Unicode: specify destination length in utf8_to_utf16 methods
String16(const char *utf8) now returns the empty string in case
a string ends halfway throw a utf8 character.
Bug: 29267949
Clean cherry-pick from 1dcc0c82394ec9cd6887c7ca39f9b5024db01ac9
Change-Id: I5223caa7d42f4582a982609a898a02043265c6d3
diff --git a/include/utils/Unicode.h b/include/utils/Unicode.h
index a006082..7316665 100644
--- a/include/utils/Unicode.h
+++ b/include/utils/Unicode.h
@@ -31,7 +31,7 @@
char16_t *strncpy16(char16_t *, const char16_t *, size_t);
char16_t *strstr16(const char16_t*, const char16_t*);
-// Version of comparison that supports embedded nulls.
+// Version of comparison that supports embedded NULs.
// This is different than strncmp() because we don't stop
// at a nul character and consider the strings to be different
// if the lengths are different (thus we need to supply the
@@ -58,7 +58,7 @@
* large enough to store the string, the part of the "src" string is stored
* into "dst" as much as possible. See the examples for more detail.
* Returns the size actually used for storing the string.
- * dst" is not null-terminated when dst_len is fully used (like strncpy).
+ * dst" is not nul-terminated when dst_len is fully used (like strncpy).
*
* Example 1
* "src" == \u3042\u3044 (\xE3\x81\x82\xE3\x81\x84)
@@ -67,7 +67,7 @@
* ->
* Returned value == 6
* "dst" becomes \xE3\x81\x82\xE3\x81\x84\0
- * (note that "dst" is null-terminated)
+ * (note that "dst" is nul-terminated)
*
* Example 2
* "src" == \u3042\u3044 (\xE3\x81\x82\xE3\x81\x84)
@@ -76,7 +76,7 @@
* ->
* Returned value == 3
* "dst" becomes \xE3\x81\x82\0
- * (note that "dst" is null-terminated, but \u3044 is not stored in "dst"
+ * (note that "dst" is nul-terminated, but \u3044 is not stored in "dst"
* since "dst" does not have enough size to store the character)
*
* Example 3
@@ -86,7 +86,7 @@
* ->
* Returned value == 6
* "dst" becomes \xE3\x81\x82\xE3\x81\x84
- * (note that "dst" is NOT null-terminated, like strncpy)
+ * (note that "dst" is NOT nul-terminated, like strncpy)
*/
void utf32_to_utf8(const char32_t* src, size_t src_len, char* dst);
@@ -108,7 +108,7 @@
/**
* Converts a UTF-16 string to UTF-8. The destination buffer must be large
* enough to fit the UTF-16 as measured by utf16_to_utf8_length with an added
- * NULL terminator.
+ * NUL terminator.
*/
void utf16_to_utf8(const char16_t* src, size_t src_len, char* dst);
@@ -118,7 +118,7 @@
* is an invalid string.
*
* This function should be used to determine whether "src" is valid UTF-8
- * characters with valid unicode codepoints. "src" must be null-terminated.
+ * characters with valid unicode codepoints. "src" must be nul-terminated.
*
* If you are going to use other utf8_to_... functions defined in this header
* with string which may not be valid UTF-8 with valid codepoint (form 0 to
@@ -138,35 +138,38 @@
/**
* Stores a UTF-32 string converted from "src" in "dst". "dst" must be large
* enough to store the entire converted string as measured by
- * utf8_to_utf32_length plus space for a NULL terminator.
+ * utf8_to_utf32_length plus space for a NUL terminator.
*/
void utf8_to_utf32(const char* src, size_t src_len, char32_t* dst);
/**
- * Returns the UTF-16 length of UTF-8 string "src".
+ * Returns the UTF-16 length of UTF-8 string "src". Returns -1 in case
+ * it's invalid utf8. No buffer over-read occurs because of bound checks. Using overreadIsFatal you
+ * can ask to log a message and fail in case the invalid utf8 could have caused an override if no
+ * bound checks were used (otherwise -1 is returned).
*/
-ssize_t utf8_to_utf16_length(const uint8_t* src, size_t srcLen);
+ssize_t utf8_to_utf16_length(const uint8_t* src, size_t srcLen, bool overreadIsFatal = false);
/**
* Convert UTF-8 to UTF-16 including surrogate pairs.
- * Returns a pointer to the end of the string (where a null terminator might go
- * if you wanted to add one).
+ * Returns a pointer to the end of the string (where a NUL terminator might go
+ * if you wanted to add one). At most dstLen characters are written; it won't emit half a surrogate
+ * pair. If dstLen == 0 nothing is written and dst is returned. If dstLen > SSIZE_MAX it aborts
+ * (this being probably a negative number returned as an error and casted to unsigned).
*/
-char16_t* utf8_to_utf16_no_null_terminator(const uint8_t* src, size_t srcLen, char16_t* dst);
+char16_t* utf8_to_utf16_no_null_terminator(
+ const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
/**
- * Convert UTF-8 to UTF-16 including surrogate pairs. The destination buffer
- * must be large enough to hold the result as measured by utf8_to_utf16_length
- * plus an added NULL terminator.
+ * Convert UTF-8 to UTF-16 including surrogate pairs. At most dstLen - 1
+ * characters are written; it won't emit half a surrogate pair; and a NUL terminator is appended
+ * after. dstLen - 1 can be measured beforehand using utf8_to_utf16_length. Aborts if dstLen == 0
+ * (at least one character is needed for the NUL terminator) or dstLen > SSIZE_MAX (the latter
+ * case being likely a negative number returned as an error and casted to unsigned) . Returns a
+ * pointer to the NUL terminator.
*/
-void utf8_to_utf16(const uint8_t* src, size_t srcLen, char16_t* dst);
-
-/**
- * Like utf8_to_utf16_no_null_terminator, but you can supply a maximum length of the
- * decoded string. The decoded string will fill up to that length; if it is longer
- * the returned pointer will be to the character after dstLen.
- */
-char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
+char16_t *utf8_to_utf16(
+ const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen);
}
diff --git a/libutils/String16.cpp b/libutils/String16.cpp
index ac12d8a..9f5cfea 100644
--- a/libutils/String16.cpp
+++ b/libutils/String16.cpp
@@ -71,7 +71,7 @@
u8cur = (const uint8_t*) u8str;
char16_t* u16str = (char16_t*)buf->data();
- utf8_to_utf16(u8cur, u8len, u16str);
+ utf8_to_utf16(u8cur, u8len, u16str, ((size_t) u16len) + 1);
//printf("Created UTF-16 string from UTF-8 \"%s\":", in);
//printHexData(1, str, buf->size(), 16, 1);
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index f1f8bc9..1aca8e7 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -16,6 +16,7 @@
#include <utils/Unicode.h>
+#include <limits.h>
#include <stddef.h>
#if defined(_WIN32)
@@ -535,7 +536,7 @@
//printf("Char at %p: len=%d, utf-16=%p\n", src, length, (void*)result);
}
-ssize_t utf8_to_utf16_length(const uint8_t* u8str, size_t u8len)
+ssize_t utf8_to_utf16_length(const uint8_t* u8str, size_t u8len, bool overreadIsFatal)
{
const uint8_t* const u8end = u8str + u8len;
const uint8_t* u8cur = u8str;
@@ -545,6 +546,20 @@
while (u8cur < u8end) {
u16measuredLen++;
int u8charLen = utf8_codepoint_len(*u8cur);
+ // Malformed utf8, some characters are beyond the end.
+ // Cases:
+ // If u8charLen == 1, this becomes u8cur >= u8end, which cannot happen as u8cur < u8end,
+ // then this condition fail and we continue, as expected.
+ // If u8charLen == 2, this becomes u8cur + 1 >= u8end, which fails only if
+ // u8cur == u8end - 1, that is, there was only one remaining character to read but we need
+ // 2 of them. This condition holds and we return -1, as expected.
+ if (u8cur + u8charLen - 1 >= u8end) {
+ if (overreadIsFatal) {
+ LOG_ALWAYS_FATAL("Attempt to overread computing length of utf8 string");
+ } else {
+ return -1;
+ }
+ }
uint32_t codepoint = utf8_to_utf32_codepoint(u8cur, u8charLen);
if (codepoint > 0xFFFF) u16measuredLen++; // this will be a surrogate pair in utf16
u8cur += u8charLen;
@@ -561,38 +576,21 @@
return u16measuredLen;
}
-char16_t* utf8_to_utf16_no_null_terminator(const uint8_t* u8str, size_t u8len, char16_t* u16str)
-{
- const uint8_t* const u8end = u8str + u8len;
- const uint8_t* u8cur = u8str;
- char16_t* u16cur = u16str;
-
- while (u8cur < u8end) {
- size_t u8len = utf8_codepoint_len(*u8cur);
- uint32_t codepoint = utf8_to_utf32_codepoint(u8cur, u8len);
-
- // Convert the UTF32 codepoint to one or more UTF16 codepoints
- if (codepoint <= 0xFFFF) {
- // Single UTF16 character
- *u16cur++ = (char16_t) codepoint;
- } else {
- // Multiple UTF16 characters with surrogates
- codepoint = codepoint - 0x10000;
- *u16cur++ = (char16_t) ((codepoint >> 10) + 0xD800);
- *u16cur++ = (char16_t) ((codepoint & 0x3FF) + 0xDC00);
- }
-
- u8cur += u8len;
- }
- return u16cur;
-}
-
-void utf8_to_utf16(const uint8_t* u8str, size_t u8len, char16_t* u16str) {
- char16_t* end = utf8_to_utf16_no_null_terminator(u8str, u8len, u16str);
+char16_t* utf8_to_utf16(const uint8_t* u8str, size_t u8len, char16_t* u16str, size_t u16len) {
+ // A value > SSIZE_MAX is probably a negative value returned as an error and casted.
+ LOG_ALWAYS_FATAL_IF(u16len == 0 || u16len > SSIZE_MAX, "u16len is %zu", u16len);
+ char16_t* end = utf8_to_utf16_no_null_terminator(u8str, u8len, u16str, u16len - 1);
*end = 0;
+ return end;
}
-char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
+char16_t* utf8_to_utf16_no_null_terminator(
+ const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
+ if (dstLen == 0) {
+ return dst;
+ }
+ // A value > SSIZE_MAX is probably a negative value returned as an error and casted.
+ LOG_ALWAYS_FATAL_IF(dstLen > SSIZE_MAX, "dstLen is %zu", dstLen);
const uint8_t* const u8end = src + srcLen;
const uint8_t* u8cur = src;
const char16_t* const u16end = dst + dstLen;
diff --git a/libutils/tests/Unicode_test.cpp b/libutils/tests/Unicode_test.cpp
index c263f75..d23e43a 100644
--- a/libutils/tests/Unicode_test.cpp
+++ b/libutils/tests/Unicode_test.cpp
@@ -98,7 +98,7 @@
char16_t output[1 + 1 + 1 + 2 + 1]; // Room for NULL
- utf8_to_utf16(str, sizeof(str), output);
+ utf8_to_utf16(str, sizeof(str), output, sizeof(output) / sizeof(output[0]));
EXPECT_EQ(0x0030, output[0])
<< "should be U+0030";
@@ -147,4 +147,15 @@
EXPECT_EQ(nullptr, result);
}
+// http://b/29267949
+// Test that overreading in utf8_to_utf16_length is detected
+TEST_F(UnicodeTest, InvalidUtf8OverreadDetected) {
+ // An utf8 char starting with \xc4 is two bytes long.
+ // Add extra zeros so no extra memory is read in case the code doesn't
+ // work as expected.
+ static char utf8[] = "\xc4\x00\x00\x00";
+ ASSERT_DEATH(utf8_to_utf16_length((uint8_t *) utf8, strlen(utf8),
+ true /* overreadIsFatal */), "" /* regex for ASSERT_DEATH */);
+}
+
}