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tuning base64 decoding implementation

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This commit is contained in:
Karel Miko 2017-02-20 23:26:10 +01:00
parent c1dd1cbe30
commit ff3a03a1d0
1 changed files with 23 additions and 18 deletions
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41
src/misc/base64/base64_decode.c
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@ -88,41 +88,38 @@ static int _base64_decode_internal(const unsigned char *in, unsigned long inlen
LTC_ARGCHK(out != NULL); LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL); LTC_ARGCHK(outlen != NULL);
g = 3; g = 0; /* '=' counter */
for (x = y = z = t = 0; x < inlen; x++) { for (x = y = z = t = 0; x < inlen; x++) {
c = map[in[x]&0xFF]; c = map[in[x]&0xFF];
if (c == 254) {
g++;
continue;
}
else if (is_strict && g > 0) {
/* we only allow '=' to be at the end */
return CRYPT_INVALID_PACKET;
}
if (c == 255) { if (c == 255) {
if (is_strict) if (is_strict)
return CRYPT_INVALID_PACKET; return CRYPT_INVALID_PACKET;
else else
continue; continue;
} }
/* the final = symbols are read and used to trim the remaining bytes */
if (c == 254) {
c = 0;
/* prevent g < 0 which would potentially allow an overflow later */
if (--g < 0) {
return CRYPT_INVALID_PACKET;
}
} else if (g != 3) {
/* we only allow = to be at the end */
return CRYPT_INVALID_PACKET;
}
t = (t<<6)|c; t = (t<<6)|c;
if (++y == 4) { if (++y == 4) {
if (z + g > *outlen) { if (z + 3 > *outlen) return CRYPT_BUFFER_OVERFLOW;
return CRYPT_BUFFER_OVERFLOW;
}
out[z++] = (unsigned char)((t>>16)&255); out[z++] = (unsigned char)((t>>16)&255);
if (g > 1) out[z++] = (unsigned char)((t>>8)&255); out[z++] = (unsigned char)((t>>8)&255);
if (g > 2) out[z++] = (unsigned char)(t&255); out[z++] = (unsigned char)(t&255);
y = t = 0; y = t = 0;
} }
} }
if (y != 0) { if (y != 0) {
if (y == 1 || map != map_base64url || is_strict == 1) return CRYPT_INVALID_PACKET; if (y == 1) return CRYPT_INVALID_PACKET;
if ((y + g) != 4 && is_strict) return CRYPT_INVALID_PACKET;
t = t << (6 * (4 - y)); t = t << (6 * (4 - y));
if (z + y - 1 > *outlen) return CRYPT_BUFFER_OVERFLOW; if (z + y - 1 > *outlen) return CRYPT_BUFFER_OVERFLOW;
if (y >= 2) out[z++] = (unsigned char) ((t >> 16) & 255); if (y >= 2) out[z++] = (unsigned char) ((t >> 16) & 255);
@ -177,6 +174,14 @@ int base64url_decode(const unsigned char *in, unsigned long inlen,
return _base64_decode_internal(in, inlen, out, outlen, map_base64url, relaxed); return _base64_decode_internal(in, inlen, out, outlen, map_base64url, relaxed);
} }
/**
Strict base64 (URL Safe, RFC 4648 section 5) decode a block of memory
@param in The base64 data to decode
@param inlen The length of the base64 data
@param out [out] The destination of the binary decoded data
@param outlen [in/out] The max size and resulting size of the decoded data
@return CRYPT_OK if successful
*/
int base64url_strict_decode(const unsigned char *in, unsigned long inlen, int base64url_strict_decode(const unsigned char *in, unsigned long inlen,
unsigned char *out, unsigned long *outlen) unsigned char *out, unsigned long *outlen)
{ {