1 files changed, 257 insertions, 0 deletions
diff --git a/librecrypt_decode.c b/librecrypt_decode.c
new file mode 100644
index 0000000..ee451a7
--- /dev/null
+++ b/librecrypt_decode.c
@@ -0,0 +1,257 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+ssize_t
+librecrypt_decode(void *out_buffer, size_t size, const char *ascii, size_t len,
+                  const unsigned char lut[restrict static 256], char pad, int strict_pad)
+{
+	const unsigned char *str = (const unsigned char *)ascii;
+	unsigned char *data = out_buffer;
+	unsigned char a, b, c, d;
+	size_t n = 0u;
+
+	for(; len >= 4u; str += 4u) {
+		len -= 4u;
+
+		a = lut[str[0u]];
+		b = lut[str[1u]];
+		if ((a | b) == 0xFFu)
+			goto einval;
+		if (n < size)
+			data[n] = (unsigned char)((a << 2) | (b >> 4));
+		n++;
+
+		c = lut[str[2u]];
+		if (c == 0xFFu) {
+			if (len || !pad || str[2u] != pad || str[3u] != pad)
+				goto einval;
+			break;
+		}
+		if (n < size)
+			data[n] = (unsigned char)((b << 4u) | (c >> 2u));
+		n++;
+
+		d = lut[str[3u]];
+		if (d == 0xFFu) {
+			if (len || !pad || str[3u] != pad)
+				goto einval;
+			break;
+		}
+		if (n < size)
+			data[n] = (unsigned char)((c << 6) | (d >> 0));
+		n++;
+	}
+
+	if (len && strict_pad && pad)
+		goto einval;
+
+	switch (len) {
+	case 0u:
+		goto out;
+	case 1u:
+		goto einval;
+
+	default:
+		a = lut[str[0u]];
+		b = lut[str[1u]];
+		if ((a | b) == 0xFFu)
+			goto einval;
+		if (n < size)
+			data[n] = (unsigned char)((a << 2) | (b >> 4));
+		n++;
+		if (len == 2u)
+			break;
+
+		c = lut[str[2u]];
+		if (c == 0xFFu) {
+			if (!pad || str[2u] != pad)
+				goto einval;
+			break;
+		}
+		if (n < size)
+			data[n] = (unsigned char)((b << 4u) | (c >> 2u));
+		n++;
+		break;
+	}
+
+out:
+	return (ssize_t)n;
+
+einval:
+	errno = EINVAL;
+	return -1;
+}
+
+
+#else
+
+
+static const unsigned char lut[256u] = {
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, 62, XX, XX, XX, 63,
+	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, XX, XX, XX, XX, XX, XX,
+	XX,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, XX, XX, XX, XX, XX,
+	XX, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX,
+	XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX, XX
+};
+
+
+#define CHECK(BINARY, ASCII, PAD)\
+	check((BINARY), sizeof(BINARY) - 1u, (ASCII PAD), sizeof(ASCII) - 1u, sizeof(ASCII PAD) - 1u)
+
+
+static void
+check(const char *binary, size_t binary_len, const char *ascii, size_t unpadded_len, size_t padded_len)
+{
+	char buf[16u];
+	size_t i, j;
+
+	assert(binary_len <= sizeof(buf));
+
+	assert(padded_len % 4u == 0u);
+	assert(padded_len / 4u == (unpadded_len + 3u) / 4u);
+	assert(padded_len >= unpadded_len);
+
+	EXPECT(librecrypt_decode(NULL, 0u, ascii, unpadded_len, lut, '\0', 0) == (ssize_t)binary_len);
+	EXPECT(librecrypt_decode(NULL, 0u, ascii, unpadded_len, lut, '\0', 1) == (ssize_t)binary_len);
+	EXPECT(librecrypt_decode(NULL, 0u, ascii, unpadded_len, lut, '=', 0) == (ssize_t)binary_len);
+
+	if (padded_len == unpadded_len) {
+		EXPECT(librecrypt_decode(NULL, 0u, ascii, unpadded_len, lut, '=', 1) == (ssize_t)binary_len);
+	} else {
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, ascii, unpadded_len, lut, '=', 1) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, ascii, padded_len, lut, '\0', 0) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, ascii, padded_len, lut, '\0', 1) == -1);
+		EXPECT(errno == EINVAL);
+	}
+
+	EXPECT(librecrypt_decode(NULL, 0u, ascii, padded_len, lut, '=', 0) == (ssize_t)binary_len);
+	EXPECT(librecrypt_decode(NULL, 0u, ascii, padded_len, lut, '=', 1) == (ssize_t)binary_len);
+
+	for (i = 0u; i < sizeof(buf); i++) {
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_decode(buf, i, ascii, unpadded_len, lut, '\0', 0) == (ssize_t)binary_len);
+		j = i < binary_len ? i : binary_len;
+		EXPECT(!memcmp(buf, binary, j));
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_decode(buf, i, ascii, unpadded_len, lut, '\0', 1) == (ssize_t)binary_len);
+		j = i < binary_len ? i : binary_len;
+		EXPECT(!memcmp(buf, binary, j));
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_decode(buf, i, ascii, unpadded_len, lut, '=', 0) == (ssize_t)binary_len);
+		j = i < binary_len ? i : binary_len;
+		EXPECT(!memcmp(buf, binary, j));
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+
+		if (padded_len == unpadded_len) {
+			memset(buf, 99, sizeof(buf));
+			EXPECT(librecrypt_decode(buf, i, ascii, unpadded_len, lut, '=', 1) == (ssize_t)binary_len);
+			j = i < binary_len ? i : binary_len;
+			EXPECT(!memcmp(buf, binary, j));
+			for (; j < sizeof(buf); j++)
+				EXPECT(buf[j] == 99);
+		} else {
+			errno = 0;
+			EXPECT(librecrypt_decode(buf, i, ascii, unpadded_len, lut, '=', 1) == -1);
+			EXPECT(errno == EINVAL);
+
+			errno = 0;
+			EXPECT(librecrypt_decode(buf, i, ascii, padded_len, lut, '\0', 0) == -1);
+			EXPECT(errno == EINVAL);
+
+			errno = 0;
+			EXPECT(librecrypt_decode(buf, i, ascii, padded_len, lut, '\0', 1) == -1);
+			EXPECT(errno == EINVAL);
+		}
+
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_decode(buf, i, ascii, padded_len, lut, '=', 0) == (ssize_t)binary_len);
+		j = i < binary_len ? i : binary_len;
+		EXPECT(!memcmp(buf, binary, j));
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+
+		memset(buf, 99, sizeof(buf));
+		EXPECT(librecrypt_decode(buf, i, ascii, padded_len, lut, '=', 1) == (ssize_t)binary_len);
+		j = i < binary_len ? i : binary_len;
+		EXPECT(!memcmp(buf, binary, j));
+		for (; j < sizeof(buf); j++)
+			EXPECT(buf[j] == 99);
+
+	}
+}
+
+
+int
+main(void)
+{
+	int i;
+
+	SET_UP_ALARM();
+
+	CHECK("", "", "");
+	CHECK("\x00", "AA", "==");
+	CHECK("\x00\x00", "AAA", "=");
+	CHECK("\x00\x00\x00", "AAAA", "");
+	CHECK("12345678", "MTIzNDU2Nzg", "=");
+	CHECK("testtest", "dGVzdHRlc3Q", "=");
+	CHECK("zy[]y21 !", "enlbXXkyMSAh", "");
+	CHECK("{~|~}~~~\x7f\x7f", "e358fn1+fn5/fw", "==");
+
+	for (i = 0; i <= 1; i++) {
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "AA=*", 4u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "AA*=", 4u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "AA**", 4u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "A===", 4u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "A", 1u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+
+		errno = 0;
+		EXPECT(librecrypt_decode(NULL, 0u, "====", 4u, lut, '=', i) == -1);
+		EXPECT(errno == EINVAL);
+	}
+
+	return 0;
+}
+
+
+#endif