From c5e5063ec9e739870045b9bb7195575fb1d686e4 Mon Sep 17 00:00:00 2001
From: 6543 <24977596+6543@users.noreply.github.com>
Date: Sun, 3 Nov 2019 15:51:32 +0100
Subject: [PATCH] Fix SSH2 conditonal in key parsing code (#8806) (#8810)

Avoid out of bounds error by using strings.HasPrefix to check for
starting SSH2 text rather than assuming user input has at least 31
characters.

Add tests for bad input as well.

Fixes #8800
---
 models/ssh_key.go      |  2 +-
 models/ssh_key_test.go | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/models/ssh_key.go b/models/ssh_key.go
index d1132bf0c61..edc6d45cd86 100644
--- a/models/ssh_key.go
+++ b/models/ssh_key.go
@@ -107,7 +107,7 @@ func parseKeyString(content string) (string, error) {
 
 	var keyType, keyContent, keyComment string
 
-	if content[:len(ssh2keyStart)] == ssh2keyStart {
+	if strings.HasPrefix(content, ssh2keyStart) {
 		// Parse SSH2 file format.
 
 		// Transform all legal line endings to a single "\n".
diff --git a/models/ssh_key_test.go b/models/ssh_key_test.go
index 4bb612a6717..95cd4eeb1a2 100644
--- a/models/ssh_key_test.go
+++ b/models/ssh_key_test.go
@@ -131,6 +131,19 @@ AAAAC3NzaC1lZDI1NTE5AAAAICV0MGX/W9IvLA4FXpIuUcdDcbj5KX4syHgsTy7soVgf
 		_, err := CheckPublicKeyString(test.content)
 		assert.NoError(t, err)
 	}
+
+	for _, invalidKeys := range []struct {
+		content string
+	}{
+		{"test"},
+		{"---- NOT A REAL KEY ----"},
+		{"bad\nkey"},
+		{"\t\t:)\t\r\n"},
+		{"\r\ntest \r\ngitea\r\n\r\n"},
+	} {
+		_, err := CheckPublicKeyString(invalidKeys.content)
+		assert.Error(t, err)
+	}
 }
 
 func Test_calcFingerprint(t *testing.T) {