bitlk: Fix unlocking bitlocker with multibyte utf8 characters

Fixes: #950

Co-authored-by: Thomas Lidén

Author: vojtechtrefny

lib/bitlk/bitlk.c

@@ -982,6 +982,7 @@ static int bitlk_kdf(const char *password,
 	struct crypt_hash *hd = NULL;
 	int len = 0;
 	char16_t *utf16Password = NULL;
+	size_t utf16Len = 0;
 	int i = 0;
 	int r = 0;
 
@@ -1007,7 +1008,8 @@ static int bitlk_kdf(const char *password,
 		if (r < 0)
 			goto out;
 
-		crypt_hash_write(hd, (char*)utf16Password, passwordLen * 2);
+		utf16Len = crypt_char16_strlen(utf16Password);
+		crypt_hash_write(hd, (char*)utf16Password, utf16Len * 2);
 		r = crypt_hash_final(hd, kdf.initial_sha256, len);
 		if (r < 0)
 			goto out;

lib/crypto_backend/crypto_backend.h

@@ -93,6 +93,7 @@ int crypt_base64_decode(char **out, size_t *out_length, const char *in, size_t i
 /* UTF8/16 */
 int crypt_utf16_to_utf8(char **out, const char16_t *s, size_t length /* bytes! */);
 int crypt_utf8_to_utf16(char16_t **out, const char *s, size_t length);
+size_t crypt_char16_strlen(const char16_t *s);
 
 /* Block ciphers */
 int crypt_cipher_ivsize(const char *name, const char *mode);

lib/crypto_backend/utf8.c

@@ -274,3 +274,20 @@ int crypt_utf8_to_utf16(char16_t **out, const char *s, size_t length)
 	*p = 0;
 	return 0;
 }
+
+/**
+ * crypt_char16_strlen()
+ * @s: string to get length of
+ *
+ * Returns: number of 16-bit words in the string
+ */
+size_t crypt_char16_strlen(const char16_t *s) {
+	size_t n = 0;
+
+	assert(s);
+
+	while (*s != 0)
+		n++, s++;
+
+	return n;
+}