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sys/base64: drop padding for base64url encoding

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The URLsafe base64 encoding variant does not require padding, using
'=' as padding is in fact an error as it is not a URL-safe character.
This commit is contained in:
Benjamin Valentin 2020-12-15 12:18:45 +01:00
parent 41a844f323
commit 48c33ae0a2
2 changed files with 15 additions and 4 deletions
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15
sys/base64/base64.c
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@ -90,6 +90,7 @@ static int base64_encode_base(const void *data_in, size_t data_in_size,
void *base64_out, size_t *base64_out_size, void *base64_out, size_t *base64_out_size,
bool urlsafe) bool urlsafe)
{ {
const uint8_t padding = urlsafe ? 0 : '=';
const uint8_t *in = data_in; const uint8_t *in = data_in;
const uint8_t *end = in + data_in_size; const uint8_t *end = in + data_in_size;
uint8_t *out = base64_out; uint8_t *out = base64_out;
@ -131,14 +132,24 @@ static int base64_encode_base(const void *data_in, size_t data_in_size,
encode_three_bytes(out, in[0], 0, 0, urlsafe); encode_three_bytes(out, in[0], 0, 0, urlsafe);
/* Replace last two bytes with "=" to signal corresponding input bytes /* Replace last two bytes with "=" to signal corresponding input bytes
* didn't exist */ * didn't exist */
out[2] = out[3] = '='; out[2] = out[3] = padding;
/* padding is not required for urlsafe application */
if (urlsafe) {
*base64_out_size -= 2;
}
return BASE64_SUCCESS; return BASE64_SUCCESS;
} }
/* Final case: 2 bytes remain for encoding, use zero as third input */ /* Final case: 2 bytes remain for encoding, use zero as third input */
encode_three_bytes(out, in[0], in[1], 0, urlsafe); encode_three_bytes(out, in[0], in[1], 0, urlsafe);
/* Replace last output with "=" to signal corresponding input byte didn't exit */ /* Replace last output with "=" to signal corresponding input byte didn't exit */
out[3] = '='; out[3] = padding;
/* padding is not required for urlsafe application */
if (urlsafe) {
*base64_out_size -= 1;
}
return BASE64_SUCCESS; return BASE64_SUCCESS;
} }

4
tests/unittests/tests-base64/tests-base64.c
View File

@ -411,7 +411,7 @@ static void test_base64_10_decode_empty(void)
static void test_base64_11_urlsafe_encode_int(void) static void test_base64_11_urlsafe_encode_int(void)
{ {
uint32_t data_in = 4345; uint32_t data_in = 4345;
unsigned char expected_encoding[] = "-RAAAA=="; unsigned char expected_encoding[] = "-RAAAA";
size_t base64_out_size = 0; size_t base64_out_size = 0;
char base64_out[sizeof(expected_encoding)]; char base64_out[sizeof(expected_encoding)];
@ -448,7 +448,7 @@ static void test_base64_11_urlsafe_encode_int(void)
static void test_base64_12_urlsafe_decode_int(void) static void test_base64_12_urlsafe_decode_int(void)
{ {
static const char encoded_base64[] = "_____wAA=="; static const char encoded_base64[] = "_____wAA";
static const uint8_t expected[] = {0xFF, 0xFF, 0xFF, 0xFF, 0x0, 0x0}; static const uint8_t expected[] = {0xFF, 0xFF, 0xFF, 0xFF, 0x0, 0x0};
size_t base64_size = strlen(encoded_base64); size_t base64_size = strlen(encoded_base64);