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Fix CBOR tag handling in cbor_tag_handler_t::store for non-binary items (#5559)

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When using cbor_tag_handler_t::store, tags 0xD8-0xDB previously assumed
that the tagged item was a byte string, unconditionally attempting to
parse binary data and failing on valid CBOR documents containing tags
applied to integers, strings, arrays, or objects (such as self-describe
tag 55799).

Check whether the tagged data item is a byte string (0x40-0x5B or 0x5F).
If it is a byte string, store the subtype on the binary value as before.
Otherwise, iteratively process the tagged value in the driver loop using
item_read so that chained tags do not consume native stack space.

Part of #5316.

Signed-off-by: ReturnKartikey <kartikeynegi2000.work@gmail.com>
This commit is contained in:
Kartikey Negi
2026-09-27 17:58:55 +05:30
committed by GitHub
parent 98e00d22e5
commit 6bd106893a
5 changed files with 127 additions and 12 deletions
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25
include/nlohmann/detail/input/binary_reader.hpp
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@@ -44,7 +44,7 @@ enum class cbor_tag_handler_t
{
error, ///< throw a parse_error exception in case of a tag
ignore, ///< ignore tags
store ///< store tags as binary type
store ///< store tagged byte strings (for bytes 0xd8..0xdb) as binary values with the tag as subtype; other tagged values are read as if the tag were ignored
};
/*!
@@ -592,14 +592,18 @@ class binary_reader
input (true) or whether the last read character should
be considered instead (false)
@param[in] tag_handler how CBOR tags should be treated
@param[out] tag_pending whether a tag was parsed and its value follows
@param[out] item_read whether the tagged value's initial byte is already in current
@return whether a valid CBOR value was passed to the SAX parser
*/
bool parse_cbor_value(const bool get_char,
const cbor_tag_handler_t tag_handler,
bool& tag_pending)
bool& tag_pending,
bool& item_read)
{
tag_pending = false;
item_read = false;
switch (get_char ? get() : current)
{
@@ -1021,7 +1025,17 @@ class binary_reader
}
}
get();
return get_cbor_binary(b) && sax->binary(b);
// a byte string (the heads accepted by get_cbor_binary) keeps the tag as subtype
if ((current >= 0x40 && current <= 0x5B) || current == 0x5F)
{
return get_cbor_binary(b) && sax->binary(b);
}
// not a byte string: the tagged value, whose first byte
// was just read, is read by the caller like for ignore
tag_pending = true;
item_read = true;
return true;
}
default: // LCOV_EXCL_LINE
@@ -1503,13 +1517,14 @@ class binary_reader
// a tag is not a value of its own: read on until the tagged value
bool tag_pending = false;
bool item_read = false;
do
{
if (JSON_HEDLEY_UNLIKELY(!parse_cbor_value(fetch, tag_handler, tag_pending)))
if (JSON_HEDLEY_UNLIKELY(!parse_cbor_value(fetch, tag_handler, tag_pending, item_read)))
{
return false;
}
fetch = true;
fetch = !item_read;
}
while (tag_pending);