Merge pull request #298 from theexiile1305/main

Support of S/MIME Signing

README.md

@@ -65,6 +65,7 @@ Here are some highlights of go-mail's featureset:
 * [X] Custom error types for delivery errors
 * [X] Custom dial-context functions for more control over the connection (proxing, DNS hooking, etc.)
 * [X] Output a go-mail message as EML file and parse EML file into a go-mail message
+* [X] S/MIME singed messages
 
 go-mail works like a programatic email client and provides lots of methods and functionalities you would consider
 standard in a MUA.

dummy-chain-cert-ecdsa.pem

@@ -0,0 +1,26 @@
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----

dummy-chain-cert-ecdsa.pem.license

@@ -0,0 +1,3 @@
+// SPDX-FileCopyrightText: Copyright (c) 2022-2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT

dummy-chain-cert-rsa.pem

@@ -0,0 +1,62 @@
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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
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+-----END CERTIFICATE-----

dummy-chain-cert-rsa.pem.license

@@ -0,0 +1,3 @@
+// SPDX-FileCopyrightText: Copyright (c) 2022-2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT

dummy-child-key-ecdsa.pem

@@ -0,0 +1,8 @@
+-----BEGIN EC PARAMETERS-----
+BggqhkjOPQMBBw==
+-----END EC PARAMETERS-----
+-----BEGIN EC PRIVATE KEY-----
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+adNUtySOBPAIm6BX+Lj0Z0YdBxpfXFEfqQ==
+-----END EC PRIVATE KEY-----

dummy-child-key-ecdsa.pem.license

@@ -0,0 +1,3 @@
+// SPDX-FileCopyrightText: Copyright (c) 2022-2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT

dummy-child-key-rsa.pem

@@ -0,0 +1,52 @@
+-----BEGIN PRIVATE KEY-----
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+S++xGnGHEUSEl7cWnO8k0RyJzzc=
+-----END PRIVATE KEY-----

dummy-child-key-rsa.pem.license

@@ -0,0 +1,3 @@
+// SPDX-FileCopyrightText: Copyright (c) 2022-2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT

encoding.go

@@ -171,17 +171,20 @@ const (
 
 	// TypeTextPlain represents the MIME type for plain text content.
 	TypeTextPlain ContentType = "text/plain"
+
+	// typeSMimeSigned represents the MIME type for S/MIME singed messages.
+	typeSMimeSigned ContentType = `application/pkcs7-signature; name="smime.p7s"`
 )
 
 const (
 	// MIMEAlternative MIMEType represents a MIME multipart/alternative type, used for emails with multiple versions.
 	MIMEAlternative MIMEType = "alternative"
-
 	// MIMEMixed MIMEType represents a MIME multipart/mixed type used for emails containing different types of content.
 	MIMEMixed MIMEType = "mixed"
-
 	// MIMERelated MIMEType represents a MIME multipart/related type, used for emails with related content entities.
 	MIMERelated MIMEType = "related"
+	// MIMESMime MIMEType represents a MIME multipart/signed type, used for siging emails with S/MIME.
+	MIMESMime MIMEType = `signed; protocol="application/pkcs7-signature"; micalg=sha-256`
 )
 
 // String satisfies the fmt.Stringer interface for the Charset type.
@@ -219,3 +222,8 @@ func (c ContentType) String() string {
 func (e Encoding) String() string {
 	return string(e)
 }
+
+// String is a standard method to convert an MIMEType into a printable format
+func (e MIMEType) String() string {
+	return string(e)
+}

encoding_test.go

@@ -61,6 +61,11 @@ func TestContentType_String(t *testing.T) {
 			"ContentType: application/pgp-encrypted", TypePGPEncrypted,
 			"application/pgp-encrypted",
 		},
+
+		{
+			"ContentType: pkcs7-signature", typeSMimeSigned,
+			`application/pkcs7-signature; name="smime.p7s"`,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -121,3 +126,24 @@ func TestCharset_String(t *testing.T) {
 		})
 	}
 }
+
+// TestContentType_String tests the mime type method of the MIMEType object
+func TestMimeType_String(t *testing.T) {
+	tests := []struct {
+		mt   MIMEType
+		want string
+	}{
+		{MIMEAlternative, "alternative"},
+		{MIMEMixed, "mixed"},
+		{MIMERelated, "related"},
+		{MIMESMime, `signed; protocol="application/pkcs7-signature"; micalg=sha-256`},
+	}
+	for _, tt := range tests {
+		t.Run(tt.mt.String(), func(t *testing.T) {
+			if tt.mt.String() != tt.want {
+				t.Errorf("wrong string for mime type returned. Expected: %s, got: %s",
+					tt.want, tt.mt.String())
+			}
+		})
+	}
+}

go.sum

@@ -63,4 +63,4 @@ golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc
 golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/tools v0.13.0/go.mod h1:HvlwmtVNQAhOuCjW7xxvovg8wbNq7LwfXh/k7wXUl58=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d/go.mod h1:aiJjzUbINMkxbQROHiO6hDPo2LHcIPhhQsa9DLh0yGk=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=