thirdparty/scummvm
2
0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

COMMON: Add strnlen for safer C string length reads

Browse source 
This API is intended for use in cases where C strings come
from untrusted sources like game files, where malformed data
missing the null terminator would cause strlen to read out of
bounds.
This commit is contained in:
Colin Snover 2016-11-26 12:56:25 -06:00 • committed by Willem Jan Palenstijn
parent 28d2f1d0df
commit 9d3893459f
3 changed files with 41 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

7
common/str.cpp
View file

@ -942,6 +942,13 @@ size_t strlcat(char *dst, const char *src, size_t size) {
return dstLength + (src - srcStart); return dstLength + (src - srcStart);
} }
size_t strnlen(const char *src, size_t maxSize) {
size_t counter = 0;
while (counter != maxSize && *src++)
++counter;
return counter;
}
} // End of namespace Common } // End of namespace Common
// Portable implementation of stricmp / strcasecmp / strcmpi. // Portable implementation of stricmp / strcasecmp / strcmpi.

11
common/str.h
View file

@ -444,6 +444,17 @@ size_t strlcpy(char *dst, const char *src, size_t size);
*/ */
size_t strlcat(char *dst, const char *src, size_t size); size_t strlcat(char *dst, const char *src, size_t size);
/**
* Determine the length of a string up to a maximum of `maxSize` characters.
* This should be used instead of `strlen` when reading the length of a C string
* from potentially unsafe or corrupt sources, like game assets.
*
* @param src The source string.
* @param maxSize The maximum size of the string.
* @return The length of the string.
*/
size_t strnlen(const char *src, size_t maxSize);
/** /**
* Convenience wrapper for tag2string which "returns" a C string. * Convenience wrapper for tag2string which "returns" a C string.
* Note: It is *NOT* safe to do anything with the return value other than directly * Note: It is *NOT* safe to do anything with the return value other than directly

23
test/common/str.h
View file

@ -403,6 +403,29 @@ class StringTestSuite : public CxxTest::TestSuite
TS_ASSERT_EQUALS(strcmp(test4, resultString), 0); TS_ASSERT_EQUALS(strcmp(test4, resultString), 0);
} }
void test_strnlen() {
static const char * const testString = "123";
TS_ASSERT_EQUALS(Common::strnlen(testString, 0), 0);
TS_ASSERT_EQUALS(Common::strnlen(testString, 1), 1);
TS_ASSERT_EQUALS(Common::strnlen(testString, 2), 2);
TS_ASSERT_EQUALS(Common::strnlen(testString, 3), 3);
TS_ASSERT_EQUALS(Common::strnlen(testString, 4), 3);
const char testArray[4] = { '1', '2', '3', '4' };
TS_ASSERT_EQUALS(Common::strnlen(testArray, 0), 0);
TS_ASSERT_EQUALS(Common::strnlen(testArray, 1), 1);
TS_ASSERT_EQUALS(Common::strnlen(testArray, 2), 2);
TS_ASSERT_EQUALS(Common::strnlen(testArray, 3), 3);
TS_ASSERT_EQUALS(Common::strnlen(testArray, 4), 4);
const char testArray2[4] = { '1', '\0', '3', '4' };
TS_ASSERT_EQUALS(Common::strnlen(testArray2, 0), 0);
TS_ASSERT_EQUALS(Common::strnlen(testArray2, 1), 1);
TS_ASSERT_EQUALS(Common::strnlen(testArray2, 2), 1);
TS_ASSERT_EQUALS(Common::strnlen(testArray2, 3), 1);
TS_ASSERT_EQUALS(Common::strnlen(testArray2, 4), 1);
}
void test_scumm_stricmp() { void test_scumm_stricmp() {
TS_ASSERT_EQUALS(scumm_stricmp("abCd", "abCd"), 0); TS_ASSERT_EQUALS(scumm_stricmp("abCd", "abCd"), 0);
TS_ASSERT_EQUALS(scumm_stricmp("abCd", "ABCd"), 0); TS_ASSERT_EQUALS(scumm_stricmp("abCd", "ABCd"), 0);