helper: add base64 encoding/decoding helpers from FreeBSD

These helpers are needed by the updated RISC-V target files.

Change-Id: I5aa9f4e58eb75e1c7a1e8e0e3961725e2a915ebb
Signed-off-by: Bernhard Rosenkränzer <bero@baylibre.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8895
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/helper/Makefile.am

@@ -3,6 +3,7 @@
 noinst_LTLIBRARIES += %D%/libhelper.la
 
 %C%_libhelper_la_SOURCES = \
+	%D%/base64.c \
 	%D%/binarybuffer.c \
 	%D%/options.c \
 	%D%/time_support_common.c \
@@ -18,6 +19,7 @@ noinst_LTLIBRARIES += %D%/libhelper.la
 	%D%/jim-nvp.c \
 	%D%/nvp.c \
 	%D%/align.h \
+	%D%/base64.h \
 	%D%/binarybuffer.h \
 	%D%/bitfield.h \
 	%D%/bits.h \

src/helper/base64.c

@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+/*
+ * Base64 encoding/decoding (RFC1341)
+ * Copyright (c) 2005-2011, Jouni Malinen <j@w1.fi>
+ *
+ * Original file from FreeBSD code
+ * https://cgit.freebsd.org/src/tree/contrib/wpa/src/utils/base64.c?id=f05cddf940db
+ */
+
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "base64.h"
+
+static const unsigned char base64_table[65] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+/**
+ * base64_encode - Base64 encode
+ * @src: Data to be encoded
+ * @len: Length of the data to be encoded
+ * @out_len: Pointer to output length variable, or %NULL if not used
+ * Returns: Allocated buffer of out_len bytes of encoded data,
+ * or %NULL on failure
+ *
+ * Caller is responsible for freeing the returned buffer. Returned buffer is
+ * nul terminated to make it easier to use as a C string. The nul terminator is
+ * not included in out_len.
+ */
+unsigned char *base64_encode(const unsigned char *src, size_t len,
+			      size_t *out_len)
+{
+	unsigned char *out, *pos;
+	const unsigned char *end, *in;
+	size_t olen;
+	int line_len;
+
+	olen = len * 4 / 3 + 4; /* 3-byte blocks to 4-byte */
+	olen += olen / 72; /* line feeds */
+	olen++; /* nul termination */
+	if (olen < len)
+		return NULL; /* integer overflow */
+	out = malloc(olen);
+	if (!out)
+		return NULL;
+
+	end = src + len;
+	in = src;
+	pos = out;
+	line_len = 0;
+	while (end - in >= 3) {
+		*pos++ = base64_table[in[0] >> 2];
+		*pos++ = base64_table[((in[0] & 0x03) << 4) | (in[1] >> 4)];
+		*pos++ = base64_table[((in[1] & 0x0f) << 2) | (in[2] >> 6)];
+		*pos++ = base64_table[in[2] & 0x3f];
+		in += 3;
+		line_len += 4;
+		if (line_len >= 72) {
+			*pos++ = '\n';
+			line_len = 0;
+		}
+	}
+
+	if (end - in) {
+		*pos++ = base64_table[in[0] >> 2];
+		if (end - in == 1) {
+			*pos++ = base64_table[(in[0] & 0x03) << 4];
+			*pos++ = '=';
+		} else {
+			*pos++ = base64_table[((in[0] & 0x03) << 4) |
+					      (in[1] >> 4)];
+			*pos++ = base64_table[(in[1] & 0x0f) << 2];
+		}
+		*pos++ = '=';
+		line_len += 4;
+	}
+
+	if (line_len)
+		*pos++ = '\n';
+
+	*pos = '\0';
+	if (out_len)
+		*out_len = pos - out;
+	return out;
+}
+
+
+/**
+ * base64_decode - Base64 decode
+ * @src: Data to be decoded
+ * @len: Length of the data to be decoded
+ * @out_len: Pointer to output length variable
+ * Returns: Allocated buffer of out_len bytes of decoded data,
+ * or %NULL on failure
+ *
+ * Caller is responsible for freeing the returned buffer.
+ */
+unsigned char *base64_decode(const unsigned char *src, size_t len,
+			      size_t *out_len)
+{
+	unsigned char dtable[256], *out, *pos, block[4], tmp;
+	size_t i, count, olen;
+	int pad = 0;
+
+	memset(dtable, 0x80, 256);
+	for (i = 0; i < sizeof(base64_table) - 1; i++)
+		dtable[base64_table[i]] = (unsigned char)i;
+	dtable['='] = 0;
+
+	count = 0;
+	for (i = 0; i < len; i++) {
+		if (dtable[src[i]] != 0x80)
+			count++;
+	}
+
+	if (count == 0 || count % 4)
+		return NULL;
+
+	olen = count / 4 * 3;
+	out = malloc(olen);
+	if (!out)
+		return NULL;
+	pos = out;
+
+	count = 0;
+	for (i = 0; i < len; i++) {
+		tmp = dtable[src[i]];
+		if (tmp == 0x80)
+			continue;
+
+		if (src[i] == '=')
+			pad++;
+		block[count] = tmp;
+		count++;
+		if (count == 4) {
+			*pos++ = (block[0] << 2) | (block[1] >> 4);
+			*pos++ = (block[1] << 4) | (block[2] >> 2);
+			*pos++ = (block[2] << 6) | block[3];
+			count = 0;
+			if (pad) {
+				if (pad == 1) {
+					pos--;
+				} else if (pad == 2) {
+					pos -= 2;
+				} else {
+					/* Invalid padding */
+					free(out);
+					return NULL;
+				}
+				break;
+			}
+		}
+	}
+
+	*out_len = pos - out;
+	return out;
+}

src/helper/base64.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+
+/*
+ * Base64 encoding/decoding (RFC1341)
+ * Copyright (c) 2005, Jouni Malinen <j@w1.fi>
+ *
+ * Original file from FreeBSD code
+ * https://cgit.freebsd.org/src/tree/contrib/wpa/src/utils/base64.h?id=f05cddf940db
+ */
+
+#ifndef BASE64_H
+#define BASE64_H
+
+unsigned char *base64_encode(const unsigned char *src, size_t len,
+			      size_t *out_len);
+unsigned char *base64_decode(const unsigned char *src, size_t len,
+			      size_t *out_len);
+
+#endif /* BASE64_H */