From eb6f0000a4b752803ff7431d24d1a0a535a4387e Mon Sep 17 00:00:00 2001 From: Kazuki Yamaguchi Date: Mon, 5 Feb 2024 21:54:32 +0900 Subject: [ruby/openssl] cipher: fix buffer overflow in Cipher#update 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 https://github.com/ruby/openssl/commit/3035559f54 --- ext/openssl/ossl_cipher.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) (limited to 'ext/openssl/ossl_cipher.c') diff --git a/ext/openssl/ossl_cipher.c b/ext/openssl/ossl_cipher.c index 1910a5cdee..6f74c925c0 100644 --- a/ext/openssl/ossl_cipher.c +++ b/ext/openssl/ossl_cipher.c @@ -386,11 +386,23 @@ ossl_cipher_update(int argc, VALUE *argv, VALUE self) in = (unsigned char *)RSTRING_PTR(data); in_len = RSTRING_LEN(data); GetCipher(self, ctx); - out_len = in_len+EVP_CIPHER_CTX_block_size(ctx); - if (out_len <= 0) { + + /* + * As of OpenSSL 3.2, there is no reliable way to determine the required + * output buffer size for arbitrary cipher modes. + * https://github.com/openssl/openssl/issues/22628 + * + * in_len+block_size is usually sufficient, but AES key wrap with padding + * ciphers require in_len+15 even though they have a block size of 8 bytes. + * + * Using EVP_MAX_BLOCK_LENGTH (32) as a safe upper bound for ciphers + * currently implemented in OpenSSL, but this can change in the future. + */ + if (in_len > LONG_MAX - EVP_MAX_BLOCK_LENGTH) { ossl_raise(rb_eRangeError, "data too big to make output buffer: %ld bytes", in_len); } + out_len = in_len + EVP_MAX_BLOCK_LENGTH; if (NIL_P(str)) { str = rb_str_new(0, out_len); @@ -401,7 +413,7 @@ ossl_cipher_update(int argc, VALUE *argv, VALUE self) if (!ossl_cipher_update_long(ctx, (unsigned char *)RSTRING_PTR(str), &out_len, in, in_len)) ossl_raise(eCipherError, NULL); - assert(out_len < RSTRING_LEN(str)); + assert(out_len <= RSTRING_LEN(str)); rb_str_set_len(str, out_len); return str; -- cgit v1.2.3