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XrdSecztn.cc
Go to the documentation of this file.
// Copyright (c) 2015 Erwin Jansen
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// Note: the code in the anonymous namespace came from Erwin Jansen but was
// heavily edited to solve this particular problem. For more info see:
// https://github.com/pokowaka/jwt-cpp
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <limits>
#ifndef __FreeBSD__
#include <alloca.h>
#endif
#define WHITESPACE 64
#define EQUALS 65
#define INVALID 66
/******************************************************************************/
/* L o c a l F u n c t i o n s */
/******************************************************************************/
namespace
{
const char b64Table[] = {
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 62, 66, 62, 66, 63, 52, 53, 54, 55, 56, 57,
58, 59, 60, 61, 66, 66, 66, 66, 66, 66, 66, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
25, 66, 66, 66, 66, 63, 66, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
66, 66, 66, 66};
/******************************************************************************/
/* D e c o d e B y t e s N e e d e d */
/******************************************************************************/
size_t DecodeBytesNeeded(size_t num_decode) {
return 3 + (num_decode / 4) * 3;
}
/******************************************************************************/
/* D e c o d e U r l */
/******************************************************************************/
int DecodeUrl(const char *decode, size_t num_decode, char *out, size_t &num_out)
{
// No integer overflows please.
if (num_decode > std::numeric_limits<size_t>::max() - (size_t)decode)
return 1;
if (num_out > std::numeric_limits<size_t>::max() - (size_t)out)
return 1;
if (num_out < DecodeBytesNeeded(num_decode))
return 1;
const char *end = decode + num_decode;
const char *out_start = out;
char iter = 0;
uint32_t buf = 0;
uint8_t ch;
char c;
while (decode < end) {
ch = *decode++;
c = b64Table[ch];
switch (c) {
case INVALID:
return 1; // invalid input, return error
default:
buf = buf << 6 | c;
iter++; // increment the number of iteration
// If the buffer is full, split it into bytes
if (iter == 4) {
*(out++) = (buf >> 16) & 0xff;
*(out++) = (buf >> 8) & 0xff;
*(out++) = buf & 0xff;
buf = 0;
iter = 0;
}
}
}
if (iter == 3) {
*(out++) = (buf >> 10) & 0xff;
*(out++) = (buf >> 2) & 0xff;
} else {
if (iter == 2) {
*(out++) = (buf >> 4) & 0xff;
}
}
num_out = (out - out_start); // modify to reflect the actual output size
return 0;
}
}
/******************************************************************************/
/* X r d S e c z t n : : i s J W T */
/******************************************************************************/
namespace XrdSecztn
{
bool isJWT(const char *b64data)
{
size_t inBytes, outBytes;
const char *dot;
char *key, *outData, inData[1024];
// Skip over the header should it exist (sommetime it does sometimes not)
//
if (!strncmp(b64data, "Bearer%20", 9)) b64data += 9;
// We are only interested in the header which must appear first and be
// separated by a dot from subsequent tokens. If it does not have the
// dot then we assume it's not returnable. Otherwise truncate it at the dot.
//
if (!(dot = index(b64data, '.'))) return false;
// Copy out the token segment we wish to check. The JWT header can never be
// more than 1K long and that's being way generous.
//
inBytes = dot - b64data;
if (inBytes >= (int)sizeof(inData)) return false;
memcpy(inData, b64data, inBytes);
inData[inBytes] = 0;
// Allocate a buffer large enough to hold the result. Get it from the stack.
//
outBytes = DecodeBytesNeeded(inBytes);
outData = (char *)alloca(outBytes);
// If we can't decode what we have then indicate this is not returnable
//
if (DecodeUrl(inData, inBytes, outData, outBytes)) return false;
// The json object must start/end with a brace and must contain the key:value
// of '"typ":"JWT"', other elements may change but not this one.
//
if (outBytes <= 0 || *outData != '{' || outData[outBytes-1] != '}')
return false;
// Search for the key
//
if (!(key = strstr(outData, "\"typ\""))) return false;
// Subsequently there should be a colon or spaces but nothing more
//
key += 5;
while(*key == ' ') key++;
if (*key != ':') return false;
// There may be more spaces but anything else must be the expected value
//
key++;
while(*key == ' ') key++;
return strncmp(key, "\"JWT\"", 5) == 0;
}
}
INVALID
#define INVALID
Definition XrdSecztn.cc:39
XrdSecztn
Definition XrdSecProtocolztn.cc:174
XrdSecztn::isJWT
bool isJWT(const char *)
Definition XrdSecztn.cc:142