Fix off-by-1 bug on provider_activate with custom error strings #11427
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added 2 commits
March 27, 2020 19:53
This test currently fails, next commit has the description of the bug and the fix.
Starting `cnt` from 1 would work if we weren't using cnt itself to access elements of the array returned calling the provider callback. As it is before this commit, we have 2 problems: - first, in the unlikely case that the incoming array was "empty" (only contains the terminator item) we would skip past it and potentially end up with oob reads; - otherwise, at the end of the while loop, `cnt` will be equal to the number of items in the input array, not 1 more. We then add 1 more to the zalloc call to account for the library name item, and we fill all of it (relying on zalloc to have zeroed the terminator item). The first read access that will read the list up to the terminator will result in a OOB read as we did not allocate enough space to also contain the terminator.
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Ping to @p-steuer that brought this item to my attention while working on testing with external providers! @levitte @paulidale I believe one of you might want to review this! |
mattcaswell
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Mar 27, 2020
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levitte
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openssl-machine
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Mar 30, 2020
This test currently fails, next commit has the description of the bug and the fix. Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from #11427)
openssl-machine
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Mar 30, 2020
Starting `cnt` from 1 would work if we weren't using cnt itself to access elements of the array returned calling the provider callback. As it is before this commit, we have 2 problems: - first, in the unlikely case that the incoming array was "empty" (only contains the terminator item) we would skip past it and potentially end up with oob reads; - otherwise, at the end of the while loop, `cnt` will be equal to the number of items in the input array, not 1 more. We then add 1 more to the zalloc call to account for the library name item, and we fill all of it (relying on zalloc to have zeroed the terminator item). The first read access that will read the list up to the terminator will result in a OOB read as we did not allocate enough space to also contain the terminator. Reviewed-by: Richard Levitte <levitte@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from #11427)
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Starting
cntfrom 1 would work if we weren't using cnt itself to access elements of the array returned calling the provider callback.As it is before this commit, we have 2 problems:
cntwill be equal to the number of items in the input array, not 1 more. We then add 1 more to the zalloc call to account for the library name item, and we fill all of it (relying on zalloc to have zeroed the terminator item).The first read access that will read the list up to the terminator will result in a OOB read as we did not allocate enough space to also contain the terminator.
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