From 61969c3073f147352a3b99297208e3690080a4d6 Mon Sep 17 00:00:00 2001
From: Aki Tuomi <aki.tuomi@dovecot.fi>
Date: Thu, 3 Mar 2016 12:40:38 +0200
Subject: [PATCH] lib-ssl-iostream: Read dh parameters from PEM string

---
 .../iostream-openssl-context.c                | 54 +++++++++++++++++++
 src/lib-ssl-iostream/iostream-ssl.h           |  1 +
 2 files changed, 55 insertions(+)

diff --git a/src/lib-ssl-iostream/iostream-openssl-context.c b/src/lib-ssl-iostream/iostream-openssl-context.c
index b1cf1af9b2..c0680c40a2 100644
--- a/src/lib-ssl-iostream/iostream-openssl-context.c
+++ b/src/lib-ssl-iostream/iostream-openssl-context.c
@@ -98,6 +98,35 @@ int openssl_iostream_load_key(const struct ssl_iostream_settings *set,
 	return pkey == NULL ? -1 : 0;
 }
 
+static
+int openssl_iostream_load_dh(const struct ssl_iostream_settings *set,
+			     DH **dh_r, const char **error_r)
+{
+	DH *dh;
+	BIO *bio;
+	char *dhvalue;
+
+	dhvalue = t_strdup_noconst(set->dh);
+	bio = BIO_new_mem_buf(dhvalue, strlen(dhvalue));
+
+	if (bio == NULL) {
+		*error_r = t_strdup_printf("BIO_new_mem_buf() failed: %s",
+					   openssl_iostream_error());
+		return -1;
+	}
+
+	dh = NULL;
+	dh = PEM_read_bio_DHparams(bio, &dh, NULL, NULL);
+
+	if (dh == NULL) {
+		*error_r = t_strdup_printf("Couldn't parse DH parameters: %s",
+					   openssl_iostream_error());
+	}
+	BIO_free(bio);
+	*dh_r = dh;
+	return dh == NULL ? -1 : 0;
+}
+
 static int
 ssl_iostream_ctx_use_key(struct ssl_iostream_context *ctx,
 			 const struct ssl_iostream_settings *set,
@@ -118,6 +147,26 @@ ssl_iostream_ctx_use_key(struct ssl_iostream_context *ctx,
 	return ret;
 }
 
+static int
+ssl_iostream_ctx_use_dh(struct ssl_iostream_context *ctx,
+			const struct ssl_iostream_settings *set,
+			const char **error_r)
+{
+	DH *dh;
+	int ret = 0;
+
+	if (openssl_iostream_load_dh(set, &dh, error_r) < 0)
+		return -1;
+	if (!SSL_CTX_set_tmp_dh(ctx->ssl_ctx, dh)) {
+		 *error_r = t_strdup_printf(
+			"Can't load DH parameters: %s",
+			openssl_iostream_key_load_error());
+		ret = -1;
+	}
+	DH_free(dh);
+	return ret;
+}
+
 static int ssl_ctx_use_certificate_chain(SSL_CTX *ctx, const char *cert)
 {
 	/* mostly just copy&pasted from SSL_CTX_use_certificate_chain_file() */
@@ -317,6 +366,11 @@ ssl_iostream_context_set(struct ssl_iostream_context *ctx,
 			return -1;
 	}
 
+	if (set->dh != NULL) {
+		if (ssl_iostream_ctx_use_dh(ctx, set, error_r) < 0)
+			return -1;
+	}
+
 	/* set trusted CA certs */
 	if (set->verify_remote_cert) {
 		if (ssl_iostream_context_load_ca(ctx, set, error_r) < 0)
diff --git a/src/lib-ssl-iostream/iostream-ssl.h b/src/lib-ssl-iostream/iostream-ssl.h
index 9aab8889f4..d4ca6cba2b 100644
--- a/src/lib-ssl-iostream/iostream-ssl.h
+++ b/src/lib-ssl-iostream/iostream-ssl.h
@@ -11,6 +11,7 @@ struct ssl_iostream_settings {
 	const char *cert;
 	const char *key;
 	const char *key_password;
+	const char *dh;
 	const char *cert_username_field;
 	const char *crypto_device; /* context-only */