* lisp/erc/erc-backend.el (erc-session-password): Add comment
explaining type is now string, nil, or function.
* lisp/erc/erc-compat.el (erc-compat--29-auth-source-pass-search):
Use obfuscation from auth-source function when available.
* lisp/erc/erc-sasl.el (erc-sasl--read-password,
erc-server-AUTHENTICATE): Use `erc--unfun'.
* lisp/erc/erc-services.el (erc-nickserv-get-password,
erc-nickserv-send-identify): Use `erc--unfun'.
* lisp/erc/erc.el (erc--unfun): New function for unwrapping a
password couched in a getter.
(erc--debug-irc-protocol-mask-secrets): Add variable to indicate
whether to mask passwords in debug logs.
(erc--mask-secrets): New function to swap masked secret with question
marks in debug logs.
(erc-log-irc-protocol): Conditionally mask secrets when
`erc--debug-irc-protocol-mask-secrets' is non-nil.
(erc--auth-source-search): Don't unwrap secret from function before
returning.
(erc-server-join-channel, erc-login): Use `erc--unfun'.
* test/lisp/erc/erc-services-tests.el
(erc-services-tests--wrap-search): Add helper for `erc--unfun'.
(erc-services-tests--auth-source-standard,
erc-services-tests--auth-source-announced,
erc-services-tests--auth-source-overrides, erc-nickserv-get-password):
Use `erc--unfun'.
* test/lisp/erc/erc-tests.el (erc--debug-irc-protocol-mask-secrets):
Add test for masking secrets with `erc--unfun' and friends.
* doc/misc/erc.texi: Add SASL section in Advanced Usage chapter to
document the new SASL module.
* etc/ERC-NEWS: Mention addition of erc-sasl module for SASL support.
* lisp/erc/erc-compat.el
(erc-compat--29-sasl-scram-construct-gs2-header,
erc-compat--29-sasl-scram-client-first-message,
erc-compat--29-sasl-scram--client-final-message): Fix encoding bug and
add minimal authorization support with copies of SASL functions
introduced in Emacs 29.
* lisp/erc/erc.el (erc-modules): Add `sasl'.
* lisp/erc/erc-sasl.el: New file (bug#29108).
* test/lisp/erc/erc-sasl-tests.el: New file.
* test/lisp/erc/erc-scenarios-sasl.el: New file.
* test/lisp/erc/resources/sasl/plain-failed.eld: New file.
* test/lisp/erc/resources/sasl/plain.eld: New file.
* test/lisp/erc/resources/sasl/scram-sha-1.eld: New file.
* test/lisp/erc/resources/sasl/scram-sha-256.eld: New file.
* test/lisp/erc/resources/sasl/external.eld: New file.
