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base64: Encoding/Decoding with URL and Filename Safe Alphabet #471

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merged 1 commit into from
Aug 25, 2022
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base64: Encoding/Decoding with URL and Filename Safe Alphabet #471

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1 change: 1 addition & 0 deletions include/re_base64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,5 +6,6 @@


int base64_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen);
int base64url_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen);
int base64_print(struct re_printf *pf, const uint8_t *ptr, size_t len);
int base64_decode(const char *in, size_t ilen, uint8_t *out, size_t *olen);
85 changes: 76 additions & 9 deletions src/base64/b64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,12 @@ static const char b64_table[65] =
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";

/* Base 64 Encoding with URL and Filename Safe Alphabet, RFC 4648 section 5 */
static const char b64url_table[65] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789-_";


/**
* Base-64 encode a buffer
Expand Down Expand Up @@ -53,10 +59,63 @@ int base64_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen)
++pad;
}

*out++ = b64_table[v>>18 & 0x3f];
*out++ = b64_table[v>>12 & 0x3f];
*out++ = (pad >= 2) ? '=' : b64_table[v>>6 & 0x3f];
*out++ = (pad >= 1) ? '=' : b64_table[v>>0 & 0x3f];
*out++ = b64_table[v >> 18 & 0x3f];
*out++ = b64_table[v >> 12 & 0x3f];
*out++ = (pad >= 2) ? '=' : b64_table[v >> 6 & 0x3f];
*out++ = (pad >= 1) ? '=' : b64_table[v >> 0 & 0x3f];
}

*olen = out - o;

return 0;
}


/**
* Base-64 url encode a buffer (without padding)
*
* @param in Input buffer
* @param ilen Length of input buffer
* @param out Output buffer
* @param olen Size of output buffer, actual written on return
*
* @return 0 if success, otherwise errorcode
*/
int base64url_encode(const uint8_t *in, size_t ilen, char *out, size_t *olen)
{
const uint8_t *in_end = in + ilen;
const char *o = out;

if (!in || !out || !olen)
return EINVAL;

if (*olen < 4 * ((ilen+2)/3))
return EOVERFLOW;

for (; in < in_end; ) {
uint32_t v;
int pad = 0;

v = *in++ << 16;
if (in < in_end) {
v |= *in++ << 8;
}
else {
++pad;
}
if (in < in_end) {
v |= *in++ << 0;
}
else {
++pad;
}

*out++ = b64url_table[v >> 18 & 0x3f];
*out++ = b64url_table[v >> 12 & 0x3f];
if (pad < 2)
*out++ = b64url_table[v >> 6 & 0x3f];
if (pad < 1)
*out++ = b64url_table[v >> 0 & 0x3f];
}

*olen = out - o;
Expand Down Expand Up @@ -103,9 +162,9 @@ static inline uint32_t b64val(char c)
return c - 'a' + 26;
else if ('0' <= c && c <= '9')
return c - '0' + 52;
else if ('+' == c)
else if ('+' == c || '-' == c)
return 62;
else if ('/' == c)
else if ('/' == c || '_' == c)
return 63;
else if ('=' == c)
return 1<<24; /* special trick */
Expand Down Expand Up @@ -135,13 +194,21 @@ int base64_decode(const char *in, size_t ilen, uint8_t *out, size_t *olen)
if (*olen < 3 * (ilen/4))
return EOVERFLOW;

for (;in+3 < in_end; ) {
for (;in+1 < in_end; ) {
uint32_t v;

v = b64val(*in++) << 18;
v |= b64val(*in++) << 12;
v |= b64val(*in++) << 6;
v |= b64val(*in++) << 0;

if (in < in_end)
v |= b64val(*in++) << 6;
else
v |= (1<<24) << 6; /* padding fallback */

if (in < in_end)
v |= b64val(*in++) << 0;
else
v |= (1<<24) << 0; /* padding fallback */

*out++ = v>>16;
if (!(v & (1<<30)))
Expand Down