[10.2.x] backport #13210: fix out-of-bounds read in ats_base64_decode#13244
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dkgkdfg65 wants to merge 1 commit into
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[10.2.x] backport #13210: fix out-of-bounds read in ats_base64_decode#13244dkgkdfg65 wants to merge 1 commit into
dkgkdfg65 wants to merge 1 commit into
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When the base64 alphabet prefix length was not a multiple of four, the decode loop ran one iteration past the prefix, reading input bytes out of bounds and then reading inBuffer[-2] in the trailing adjustment. Found with AddressSanitizer. Decode only complete 4-character groups and handle a 2- or 3-character tail explicitly, dropping a lone trailing character. Decoded length and bytes are unchanged for every well-defined input; only the out-of-bounds reads are removed. Add unit_tests/test_ink_base64.cc covering both alphabets, round-trips, in-place decode, undersized buffers, and truncation. Inputs sit in exact-size heap buffers so ASan faults on the old decoder and passes after the fix. (cherry picked from commit 1e1dd1a)
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10.2.x is missing the base64-decode bounds fix that's on master (#13210). On 10.2.x ats_base64_decode walks the input in 4-char groups but doesn't guard the tail when the length isn't a multiple of 4, so a crafted non-aligned base64 string reads past the input buffer.
checked it actually over-reads on 10.2.x (not just a missing line): built ats_base64_decode with -fsanitize=address on ubuntu:22.04 and fed a non-4-multiple input. pre-fix ASan reports a heap-buffer-overflow READ just past the buffer and aborts; with the master fix cherry-picked it decodes cleanly. the upstream unit test (test_ink_base64.cc) comes along in the cherry-pick.
clean cherry-pick (-x), original author (Phong Nguyen) preserved. happy to rebase if you'd prefer.
upstream: 1e1dd1a