SIGSEGV from EVP_MAC_CTX_get_mac_size()

Hal Murray <halmurray+openssl@xxxxxxxxx> · Mon, 27 Nov 2023 15:25:17 -0800

I have a fresh ctx using cmac with AES-128-CBC all ready to go.
No key yet.

If I call EVP_MAC_CTX_get_mac_size(), I get a SIGSEGV.
If I call EVP_MAC_init() with a key first, it works.

Is this a bug?  Is there a setup step I've missed?

This is from OpenSSL 3.1.1 on Fedora:
#0  0x00007ffff7b88d14 in EVP_CIPHER_get_block_size ()
   from /lib64/libcrypto.so.3
#1  0x00007ffff7c8066f in cmac_get_ctx_params.lto_priv ()
   from /lib64/libcrypto.so.3
#2  0x00007ffff7b96b24 in get_size_t_ctx_param () from /lib64/libcrypto.so.3
#3  0x0000000000401441 in main ()

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