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[ink_base64] Fix buffer size computation #8736

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Merged
randall merged 2 commits into from
Mar 28, 2022
Merged

[ink_base64] Fix buffer size computation #8736

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2a9ba82
[ink_base64] Fix buffer size computation
moonchen Mar 1, 2022
3c23b04
Convert macro to an inline function
moonchen Mar 21, 2022
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15 changes: 13 additions & 2 deletions include/tscore/ink_base64.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,5 +42,16 @@ bool ats_base64_encode(const unsigned char *inBuffer, size_t inBufferSize, char
bool ats_base64_decode(const char *inBuffer, size_t inBufferSize, unsigned char *outBuffer, size_t outBufSize, size_t *length);

// Little helper functions to calculate minimum required output buffer for encoding/decoding.
#define ATS_BASE64_ENCODE_DSTLEN(_length) ((_length * 8) / 6 + 4)
#define ATS_BASE64_DECODE_DSTLEN(_length) (((_length + 3) / 4) * 3)
// These sizes include one byte for null termination, because ats_base64_encode and ats_base64_decode will always write a null
// terminator.
inline constexpr size_t
ats_base64_encode_dstlen(size_t length)
{
return ((length + 2) / 3) * 4 + 1;
}

inline constexpr size_t
ats_base64_decode_dstlen(size_t length)
{
return ((length + 3) / 4) * 3 + 1;
}
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@ywkaras ywkaras Mar 22, 2022

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Why not?

inline constexpr size_t
ats_base64_encode_dstlen(size_t length, bool pad = true)
{
  size_t num_bit_pairs = 4 * length;
  return (pad ? (((num_bit_pairs + 11) / 12) * 4) : ((num_bit_pairs + 2) / 3)) + 1;
}

inline constexpr size_t
ats_base64_unpadded_decode_dstlen(size_t length)
{
  return (((length / 4) * 3) + (length % 4)) + 1;
}

inline size_t
ats_base64_padded_decode_dstlen(char const *data, size_t length)
{
  ink_assert(!(length % 4));

  if (length && ('=' == data[length - 1])) {
    --length;
  }
  if (length && ('=' == data[length - 1])) {
    --length;
  }

  return ats_base64_unpadded_decode_dstlen(length);
}

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@moonchen moonchen Mar 23, 2022

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The length calculation is meant for ats_base64_encode(), so the goal is to just give the length of the buffer needed to store the encoded output. Both ats_base64_encode() and the RFC specify padding that is non-optional.

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@ywkaras ywkaras Mar 23, 2022

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Then why not?

inline size_t
ats_base64_decode_dstlen(char const *data, size_t length)
{
  ink_assert(!(length % 4));

  size_t adjust = 0;
  if (length && ('=' == data[length - 1])) {
    adjust = ('=' == data[length - 2])) ? 2 : 1;
  }
  return (((length / 4) * 3) - adjust + 1;
}

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@moonchen moonchen Mar 23, 2022

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If I'm reading this right, you're trying to give a buffer size that is as small as possible, accounting for the possibility of padding characters at the end. While I appreciate being frugal with allocation size, I think that the size savings of possibly one or two bytes may not warrant such an increase in complexity when computing the buffer size.

18 changes: 9 additions & 9 deletions plugins/experimental/access_control/unit_tests/test_utils.cc
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Expand Up @@ -36,19 +36,19 @@ TEST_CASE("Base64: estimate buffer size needed to encode a message", "[Base64][a

/* Test with a zero decoded message length */
encodedLen = cryptoBase64EncodedSize(0);
CHECK(4 == encodedLen);
CHECK(1 == encodedLen);

/* Test with a random non-zero decoded message length */
encodedLen = cryptoBase64EncodedSize(64);
CHECK(89 == encodedLen);

/* Test the space for padding. Size of encoding that would result in 2 x "=" padding */
encodedLen = cryptoBase64EncodedSize(strlen("176a1620e31b14782ba2b66de3edc5b3cb19630475b2ce2ee292d5fd0fe41c3abc"));
CHECK(92 == encodedLen);
CHECK(89 == encodedLen);

/* Test the space for padding. Size of encoding that would result in 1 x "=" padding */
encodedLen = cryptoBase64EncodedSize(strlen("176a1620e31b14782ba2b66de3edc5b3cb19630475b2ce2ee292d5fd0fe41c3ab"));
CHECK(90 == encodedLen);
CHECK(89 == encodedLen);

/* Test the space for padding. Size of encoding that would result in no padding */
encodedLen = cryptoBase64EncodedSize(strlen("176a1620e31b14782ba2b66de3edc5b3cb19630475b2ce2ee292d5fd0fe41c3a"));
Expand All @@ -63,27 +63,27 @@ TEST_CASE("Base64: estimate buffer size needed to decode a message", "[Base64][a
/* Padding with 2 x '=' */
encoded = "MTc2YTE2MjBlMzFiMTQ3ODJiYTJiNjZkZTNlZGM1YjNjYjE5NjMwNDc1YjJjZTJlZTI5MmQ1ZmQwZmU0MWMzYQ==";
encodedLen = cryptoBase64DecodeSize(encoded, strlen(encoded));
CHECK(66 == encodedLen);
CHECK(67 == encodedLen);

/* Padding with 1 x '=' */
encoded = "MTc2YTE2MjBlMzFiMTQ3ODJiYTJiNjZkZTNlZGM1YjNjYjE5NjMwNDc1YjJjZTJlZTI5MmQ1ZmQwZmU0MWMzYWI=";
encodedLen = cryptoBase64DecodeSize(encoded, strlen(encoded));
CHECK(66 == encodedLen);
CHECK(67 == encodedLen);

/* Padding with 0 x "=" */
encoded = "MTc2YTE2MjBlMzFiMTQ3ODJiYTJiNjZkZTNlZGM1YjNjYjE5NjMwNDc1YjJjZTJlZTI5MmQ1ZmQwZmU0MWMzYWJj";
encodedLen = cryptoBase64DecodeSize(encoded, strlen(encoded));
CHECK(66 == encodedLen);
CHECK(67 == encodedLen);

/* Test empty encoded message calculation */
encoded = "";
encodedLen = cryptoBase64DecodeSize(encoded, strlen(encoded));
CHECK(0 == encodedLen);
CHECK(1 == encodedLen);

/* Test empty encoded message calculation */
encoded = nullptr;
encodedLen = cryptoBase64DecodeSize(encoded, 0);
CHECK(0 == encodedLen);
CHECK(1 == encodedLen);
}

TEST_CASE("Base64: quick encode / decode", "[Base64][access_control][utility]")
Expand All @@ -103,7 +103,7 @@ TEST_CASE("Base64: quick encode / decode", "[Base64][access_control][utility]")
encodedMessageLen));

size_t decodedMessageEstimatedLen = cryptoBase64DecodeSize(encodedMessage, encodedMessageLen);
CHECK(66 == decodedMessageEstimatedLen);
CHECK(67 == decodedMessageEstimatedLen);
char decodedMessage[encodedMessageEstimatedLen];
size_t decodedMessageLen = cryptoBase64Decode(encodedMessage, encodedMessageLen, decodedMessage, encodedMessageLen);

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4 changes: 2 additions & 2 deletions plugins/experimental/access_control/utils.cc
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Expand Up @@ -296,7 +296,7 @@ cryptoMessageDigestEqual(const char *md1, size_t md1Len, const char *md2, size_t
size_t
cryptoBase64EncodedSize(size_t decodedSize)
{
return ATS_BASE64_ENCODE_DSTLEN(decodedSize);
return ats_base64_encode_dstlen(decodedSize);
}

/**
Expand All @@ -308,7 +308,7 @@ cryptoBase64EncodedSize(size_t decodedSize)
size_t
cryptoBase64DecodeSize(const char *encoded, size_t encodedLen)
{
return ATS_BASE64_DECODE_DSTLEN(encodedLen);
return ats_base64_decode_dstlen(encodedLen);
}

/**
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2 changes: 1 addition & 1 deletion plugins/experimental/metalink/metalink.cc
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Expand Up @@ -693,7 +693,7 @@ location_handler(TSCont contp, TSEvent event, void * /* edata ATS_UNUSED */)
const char *value;
int length;

char digest[33]; /* ATS_BASE64_DECODE_DSTLEN() */
char digest[33]; /* ats_base64_decode_dstlen() */

SendData *data = static_cast<SendData *>(TSContDataGet(contp));
TSContDestroy(contp);
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6 changes: 2 additions & 4 deletions src/tscore/ink_base64.cc
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Expand Up @@ -28,8 +28,6 @@
* authentication scheme does not require them. This implementation is
* intended for web-related use, and line breaks are not implemented.
*
* These routines return char*'s to malloc-ed strings. The caller is
* responsible for freeing the strings.
*/
#include "tscore/ink_platform.h"
#include "tscore/ink_base64.h"
Expand All @@ -44,7 +42,7 @@ ats_base64_encode(const unsigned char *inBuffer, size_t inBufferSize, char *outB
char *obuf = outBuffer;
char in_tail[4];

if (outBufSize < ATS_BASE64_ENCODE_DSTLEN(inBufferSize)) {
if (outBufSize < ats_base64_encode_dstlen(inBufferSize)) {
return false;
}

Expand Down Expand Up @@ -130,7 +128,7 @@ ats_base64_decode(const char *inBuffer, size_t inBufferSize, unsigned char *outB
int inputBytesDecoded = 0;

// Make sure there is sufficient space in the output buffer
if (outBufSize < ATS_BASE64_DECODE_DSTLEN(inBufferSize)) {
if (outBufSize < ats_base64_decode_dstlen(inBufferSize)) {
return false;
}

Expand Down