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path: root/main/axel/CVE-2020-13614.patch
blob: 8030fb70ad88d6090219d572ad416679cdd1a0d4 (plain) (blame)
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diff --git a/src/Makefile.am b/src/Makefile.am
index 728b4f8..4f92b03 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -14,6 +14,7 @@ axel_SOURCES = \
 	search.c \
 	search.h \
 	ssl.c \
+	ssl_verify.c \
 	ssl.h \
 	tcp.c \
 	tcp.h \
diff --git a/src/ssl.c b/src/ssl.c
index 6c7ae75..fc1ef05 100644
--- a/src/ssl.c
+++ b/src/ssl.c
@@ -71,7 +71,7 @@ ssl_startup(void)
 SSL *
 ssl_connect(int fd, char *hostname, char *message)
 {
-
+	X509 *server_cert;
 	SSL_CTX *ssl_ctx;
 	SSL *ssl;
 
@@ -92,9 +92,33 @@ ssl_connect(int fd, char *hostname, char *message)
 	if (err <= 0) {
 		sprintf(message, _("SSL error: %s\n"),
 			ERR_reason_error_string(ERR_get_error()));
+		SSL_CTX_free(ssl_ctx);
+		return NULL;
+	}
+
+	err = SSL_get_verify_result(ssl);
+	if (err != X509_V_OK) {
+		fprintf(stderr, _("SSL error: Certificate error"));
+		SSL_CTX_free(ssl_ctx);
 		return NULL;
 	}
 
+	server_cert =  SSL_get_peer_certificate(ssl);
+	if (server_cert == NULL) {
+		fprintf(stderr, _("SSL error: Certificate not found"));
+		SSL_CTX_free(ssl_ctx);
+		return NULL;
+	}
+
+	if (!ssl_validate_hostname(hostname, server_cert)) {
+		fprintf(stderr, _("SSL error: Hostname verification failed"));
+		X509_free(server_cert);
+		SSL_CTX_free(ssl_ctx);
+		return NULL;
+	}
+
+	X509_free(server_cert);
+
 	return ssl;
 }
 
diff --git a/src/ssl.h b/src/ssl.h
index cc00eaf..64fb933 100644
--- a/src/ssl.h
+++ b/src/ssl.h
@@ -44,5 +44,6 @@
 void ssl_init(conf_t *conf);
 SSL *ssl_connect(int fd, char *hostname, char *message);
 void ssl_disconnect(SSL *ssl);
+bool ssl_validate_hostname(const char *hostname, const X509 *server_cert);
 
 #endif				/* AXEL_SSL_H */
diff --git a/src/ssl_verify.c b/src/ssl_verify.c
new file mode 100644
index 0000000..8a67a3c
--- /dev/null
+++ b/src/ssl_verify.c
@@ -0,0 +1,147 @@
+/*
+  Helper functions to perform basic hostname validation using OpenSSL.
+
+  Author:  Alban Diquet
+  Copyright (C) 2012, iSEC Partners.
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy of
+  this software and associated documentation files (the "Software"), to deal in
+  the Software without restriction, including without limitation the rights to
+  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+  of the Software, and to permit persons to whom the Software is furnished to do
+  so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in all
+  copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+ */
+
+#include "axel.h"
+
+#ifdef HAVE_SSL
+
+#include <openssl/ssl.h>
+#include <openssl/x509v3.h>
+
+#if OPENSSL_VERSION_NUMBER < 0x10101000L
+#define ASN1_STRING_data_compat ASN1_STRING_data
+#else
+#define ASN1_STRING_data_compat ASN1_STRING_get0_data
+#endif
+
+typedef enum {
+	MatchFound,
+	MatchNotFound,
+	NoSANPresent,
+	MalformedCertificate,
+	Error
+} validate_result;
+
+static validate_result
+ssl_matches_common_name(const char *hostname, const X509 *server_cert)
+{
+	int common_name_loc = -1;
+	X509_NAME_ENTRY *common_name_entry = NULL;
+	ASN1_STRING *common_name_asn1 = NULL;
+	char *common_name_str = NULL;
+
+	// Find the position of the CN field in the Subject field of the certificate
+	common_name_loc = X509_NAME_get_index_by_NID(X509_get_subject_name((X509 *) server_cert), NID_commonName, -1);
+	if (common_name_loc < 0) {
+		return Error;
+	}
+
+	// Extract the CN field
+	common_name_entry = X509_NAME_get_entry(X509_get_subject_name((X509 *) server_cert), common_name_loc);
+	if (common_name_entry == NULL) {
+		return Error;
+	}
+
+	// Convert the CN field to a C string
+	common_name_asn1 = X509_NAME_ENTRY_get_data(common_name_entry);
+	if (common_name_asn1 == NULL) {
+		return Error;
+	}
+	common_name_str = (char *) ASN1_STRING_data_compat(common_name_asn1);
+
+	// Make sure there isn't an embedded NUL character in the CN
+	if ((size_t) ASN1_STRING_length(common_name_asn1) != strlen(common_name_str)) {
+		return MalformedCertificate;
+	}
+
+	// Compare expected hostname with the CN
+	if (strcasecmp(hostname, common_name_str) == 0) {
+		return MatchFound;
+	} else {
+		return MatchNotFound;
+	}
+}
+
+static validate_result
+ssl_matches_subject_alternative_name(const char *hostname, const X509 *server_cert)
+{
+	validate_result result = MatchNotFound;
+	int i;
+	int san_names_nb = -1;
+	STACK_OF(GENERAL_NAME) *san_names = NULL;
+
+	// Try to extract the names within the SAN extension from the certificate
+	san_names = X509_get_ext_d2i((X509 *) server_cert, NID_subject_alt_name, NULL, NULL);
+	if (san_names == NULL) {
+		return NoSANPresent;
+	}
+	san_names_nb = sk_GENERAL_NAME_num(san_names);
+
+	// Check each name within the extension
+	for (i = 0; i < san_names_nb; i++) {
+		const GENERAL_NAME *current_name = sk_GENERAL_NAME_value(san_names, i);
+
+		if (current_name->type == GEN_DNS) {
+			// Current name is a DNS name, let's check it
+			char *dns_name = (char *) ASN1_STRING_data_compat(current_name->d.dNSName);
+
+			// Make sure there isn't an embedded NUL character in the DNS name
+			if ((size_t) ASN1_STRING_length(current_name->d.dNSName) != strlen(dns_name)) {
+				result = MalformedCertificate;
+				break;
+			} else {
+				// Compare expected hostname with the DNS name
+				if (strcasecmp(hostname, dns_name) == 0) {
+					result = MatchFound;
+					break;
+				}
+			}
+		}
+	}
+	sk_GENERAL_NAME_pop_free(san_names, GENERAL_NAME_free);
+
+	return result;
+}
+
+bool
+ssl_validate_hostname(const char *hostname, const X509 *server_cert)
+{
+	validate_result result;
+
+	if ((hostname == NULL) || (server_cert == NULL)) {
+		return false;
+	}
+
+	// First try the Subject Alternative Names extension
+	result = ssl_matches_subject_alternative_name(hostname, server_cert);
+	if (result == NoSANPresent) {
+		// Extension was not found: try the Common Name
+		result = ssl_matches_common_name(hostname, server_cert);
+	}
+
+	return result == MatchFound;
+}
+
+#endif				/* HAVE_SSL */