Remove PQC-based buffer size increase for PreMasterSecret #9610
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The size of the PreMasterSecret buffer is based on the ENCRYPT_LEN constant, which has been increased to 5kB for PQC support (Dilithium and Falcon, as their signatures are that large). However, only in the TLS 1.2 case, the PreMasterSecret buffer is used to store signatures. In the TLS 1.3 path, only actual symmetric secrets are stored in that buffer, which are much smaller in size (the "old" size of the constant without the PQC increase). As PQC is only allowed in TLS 1.3 and NOT in TLS 1.2, we can revert that size increase, saving around 4,5kB of dynamic memory during the handshake.
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Can one of the admins verify this patch? |
Contributor
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Okay to test |
Contributor
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Jenkins retest this please. |
1 similar comment
Contributor
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Jenkins retest this please. |
dgarske
approved these changes
Jan 8, 2026
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The size of the PreMasterSecret buffer is based on the
ENCRYPT_LENconstant, which has been increased to 5kB for PQC support (Dilithium and Falcon, as their signatures are that large).However, only in the TLS 1.2 case, the PreMasterSecret buffer is used to store signatures. In the TLS 1.3 path, only actual symmetric secrets are stored in that buffer, which are much smaller (the "old" size of the constant without the PQC increase).
As PQC is only allowed in TLS 1.3 and NOT in TLS 1.2, we can revert that size increase, saving around 4,5kB of dynamic memory during the handshake.