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Harden Base64 bounds and JSON parser nesting #268

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7b67b55
Harden Base64 bounds checks
idrassi May 18, 2026
12eedc6
Harden JSON parse and binary failures
idrassi May 18, 2026
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181 changes: 167 additions & 14 deletions src/encode/base64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,48 @@
#include <core/strings.h>
#include <sewer/cassert.h>

#define i_B64_MAX_ENCODED_SIZE ((uint64_t)UINT32_MAX - 1024ULL)

static char_t i_B64_CHR[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/*---------------------------------------------------------------------------*/

static bool_t i_b64_encoded_size(const uint32_t data_size, uint32_t *encoded_size)
{
uint64_t size = 4ULL * ((uint64_t)data_size / 3ULL) + 5ULL;

cassert_no_null(encoded_size);

if (size > i_B64_MAX_ENCODED_SIZE)
{
*encoded_size = 0;
return FALSE;
}

*encoded_size = (uint32_t)size;
return TRUE;
}

/*---------------------------------------------------------------------------*/

static bool_t i_b64_required_size(const uint32_t data_size, uint32_t *required_size)
{
uint64_t size = ((((uint64_t)data_size + 2ULL) / 3ULL) * 4ULL) + 1ULL;

cassert_no_null(required_size);

if (size > (uint64_t)UINT32_MAX)
{
*required_size = 0;
return FALSE;
}

*required_size = (uint32_t)size;
return TRUE;
}

/*---------------------------------------------------------------------------*/

static uint32_t i_b64_int(const uint32_t ch)
{
/* ASCII to base64_int
Expand Down Expand Up @@ -49,10 +87,43 @@ static uint32_t i_b64_int(const uint32_t ch)

/*---------------------------------------------------------------------------*/

static bool_t i_b64_decoded_bytes(const char_t *base64, const uint32_t size, uint32_t *decoded_size)
{
uint32_t i = 0, j = 0, k = 0, s[4];

cassert_no_null(decoded_size);
*decoded_size = 0;

if (base64 == NULL)
return FALSE;

for (i = 0; i < size; i++)
{
s[j++] = i_b64_int((uint32_t) * (base64 + i));
if (j == 4)
{
if (s[2] == 64)
k += 1;
else if (s[3] == 64)
k += 2;
else
k += 3;

j = 0;
}
}

*decoded_size = k;
return TRUE;
}

/*---------------------------------------------------------------------------*/

uint32_t b64_encoded_size(const uint32_t data_size)
{
uint32_t size = 4 * (data_size / 3);
return size + 4 + 1;
uint32_t size = 0;
i_b64_encoded_size(data_size, &size);
return size;
}

/*---------------------------------------------------------------------------*/
Expand All @@ -65,11 +136,9 @@ uint32_t b64_decoded_size(const uint32_t encoded_size)

/*---------------------------------------------------------------------------*/

uint32_t b64_encode(const byte_t *data, const uint32_t size, char_t *base64, const uint32_t esize)
static uint32_t i_b64_encode(const byte_t *data, const uint32_t size, char_t *base64)
{
uint32_t i = 0, j = 0, k = 0, s[3];
cassert_no_null(data);
cassert_no_null(base64);
for (i = 0; i < size; i++)
{
s[j++] = *(data + i);
Expand Down Expand Up @@ -105,19 +174,59 @@ uint32_t b64_encode(const byte_t *data, const uint32_t size, char_t *base64, con
k += 4;
}

cassert_unref(k < esize, esize);
base64[k] = '\0';
return k;
}

/*---------------------------------------------------------------------------*/

uint32_t b64_decode(const char_t *base64, const uint32_t size, byte_t *data)
bool_t b64_encode_ex(const byte_t *data, const uint32_t size, char_t *base64, const uint32_t esize, uint32_t *written)
{
uint32_t i = 0, j = 0, k = 0, s[4];
uint32_t required_size = 0;
uint32_t n = 0;

if (written != NULL)
*written = 0;

if (base64 == NULL || (data == NULL && size > 0))
return FALSE;

if (i_b64_required_size(size, &required_size) == FALSE || esize < required_size)
{
if (base64 != NULL && esize > 0)
base64[0] = '\0';
return FALSE;
}

n = i_b64_encode(data, size, base64);
if (written != NULL)
*written = n;
return TRUE;
}

/*---------------------------------------------------------------------------*/

uint32_t b64_encode(const byte_t *data, const uint32_t size, char_t *base64, const uint32_t esize)
{
uint32_t required_size = 0;
bool_t required_ok = FALSE;

cassert_no_null(base64);
cassert_no_null(data);
cassert_no_null(base64);
required_ok = i_b64_required_size(size, &required_size);
cassert(required_ok == TRUE);
cassert_unref(required_size <= esize, esize);
unref(required_ok);
unref(required_size);

return i_b64_encode(data, size, base64);
}

/*---------------------------------------------------------------------------*/

static uint32_t i_b64_decode(const char_t *base64, const uint32_t size, byte_t *data)
{
uint32_t i = 0, j = 0, k = 0, s[4];

for (i = 0; i < size; i++)
{
Expand Down Expand Up @@ -154,12 +263,53 @@ uint32_t b64_decode(const char_t *base64, const uint32_t size, byte_t *data)

/*---------------------------------------------------------------------------*/

bool_t b64_decode_ex(const char_t *base64, const uint32_t size, byte_t *data, const uint32_t dsize, uint32_t *written)
{
uint32_t k = 0;
uint32_t required_size = 0;

if (written != NULL)
*written = 0;

if (base64 == NULL || data == NULL)
return FALSE;

if (i_b64_decoded_bytes(base64, size, &required_size) == FALSE || required_size > dsize)
return FALSE;

k = i_b64_decode(base64, size, data);
if (written != NULL)
*written = k;

return TRUE;
}

/*---------------------------------------------------------------------------*/

uint32_t b64_decode(const char_t *base64, const uint32_t size, byte_t *data)
{
cassert_no_null(base64);
cassert_no_null(data);

return i_b64_decode(base64, size, data);
}

/*---------------------------------------------------------------------------*/

static String *i_encode_from_data(const byte_t *data, const uint32_t size)
{
uint32_t b64size = b64_encoded_size(size);
String *str = str_reserve(b64size);
char_t *b64data = tcc(str);
uint32_t n = b64_encode(data, size, b64data, b64size);
String *str = NULL;
char_t *b64data = NULL;
uint32_t n = 0;

if (b64size == 0)
return str_c("");

str = str_reserve(b64size);
b64data = tcc(str);
if (b64_encode_ex(data, size, b64data, b64size, &n) == FALSE)
n = 0;
b64data[n] = '\0';
return str;
}
Expand Down Expand Up @@ -231,8 +381,11 @@ Buffer *b64_decode_from_data(const byte_t *data, const uint32_t size)
{
uint32_t dsize = b64_decoded_size(size);
byte_t *binary = heap_malloc(dsize, "b64_decode");
uint32_t binsize = b64_decode(cast_const(data, char_t), size, binary);
Buffer *buffer = buffer_with_data(binary, binsize);
uint32_t binsize = 0;
Buffer *buffer = NULL;

b64_decode_ex(cast_const(data, char_t), size, binary, dsize, &binsize);
buffer = buffer_with_data(binary, binsize);
heap_free(&binary, dsize, "b64_decode");
return buffer;
}
4 changes: 4 additions & 0 deletions src/encode/base64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,8 +19,12 @@ _encode_api uint32_t b64_encoded_size(const uint32_t data_size);

_encode_api uint32_t b64_decoded_size(const uint32_t encoded_size);

_encode_api bool_t b64_encode_ex(const byte_t *data, const uint32_t size, char_t *base64, const uint32_t esize, uint32_t *written);

_encode_api uint32_t b64_encode(const byte_t *data, const uint32_t size, char_t *base64, const uint32_t esize);

_encode_api bool_t b64_decode_ex(const char_t *base64, const uint32_t size, byte_t *data, const uint32_t dsize, uint32_t *written);

_encode_api uint32_t b64_decode(const char_t *base64, const uint32_t size, byte_t *data);

_encode_api String *b64_encode_from_stm(Stream *stm);
Expand Down
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