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Fix error detection in 'base64Decode()'

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Fixed a bug in initialization of 'base64DecodeChars' variable.
Currently decoder do not fail on invalid Base64 strings.
Added test-case to verify the fix.

Also have made 'base64DecodeChars' to be computed at compile time.
And added a test case to encode/decode string with non-printable charactes.
This commit is contained in:
Alexey Novikov 2021-10-17 11:51:33 +04:00
parent 130284b850
commit 64a3b045c1
2 changed files with 27 additions and 8 deletions
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17
src/libutil/tests/tests.cc
View file

@ -4,6 +4,8 @@
#include <limits.h>
#include <gtest/gtest.h>
#include <numeric>
namespace nix {
/* ----------- tests for util.hh ------------------------------------------------*/
@ -282,6 +284,17 @@ namespace nix {
ASSERT_EQ(decoded, s);
}
TEST(base64Encode, encodeAndDecodeNonPrintable) {
char s[256];
std::iota(std::rbegin(s), std::rend(s), 0);
auto encoded = base64Encode(s);
auto decoded = base64Decode(encoded);
EXPECT_EQ(decoded.length(), 255);
ASSERT_EQ(decoded, s);
}
/* ----------------------------------------------------------------------------
* base64Decode
* --------------------------------------------------------------------------*/
@ -294,6 +307,10 @@ namespace nix {
ASSERT_EQ(base64Decode("cXVvZCBlcmF0IGRlbW9uc3RyYW5kdW0="), "quod erat demonstrandum");
}
TEST(base64Decode, decodeThrowsOnInvalidChar) {
ASSERT_THROW(base64Decode("cXVvZCBlcm_0IGRlbW9uc3RyYW5kdW0="), Error);
}
/* ----------------------------------------------------------------------------
* toLower
* --------------------------------------------------------------------------*/

18
src/libutil/util.cc
View file

@ -1436,8 +1436,7 @@ std::string filterANSIEscapes(const std::string & s, bool filterAll, unsigned in
}
static char base64Chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static std::array<char, 256> base64DecodeChars;
constexpr char base64Chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
string base64Encode(std::string_view s)
{
@ -1462,12 +1461,15 @@ string base64Encode(std::string_view s)
string base64Decode(std::string_view s)
{
static std::once_flag flag;
std::call_once(flag, [](){
base64DecodeChars = { (char)-1 };
constexpr char npos = -1;
constexpr std::array<char, 256> base64DecodeChars = [&]() {
std::array<char, 256> result{};
for (auto& c : result)
c = npos;
for (int i = 0; i < 64; i++)
base64DecodeChars[(int) base64Chars[i]] = i;
});
result[base64Chars[i]] = i;
return result;
}();
string res;
unsigned int d = 0, bits = 0;
@ -1477,7 +1479,7 @@ string base64Decode(std::string_view s)
if (c == '\n') continue;
char digit = base64DecodeChars[(unsigned char) c];
if (digit == -1)
if (digit == npos)
throw Error("invalid character in Base64 string: '%c'", c);
bits += 6;