1 files changed, 276 insertions, 0 deletions
diff --git a/lib/crypto_backend/base64.c b/lib/crypto_backend/base64.c
new file mode 100644
index 0000000..42f70cb
--- /dev/null
+++ b/lib/crypto_backend/base64.c
@@ -0,0 +1,276 @@
+/*
+ * Base64 "Not encryption" helpers, copied and adapted from systemd project.
+ *
+ * Copyright (C) 2010 Lennart Poettering
+ *
+ * cryptsetup related changes
+ * Copyright (C) 2021-2023 Milan Broz
+ *
+ * This file is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This file is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this file; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#include "crypto_backend.h"
+
+#define WHITESPACE " \t\n\r"
+
+/* https://tools.ietf.org/html/rfc4648#section-4 */
+static char base64char(int x)
+{
+	static const char table[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+				      "abcdefghijklmnopqrstuvwxyz"
+				      "0123456789+/";
+	return table[x & 63];
+}
+
+static int unbase64char(char c)
+{
+	unsigned offset;
+
+	if (c >= 'A' && c <= 'Z')
+		return c - 'A';
+
+	offset = 'Z' - 'A' + 1;
+
+	if (c >= 'a' && c <= 'z')
+		return c - 'a' + offset;
+
+	offset += 'z' - 'a' + 1;
+
+	if (c >= '0' && c <= '9')
+		return c - '0' + offset;
+
+	offset += '9' - '0' + 1;
+
+	if (c == '+')
+		return offset;
+
+	offset++;
+
+	if (c == '/')
+		return offset;
+
+	return -EINVAL;
+}
+
+int crypt_base64_encode(char **out, size_t *out_length, const char *in, size_t in_length)
+{
+	char *r, *z;
+	const uint8_t *x;
+
+	assert(in || in_length == 0);
+	assert(out);
+
+	/* three input bytes makes four output bytes, padding is added so we must round up */
+	z = r = malloc(4 * (in_length + 2) / 3 + 1);
+	if (!r)
+		return -ENOMEM;
+
+	for (x = (const uint8_t *)in; x < (const uint8_t*)in + (in_length / 3) * 3; x += 3) {
+		/* x[0] == XXXXXXXX; x[1] == YYYYYYYY; x[2] == ZZZZZZZZ */
+		*(z++) = base64char(x[0] >> 2);                    /* 00XXXXXX */
+		*(z++) = base64char((x[0] & 3) << 4 | x[1] >> 4);  /* 00XXYYYY */
+		*(z++) = base64char((x[1] & 15) << 2 | x[2] >> 6); /* 00YYYYZZ */
+		*(z++) = base64char(x[2] & 63);                    /* 00ZZZZZZ */
+	}
+
+	switch (in_length % 3) {
+	case 2:
+		*(z++) = base64char(x[0] >> 2);                   /* 00XXXXXX */
+		*(z++) = base64char((x[0] & 3) << 4 | x[1] >> 4); /* 00XXYYYY */
+		*(z++) = base64char((x[1] & 15) << 2);            /* 00YYYY00 */
+		*(z++) = '=';
+
+		break;
+	case 1:
+		*(z++) = base64char(x[0] >> 2);        /* 00XXXXXX */
+		*(z++) = base64char((x[0] & 3) << 4);  /* 00XX0000 */
+		*(z++) = '=';
+		*(z++) = '=';
+
+		break;
+	}
+
+	*z = 0;
+	*out = r;
+	if (out_length)
+		*out_length = z - r;
+	return 0;
+}
+
+static int unbase64_next(const char **p, size_t *l)
+{
+	int ret;
+
+	assert(p);
+	assert(l);
+
+	/* Find the next non-whitespace character, and decode it. If we find padding, we return it as INT_MAX. We
+	 * greedily skip all preceding and all following whitespace. */
+
+	for (;;) {
+		if (*l == 0)
+			return -EPIPE;
+
+		if (!strchr(WHITESPACE, **p))
+			break;
+
+		/* Skip leading whitespace */
+		(*p)++, (*l)--;
+	}
+
+	if (**p == '=')
+		ret = INT_MAX; /* return padding as INT_MAX */
+	else {
+		ret = unbase64char(**p);
+		if (ret < 0)
+			return ret;
+	}
+
+	for (;;) {
+		(*p)++, (*l)--;
+
+		if (*l == 0)
+			break;
+		if (!strchr(WHITESPACE, **p))
+			break;
+
+		/* Skip following whitespace */
+	}
+
+	return ret;
+}
+
+int crypt_base64_decode(char **out, size_t *out_length, const char *in, size_t in_length)
+{
+	uint8_t *buf = NULL;
+	const char *x;
+	uint8_t *z;
+	size_t len;
+	int r;
+
+	assert(in || in_length == 0);
+	assert(out);
+	assert(out_length);
+
+	if (in_length == (size_t) -1)
+		in_length = strlen(in);
+
+	/* A group of four input bytes needs three output bytes, in case of padding we need to add two or three extra
+	 * bytes. Note that this calculation is an upper boundary, as we ignore whitespace while decoding */
+	len = (in_length / 4) * 3 + (in_length % 4 != 0 ? (in_length % 4) - 1 : 0);
+
+	buf = malloc(len + 1);
+	if (!buf)
+		return -ENOMEM;
+
+	for (x = in, z = buf;;) {
+		int a, b, c, d; /* a == 00XXXXXX; b == 00YYYYYY; c == 00ZZZZZZ; d == 00WWWWWW */
+
+		a = unbase64_next(&x, &in_length);
+		if (a == -EPIPE) /* End of string */
+			break;
+		if (a < 0) {
+			r = a;
+			goto err;
+		}
+		if (a == INT_MAX) { /* Padding is not allowed at the beginning of a 4ch block */
+			r = -EINVAL;
+			goto err;
+		}
+
+		b = unbase64_next(&x, &in_length);
+		if (b < 0) {
+			r = b;
+			goto err;
+		}
+		if (b == INT_MAX) { /* Padding is not allowed at the second character of a 4ch block either */
+			r = -EINVAL;
+			goto err;
+		}
+
+		c = unbase64_next(&x, &in_length);
+		if (c < 0) {
+			r = c;
+			goto err;
+		}
+
+		d = unbase64_next(&x, &in_length);
+		if (d < 0) {
+			r = d;
+			goto err;
+		}
+
+		if (c == INT_MAX) { /* Padding at the third character */
+
+			if (d != INT_MAX) { /* If the third character is padding, the fourth must be too */
+				r = -EINVAL;
+				goto err;
+			}
+
+			/* b == 00YY0000 */
+			if (b & 15) {
+				r = -EINVAL;
+				goto err;
+			}
+
+			if (in_length > 0) { /* Trailing rubbish? */
+				r = -ENAMETOOLONG;
+				goto err;
+			}
+
+			*(z++) = (uint8_t) a << 2 | (uint8_t) (b >> 4); /* XXXXXXYY */
+			break;
+		}
+
+		if (d == INT_MAX) {
+			/* c == 00ZZZZ00 */
+			if (c & 3) {
+				r = -EINVAL;
+				goto err;
+			}
+
+			if (in_length > 0) { /* Trailing rubbish? */
+				r = -ENAMETOOLONG;
+				goto err;
+			}
+
+			*(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
+			*(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
+			break;
+		}
+
+		*(z++) = (uint8_t) a << 2 | (uint8_t) b >> 4; /* XXXXXXYY */
+		*(z++) = (uint8_t) b << 4 | (uint8_t) c >> 2; /* YYYYZZZZ */
+		*(z++) = (uint8_t) c << 6 | (uint8_t) d;      /* ZZWWWWWW */
+	}
+
+	*z = 0;
+
+	*out_length = (size_t) (z - buf);
+	*out = (char *)buf;
+	return 0;
+err:
+	free(buf);
+
+	/* Ignore other errors in crypt_backend */
+	if (r != -ENOMEM)
+		r = -EINVAL;
+
+	return r;
+}