Fix integer overflow in utf{16,32}_to_utf8_length
Without an explicit check, the return value can wrap around and return
a value that is far too small to hold the data from the resulting
conversion.
No CTS test is provided because it would need to allocate at least
SSIZE_MAX / 2 bytes of UTF-16 data, which is unreasonable on 64-bit
devices.
Bug: 37723026
Test: run cts -p android.security
Change-Id: Ie2606b92b9eab1acfe8ce4663b43b81156a4cad7
Merged-In: I56ba5e31657633b7f33685dd8839d4b3b998e586
(cherry picked from commit f0a43dede921178b3048d40c330a8b664e94cca3)
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index ba084f6..bfacf1e 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -18,6 +18,7 @@
#include <utils/Unicode.h>
#include <stddef.h>
+#include <limits.h>
#if defined(_WIN32)
# undef nhtol
@@ -178,7 +179,15 @@
size_t ret = 0;
const char32_t *end = src + src_len;
while (src < end) {
- ret += utf32_codepoint_utf8_length(*src++);
+ size_t char_len = utf32_codepoint_utf8_length(*src++);
+ if (SSIZE_MAX - char_len < ret) {
+ // If this happens, we would overflow the ssize_t type when
+ // returning from this function, so we cannot express how
+ // long this string is in an ssize_t.
+ android_errorWriteLog(0x534e4554, "37723026");
+ return -1;
+ }
+ ret += char_len;
}
return ret;
}
@@ -438,14 +447,23 @@
size_t ret = 0;
const char16_t* const end = src + src_len;
while (src < end) {
+ size_t char_len;
if ((*src & 0xFC00) == 0xD800 && (src + 1) < end
&& (*(src + 1) & 0xFC00) == 0xDC00) {
// surrogate pairs are always 4 bytes.
- ret += 4;
+ char_len = 4;
src += 2;
} else {
- ret += utf32_codepoint_utf8_length((char32_t) *src++);
+ char_len = utf32_codepoint_utf8_length((char32_t)*src++);
}
+ if (SSIZE_MAX - char_len < ret) {
+ // If this happens, we would overflow the ssize_t type when
+ // returning from this function, so we cannot express how
+ // long this string is in an ssize_t.
+ android_errorWriteLog(0x534e4554, "37723026");
+ return -1;
+ }
+ ret += char_len;
}
return ret;
}
