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

2 files changed, 14 insertions, 1 deletions

diff --git a/models/ssh_key.go b/models/ssh_key.go
index d1132bf0c6..edc6d45cd8 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 4bb612a671..95cd4eeb1a 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) {