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ENT-14407: Replaced ssh-keyscan with reading host keys in federation setup status #3237

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ENT-14407: Replaced ssh-keyscan with reading host keys in federation setup status #3237

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48 changes: 35 additions & 13 deletions cfe_internal/enterprise/federation/federation.cf
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Original file line number Diff line number Diff line change
Expand Up @@ -1187,17 +1187,38 @@ bundle agent setup_status
"$(cfengine_enterprise_federation:transport_user.ssh_pub_key)"
);

"ssh_server_fingerprint"
# ssh-keyscan is used because it's more reliable/easy than trying to
# parse sshd config to find the file and then readfile():
string => execresult(
"ssh-keyscan localhost 2>/dev/null | sed 's/localhost //g' | sort",
useshell
# Read the host keys sshd uses from disk instead of ssh-keyscan localhost.
# OpenSSH 9.8+ PerSourcePenalties penalise repeated unauthenticated
# connections, so ssh-keyscan starts returning nothing.
Comment on lines +1190 to +1192

@craigcomstock craigcomstock Nov 9, 2026

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I don't know that this comment really belongs in the code. It is already in the commit comment.

"_sshd_config"
slist => string_split(
execresult("/usr/sbin/sshd -T", "noshell"), "$(const.n)", "inf"
);

"_hostkey_paths"
slist => maplist(
regex_replace($(this), "^hostkey\s+", "", ""),
grep("hostkey\s+.+", _sshd_config)
);

# Keep "<type> <key>" and drop the trailing comment
"_host_public_key[$(_hostkey_paths)]"
string => regex_replace(
readfile("$(_hostkey_paths).pub"), "^(\S+\s+\S+).*", "$1", "s"
),
if => fileexists("$(_hostkey_paths).pub");

"_host_public_keys" slist => sort(getvalues(_host_public_key), "lex");

# Same format as ssh-keyscan output: "<type> <key>" per line, sorted
"ssh_server_fingerprint" string => join("$(const.n)", _host_public_keys);

classes:
"ssh_server_fingerprint_collected"
expression => not(strcmp("$(ssh_server_fingerprint)", ""));
expression => and(
isvariable("ssh_server_fingerprint"),
not(strcmp("$(ssh_server_fingerprint)", ""))
);

"superhub_setup_status_complete"
expression => "any",
Expand All @@ -1210,11 +1231,12 @@ bundle agent setup_status
};

files:
# An empty fingerprint (ssh-keyscan returned nothing, e.g. sshd not yet
# reachable on localhost) must not be advertised: a superhub would render
# an empty known_hosts entry for this host and its rsync pull would later
# fail with "Host key verification failed". Skip the status update until
# the fingerprint is collected; the next agent run will retry.
# An empty fingerprint (no readable host public keys, e.g. sshd not
# installed or host keys not yet generated) must not be advertised: a
# superhub would render an empty known_hosts entry for this host and its
# rsync pull would later fail with "Host key verification failed". Skip
# the status update until the fingerprint is collected; the next agent
# run will retry.
superhub_setup_status_complete.ssh_server_fingerprint_collected::
"$(cfengine_enterprise_federation:config.path_setup_status)"
create => "true",
Expand All @@ -1232,7 +1254,7 @@ bundle agent setup_status

reports:
superhub_setup_status_complete.!ssh_server_fingerprint_collected::
"warning: 'ssh-keyscan localhost' returned no SSH host key; federation setup status not written yet. Will retry next run.";
"warning: Found no readable SSH host public keys (from 'sshd -T'); federation setup status not written yet. Will retry next run.";
}

bundle agent distributed_cleanup_setup
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