When the SAX parser asks to recover, the binary readers now repair an
item whose end is known and read on after it, as RFC 8949, Section 5.3
describes for CBOR:
- CBOR: tags are ignored, and simple values other than false, true, and
null become null (RFC 8949, Section 6.1); a negative integer below the
range of number_integer_t becomes the nearest floating-point number.
- Strings that are not valid UTF-8 get U+FFFD for each ill-formed
sequence, as in JSON text; so does a UBJSON/BJData char above 0x7F.
- UBJSON/BJData high-precision numbers keep their longest valid
beginning (via the lexer's recover_token()), or become infinity.
- Members whose key is not a string are skipped (CBOR, MessagePack,
BON8), like members without a key in JSON text.
- BSON elements of types the library does not read (ObjectId, datetime,
decimal128, ...) become null; a string without its terminator and a
document whose size does not match are kept.
Where the end of an item is unknown, reading stops as before, except
that BSON skips to the end of the document, whose size it knows.
The value read before such an error is now completed by the reader from
its container stack, as the JSON parser does, instead of by a proxy SAX
parser, which is removed. Like the parser, binary_reader gets an
AllowRecovery template parameter, so that from_*() compile without the
new code.
Tests: a table of repairs, numbers out of range, errors that stop, and
a sweep over changed and removed bytes of eight encodings that checks
balanced events and that the first error is the one from_*() reports.
All fuzzers now run a recovering checker; the binary ones also check
that it reports an error exactly when from_*() fails.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🐛 fix BSON conformance issue
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🐛 fix BSON conformance issue
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* 🐛 reject ill-formed UTF-8 in CBOR/MessagePack/BSON text strings at decode time (#5531)
from_cbor()/from_msgpack()/from_bson() copied the raw bytes of a decoded
text string into the resulting json value without any UTF-8 validation,
even though RFC 8949 §3.1 (CBOR) and the MessagePack/BSON specifications
all require text strings to be valid UTF-8. Malformed input only failed
later, if the value was dump()'d, with a type_error.316 - so the
allow_exceptions=false pattern used specifically to get a discarded
sentinel instead of an exception did not discard this category of
malformed input, unlike every other kind of malformed binary input this
library rejects at decode time (see #5529).
Fix this at the single choke point shared by BSON/CBOR/MessagePack/UBJSON
string reads, binary_reader::get_string(): validate the bytes with the
UTF-8 DFA right after they are read, and report failures the same way as
every other binary_reader error (parse_error.113), so allow_exceptions
and strict discarding behave consistently. get_binary()/binary blob reads
are untouched and still accept arbitrary bytes, since only text strings
are required to be UTF-8.
There were two independent implementations of a UTF-8 validator: the
lexer's streaming scanner, and the serializer's Hoehrmann DFA used by
dump_escaped_impl(). Rather than write a third, the serializer's decode()
function, its utf8d table and the UTF8_ACCEPT/UTF8_REJECT constants are
extracted into detail/string_utils.hpp (a low-level header already
included before both detail/input/ and detail/output/), alongside a new
is_valid_utf8() helper built on the same decode() step. serializer.hpp's
dump_escaped_impl() now calls the shared decode(), so there is exactly
one UTF-8 validator in the codebase; dump()'s exact type_error.316
messages and byte-index reporting are unchanged (see the added
regression-guard test in unit-serialization.cpp).
Claude-Session: https://claude.ai/code/session_01N4RQ1Ahan5YAGbnAQGjZTY
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
* ⚡ validate only newly read bytes of binary-format strings
get_string() validated the whole result after each call, but get_bytes()
appends to it and CBOR indefinite-length strings collect all chunks in
the same result, so every chunk re-validated everything read before it.
An input of many small chunks took quadratic time (80000 one-byte chunks,
160 KB of input, took about 7 seconds). Only the newly read bytes are
validated now, which also matches RFC 8949's requirement that every
chunk is valid UTF-8 on its own.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
Niels Lohmann
