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Check HPACK Huffman code strictly #2172

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Merged
maskit merged 2 commits into from
Jun 26, 2017
Merged

Check HPACK Huffman code strictly #2172

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ea9efb1
Check padding length of Huffman code strictly
maskit Jun 21, 2017
b228c13
Check padding bits of Huffman code strictly
maskit Jun 21, 2017
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2 changes: 1 addition & 1 deletion proxy/http2/HPACK.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -708,7 +708,7 @@ decode_string(Arena &arena, char **str, uint32_t &str_length, const uint8_t *buf
*str = arena.str_alloc(encoded_string_len * 2);

len = huffman_decode(*str, p, encoded_string_len);
if (len == HPACK_ERROR_COMPRESSION_ERROR) {
if (len < 0) {
return HPACK_ERROR_COMPRESSION_ERROR;
}
str_length = len;
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25 changes: 20 additions & 5 deletions proxy/http2/HuffmanCodec.cc
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Expand Up @@ -151,29 +151,44 @@ hpack_huffman_fin()
int64_t
huffman_decode(char *dst_start, const uint8_t *src, uint32_t src_len)
{
char *dst_end = dst_start;
uint8_t shift = 7;
Node *current = HUFFMAN_TREE_ROOT;
char *dst_end = dst_start;
uint8_t shift = 7;
Node *current = HUFFMAN_TREE_ROOT;
int byte_boundary_crossed = 0;
bool includes_zero = false;

while (src_len) {
if (*src & (1 << shift)) {
current = current->right;
} else {
current = current->left;
current = current->left;
includes_zero = true;
}

if (current->leaf_node == true) {
*dst_end = current->ascii_code;
++dst_end;
current = HUFFMAN_TREE_ROOT;
current = HUFFMAN_TREE_ROOT;
byte_boundary_crossed = 0;
includes_zero = false;
}
if (shift) {
--shift;
} else {
shift = 7;
++src;
--src_len;
++byte_boundary_crossed;
}
if (byte_boundary_crossed > 3) {
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@masaori335 masaori335 Jun 21, 2017

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This is checking length of encoded data, right? It looks like some Huffman code has 3 byte boundaries. Is this should be 4? ( e.g. |11111111|11111111|11111110|0010 fffffe2 [28])

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@masaori335 masaori335 Jun 21, 2017

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Never mind, I thought >= 3 :p

return -1;
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@masaori335 masaori335 Jun 21, 2017

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Why not use HPACK_ERROR_COMPRESSION_ERROR?

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@maskit maskit Jun 21, 2017

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Because that's in HPACK.h, so we shouldn't use it here.

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@masaori335 masaori335 Jun 21, 2017

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Ah, here is HuffmanCodec. Got it.

}
}
if (byte_boundary_crossed > 1) {
return -1;
}
if (includes_zero) {
return -1;
}

return dst_end - dst_start;
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