| commit | fee8709f691f7a35070a76cb38b7dca6116e7687 | [log] [tgz] |
|---|---|---|
| author | Brian Smith <brian@briansmith.org> | Wed May 16 17:24:20 2018 -1000 |
| committer | CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> | Mon May 21 19:43:05 2018 +0000 |
| tree | 7ea5055249b82bcbecd03564c5434e86663c76b1 | |
| parent | 63e2a081231715573d17a35c737e292553d668d7 [diff] |
Replace |alloca| in |BN_mod_exp_mont_consttime|. |alloca| is dangerous and poorly specified, according to any description of |alloca|. It's also hard for some analysis tools to reason about. The code here assumed |alloca| is a macro, which isn't a valid assumption. Depending on what which headers are included and what toolchain is being used, |alloca| may or may not be defined as a macro, and this might change over time if/when toolchains are updated. Or, we might be doing static analysis and/or dynamic analysis with a different configuration w.r.t. the availability of |alloca| than production builds use. Regardless, the |alloca| code path only kicked in when the inputs are 840 bits or smaller. Since the multi-prime RSA support was removed, for interesting RSA key sizes the input will be at least 1024 bits and this code path won't be triggered since powerbufLen will be larger than 3072 bytes in those cases. ECC inversion via Fermat's Little Theorem has its own constant-time exponentiation so there are no cases where smaller inputs need to be fast. The RSAZ code avoids the |OPENSSL_malloc| for 2048-bit RSA keys. Increasingly the RSAZ code won't be used though, since it will be skipped over on Broadwell+ CPUs. Generalize the RSAZ stack allocation to work for non-RSAZ code paths. In order to ensure this doesn't cause too much stack usage on platforms where RSAZ wasn't already being used, only do so on x86-64, which already has this large stack size requirement due to RSAZ. This change will make it easier to refactor |BN_mod_exp_mont_consttime| to do that more safely and in a way that's more compatible with various analysis tools. This is also a step towards eliminating the |uintptr_t|-based alignment hack. Since this change increases the number of times |OPENSSL_free| is skipped, I've added an explicit |OPENSSL_cleanse| to ensure the zeroization is done. This should be done regardless of the other changes here. Change-Id: I8a161ce2720a26127e85fff7513f394883e50b2e Reviewed-on: https://boringssl-review.googlesource.com/28584 Commit-Queue: David Benjamin <davidben@google.com> CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> Reviewed-by: David Benjamin <davidben@google.com>
BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.
Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.
Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.
BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.
Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.
There are other files in this directory which might be helpful: