diff options
author | Kazuki Yamaguchi <k@rhe.jp> | 2024-02-05 21:54:32 +0900 |
---|---|---|
committer | Kazuki Yamaguchi <k@rhe.jp> | 2024-05-01 01:30:44 +0900 |
commit | 3035559f54eaa42347b9fe2d91bd25a7b0563a44 (patch) | |
tree | de345db930954237de624a18e381a5c5b8a56172 /ext/openssl | |
parent | 3bdde7d88dc12f8e25d42c100d4f5717b1e8853c (diff) | |
download | ruby-openssl-3035559f54eaa42347b9fe2d91bd25a7b0563a44.tar.gz |
cipher: fix buffer overflow in Cipher#updateky/cipher-update-fix-buffer-size
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
Diffstat (limited to 'ext/openssl')
-rw-r--r-- | ext/openssl/ossl_cipher.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/ext/openssl/ossl_cipher.c b/ext/openssl/ossl_cipher.c index d9c78914..e5d0f5be 100644 --- a/ext/openssl/ossl_cipher.c +++ b/ext/openssl/ossl_cipher.c @@ -387,11 +387,23 @@ ossl_cipher_update(int argc, VALUE *argv, VALUE self) if ((in_len = RSTRING_LEN(data)) == 0) ossl_raise(rb_eArgError, "data must not be empty"); 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); @@ -402,7 +414,7 @@ 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; |