base64: add implementation for encoding binary into base64

In the Cr50 tree there is no really output devices other than console
where base64 encoding output could be sent, and there is no use for
decoding function yet.

Add the encoding function implementation, make it possible to send
output to console by default and optionally to a passed in function.

Add test to verify proper encoding.

BUG=b:234745585
TEST='make run-base64' succeeds.

Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Change-Id: Ibc10681632bc649320d602e319e4f634b4b3a1d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3701141
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>

1 files changed, 104 insertions, 0 deletions

diff --git a/common/base64.c b/common/base64.c
new file mode 100644
index 0000000000..e3f979cce2
--- /dev/null
+++ b/common/base64.c
@@ -0,0 +1,104 @@
+/* Copyright 2022 The Chromium OS Authors.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Yet another from scratch implementation of base64 encoding. */
+
+#include "base64.h"
+#include "common.h"
+#include "console.h"
+
+/*
+ * Translation Table as described in RFC1113
+ */
+static const char cb64[] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/* Number of bytes converted into the output block of characters. */
+#define BASE64_BYTE_SIZE 3
+
+/* Number of characters in a single encoded block. */
+#define BASE64_CHAR_SIZE 4
+
+/*
+ * encodeblock
+ *
+ * encode up to 3 bytes 6-bit characters, pad output with '=' if input is
+ * shorter than 3 bytes.
+ *
+ * @param in: pointer to the input bytes
+ * @param out: pointer to the output, guaranteed to be 4 bytes long.
+ * @param len: number of input bytes to process, guaranteed to be in 1..3
+ *              range.
+ */
+static void encodeblock(const uint8_t *in, uint8_t *out, size_t len)
+{
+	uint32_t input;
+	int i;
+	int limit;
+
+	/* Place input bytes into a 32 bit value in big endian format. */
+	input = 0;
+	for (i = 0; i < len; i++)
+		((uint8_t *)&input)[3 - i] = in[i];
+
+	/*
+	 * Map each 6 bit quantity of the input into an output character, make
+	 * sure partial bit quantities are mapped too in case input is shorter
+	 * than 3 bytes.
+	 */
+	limit = ((len * 8) + 7) / 6;
+	for (i = 0; i < limit; i++) {
+		int index = (input >> (26 - i * 6)) & 0x3f;
+
+		out[i] = cb64[index];
+	}
+
+	while (i < BASE64_CHAR_SIZE)
+		out[i++] = '=';
+}
+
+/* Pass one output character to the caller. */
+static void printit(char c, void (*f)(char c))
+{
+	if (f)
+		f(c);
+	else
+		ccprintf("%c", c);
+}
+
+#define LINE_SIZE 64
+void base64_encode_to_console(const uint8_t *data, size_t size,
+			      void (*func)(char c))
+{
+	uint8_t out[4];
+	int blocksout;
+
+	blocksout = 0;
+	while (size) {
+		int i;
+		int in_length;
+
+		if (size > BASE64_BYTE_SIZE)
+			in_length = BASE64_BYTE_SIZE;
+		else
+			in_length = size;
+
+		encodeblock(data, out, in_length);
+		for (i = 0; i < sizeof(out); i++)
+			printit(out[i], func);
+
+		blocksout++;
+		data += in_length;
+		size -= in_length;
+		if (blocksout >= (LINE_SIZE / BASE64_CHAR_SIZE)) {
+			printit('\n', func);
+			blocksout = 0;
+			if (!func)
+				cflush();
+		}
+	}
+	if (blocksout)
+		printit('\n', func);
+}