GHSA-45w3-v3g4-54pm: Chrono has potential segfault issue in SPIFFE authenticator

Several vulnerabilities have been reported in the time and chrono crates related to handling of calls to localtime_r. You can follow some of the discussions here and here, and the associated CVE here. In our case, the issue with the dependency was flagged by our nightly CI build running cargo-audit.

The vulnerability leads to a segfault in specific circumstances - namely, when one of a number of functions in the time crate is called while any other thread is setting an environment variable. Given that in the case of the Parsec service this affects the SPIFFE authenticator, Parsec service users can encounter the issue only when the JWT SVID authenticator is enabled and being used. We have not undergone any manual tracing to understand if the vulnerable methods are called anywhere in our stack, however it seems reasonable to expect that if that were to be the case, the issue would lie in JWT validation (i.e. when handling the dates found within a Json Web Token). JWT validation could thus fail, bringing down the thread in which the request happens. The rest of the threads continue to work. Since the threadpool implementation that we use continues replenishing the pool when one thread panics, the impact on the service should be minimal.