rpcserver: Support dynamic cert reload. #3153
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davecgh
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JoeGruffins
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| changed := fi.Size() != f.curSize || fi.ModTime() != f.curTime | ||
| if changed { | ||
| f.curSize = fi.Size() | ||
| f.curTime = fi.ModTime() | ||
| } |
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No big deal, but shouldn't the modified time be enough?
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Most of the time, yes, but it isn't always.
For example, it is quite common on some shared file systems to preserve the modification time when copying files. Another example is cp -p which various sync methods use.
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This modifies the RPC server to support dynamically reloading (aka hot reload) the RPC certificate/key pair as well as the client CAs (when configured with --authtype=clientcert). In other words, dcrd will now notice when the certificates have been changed on the file system on new connections and reload and cache the new ones. In terms of deciding when to reload the files, this implementation opts for a highly portable stat-based approach that does not require any additional dependencies over using platform specific file change notifications such as inotify on Linux. This implementation also aims to provide nice error handling semantics and includes additional logic to minimize the amount of disk accesses needed to determine with the files have changed. The following is an overview of the semantics: - All connections used a cached TLS config - Certs are only tested for changes and reloaded when: - A new connection is established - At least 5 seconds have passed since the last check - The file modification times and/or sizes have changed - The existing working certs are retained if any errors are encountered when loading the new ones in order to avoid breaking a working config - Only a single error will be shown for attempt at loading an invalid config as opposed to spamming the same error on every new connection
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This modifies the RPC server to support dynamically reloading (aka hot reload) the RPC certificate/key pair as well as the client CAs (when configured with
--authtype=clientcert).In other words, dcrd will now notice when the certificates have been changed on the file system on new connections and reload and cache the new ones.
In terms of deciding when to reload the files, this implementation opts for a highly portable stat-based approach that does not require any additional dependencies over using platform specific file change notifications such as
inotifyon Linux.This implementation also aims to provide nice error handling semantics and includes additional logic to minimize the amount of disk accesses needed to determine when the files have changed.
The following is an overview of the semantics: