\"//smg' | grep -Po "(\w{3,10} ){11,23}(\w{3,10})" | sort | uniq | while read -r line ; do
+multiline_string_search | grep -Po "(\w{3,10} ){11,23}(\w{3,10})" | sort | uniq | while read -r line ; do
   echo "\"$line\"" >> $OUTPUT_FILE
 done
-

crypto/fuzzer/fuzzer.c

@@ -1,5 +1,5 @@
 /**
- * Copyright (c) 2020-2021 Christian Reitter
+ * Copyright (c) 2020-2022 Christian Reitter
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the "Software"),
@@ -43,6 +43,7 @@
 #include "ed25519-donna/ed25519-donna.h"
 #include "ed25519-donna/ed25519-keccak.h"
 #include "ed25519-donna/ed25519.h"
+#include "hasher.h"
 #include "hmac_drbg.h"
 #include "memzero.h"
 #include "monero/monero.h"
@@ -60,11 +61,9 @@
 #include "shamir.h"
 #include "slip39.h"
 #include "slip39_wordlist.h"
-#include "hasher.h"
-#include "nist256p1.h"
-#include "rand.h"
-#include "secp256k1.h"
-
+#include "zkp_bip340.h"
+#include "zkp_context.h"
+#include "zkp_ecdsa.h"
 
 /* fuzzer input data handling */
 const uint8_t *fuzzer_ptr;
@@ -126,7 +125,7 @@ int fuzz_bn_format(void) {
   } else {
     return 0;
   }
-  // TODO fuzzer idea: allow prefix=NULL
+  // TODO idea: : allow prefix == NULL
 
   uint8_t suffixlen = 0;
   if (fuzzer_length < 1) {
@@ -143,7 +142,7 @@ int fuzz_bn_format(void) {
   } else {
     return 0;
   }
-  // TODO fuzzer idea: allow suffix=NULL
+  // TODO idea: allow suffix == NULL
   uint32_t decimals = 0;
   int32_t exponent = 0;
   bool trailing = false;
@@ -397,7 +396,7 @@ int fuzz_nem_get_address(void) {
 
 #if defined(__has_feature)
 #if __has_feature(memory_sanitizer)
-  // TODO check `address` for memory info leakage
+  // TODO idea: check `address` for memory info leakage
 #endif
 #endif
 
@@ -504,20 +503,22 @@ int fuzz_shamir_interpolate(void) {
   return 0;
 }
 
-int fuzz_ecdsa_sign_digest(void) {
+int fuzz_ecdsa_sign_digest_functions(void) {
+  // bug result reference: https://github.com/trezor/trezor-firmware/pull/1697
+
   uint8_t curve_decider = 0;
-  uint8_t sig[64] = {0};
   uint8_t priv_key[32] = {0};
   uint8_t digest[32] = {0};
 
-  if (fuzzer_length < 1 + sizeof(sig) + sizeof(priv_key) + sizeof(digest)) {
+  uint8_t sig1[64] = {0};
+  uint8_t sig2[64] = {0};
+  uint8_t pby1, pby2 = 0;
+  if (fuzzer_length < 1 + sizeof(priv_key) + sizeof(digest)) {
     return 0;
   }
   const ecdsa_curve *curve;
-  uint8_t pby = 0;
 
   memcpy(&curve_decider, fuzzer_input(1), 1);
-  memcpy(&sig, fuzzer_input(sizeof(sig)), sizeof(sig));
   memcpy(&priv_key, fuzzer_input(sizeof(priv_key)), sizeof(priv_key));
   memcpy(&digest, fuzzer_input(sizeof(digest)), sizeof(digest));
 
@@ -528,11 +529,29 @@ int fuzz_ecdsa_sign_digest(void) {
     curve = &nist256p1;
   }
 
-  // TODO optionally set a function for is_canonical() callback
-  int res = ecdsa_sign_digest(curve, priv_key, digest, sig, &pby, NULL);
+  int res = 0;
+
+  // TODO idea: optionally set a function for is_canonical() callback
+  int res1 = ecdsa_sign_digest(curve, priv_key, digest, sig1, &pby1, NULL);
+
+  // the zkp function variant is only defined for a specific curve
+  if (curve == &secp256k1) {
+    int res2 =
+        zkp_ecdsa_sign_digest(curve, priv_key, digest, sig2, &pby2, NULL);
+    if ((res1 == 0 && res2 != 0) || (res1 != 0 && res2 == 0)) {
+      // one variant succeeded where the other did not
+      crash();
+    }
+    if (res1 == 0 && res2 == 0) {
+      if ((pby1 != pby2) || memcmp(&sig1, &sig2, sizeof(sig1)) != 0) {
+        // result values are different
+        crash();
+      }
+    }
+  }
 
   // successful signing
-  if (res == 0) {
+  if (res1 == 0) {
     uint8_t pub_key[33] = {0};
     res = ecdsa_get_public_key33(curve, priv_key, pub_key);
     if (res != 0) {
@@ -540,7 +559,7 @@ int fuzz_ecdsa_sign_digest(void) {
       crash();
     }
 
-    res = ecdsa_verify_digest(curve, pub_key, sig, digest);
+    res = ecdsa_verify_digest(curve, pub_key, sig1, digest);
     if (res != 0) {
       // verification did not succeed
       crash();
@@ -549,7 +568,7 @@ int fuzz_ecdsa_sign_digest(void) {
   return 0;
 }
 
-int fuzz_ecdsa_verify_digest(void) {
+int fuzz_ecdsa_verify_digest_functions(void) {
   uint8_t curve_decider = 0;
   uint8_t hash[32] = {0};
   uint8_t sig[64] = {0};
@@ -572,23 +591,35 @@ int fuzz_ecdsa_verify_digest(void) {
     curve = &nist256p1;
   }
 
-  int res = ecdsa_verify_digest(curve, (const uint8_t *)&pub_key,
-                                (const uint8_t *)&sig, (const uint8_t *)&hash);
-
-  if (res == 0) {
+  int res1 = ecdsa_verify_digest(curve, (const uint8_t *)&pub_key,
+                                 (const uint8_t *)&sig, (const uint8_t *)&hash);
+  if (res1 == 0) {
     // See if the fuzzer ever manages to get find a correct verification
     // intentionally trigger a crash to make this case observable
     // TODO this is not an actual problem, remove in the future
     crash();
   }
 
+  // the zkp_ecdsa* function only accepts the secp256k1 curve
+  if (curve == &secp256k1) {
+    int res2 =
+        zkp_ecdsa_verify_digest(curve, (const uint8_t *)&pub_key,
+                                (const uint8_t *)&sig, (const uint8_t *)&hash);
+
+    // the error code behavior is different between both functions, compare only
+    // verification state
+    if ((res1 == 0 && res2 != 0) || (res1 != 0 && res2 == 0)) {
+      // results differ, this is a problem
+      crash();
+    }
+  }
+
   return 0;
 }
 
 int fuzz_word_index(void) {
 #define MAX_WORD_LENGTH 12
 
-  // TODO exact match?
   if (fuzzer_length < MAX_WORD_LENGTH) {
     return 0;
   }
@@ -683,6 +714,27 @@ int fuzz_mnemonic_to_seed(void) {
   return 0;
 }
 
+int fuzz_ethereum_address_checksum(void) {
+  uint8_t addr[20] = {0};
+  char address[41] = {0};
+  uint64_t chain_id = 0;
+  bool rskip60 = false;
+
+  if (fuzzer_length < sizeof(addr) + sizeof(address) + sizeof(chain_id) + 1) {
+    return 0;
+  }
+
+  memcpy(addr, fuzzer_input(sizeof(addr)), sizeof(addr));
+  memcpy(address, fuzzer_input(sizeof(address)), sizeof(address));
+  memcpy(&chain_id, fuzzer_input(sizeof(chain_id)), sizeof(chain_id));
+  // usually dependent on chain_id, but determined separately here
+  rskip60 = (*fuzzer_input(1)) & 0x1;
+
+  ethereum_address_checksum(addr, address, rskip60, chain_id);
+
+  return 0;
+}
+
 int fuzz_aes(void) {
   if (fuzzer_length < 1 + 16 + 16 + 32) {
     return 0;
@@ -776,7 +828,7 @@ int fuzz_b58gph_encode_decode(void) {
     return 0;
   }
 
-  // TODO switch to malloc()'ed buffers for better out of bounds access
+  // TODO idea: switch to malloc()'ed buffers for better out of bounds access
   // detection?
 
   uint8_t encode_in_buffer[BASE58_GPH_MAX_INPUT_LEN] = {0};
@@ -819,7 +871,7 @@ int fuzz_schnorr_verify_digest(void) {
     return 0;
   }
 
-  // TODO optionally try nist256p1 ?
+  // TODO idea: optionally try nist256p1 ?
   const ecdsa_curve *curve = &secp256k1;
   uint8_t digest[SHA256_DIGEST_LENGTH] = {0};
   uint8_t pub_key[SCHNORR_VERIFY_PUBKEY_DATA_LENGTH] = {0};
@@ -887,9 +939,6 @@ int fuzz_schnorr_sign_digest(void) {
   return 0;
 }
 
-// TODO zkp_bip340_sign, see test_check.c
-// TODO zkp_bip340_verify, see test_check.c
-
 int fuzz_chacha_drbg(void) {
 #define CHACHA_DRBG_ENTROPY_LENGTH 32
 #define CHACHA_DRBG_RESEED_LENGTH 32
@@ -907,7 +956,7 @@ int fuzz_chacha_drbg(void) {
   uint8_t result[CHACHA_DRBG_RESULT_LENGTH] = {0};
   CHACHA_DRBG_CTX ctx;
 
-  // TODO improvement idea: switch to variable input sizes
+  // TODO idea: switch to variable input sizes
   memcpy(&entropy, fuzzer_input(CHACHA_DRBG_ENTROPY_LENGTH),
          CHACHA_DRBG_ENTROPY_LENGTH);
   memcpy(&reseed, fuzzer_input(CHACHA_DRBG_RESEED_LENGTH),
@@ -947,24 +996,215 @@ int fuzz_ed25519_sign_verify(void) {
   // verify message, we expect this to work
   ret = ed25519_sign_open(message, sizeof(message), public_key, signature);
 
-  // TODO are there other error values?
-  if (ret == -1) {
+  if (ret != 0) {
+    // verification did not succeed
     crash();
   }
 
   return 0;
 }
 
-// TODO more XMR functions
-// extern void xmr_hash_to_ec(ge25519 *P, const void *data, size_t length);
+int fuzz_zkp_bip340_sign_digest(void) {
+  // int res = 0;
+  uint8_t priv_key[32] = {0};
+  uint8_t aux_input[32] = {0};
+  uint8_t digest[32] = {0};
+  uint8_t pub_key[32] = {0};
+  uint8_t sig[64] = {0};
 
-// this function directly calls
-// hasher_Raw(HASHER_SHA3K, data, length, hash)
-// is this interesting at all?
-// extern void xmr_fast_hash(uint8_t *hash, const void *data, size_t length);
+  if (fuzzer_length <
+      sizeof(priv_key) + sizeof(aux_input) + sizeof(digest) + sizeof(sig)) {
+    return 0;
+  }
+  memcpy(priv_key, fuzzer_input(sizeof(priv_key)), sizeof(priv_key));
+  memcpy(aux_input, fuzzer_input(sizeof(aux_input)), sizeof(aux_input));
+  memcpy(digest, fuzzer_input(sizeof(digest)), sizeof(digest));
+  memcpy(sig, fuzzer_input(sizeof(sig)), sizeof(sig));
 
-// TODO target idea: re-create openssl_check() from test_openssl.c
-// to do differential fuzzing against OpenSSL functions
+  zkp_bip340_get_public_key(priv_key, pub_key);
+  zkp_bip340_sign_digest(priv_key, digest, sig, aux_input);
+  // TODO idea: test sign result?
+
+  return 0;
+}
+
+int fuzz_zkp_bip340_verify_digest(void) {
+  int res = 0;
+  uint8_t pub_key[32] = {0};
+  uint8_t digest[32] = {0};
+  uint8_t sig[64] = {0};
+
+  if (fuzzer_length < sizeof(digest) + sizeof(pub_key) + sizeof(sig)) {
+    return 0;
+  }
+  memcpy(pub_key, fuzzer_input(sizeof(pub_key)), sizeof(pub_key));
+  memcpy(digest, fuzzer_input(sizeof(digest)), sizeof(digest));
+  memcpy(sig, fuzzer_input(sizeof(sig)), sizeof(sig));
+
+  res = zkp_bip340_verify_digest(pub_key, sig, digest);
+
+  // res == 0 is valid, but crash to make successful passes visible
+  if (res == 0) {
+    crash();
+  }
+
+  return 0;
+}
+
+int fuzz_zkp_bip340_tweak_keys(void) {
+  int res = 0;
+  uint8_t internal_priv[32] = {0};
+  uint8_t root_hash[32] = {0};
+  uint8_t internal_pub[32] = {0};
+  uint8_t result[32] = {0};
+
+  if (fuzzer_length <
+      sizeof(internal_priv) + sizeof(root_hash) + sizeof(internal_pub)) {
+    return 0;
+  }
+  memcpy(internal_priv, fuzzer_input(sizeof(internal_priv)),
+         sizeof(internal_priv));
+  memcpy(root_hash, fuzzer_input(sizeof(root_hash)), sizeof(root_hash));
+  memcpy(internal_pub, fuzzer_input(sizeof(internal_pub)),
+         sizeof(internal_pub));
+
+  res = zkp_bip340_tweak_private_key(internal_priv, root_hash, result);
+  res = zkp_bip340_tweak_public_key(internal_pub, root_hash, result);
+  (void)res;
+
+  return 0;
+}
+
+int fuzz_ecdsa_get_public_key_functions(void) {
+  uint8_t privkey[32] = {0};
+  uint8_t pubkey33_1[33] = {0};
+  uint8_t pubkey33_2[33] = {0};
+  uint8_t pubkey65_1[65] = {0};
+  uint8_t pubkey65_2[65] = {0};
+
+  // note: the zkp_ecdsa_* variants require this specific curve
+  const ecdsa_curve *curve = &secp256k1;
+
+  if (fuzzer_length < sizeof(privkey)) {
+    return 0;
+  }
+  memcpy(privkey, fuzzer_input(sizeof(privkey)), sizeof(privkey));
+
+  int res_33_1 = ecdsa_get_public_key33(curve, privkey, pubkey33_1);
+  int res_33_2 = zkp_ecdsa_get_public_key33(curve, privkey, pubkey33_2);
+  int res_65_1 = ecdsa_get_public_key65(curve, privkey, pubkey65_1);
+  int res_65_2 = zkp_ecdsa_get_public_key65(curve, privkey, pubkey65_2);
+
+  // the function pairs have different return error codes for the same input
+  // so only fail if the one succeeds where the other does not
+  if ((res_33_1 == 0 && res_33_2 != 0) || (res_33_1 != 0 && res_33_2 == 0)) {
+    // function result mismatch
+    crash();
+  }
+  if ((res_65_1 == 0 && res_65_2 != 0) || (res_65_1 != 0 && res_65_2 == 0)) {
+    // function result mismatch
+    crash();
+  }
+
+  if (res_33_1 == 0 && res_33_2 == 0 &&
+      memcmp(&pubkey33_1, &pubkey33_2, sizeof(pubkey33_1)) != 0) {
+    // function result data mismatch
+    crash();
+  }
+
+  if (res_65_1 == 0 && res_65_2 == 0 &&
+      memcmp(&pubkey65_1, &pubkey65_2, sizeof(pubkey65_1)) != 0) {
+    // function result data mismatch
+    crash();
+  }
+
+  return 0;
+}
+
+int fuzz_ecdsa_recover_pub_from_sig_functions(void) {
+  uint8_t digest[32] = {0};
+  uint8_t sig[64] = {0};
+  const ecdsa_curve *curve = &secp256k1;
+  uint8_t recid = 0;
+  uint8_t pubkey1[65] = {0};
+  uint8_t pubkey2[65] = {0};
+
+  if (fuzzer_length < sizeof(digest) + sizeof(sig) + sizeof(recid)) {
+    return 0;
+  }
+  memcpy(digest, fuzzer_input(sizeof(digest)), sizeof(digest));
+  memcpy(sig, fuzzer_input(sizeof(sig)), sizeof(sig));
+  memcpy(&recid, fuzzer_input(sizeof(recid)), sizeof(recid));
+  // conform to parameter requirements
+  recid = recid & 0x03;
+
+  int res1 = zkp_ecdsa_recover_pub_from_sig(curve, pubkey1, sig, digest, recid);
+  int res2 = ecdsa_recover_pub_from_sig(curve, pubkey2, sig, digest, recid);
+
+  uint8_t zero_pubkey[65] = {0};
+  zero_pubkey[0] = 0x04;
+
+  if ((res1 == 0 && res2 != 0) || (res1 != 0 && res2 == 0)) {
+    // result mismatch
+    // bug result reference: https://github.com/trezor/trezor-firmware/pull/2050
+    crash();
+  }
+
+  if (res1 == 0 && res2 == 0 &&
+      memcmp(&pubkey1, &pubkey2, sizeof(pubkey1)) != 0) {
+    // pubkey result mismatch
+    crash();
+  }
+
+  return 0;
+}
+
+int fuzz_ecdsa_sig_from_der(void) {
+  // bug result reference: https://github.com/trezor/trezor-firmware/pull/2058
+  uint8_t der[72] = {0};
+  uint8_t out[72] = {0};
+
+  if (fuzzer_length < sizeof(der)) {
+    return 0;
+  }
+  memcpy(der, fuzzer_input(sizeof(der)), sizeof(der));
+  // null-terminate
+  der[sizeof(der) - 1] = 0;
+  size_t der_len = strlen((const char *)der);
+
+  // TODO idea: use different fuzzer-controlled der_len such as 1 to 73
+  int ret = ecdsa_sig_from_der(der, der_len, out);
+  (void)ret;
+  // TODO idea: check if back conversion works
+
+  return 0;
+}
+
+int fuzz_ecdsa_sig_to_der(void) {
+  uint8_t sig[64] = {0};
+  uint8_t der[72] = {0};
+
+  if (fuzzer_length < sizeof(sig)) {
+    return 0;
+  }
+  memcpy(sig, fuzzer_input(sizeof(sig)), sizeof(sig));
+
+  int ret = ecdsa_sig_to_der((const uint8_t *)&sig, der);
+  (void)ret;
+  // TODO idea: check if back conversion works
+
+  return 0;
+}
+
+void zkp_initialize_context_or_crash(void) {
+  // The current context usage has persistent side effects
+  // TODO switch to frequent re-initialization where necessary
+  if (!zkp_context_is_initialized()) {
+    if (zkp_context_init() != 0) {
+      crash();
+    }
+  }
+}
 
 #define META_HEADER_SIZE 3
 
@@ -977,12 +1217,13 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 
   fuzzer_reset_state();
 
+  // this controls up to 256 different test cases
   uint8_t target_decision = data[0];
 
-  // TODO use once necessary
-  // uint8_t subdecision = data[1];
+  // data[1] is reserved for explicit sub decisions
+  // uint8_t target_sub_decision = data[1];
 
-  // note: data[2] is reserved for future use
+  // data[2] is reserved for future use
 
   // assign the fuzzer payload data for the target functions
   fuzzer_ptr = data + META_HEADER_SIZE;
@@ -1042,8 +1283,9 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
       break;
     case 14:
 #ifdef FUZZ_ALLOW_SLOW
+      zkp_initialize_context_or_crash();
       // slow through expensive bignum operations
-      fuzz_ecdsa_verify_digest();
+      fuzz_ecdsa_verify_digest_functions();
 #endif
       break;
     case 15:
@@ -1074,8 +1316,9 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
       break;
     case 23:
 #ifdef FUZZ_ALLOW_SLOW
+      zkp_initialize_context_or_crash();
       // slow through expensive bignum operations
-      fuzz_ecdsa_sign_digest();
+      fuzz_ecdsa_sign_digest_functions();
 #endif
       break;
     case 24:
@@ -1087,7 +1330,35 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case 26:
       fuzz_mnemonic_to_seed();
       break;
-
+    case 30:
+      fuzz_ethereum_address_checksum();
+      break;
+    case 41:
+      zkp_initialize_context_or_crash();
+      fuzz_zkp_bip340_sign_digest();
+      break;
+    case 42:
+      zkp_initialize_context_or_crash();
+      fuzz_zkp_bip340_verify_digest();
+      break;
+    case 43:
+      zkp_initialize_context_or_crash();
+      fuzz_zkp_bip340_tweak_keys();
+      break;
+    case 50:
+      zkp_initialize_context_or_crash();
+      fuzz_ecdsa_get_public_key_functions();
+      break;
+    case 51:
+      zkp_initialize_context_or_crash();
+      fuzz_ecdsa_recover_pub_from_sig_functions();
+      break;
+    case 52:
+      fuzz_ecdsa_sig_from_der();
+      break;
+    case 53:
+      fuzz_ecdsa_sig_to_der();
+      break;
     default:
       // do nothing
       break;