cipher: fix buffer overflow in Cipher#update #717
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OpenSSL::Cipher#update currently allocates the output buffer with size
(input data length)+(the block size of the cipher). This is insufficient
for the id-aes{128,192,256}-wrap-pad (AES keywrap with padding) ciphers.
They have a block size of 8 bytes, but the output may be up to 15 bytes
larger than the input.
Use (input data length)+EVP_MAX_BLOCK_LENGTH (== 32) as the output
buffer size, instead. OpenSSL doesn't provide a generic way to tell the
maximum required buffer size for ciphers, but this is large enough for
all algorithms implemented in current versions of OpenSSL.
Fixes: https://bugs.ruby-lang.org/issues/20236
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OpenSSL::Cipher#update currently allocates the output buffer with size (input data length)+(the block size of the cipher). This is insufficient for the id-aes{128,192,256}-wrap-pad (AES keywrap with padding) ciphers. They have a block size of 8 bytes, but the output may be 15 bytes larger than the input.
Use (input data length)+EVP_MAX_BLOCK_LENGTH (== 32) as the output buffer size, instead. OpenSSL doesn't provide a way to tell the maximum required buffer size for arbitrary ciphers, but this is large enough for all algorithms implemented in current versions of OpenSSL.
Fixes: https://bugs.ruby-lang.org/issues/20236