From e24e6af76a1dcd64889f47e3fae03d7c3fa6f7a3 Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Mon, 7 Feb 2022 12:09:55 -0500
Subject: cvss: add score severity and tests

---
 cvss/score.go      | 30 ++++++++++++++++++++++++++++++
 cvss/score_test.go | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/cvss/score.go b/cvss/score.go
index e6a6faa..94a15a5 100644
--- a/cvss/score.go
+++ b/cvss/score.go
@@ -30,3 +30,33 @@ func (s Score) String() string {
 func (s Score) Float() float32 {
   return float32(s) / 10.0
 }
+
+// Score to severity mapping.
+var scoreSeverities = []struct {
+  min       uint8     // min score (inclusive)
+  max       uint8     // max score (inclusive)
+  severity  Severity  // severity
+} {
+  {  0,   0, None },
+  {  1,  39, Low },
+  { 40,  69, Medium },
+  { 70,  89, High },
+  { 90, 100, Critical },
+}
+
+// Return score severity.
+//
+// Returns Unknown if the score does not map to a known severity.
+//
+// Score severity is based on mapping from section 5 of CVSS 3.1
+// specification.
+func (s Score) Severity() Severity {
+  for _, row := range(scoreSeverities) {
+    if uint8(s) >= row.min && uint8(s) <= row.max {
+      return row.severity
+    }
+  }
+
+  // return unknown severity
+  return Unknown
+}
diff --git a/cvss/score_test.go b/cvss/score_test.go
index d35c4c8..5bff327 100644
--- a/cvss/score_test.go
+++ b/cvss/score_test.go
@@ -90,3 +90,51 @@ func TestScoreFloat(t *testing.T) {
     })
   }
 }
+
+func TestScoreSeverity(t *testing.T) {
+  passTests := []struct {
+    val float64
+    exp Severity
+  } {
+    { 0.0, None },
+    { 0.1, Low },
+    { 3.9, Low },
+    { 4.0, Medium },
+    { 6.9, Medium },
+    { 7.0, High },
+    { 8.9, High },
+    { 9.0, Critical },
+    { 10.0, Critical },
+  }
+
+  for _, test := range(passTests) {
+    t.Run(strconv.FormatFloat(test.val, 'f', 2, 64), func(t *testing.T) {
+      s, err := NewScore(test.val)
+      if err != nil {
+        t.Error(err)
+        return
+      }
+
+      got := s.Severity()
+      if got != test.exp {
+        t.Errorf("got \"%s\", exp \"%s\"", got, test.exp)
+      }
+    })
+  }
+
+  failTests := []struct {
+    val Score
+    exp Severity
+  } {
+    { Score(uint8(110)), Unknown },
+  }
+
+  for _, test := range(failTests) {
+    t.Run(test.val.String(), func(t *testing.T) {
+      got := test.val.Severity()
+      if got != test.exp {
+        t.Errorf("got \"%s\", exp \"%s\"", got, test.exp)
+      }
+    })
+  }
+}
-- 
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