Initial commit

checker/rules_banner.go

@@ -0,0 +1,122 @@
+// This file is part of the happyDomain (R) project.
+// Copyright (c) 2020-2026 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package checker
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	sdk "git.happydns.org/checker-sdk-go/checker"
+)
+
+// protocolVersionRule flags servers advertising SSH-1.x, which has
+// not been safe for decades.
+type protocolVersionRule struct{}
+
+func (r *protocolVersionRule) Name() string { return "ssh.protocol_version" }
+func (r *protocolVersionRule) Description() string {
+	return "Verifies every endpoint advertises SSH-2 and rejects the legacy SSH-1 protocol."
+}
+
+func (r *protocolVersionRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
+	data, errSt := loadSSHData(ctx, obs)
+	if errSt != nil {
+		return []sdk.CheckState{*errSt}
+	}
+	if len(data.Endpoints) == 0 {
+		return []sdk.CheckState{noEndpointsState("ssh.protocol_version.no_endpoints")}
+	}
+	var states []sdk.CheckState
+	for _, ep := range data.Endpoints {
+		if ep.Banner == "" {
+			continue
+		}
+		if !strings.HasPrefix(ep.ProtoVer, "2.") && ep.ProtoVer != "2" {
+			states = append(states, sdk.CheckState{
+				Status:  sdk.StatusCrit,
+				Code:    "ssh_legacy_protocol",
+				Subject: ep.Address,
+				Message: fmt.Sprintf("Server advertises SSH protocol %q (banner %q). SSH-1 is obsolete and insecure.", ep.ProtoVer, ep.Banner),
+				Meta:    map[string]any{"fix": "Disable SSH-1 support; run an sshd that only speaks SSH-2."},
+			})
+		}
+	}
+	if len(states) == 0 {
+		return []sdk.CheckState{passState("ssh.protocol_version.ok", "Every endpoint advertises SSH-2.")}
+	}
+	return states
+}
+
+// bannerSoftwareRule reports when a server's software identifier does
+// not look like a recognised OpenSSH build.
+type bannerSoftwareRule struct{}
+
+func (r *bannerSoftwareRule) Name() string { return "ssh.banner_software" }
+func (r *bannerSoftwareRule) Description() string {
+	return "Flags servers whose banner is not a recognised OpenSSH build (so their maintenance status cannot be inferred)."
+}
+
+func (r *bannerSoftwareRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
+	data, errSt := loadSSHData(ctx, obs)
+	if errSt != nil {
+		return []sdk.CheckState{*errSt}
+	}
+	if len(data.Endpoints) == 0 {
+		return []sdk.CheckState{noEndpointsState("ssh.banner_software.no_endpoints")}
+	}
+	var issues []Issue
+	for _, ep := range data.Endpoints {
+		issues = append(issues, analyseBannerSoftware(ep.Address, ep.Banner, ep.SoftVer)...)
+	}
+	if len(issues) == 0 {
+		return []sdk.CheckState{passState("ssh.banner_software.ok", "All probed servers advertise a recognised OpenSSH build.")}
+	}
+	return statesFromIssues(issues)
+}
+
+// knownVulnsRule maps the observed banner against an OpenSSH CVE
+// catalog and emits one state per matched vulnerability.
+type knownVulnsRule struct{}
+
+func (r *knownVulnsRule) Name() string { return "ssh.known_vulnerabilities" }
+func (r *knownVulnsRule) Description() string {
+	return "Matches the advertised OpenSSH version against a curated catalog of remotely-observable CVEs."
+}
+
+func (r *knownVulnsRule) Evaluate(ctx context.Context, obs sdk.ObservationGetter, _ sdk.CheckerOptions) []sdk.CheckState {
+	data, errSt := loadSSHData(ctx, obs)
+	if errSt != nil {
+		return []sdk.CheckState{*errSt}
+	}
+	if len(data.Endpoints) == 0 {
+		return []sdk.CheckState{noEndpointsState("ssh.known_vulnerabilities.no_endpoints")}
+	}
+	var issues []Issue
+	for _, ep := range data.Endpoints {
+		issues = append(issues, analyseBannerVulns(ep.Address, ep.Banner, ep.SoftVer)...)
+	}
+	if len(issues) == 0 {
+		return []sdk.CheckState{passState("ssh.known_vulnerabilities.ok", "No known CVE match against the advertised OpenSSH versions.")}
+	}
+	return statesFromIssues(issues)
+}