Improve SSH key parser to handle newlines in keys (#7522)

* Strip newlines from SSH keys before adding them

Fixes: https://github.com/go-gitea/gitea/issues/7500

* add test for CheckPublicKeyString

* add one more test

* simplify test

* further simplify

* make fmt

2 files changed, 28 insertions, 6 deletions

diff --git a/models/ssh_key.go b/models/ssh_key.go
index ceb4d97560..cbd68a307e 100644
--- a/models/ssh_key.go
+++ b/models/ssh_key.go
@@ -96,17 +96,18 @@ func extractTypeFromBase64Key(key string) (string, error) {
 
 // parseKeyString parses any key string in OpenSSH or SSH2 format to clean OpenSSH string (RFC4253).
 func parseKeyString(content string) (string, error) {
-	// Transform all legal line endings to a single "\n".
-	content = strings.NewReplacer("\r\n", "\n", "\r", "\n").Replace(content)
-	// remove trailing newline (and beginning spaces too)
+	// remove whitespace at start and end
 	content = strings.TrimSpace(content)
-	lines := strings.Split(content, "\n")
 
 	var keyType, keyContent, keyComment string
 
-	if len(lines) == 1 {
+	if !strings.Contains(content, "-----BEGIN") {
 		// Parse OpenSSH format.
-		parts := strings.SplitN(lines[0], " ", 3)
+
+		// Remove all newlines
+		content = strings.NewReplacer("\r\n", "", "\n", "").Replace(content)
+
+		parts := strings.SplitN(content, " ", 3)
 		switch len(parts) {
 		case 0:
 			return "", errors.New("empty key")
@@ -133,6 +134,11 @@ func parseKeyString(content string) (string, error) {
 		}
 	} else {
 		// Parse SSH2 file format.
+
+		// Transform all legal line endings to a single "\n".
+		content = strings.NewReplacer("\r\n", "\n", "\r", "\n").Replace(content)
+
+		lines := strings.Split(content, "\n")
 		continuationLine := false
 
 		for _, line := range lines {
diff --git a/models/ssh_key_test.go b/models/ssh_key_test.go
index 5d095f6378..568211a777 100644
--- a/models/ssh_key_test.go
+++ b/models/ssh_key_test.go
@@ -56,6 +56,22 @@ func Test_SSHParsePublicKey(t *testing.T) {
 	}
 }
 
+func Test_CheckPublicKeyString(t *testing.T) {
+	for _, test := range []struct {
+		content string
+	}{
+		{"ssh-dss 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 nocomment"},
+		{"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQDAu7tvIvX6ZHrRXuZNfkR3XLHSsuCK9Zn3X58lxBcQzuo5xZgB6vRwwm/QtJuF+zZPtY5hsQILBLmF+BZ5WpKZp1jBeSjH2G7lxet9kbcH+kIVj0tPFEoyKI9wvWqIwC4prx/WVk2wLTJjzBAhyNxfEq7C9CeiX9pQEbEqJfkKCQ== nocomment\n"},
+		{"ssh-rsa AAAAB3NzaC1yc2EA\r\nAAADAQABAAAAgQDAu7tvIvX6ZHrRXuZNfkR3XLHSsuCK9Zn3X58lxBcQzuo5xZgB6vRwwm/QtJuF+zZPtY5hsQILBLmF+\r\nBZ5WpKZp1jBeSjH2G7lxet9kbcH+kIVj0tPFEoyKI9wvWqIwC4prx/WVk2wLTJjzBAhyNx\r\nfEq7C9CeiX9pQEbEqJfkKCQ== nocomment\r\n\r\n"},
+		{"ssh-rsa AAAAB3NzaC1yc2EA\r\nAAADAQABAAAAgQDAu7tvI\nvX6ZHrRXuZNfkR3XLHSsuCK9Zn3X58lxBcQzuo5xZgB6vRwwm/QtJuF+zZPtY5hsQILBLmF+\r\nBZ5WpKZp1jBeSjH2G7lxet9kbcH+kIVj0tPFEoyKI9wvW\nqIwC4prx/WVk2wLTJjzBAhyNx\r\nfEq7C9CeiX9pQEbEqJfkKCQ== nocomment\r\n\r\n"},
+		{"ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICV0MGX/W9IvLA4FXpIuUcdDcbj5KX4syHgsTy7soVgf"},
+		{"\r\nssh-ed25519 \r\nAAAAC3NzaC1lZDI1NTE5AAAAICV0MGX/W9IvLA4FXpIuUcdDcbj5KX4syHgsTy7soVgf\r\n\r\n"},
+	} {
+		_, err := CheckPublicKeyString(test.content)
+		assert.NoError(t, err)
+	}
+}
+
 func Test_calcFingerprint(t *testing.T) {
 	testCases := []struct {
 		name    string