Files
scylladb/utils
Nadav Har'El ff91027eac utils, alternator: fix detection of invalid base-64
This patch fixes an error-path bug in the base-64 decoding code in
utils/base64.cc, which among other things is used in Alternator to decode
blobs in JSON requests.

The base-64 decoding code has a lookup table, which was wrongly sized 255
bytes, but needed to be 256 bytes. This meant that if the byte 255 (0xFF)
was included in an invalid base-64 string, instead of detecting that this
is an invalid byte (since the only valid bytes in a base-64 string are
A-Z,a-z,0-9,+,/ and =), the code would either think it's valid with a
nonsense 6-bit part, or even crash on an out-of-bounds read.

Besides the trivial fix, this patch also includes a reproducing test,
which tries to write a blob as a supposedly base-64 encoded string with
a 0xFF byte in it. The test fails before this patch (the write succeeds,
unexpectedly), and passes after this patch (the write fails as
expected). The test also passes on DynamoDB.

Fixes #25701

Signed-off-by: Nadav Har'El <nyh@scylladb.com>

Closes scylladb/scylladb#25705
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