|author||David Benjamin <firstname.lastname@example.org>||Wed Nov 17 14:01:11 2021 -0500|
|committer||Adam Langley <email@example.com>||Thu Nov 18 20:48:43 2021 +0000|
Add various OpenSSL compatibility functions. The non-_ex EVP_CIPHER_CTX Final functions are a bit interesting. Unlike EVP_DigestFinal(_ex), where the non-_ex version calls EVP_MD_CTX_cleanup for you, the EVP_CIPHER_CTX ones do not automatically cleanup. EVP_CipherFinal and EVP_CipherFinal_ex are identical in all releases where they exist. This appears to date to OpenSSL 0.9.7: Prior to OpenSSL 0.9.7, EVP_MD_CTX and EVP_CIPHER_CTX did not use void* data fields. Instead, they just had a union of context structures for every algorithm OpenSSL implemented. EVP_MD_CTX was truly cleanup-less. There were no EVP_MD_CTX_init or EVP_MD_CTX_cleanup functions at all. EVP_DigestInit filled things in without reference to the previous state. EVP_DigestFinal didn't cleanup because there was nothing to cleanup. EVP_CIPHER_CTX was also a union, but for some reason did include EVP_CIPHER_CTX_init and EVP_CIPHER_CTX_cleanup. EVP_CIPHER_CTX_init seemed to be optional: EVP_CipherInit with non-NULL EVP_CIPHER similarly didn't reference the previous state. EVP_CipherFinal did not call EVP_CIPHER_CTX_cleanup, but EVP_CIPHER_CTX_cleanup didn't do anything. It called an optional cleanup hook on the EVP_CIPHER, but as far as I can tell, no EVP_CIPHER implemented it. Then OpenSSL 0.9.7 introduced ENGINE. The union didn't work anymore, so EVP_MD_CTX and EVP_CIPHER_CTX contained void* with allocated type-specific data. The introduced EVP_MD_CTX_init and EVP_MD_CTX_cleanup. For (imperfect!) backwards compatibility, EVP_DigestInit and EVP_DigestFinal transparently called init/cleanup for you. EVP_DigestInit_ex and EVP_DigestFinal_ex became the more flexible versions that left init/cleanup to the caller. EVP_CIPHER_CTX got the same treatment with EVP_CipherInit/EVP_CipherInit_ex, but *not* EVP_CipherFinal/EVP_CipherFinal_ex. The latter did the same thing. The history seems to be that 581f1c84940d77451c2592e9fa470893f6c3c3eb introduced the Final/Final_ex split, with the former doing an auto-cleanup, then 544a2aea4ba1fad76f0802fb70d92a5a8e6ad85a undid it. Looks like the motivation is that EVP_CIPHER_CTX objects are often reused to do multiple operations with a single key. But they missed that the split functions are now unnecessary. Amusingly, OpenSSL's documentation incorrectly said that EVP_CipherFinal cleaned up after the call until it was fixed in 538860a3ce0b9fd142a7f1a62e597cccb74475d3. The fix says that some releases cleaned up, but there were, as far as I can tell, no actual releases with that behavior. I've put the new Final functions in the deprecated section, purely because there is no sense in recommending two different versions of the same function to users, and Final_ex seems to be more popular. But there isn't actually anything wrong with plain Final. Change-Id: Ic2bfda48fdcf30f292141add8c5f745348036852 Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/50485 Reviewed-by: Adam Langley <firstname.lastname@example.org>
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: