Add some basic test programs for libfsverity

Add three test programs: 'test_hash_algs', 'test_compute_digest', and
'test_sign_digest'.  Nothing fancy yet, just some basic tests to test
each library function.

With the new Makefile, these get run by 'make check'.

Reviewed-by: Jes Sorensen <jsorensen@fb.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

programs/test_compute_digest.c

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Test libfsverity_compute_digest().
+ *
+ * Copyright 2020 Google LLC
+ */
+#include "utils.h"
+
+#define SHA256_DIGEST_SIZE 32
+
+struct mem_file {
+	u8 *data;
+	size_t size;
+	size_t offset;
+};
+
+static int read_fn(void *fd, void *buf, size_t count)
+{
+	struct mem_file *f = fd;
+
+	ASSERT(count <= f->size - f->offset);
+	memcpy(buf, &f->data[f->offset], count);
+	f->offset += count;
+	return 0;
+}
+
+int main(void)
+{
+	struct mem_file f = { .size = 1000000 };
+	size_t i;
+	const struct libfsverity_merkle_tree_params params = {
+		.version = 1,
+		.hash_algorithm = FS_VERITY_HASH_ALG_SHA256,
+		.block_size = 4096,
+		.salt_size = 4,
+		.salt = (u8 *)"abcd",
+		.file_size = f.size,
+	};
+	struct libfsverity_digest *d;
+	static const u8 expected_digest[SHA256_DIGEST_SIZE] =
+		"\x91\x79\x00\xb0\xd2\x99\x45\x4a\xa3\x04\xd5\xde\xbc\x6f\x39"
+		"\xe4\xaf\x7b\x5a\xbe\x33\xbd\xbc\x56\x8d\x5d\x8f\x1e\x5c\x4d"
+		"\x86\x52";
+	int err;
+
+	f.data = xmalloc(f.size);
+	for (i = 0; i < f.size; i++)
+		f.data[i] = (i % 11) + (i % 439) + (i % 1103);
+
+	err = libfsverity_compute_digest(&f, read_fn, &params, &d);
+	ASSERT(err == 0);
+
+	ASSERT(d->digest_algorithm == FS_VERITY_HASH_ALG_SHA256);
+	ASSERT(d->digest_size == SHA256_DIGEST_SIZE);
+	ASSERT(!memcmp(d->digest, expected_digest, SHA256_DIGEST_SIZE));
+
+	free(f.data);
+	free(d);
+	printf("test_compute_digest passed\n");
+	return 0;
+}

programs/test_hash_algs.c

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Test the hash algorithm-related libfsverity APIs.
+ *
+ * Copyright 2020 Google LLC
+ */
+#include "utils.h"
+
+#define SHA256_DIGEST_SIZE 32
+#define SHA512_DIGEST_SIZE 64
+
+int main(void)
+{
+	ASSERT(libfsverity_get_digest_size(0) == -1);
+	ASSERT(libfsverity_get_hash_name(0) == NULL);
+	ASSERT(libfsverity_find_hash_alg_by_name("bad") == 0);
+	ASSERT(libfsverity_find_hash_alg_by_name(NULL) == 0);
+
+	ASSERT(libfsverity_get_digest_size(100) == -1);
+	ASSERT(libfsverity_get_hash_name(100) == NULL);
+
+	ASSERT(libfsverity_get_digest_size(FS_VERITY_HASH_ALG_SHA256) ==
+	       SHA256_DIGEST_SIZE);
+	ASSERT(!strcmp("sha256",
+		       libfsverity_get_hash_name(FS_VERITY_HASH_ALG_SHA256)));
+	ASSERT(libfsverity_find_hash_alg_by_name("sha256") ==
+	       FS_VERITY_HASH_ALG_SHA256);
+
+	ASSERT(libfsverity_get_digest_size(FS_VERITY_HASH_ALG_SHA512) ==
+	       SHA512_DIGEST_SIZE);
+	ASSERT(!strcmp("sha512",
+		       libfsverity_get_hash_name(FS_VERITY_HASH_ALG_SHA512)));
+	ASSERT(libfsverity_find_hash_alg_by_name("sha512") ==
+	       FS_VERITY_HASH_ALG_SHA512);
+
+	printf("test_hash_algs passed\n");
+	return 0;
+}

programs/test_sign_digest.c

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Test libfsverity_sign_digest().
+ *
+ * Copyright 2020 Google LLC
+ */
+#include "utils.h"
+
+#include <fcntl.h>
+
+#define SHA256_DIGEST_SIZE 32
+
+int main(void)
+{
+	struct libfsverity_digest *d = xzalloc(sizeof(*d) + SHA256_DIGEST_SIZE);
+	const struct libfsverity_signature_params params = {
+		.keyfile = "testdata/key.pem",
+		.certfile = "testdata/cert.pem",
+	};
+	u8 *sig;
+	size_t sig_size;
+	struct filedes file;
+	u8 *expected_sig;
+	u64 expected_sig_size;
+	int err;
+
+	d->digest_algorithm = FS_VERITY_HASH_ALG_SHA256;
+	d->digest_size = SHA256_DIGEST_SIZE;
+	memcpy(d->digest,
+	       "\x91\x79\x00\xb0\xd2\x99\x45\x4a\xa3\x04\xd5\xde\xbc\x6f\x39"
+	       "\xe4\xaf\x7b\x5a\xbe\x33\xbd\xbc\x56\x8d\x5d\x8f\x1e\x5c\x4d"
+	       "\x86\x52", SHA256_DIGEST_SIZE);
+
+	err = libfsverity_sign_digest(d, &params, &sig, &sig_size);
+	ASSERT(err == 0);
+
+	ASSERT(open_file(&file, "testdata/file.sig", O_RDONLY, 0));
+	ASSERT(get_file_size(&file, &expected_sig_size));
+	ASSERT(sig_size == expected_sig_size);
+	expected_sig = xmalloc(sig_size);
+	ASSERT(full_read(&file, expected_sig, sig_size));
+	ASSERT(!memcmp(sig, expected_sig, sig_size));
+
+	free(d);
+	free(sig);
+	free(expected_sig);
+	filedes_close(&file);
+	printf("test_sign_digest passed\n");
+	return 0;
+}

testdata/cert.pem

@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----
+MIIFazCCA1OgAwIBAgIUYaRYcyZGDIv9fIxx/RoJwQu23+owDQYJKoZIhvcNAQEL
+BQAwRTELMAkGA1UEBhMCQVUxEzARBgNVBAgMClNvbWUtU3RhdGUxITAfBgNVBAoM
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+-----END CERTIFICATE-----

testdata/key.pem

@@ -0,0 +1,52 @@
+-----BEGIN PRIVATE KEY-----
+MIIJQQIBADANBgkqhkiG9w0BAQEFAASCCSswggknAgEAAoICAQC5lXk9otBz/VM/
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+x55d2r87sh6ScDvl57EIav09Y6W/
+-----END PRIVATE KEY-----