hx509: Add a JWT fuzzer

lib/hx509/FUZZING.md

@@ -0,0 +1,94 @@
+# Fuzzing lib/hx509
+
+This directory contains a fuzzer for JWS/JWT parsing (`jose.c`).
+
+## fuzz_jose
+
+Fuzzes `hx509_jws_verify()` and `hx509_jwt_verify()` with various key types.
+
+Note: This fuzzer primarily exercises the parsing paths (base64url decoding,
+JSON header/payload parsing, signature format handling). Signature verification
+itself will reject most mutations early, so this is less effective than fuzzing
+pure codecs like the JSON parser.
+
+### Building
+
+#### Standalone (for testing)
+
+```bash
+cd build
+make -C lib/hx509 fuzz_jose
+```
+
+#### With libFuzzer + AddressSanitizer (recommended)
+
+```bash
+cd build
+CC=clang CXX=clang++ \
+  CFLAGS="-fsanitize=fuzzer-no-link,address -g -O1" \
+  LDFLAGS="-fsanitize=fuzzer,address" \
+  ../configure --enable-maintainer-mode --enable-developer
+
+make -C lib/hx509 fuzz_jose
+```
+
+#### With AFL++
+
+```bash
+cd build
+CC=afl-clang-fast CXX=afl-clang-fast++ \
+  ../configure --enable-maintainer-mode --enable-developer
+
+make -C lib/hx509 fuzz_jose
+```
+
+### Running
+
+#### Standalone mode (reads from files or stdin)
+
+```bash
+# Test with corpus files
+./lib/hx509/fuzz_jose ../lib/hx509/fuzz_jose_corpus/*.txt
+
+# Test single input
+echo 'eyJhbGciOiJSUzI1NiJ9.e30.AA' | ./lib/hx509/fuzz_jose
+```
+
+#### libFuzzer mode
+
+```bash
+# Basic fuzzing
+./lib/hx509/fuzz_jose ../lib/hx509/fuzz_jose_corpus/
+
+# With options
+./lib/hx509/fuzz_jose ../lib/hx509/fuzz_jose_corpus/ \
+  -max_len=65536 \
+  -timeout=10 \
+  -jobs=4 \
+  -workers=4
+```
+
+#### AFL++ mode
+
+```bash
+afl-fuzz -i ../lib/hx509/fuzz_jose_corpus -o findings -- ./lib/hx509/fuzz_jose @@
+```
+
+### Seed Corpus
+
+The `fuzz_jose_corpus/` directory contains seed inputs covering:
+
+- Valid RFC test vectors (RS256, ES256, EdDSA from RFC 7515/8037)
+- Various algorithms (RS384, RS512, ES384, ES512, HS256, unknown)
+- Edge cases (empty parts, minimal tokens, algorithm "none")
+- Malformed inputs (bad base64, wrong signature lengths)
+- Long headers, nested JSON, Unicode payloads
+
+### What it tests
+
+1. **JWS verification** with RSA, EC, and Ed25519 public keys
+2. **JWT verification** including claims parsing
+3. **Base64URL decoding** of header, payload, and signature
+4. **JSON parsing** of header and claims
+5. **ECDSA signature format** conversion (JWS r||s to DER)
+6. **Key type matching** against declared algorithm

lib/hx509/Makefile.am

@@ -162,6 +162,12 @@ LDADD = libhx509.la
 test_soft_pkcs11_LDADD = libhx509.la $(top_builddir)/lib/asn1/libasn1.la
 
 test_name_LDADD = libhx509.la $(LIB_roken) $(top_builddir)/lib/asn1/libasn1.la
+
+# Fuzzer for JWS/JWT parsing (build with: make fuzz_jose CFLAGS="-fsanitize=fuzzer,address")
+noinst_PROGRAMS = fuzz_jose
+fuzz_jose_SOURCES = fuzz_jose.c
+fuzz_jose_LDADD = libhx509.la $(LIB_roken) $(top_builddir)/lib/base/libheimbase.la
+fuzz_jose.$(OBJEXT): $(HX509_PROTOS) $(nodist_include_HEADERS)
 test_expr_LDADD = libhx509.la $(LIB_roken) $(top_builddir)/lib/asn1/libasn1.la
 
 TESTS = $(SCRIPT_TESTS) $(PROGRAM_TESTS)

lib/hx509/fuzz_jose.c

@@ -0,0 +1,234 @@
+/*
+ * Copyright (c) 2025 Kungliga Tekniska Högskolan
+ * (Royal Institute of Technology, Stockholm, Sweden).
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * libFuzzer harness for JWS/JWT parsing in jose.c
+ *
+ * Build with:
+ *   clang -g -O1 -fno-omit-frame-pointer -fsanitize=fuzzer,address \
+ *         -I... fuzz_jose.c -o fuzz_jose -lhx509 -lroken ...
+ *
+ * Run with:
+ *   ./fuzz_jose corpus_dir/
+ */
+
+#include <config.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <hx509.h>
+
+/* libFuzzer entry points */
+int LLVMFuzzerInitialize(int *argc, char ***argv);
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
+
+/* Test keys for signature verification fuzzing */
+
+/* RSA-2048 public key */
+static const char *rsa_pubkey_pem =
+    "-----BEGIN PUBLIC KEY-----\n"
+    "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAofgWCuLjybRlzo0tZWJj\n"
+    "NiuSfb4p4fAkd/wWJcyQoTbji9k0l8W26mPddxHmfHQp+Vaw+4qPCJrcS2mJPMEz\n"
+    "P1Pt0Bm4d4QlL+yRT+SFd2lZS+pCgNMsD1W/YpRPEwOWvG6b32690r2jZ47soMZo\n"
+    "9wGzjb/7OMg0LOL+bSf63kpaSHSXndS5z5rexMdbBYUsLA9e+KXBdQOS+UTo7WTB\n"
+    "EMa2R2CapHg665xsmtdVMTBQY4uDZlxvb3qCo5ZwKh9kG4LT6/I5IhlJH7aGhyxX\n"
+    "FvUK+DWNmoudF8NAco9/h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXp\n"
+    "oQIDAQAB\n"
+    "-----END PUBLIC KEY-----\n";
+
+/* EC P-256 public key */
+static const char *ec_pubkey_pem =
+    "-----BEGIN PUBLIC KEY-----\n"
+    "MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEf83OJ3D2xF1Bg8vub9tLe1gHMzV7\n"
+    "6e8Tus9uPHvRVEXH8UTNG72bfocs3+257rn0s2ldbqkLJK2KRiMohYjlrQ==\n"
+    "-----END PUBLIC KEY-----\n";
+
+/* Ed25519 public key */
+static const char *ed25519_pubkey_pem =
+    "-----BEGIN PUBLIC KEY-----\n"
+    "MCowBQYDK2VwAyEA11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo=\n"
+    "-----END PUBLIC KEY-----\n";
+
+static hx509_context ctx = NULL;
+
+/*
+ * Initialize hx509 context once.
+ * Called by libFuzzer before fuzzing starts.
+ */
+int LLVMFuzzerInitialize(int *argc, char ***argv)
+{
+    (void)argc;
+    (void)argv;
+
+    if (hx509_context_init(&ctx) != 0) {
+        ctx = NULL;
+    }
+    return 0;
+}
+
+/*
+ * Main fuzzing entry point.
+ * Input is treated as a potential JWS/JWT token.
+ */
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
+{
+    char *token = NULL;
+    void *payload = NULL;
+    size_t payload_len = 0;
+    heim_dict_t claims = NULL;
+    const char *keys[3];
+    int ret;
+
+    if (ctx == NULL)
+        return 0;
+
+    /* Need at least "a.b.c" for a valid JWS structure */
+    if (size < 5)
+        return 0;
+
+    /* Limit input size to avoid OOM */
+    if (size > 1024 * 1024)
+        return 0;
+
+    /* Make null-terminated copy */
+    token = malloc(size + 1);
+    if (token == NULL)
+        return 0;
+    memcpy(token, data, size);
+    token[size] = '\0';
+
+    /* Set up key array for verification attempts */
+    keys[0] = rsa_pubkey_pem;
+    keys[1] = ec_pubkey_pem;
+    keys[2] = ed25519_pubkey_pem;
+
+    /*
+     * Test 1: JWS verification with multiple key types.
+     * This exercises:
+     *   - Base64URL decoding of header, payload, signature
+     *   - JSON parsing of header
+     *   - Algorithm detection and validation
+     *   - Key type matching
+     *   - Signature format handling (ECDSA JWS->DER conversion)
+     */
+    ret = hx509_jws_verify(ctx, token, keys, 3, &payload, &payload_len);
+    if (ret == 0) {
+        free(payload);
+        payload = NULL;
+    }
+
+    /*
+     * Test 2: JWT verification (includes claims parsing).
+     * This exercises:
+     *   - Everything from JWS verification
+     *   - JSON parsing of claims payload
+     *   - Claims validation (exp, nbf, aud)
+     */
+    ret = hx509_jwt_verify(ctx, token, keys, 3, NULL, 0, &claims);
+    if (ret == 0 && claims) {
+        heim_release(claims);
+        claims = NULL;
+    }
+
+    /*
+     * Test 3: Try with just one key at a time.
+     * This ensures we hit different code paths for key type mismatches.
+     */
+    keys[0] = rsa_pubkey_pem;
+    ret = hx509_jws_verify(ctx, token, keys, 1, &payload, &payload_len);
+    if (ret == 0) {
+        free(payload);
+        payload = NULL;
+    }
+
+    keys[0] = ec_pubkey_pem;
+    ret = hx509_jws_verify(ctx, token, keys, 1, &payload, &payload_len);
+    if (ret == 0) {
+        free(payload);
+        payload = NULL;
+    }
+
+    keys[0] = ed25519_pubkey_pem;
+    ret = hx509_jws_verify(ctx, token, keys, 1, &payload, &payload_len);
+    if (ret == 0) {
+        free(payload);
+        payload = NULL;
+    }
+
+    /* Clear any error state */
+    hx509_clear_error_string(ctx);
+
+    free(token);
+    return 0;
+}
+
+#ifndef HAS_LIBFUZZER_MAIN
+/*
+ * Standalone mode for testing without libFuzzer.
+ * Reads input from stdin or file arguments.
+ */
+int main(int argc, char **argv)
+{
+    uint8_t buf[1024 * 1024];
+    size_t len;
+    FILE *fp;
+    int i;
+
+    LLVMFuzzerInitialize(&argc, &argv);
+
+    if (argc < 2) {
+        /* Read from stdin */
+        len = fread(buf, 1, sizeof(buf), stdin);
+        if (len > 0)
+            LLVMFuzzerTestOneInput(buf, len);
+    } else {
+        /* Read from each file argument */
+        for (i = 1; i < argc; i++) {
+            fp = fopen(argv[i], "rb");
+            if (fp == NULL)
+                continue;
+            len = fread(buf, 1, sizeof(buf), fp);
+            fclose(fp);
+            if (len > 0)
+                LLVMFuzzerTestOneInput(buf, len);
+        }
+    }
+
+    if (ctx)
+        hx509_context_free(&ctx);
+
+    return 0;
+}
+#endif

lib/hx509/fuzz_jose_corpus/README

@@ -0,0 +1,3 @@
+Seed corpus for fuzz_jose
+
+These files contain various JWS/JWT tokens to seed the fuzzer.

lib/hx509/fuzz_jose_corpus/alg_none.txt

@@ -0,0 +1 @@
+eyJhbGciOiJub25lIn0..

lib/hx509/fuzz_jose_corpus/bad_base64.txt

@@ -0,0 +1 @@
+!!!.@@@.###

lib/hx509/fuzz_jose_corpus/eddsa_valid.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFZERTQSJ9.RXhhbXBsZSBvZiBFZDI1NTE5IHNpZ25pbmc.hgyY0il_MGCjP0JzlnLWG1PPOt7-09PGcvMg3AIbQR6dWbhijcNR4ki4iylGjg5BhVsPt9g7sVvpAr_MuM0KAg

lib/hx509/fuzz_jose_corpus/empty_parts.txt

@@ -0,0 +1 @@
+...

lib/hx509/fuzz_jose_corpus/es256_long_sig.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFUzI1NiJ9.e30.QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUE

lib/hx509/fuzz_jose_corpus/es256_short_sig.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFUzI1NiJ9.e30.AAAA

lib/hx509/fuzz_jose_corpus/es256_valid.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q

lib/hx509/fuzz_jose_corpus/es384.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFUzM4NCJ9.e30.AA

lib/hx509/fuzz_jose_corpus/es512.txt

@@ -0,0 +1 @@
+eyJhbGciOiJFUzUxMiJ9.e30.AA

lib/hx509/fuzz_jose_corpus/hs256.txt

@@ -0,0 +1 @@
+eyJhbGciOiJIUzI1NiJ9.e30.AA

lib/hx509/fuzz_jose_corpus/minimal.txt

@@ -0,0 +1 @@
+e30.e30.AA

lib/hx509/fuzz_jose_corpus/nested_header.txt

@@ -0,0 +1 @@
+eyJhbGciOiJSUzI1NiIsImV4dHJhIjp7Im5lc3RlZCI6eyJkZWVwIjp0cnVlfX19.e30.AA

lib/hx509/fuzz_jose_corpus/rs256_valid.txt

@@ -0,0 +1 @@
+eyJhbGciOiJSUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw

lib/hx509/fuzz_jose_corpus/rs384.txt

@@ -0,0 +1 @@
+eyJhbGciOiJSUzM4NCJ9.e30.AA

lib/hx509/fuzz_jose_corpus/rs512.txt

@@ -0,0 +1 @@
+eyJhbGciOiJSUzUxMiJ9.e30.AA

lib/hx509/fuzz_jose_corpus/unicode_payload.txt

@@ -0,0 +1 @@
+eyJhbGciOiJSUzI1NiJ9.eyJzdWIiOiLnlKjmiLciLCJpc3MiOiLlj5HooYzogIUifQ.AA

lib/hx509/fuzz_jose_corpus/unknown_alg.txt

@@ -0,0 +1 @@
+eyJhbGciOiJ1bmtub3duIn0.e30.AA