2139145b72
The drbg's lock must be held across calls to RAND_DRBG_generate() to prevent simultaneous modification of internal state. This was observed in practice with simultaneous SSL_new() calls attempting to seed the (separate) per-SSL RAND_DRBG instances from the global rand_drbg instance; this eventually led to simultaneous calls to ctr_BCC_update() attempting to increment drbg->bltmp_pos for their respective partial final block, violating the invariant that bltmp_pos < 16. The AES operations performed in ctr_BCC_blocks() makes the race window quite easy to trigger. A value of bltmp_pos greater than 16 induces catastrophic failure in ctr_BCC_final(), with subtraction overflowing and leading to an attempt to memset() to zero a very large range, which eventually reaches an unmapped page and segfaults. Provide the needed locking in get_entropy_from_parent(), as well as fixing a similar issue in RAND_priv_bytes(). There is also an unlocked call to RAND_DRBG_generate() in ssl_randbytes(), but the requisite serialization is already guaranteed by the requirements on the application's usage of SSL objects, and no further locking is needed for correct behavior. In that case, leave a comment noting the apparent discrepancy and the reason for its safety (at present). Reviewed-by: Paul Dale <paul.dale@oracle.com> Reviewed-by: Kurt Roeckx <kurt@roeckx.be> Reviewed-by: Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/4328) |
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| .. | ||
| build.info | ||
| drbg_lib.c | ||
| drbg_rand.c | ||
| rand_egd.c | ||
| rand_err.c | ||
| rand_lcl.h | ||
| rand_lib.c | ||
| rand_unix.c | ||
| rand_vms.c | ||
| rand_win.c | ||
| randfile.c | ||