From ab24895f0ab201bcb50b7dc17f01e8eed482c93d Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Thu, 1 Jun 2023 13:56:54 +0000
Subject: [PATCH] util: Implement decoding base64 data and add tests

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---
 src/libpakfire/include/pakfire/util.h |  2 +
 src/libpakfire/util.c                 | 86 +++++++++++++++++++++++++++
 tests/libpakfire/util.c               | 37 ++++++++++++
 3 files changed, 125 insertions(+)

diff --git a/src/libpakfire/include/pakfire/util.h b/src/libpakfire/include/pakfire/util.h
index fee3ab311..c402b38f5 100644
--- a/src/libpakfire/include/pakfire/util.h
+++ b/src/libpakfire/include/pakfire/util.h
@@ -125,6 +125,8 @@ int pakfire_compile_regex(struct pakfire* pakfire, pcre2_code** regex,
 
 int pakfire_b64encode(struct pakfire* pakfire, char** output,
 	const void* buffer, const size_t length);
+int pakfire_b64decode(struct pakfire* pakfire, void** output, size_t* length,
+	const char* buffer);
 
 #endif
 
diff --git a/src/libpakfire/util.c b/src/libpakfire/util.c
index 74606f7a0..af58be28b 100644
--- a/src/libpakfire/util.c
+++ b/src/libpakfire/util.c
@@ -1020,3 +1020,89 @@ ERROR:
 
 	return r;
 }
+
+int pakfire_b64decode(struct pakfire* pakfire, void** output, size_t* length,
+		const char* buffer) {
+	char error[OPENSSL_ERROR_MAX];
+	char chunk[1024];
+	BIO* b64 = NULL;
+	BIO* bio = NULL;
+	char* p = NULL;
+	int r;
+
+	// Reset length
+	*length = 0;
+
+	// Initialize the base64 decoder
+	b64 = BIO_new(BIO_f_base64());
+	if (!b64) {
+		ERR_error_string_n(ERR_get_error(), error, sizeof(error));
+
+		ERROR(pakfire, "Could not initialize the base64 decoder: %s\n", error);
+		r = 1;
+		goto ERROR;
+	}
+
+	BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
+
+	// Initialize a memory buffer
+	bio = BIO_new_mem_buf(buffer, strlen(buffer));
+	if (!bio) {
+		ERR_error_string_n(ERR_get_error(), error, sizeof(error));
+
+		ERROR(pakfire, "Could not initialize memory buffer: %s\n", error);
+		r = 1;
+		goto ERROR;
+	}
+
+	// Connect both things
+	bio = BIO_push(b64, bio);
+
+	for (;;) {
+		// Read a chunk of data
+		ssize_t bytes_read = BIO_read(bio, chunk, sizeof(chunk));
+
+		// Handle any errors
+		if (bytes_read < 0) {
+			ERR_error_string_n(ERR_get_error(), error, sizeof(error));
+
+			ERROR(pakfire, "Could not read data: %s\n", error);
+			r = 1;
+			goto ERROR;
+
+		// Break if no more data could be read
+		} else if (bytes_read == 0) {
+			break;
+
+		// Handle the chunk
+		} else {
+			// Update total length of data
+			*length += bytes_read;
+
+			// Allocate an output buffer
+			p = realloc(p, *length);
+			if (!p) {
+				ERROR(pakfire, "Could not allocate buffer: %m\n");
+				r = 1;
+				goto ERROR;
+			}
+
+			// Copy the chunk
+			memcpy(p + *length - bytes_read, chunk, bytes_read);
+		}
+	}
+
+	// Set output pointer
+	*output = p;
+
+	// Success!
+	r = 0;
+
+ERROR:
+	if (r && p)
+		free(p);
+	if (bio)
+		BIO_free_all(bio);
+
+	return r;
+}
diff --git a/tests/libpakfire/util.c b/tests/libpakfire/util.c
index 28f5dcee2..6cf8c8339 100644
--- a/tests/libpakfire/util.c
+++ b/tests/libpakfire/util.c
@@ -108,11 +108,48 @@ FAIL:
 	return EXIT_FAILURE;
 }
 
+static int test_base64(const struct test* t) {
+	int r = EXIT_FAILURE;
+
+	const char data[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
+	char* base64 = NULL;
+	void* output = NULL;
+	size_t length = 0;
+
+	// Encode data as base64
+	ASSERT_SUCCESS(pakfire_b64encode(t->pakfire, &base64, data, sizeof(data)));
+
+	// Print the encoded data
+	printf("%s\n", base64);
+
+	// Decode the data
+	ASSERT_SUCCESS(pakfire_b64decode(t->pakfire, &output, &length, base64));
+
+	// Print the decoded data
+	printf("%.*s\n", length, output);
+
+	// Check that we encoded the correct amount of data
+	ASSERT_EQUALS(length, sizeof(data));
+
+	// Check that the output matches the input
+	ASSERT(memcmp(data, output, sizeof(data)) == 0);
+
+	// Everything passed
+	r = EXIT_SUCCESS;
+
+FAIL:
+	if (base64)
+		free(base64);
+
+	return r;
+}
+
 int main(int argc, const char* argv[]) {
 	testsuite_add_test(test_basename);
 	testsuite_add_test(test_dirname);
 	testsuite_add_test(test_mkdir);
 	testsuite_add_test(test_path_match);
+	testsuite_add_test(test_base64);
 
 	return testsuite_run(argc, argv);
 }
-- 
2.39.5