big_mod_exp syscall: exclude inputs of numbers larger than 4096-bits #32520
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Codecov Report
@@ Coverage Diff @@
## master #32520 +/- ##
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Coverage 82.0% 82.0%
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Files 779 779
Lines 210609 210649 +40
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+ Hits 172742 172848 +106
+ Misses 37867 37801 -66 |
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…32520) * limit inputs length * fix clippy * add test_syscall_big_mod_exp test * cargo fmt * add SBPFVersion --------- Co-authored-by: valiksinev <[email protected]> Co-authored-by: derrek <[email protected]> (cherry picked from commit 5d9c1d8)
mvines
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…6-bits (backport of #32520) (#32526) big_mod_exp syscall: exclude inputs of numbers larger than 4096-bits (#32520) * limit inputs length * fix clippy * add test_syscall_big_mod_exp test * cargo fmt * add SBPFVersion --------- Co-authored-by: valiksinev <[email protected]> Co-authored-by: derrek <[email protected]> (cherry picked from commit 5d9c1d8) Co-authored-by: samkim-crypto <[email protected]>
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Problem
The changes related to Big integer modular exponentiation (EIP-198). The calculation is implemented as syscall.
The formula that was used to approximate the compute budgets for large number exponentiation seems to under-approximate the costs for exponentiation of very large numbers (i.e. >>1000 byte numbers). This could lead to a negative impact on the network if the syscall was to be invoked with very large numbers.
In practice, it seems like any normal/non-adversarial use of the syscall will be on numbers of size less than or equal to 4096-bits (i.e. for RSA-4096)
Summary of Changes
Inside syscall all inputs are limited by value 4069 bits (512 bytes).
If the length is exceeded, an error SyscallError::InvalidLength returned.
This is a combination of the fixes by @valiksinev and the tests by @derrekr and subsumes #31859.
Fixes #