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Fix base64 validation and add unittests (#10515)
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Implement proper padding character checks
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@appgurueu
appgurueu committed May 30, 2021
1 parent 1bc753f commit 89f3991
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Showing 4 changed files with 124 additions and 6 deletions.
4 changes: 3 additions & 1 deletion doc/client_lua_api.txt
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Expand Up @@ -910,7 +910,9 @@ Call these functions only at load time!
* Example: `minetest.rgba(10, 20, 30, 40)`, returns `"#0A141E28"`
* `minetest.encode_base64(string)`: returns string encoded in base64
* Encodes a string in base64.
* `minetest.decode_base64(string)`: returns string
* `minetest.decode_base64(string)`: returns string or nil on failure
* Padding characters are only supported starting at version 5.4.0, where
5.5.0 and newer perform proper checks.
* Decodes a string encoded in base64.
* `minetest.gettext(string)` : returns string
* look up the translation of a string in the gettext message catalog
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4 changes: 3 additions & 1 deletion doc/lua_api.txt
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Expand Up @@ -5773,7 +5773,9 @@ Misc.
* Example: `minetest.rgba(10, 20, 30, 40)`, returns `"#0A141E28"`
* `minetest.encode_base64(string)`: returns string encoded in base64
* Encodes a string in base64.
* `minetest.decode_base64(string)`: returns string or nil for invalid base64
* `minetest.decode_base64(string)`: returns string or nil on failure
* Padding characters are only supported starting at version 5.4.0, where
5.5.0 and newer perform proper checks.
* Decodes a string encoded in base64.
* `minetest.is_protected(pos, name)`: returns boolean
* Returning `true` restricts the player `name` from modifying (i.e. digging,
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93 changes: 93 additions & 0 deletions src/unittest/test_utilities.cpp
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Expand Up @@ -23,6 +23,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "util/enriched_string.h"
#include "util/numeric.h"
#include "util/string.h"
#include "util/base64.h"

class TestUtilities : public TestBase {
public:
Expand Down Expand Up @@ -56,6 +57,7 @@ class TestUtilities : public TestBase {
void testMyround();
void testStringJoin();
void testEulerConversion();
void testBase64();
};

static TestUtilities g_test_instance;
Expand Down Expand Up @@ -87,6 +89,7 @@ void TestUtilities::runTests(IGameDef *gamedef)
TEST(testMyround);
TEST(testStringJoin);
TEST(testEulerConversion);
TEST(testBase64);
}

////////////////////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -537,3 +540,93 @@ void TestUtilities::testEulerConversion()
setPitchYawRoll(m2, v2);
UASSERT(within(m1, m2, tolL));
}

void TestUtilities::testBase64()
{
// Test character set
UASSERT(base64_is_valid("ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/") == true);
UASSERT(base64_is_valid("/+9876543210"
"zyxwvutsrqponmlkjihgfedcba"
"ZYXWVUTSRQPONMLKJIHGFEDCBA") == true);
UASSERT(base64_is_valid("ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+.") == false);
UASSERT(base64_is_valid("ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789 /") == false);

// Test empty string
UASSERT(base64_is_valid("") == true);

// Test different lengths, with and without padding,
// with correct and incorrect padding
UASSERT(base64_is_valid("A") == false);
UASSERT(base64_is_valid("AA") == true);
UASSERT(base64_is_valid("AAA") == true);
UASSERT(base64_is_valid("AAAA") == true);
UASSERT(base64_is_valid("AAAAA") == false);
UASSERT(base64_is_valid("AAAAAA") == true);
UASSERT(base64_is_valid("AAAAAAA") == true);
UASSERT(base64_is_valid("AAAAAAAA") == true);
UASSERT(base64_is_valid("A===") == false);
UASSERT(base64_is_valid("AA==") == true);
UASSERT(base64_is_valid("AAA=") == true);
UASSERT(base64_is_valid("AAAA") == true);
UASSERT(base64_is_valid("AAAA====") == false);
UASSERT(base64_is_valid("AAAAA===") == false);
UASSERT(base64_is_valid("AAAAAA==") == true);
UASSERT(base64_is_valid("AAAAAAA=") == true);
UASSERT(base64_is_valid("AAAAAAA==") == false);
UASSERT(base64_is_valid("AAAAAAA===") == false);
UASSERT(base64_is_valid("AAAAAAA====") == false);
UASSERT(base64_is_valid("AAAAAAAA") == true);
UASSERT(base64_is_valid("AAAAAAAA=") == false);
UASSERT(base64_is_valid("AAAAAAAA==") == false);
UASSERT(base64_is_valid("AAAAAAAA===") == false);
UASSERT(base64_is_valid("AAAAAAAA====") == false);

// Test if canonical encoding
// Last character limitations, length % 4 == 3
UASSERT(base64_is_valid("AAB") == false);
UASSERT(base64_is_valid("AAE") == true);
UASSERT(base64_is_valid("AAQ") == true);
UASSERT(base64_is_valid("AAB=") == false);
UASSERT(base64_is_valid("AAE=") == true);
UASSERT(base64_is_valid("AAQ=") == true);
UASSERT(base64_is_valid("AAAAAAB=") == false);
UASSERT(base64_is_valid("AAAAAAE=") == true);
UASSERT(base64_is_valid("AAAAAAQ=") == true);
// Last character limitations, length % 4 == 2
UASSERT(base64_is_valid("AB") == false);
UASSERT(base64_is_valid("AE") == false);
UASSERT(base64_is_valid("AQ") == true);
UASSERT(base64_is_valid("AB==") == false);
UASSERT(base64_is_valid("AE==") == false);
UASSERT(base64_is_valid("AQ==") == true);
UASSERT(base64_is_valid("AAAAAB==") == false);
UASSERT(base64_is_valid("AAAAAE==") == false);
UASSERT(base64_is_valid("AAAAAQ==") == true);

// Extraneous character present
UASSERT(base64_is_valid(".") == false);
UASSERT(base64_is_valid("A.") == false);
UASSERT(base64_is_valid("AA.") == false);
UASSERT(base64_is_valid("AAA.") == false);
UASSERT(base64_is_valid("AAAA.") == false);
UASSERT(base64_is_valid("AAAAA.") == false);
UASSERT(base64_is_valid("A.A") == false);
UASSERT(base64_is_valid("AA.A") == false);
UASSERT(base64_is_valid("AAA.A") == false);
UASSERT(base64_is_valid("AAAA.A") == false);
UASSERT(base64_is_valid("AAAAA.A") == false);
UASSERT(base64_is_valid("\xE1""AAA") == false);

// Padding in wrong position
UASSERT(base64_is_valid("A=A") == false);
UASSERT(base64_is_valid("AA=A") == false);
UASSERT(base64_is_valid("AAA=A") == false);
UASSERT(base64_is_valid("AAAA=A") == false);
UASSERT(base64_is_valid("AAAAA=A") == false);
}
29 changes: 25 additions & 4 deletions src/util/base64.cpp
View file
Expand Up @@ -33,18 +33,39 @@ static const std::string base64_chars =
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";

static const std::string base64_chars_padding_1 = "AEIMQUYcgkosw048";
static const std::string base64_chars_padding_2 = "AQgw";

static inline bool is_base64(unsigned char c)
{
return isalnum(c) || c == '+' || c == '/' || c == '=';
return (c >= '0' && c <= '9')
|| (c >= 'A' && c <= 'Z')
|| (c >= 'a' && c <= 'z')
|| c == '+' || c == '/';
}

bool base64_is_valid(std::string const& s)
{
for (char i : s)
if (!is_base64(i))
size_t i = 0;
for (; i < s.size(); ++i)
if (!is_base64(s[i]))
break;
unsigned char padding = 3 - ((i + 3) % 4);
if ((padding == 1 && base64_chars_padding_1.find(s[i - 1]) == std::string::npos)
|| (padding == 2 && base64_chars_padding_2.find(s[i - 1]) == std::string::npos)
|| padding == 3)
return false;
int actual_padding = s.size() - i;
// omission of padding characters is allowed
if (actual_padding == 0)
return true;

// remaining characters (max. 2) may only be padding
for (; i < s.size(); ++i)
if (s[i] != '=')
return false;
return true;
// number of padding characters needs to match
return padding == actual_padding;
}

std::string base64_encode(unsigned char const* bytes_to_encode, unsigned int in_len) {
Expand Down

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