openssl: avoid resetting the HMAC key on every packet - #1088
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dormancygrace wants to merge 1 commit into
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openssl: avoid resetting the HMAC key on every packet#1088dormancygrace wants to merge 1 commit into
dormancygrace wants to merge 1 commit into
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OpenSSL 3.0.3 and newer can reinitialize an EVP_MAC HMAC context with its existing key when EVP_MAC_init is called without parameters. Use that path instead of supplying the digest and key again on every OpenVPN HMAC reset. Retain the old parameter-based reset for OpenSSL 3.0.0 through 3.0.2, where parameterless EVP_MAC reinitialization did not reset the underlying HMAC implementation.
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Summary
Rationale
OpenVPN currently supplies the saved digest and key parameters on every
hmac_ctx_reset(). The OpenSSL provider consequently reinstalls the same key and rebuilds the HMAC inner and outer digest states for every packet.OpenSSL PR #18100, included since 3.0.3, fixed parameterless
EVP_MAC_init()reinitialization with an existing key. Using that path avoids the repeated setup without changing the key or output.Validation
The existing
crypto_test_hmac()also exercises context reset and verifies that changing the original key buffer after initialization does not change the result.