From 9edbdaa84e38b1bfb53a7d72c1de44f8de373405 Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Thu, 11 Jan 2024 15:45:11 +0900
Subject: [PATCH] x509: detect loop in certificate chain
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There can be a loop in a certificate chain, when multiple CA
certificates are cross-signed with each other, such as A → B, B → C,
and C → A.  Previously, the verification logic was not capable of
handling this scenario while sorting the certificates in the chain in
_gnutls_sort_clist, resulting in an assertion failure.  This patch
properly detects such loop and aborts further processing in a graceful
manner.

Signed-off-by: Daiki Ueno <ueno@gnu.org>

Reference: https://gitlab.com/gnutls/gnutls/-/commit/9edbdaa84e38b1bfb53a7d72c1de44f8de373405
Conflict:  tests/test-chains.h

---
 lib/x509/common.c   |   4 ++
 tests/test-chains.h | 124 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 128 insertions(+)

diff --git a/lib/x509/common.c b/lib/x509/common.c
index 2cc95c9..44317ba 100644
--- a/lib/x509/common.c
+++ b/lib/x509/common.c
@@ -1771,6 +1771,10 @@ unsigned int _gnutls_sort_clist(gnutls_x509_crt_t * clist,
 			break;
 		}
 
+		if (insorted[prev]) { /* loop detected */
+			break;
+		}
+
 		sorted[i] = clist[prev];
 		insorted[prev] = 1;
 	}
diff --git a/tests/test-chains.h b/tests/test-chains.h
index 6355f28..c11a097 100644
--- a/tests/test-chains.h
+++ b/tests/test-chains.h
@@ -4263,6 +4263,129 @@ static const char *rsa_sha1_not_in_trusted_ca[] = {
 	NULL
 };
 
+static const char *cross_signed[] = {
+	/* server (signed by A1) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBqDCCAVqgAwIBAgIUejlil+8DBffazcnMNwyOOP6yCCowBQYDK2VwMBoxGDAW\n"
+	"BgNVBAMTD0ludGVybWVkaWF0ZSBBMTAgFw0yNDAxMTEwNjI3MjJaGA85OTk5MTIz\n"
+	"MTIzNTk1OVowNzEbMBkGA1UEChMSR251VExTIHRlc3Qgc2VydmVyMRgwFgYDVQQD\n"
+	"Ew90ZXN0LmdudXRscy5vcmcwKjAFBgMrZXADIQA1ZVS0PcNeTPQMZ+FuVz82AHrj\n"
+	"qL5hWEpCDgpG4M4fxaOBkjCBjzAMBgNVHRMBAf8EAjAAMBoGA1UdEQQTMBGCD3Rl\n"
+	"c3QuZ251dGxzLm9yZzATBgNVHSUEDDAKBggrBgEFBQcDATAOBgNVHQ8BAf8EBAMC\n"
+	"B4AwHQYDVR0OBBYEFGtEUv+JSt+zPoO3lu0IiObZVoiNMB8GA1UdIwQYMBaAFPnY\n"
+	"v6Pw0IvKSqIlb6ewHyEAmTA3MAUGAytlcANBAAS2lyc87kH/aOvNKzPjqDwUYxPA\n"
+	"CfYjyaKea2d0DZLBM5+Bjnj/4aWwTKgVTJzWhLJcLtaSdVHrXqjr9NhEhQ0=\n"
+	"-----END CERTIFICATE-----\n",
+	/* A1 (signed by A) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBUjCCAQSgAwIBAgIUe/R+NVp04e74ySw2qgI6KZgFR20wBQYDK2VwMBExDzAN\n"
+	"BgNVBAMTBlJvb3QgQTAgFw0yNDAxMTEwNjI1MDFaGA85OTk5MTIzMTIzNTk1OVow\n"
+	"GjEYMBYGA1UEAxMPSW50ZXJtZWRpYXRlIEExMCowBQYDK2VwAyEAlkTNqwz973sy\n"
+	"u3whMjSiUMs77CZu5YA7Gi5KcakExrKjYzBhMA8GA1UdEwEB/wQFMAMBAf8wDgYD\n"
+	"VR0PAQH/BAQDAgIEMB0GA1UdDgQWBBT52L+j8NCLykqiJW+nsB8hAJkwNzAfBgNV\n"
+	"HSMEGDAWgBRbYgOkRGsd3Z74+CauX4htzLg0lzAFBgMrZXADQQBM0NBaFVPd3cTJ\n"
+	"DSaZNT34fsHuJk4eagpn8mBxKQpghq4s8Ap+nYtp2KiXjcizss53PeLXVnkfyLi0\n"
+	"TLVBHvUJ\n"
+	"-----END CERTIFICATE-----\n",
+	/* A (signed by B) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhQtdJpg+qlPcLoRW8iiztJUD4xNvDAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBCMCAXDTI0MDExMTA2MTk1OVoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEEwKjAFBgMrZXADIQA0vDYyg3tgotSETL1Wq2hBs32p\n"
+	"WbnINkmOSNmOiZlGHKNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFFtiA6REax3dnvj4Jq5fiG3MuDSXMB8GA1UdIwQYMBaAFJFA\n"
+	"s2rg6j8w9AKItRnOOOjG2FG6MAUGAytlcANBAPv674p9ek5GjRcRfVQhgN+kQlHU\n"
+	"u774wL3Vx3fWA1E7+WchdMzcHrPoa5OKtKmxjIKUTO4SeDZL/AVpvulrWwk=\n"
+	"-----END CERTIFICATE-----\n",
+	/* A (signed by C) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhReNpCiVn7eFDUox3mvM5qE942AVzAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBDMCAXDTI0MDExMTA2MjEyMVoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEIwKjAFBgMrZXADIQAYX92hS97OGKbMzwrD7ReVifwM\n"
+	"3iz5tnfQHWQSkvvYMKNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFJFAs2rg6j8w9AKItRnOOOjG2FG6MB8GA1UdIwQYMBaAFEh/\n"
+	"XKjIuMeEavX5QVoy39Q+GhnwMAUGAytlcANBAIwghH3gelXty8qtoTGIEJb0+EBv\n"
+	"BH4YOUh7TamxjxkjvvIhDA7ZdheofFb7NrklJco7KBcTATUSOvxakYRP9Q8=\n"
+	"-----END CERTIFICATE-----\n",
+	/* B1 (signed by B) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBUjCCAQSgAwIBAgIUfpmrVDc1XBA5/7QYMyGBuB9mTtUwBQYDK2VwMBExDzAN\n"
+	"BgNVBAMTBlJvb3QgQjAgFw0yNDAxMTEwNjI1MjdaGA85OTk5MTIzMTIzNTk1OVow\n"
+	"GjEYMBYGA1UEAxMPSW50ZXJtZWRpYXRlIEIxMCowBQYDK2VwAyEAh6ZTuJWsweVB\n"
+	"a5fsye5iq89kWDC2Y/Hlc0htLmjzMP+jYzBhMA8GA1UdEwEB/wQFMAMBAf8wDgYD\n"
+	"VR0PAQH/BAQDAgIEMB0GA1UdDgQWBBTMQu37PKyLjKfPODZgxYCaayff+jAfBgNV\n"
+	"HSMEGDAWgBSRQLNq4Oo/MPQCiLUZzjjoxthRujAFBgMrZXADQQBblmguY+lnYvOK\n"
+	"rAZJnqpEUGfm1tIFyu3rnlE7WOVcXRXMIoNApLH2iHIipQjlvNWuSBFBTC1qdewh\n"
+	"/e+0cgQB\n"
+	"-----END CERTIFICATE-----\n",
+	/* B (signed by A) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhRpEm+dWNX6DMZh/nottkFfFFrXXDAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBBMCAXDTI0MDExMTA2MTcyNloYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEIwKjAFBgMrZXADIQAYX92hS97OGKbMzwrD7ReVifwM\n"
+	"3iz5tnfQHWQSkvvYMKNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFJFAs2rg6j8w9AKItRnOOOjG2FG6MB8GA1UdIwQYMBaAFFti\n"
+	"A6REax3dnvj4Jq5fiG3MuDSXMAUGAytlcANBAFvmcK3Ida5ViVYDzxKVLPcPsCHe\n"
+	"3hxz99lBrerJC9iJSvRYTJoPBvjTxDYnBn5EFrQYMrUED+6i71lmGXNU9gs=\n"
+	"-----END CERTIFICATE-----\n",
+	/* B (signed by C) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhReNpCiVn7eFDUox3mvM5qE942AVzAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBDMCAXDTI0MDExMTA2MjEyMVoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEIwKjAFBgMrZXADIQAYX92hS97OGKbMzwrD7ReVifwM\n"
+	"3iz5tnfQHWQSkvvYMKNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFJFAs2rg6j8w9AKItRnOOOjG2FG6MB8GA1UdIwQYMBaAFEh/\n"
+	"XKjIuMeEavX5QVoy39Q+GhnwMAUGAytlcANBAIwghH3gelXty8qtoTGIEJb0+EBv\n"
+	"BH4YOUh7TamxjxkjvvIhDA7ZdheofFb7NrklJco7KBcTATUSOvxakYRP9Q8=\n"
+	"-----END CERTIFICATE-----\n",
+	/* C1 (signed by C) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBUjCCAQSgAwIBAgIUSKsfY1wD3eD2VmaaK1wt5naPckMwBQYDK2VwMBExDzAN\n"
+	"BgNVBAMTBlJvb3QgQzAgFw0yNDAxMTEwNjI1NDdaGA85OTk5MTIzMTIzNTk1OVow\n"
+	"GjEYMBYGA1UEAxMPSW50ZXJtZWRpYXRlIEMxMCowBQYDK2VwAyEA/t7i1chZlKkV\n"
+	"qxJOrmmyATn8XnpK+nV/iT4OMHSHfAyjYzBhMA8GA1UdEwEB/wQFMAMBAf8wDgYD\n"
+	"VR0PAQH/BAQDAgIEMB0GA1UdDgQWBBRmpF3JjoP3NiBzE5J5ANT0bvfRmjAfBgNV\n"
+	"HSMEGDAWgBRIf1yoyLjHhGr1+UFaMt/UPhoZ8DAFBgMrZXADQQAeRBXv6WCTOp0G\n"
+	"3wgd8bbEGrrILfpi+qH7aj/MywgkPIlppDYRQ3jL6ASd+So/408dlE0DV9DXKBi0\n"
+	"725XUUYO\n"
+	"-----END CERTIFICATE-----\n",
+	/* C (signed by A) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhRvbZv3SRTjDOiAbyFWHH4y0yMZkjAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBBMCAXDTI0MDExMTA2MTg1MVoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEMwKjAFBgMrZXADIQDxm6Ubhsa0gSa1vBCIO5e+qZEH\n"
+	"8Oocz+buNHfIJbh5NaNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFEh/XKjIuMeEavX5QVoy39Q+GhnwMB8GA1UdIwQYMBaAFFti\n"
+	"A6REax3dnvj4Jq5fiG3MuDSXMAUGAytlcANBAPl+SyiOfXJnjSWx8hFMhJ7w92mn\n"
+	"tkGifCFHBpUhYcBIMeMtLw0RBLXqaaN0EKlTFimiEkLClsU7DKYrpEEJegs=\n"
+	"-----END CERTIFICATE-----\n",
+	/* C (signed by B) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBSDCB+6ADAgECAhQU1OJWRVOLrGrgJiLwexd1/MwKkTAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBCMCAXDTI0MDExMTA2MjAzMFoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEMwKjAFBgMrZXADIQDxm6Ubhsa0gSa1vBCIO5e+qZEH\n"
+	"8Oocz+buNHfIJbh5NaNjMGEwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFEh/XKjIuMeEavX5QVoy39Q+GhnwMB8GA1UdIwQYMBaAFJFA\n"
+	"s2rg6j8w9AKItRnOOOjG2FG6MAUGAytlcANBALXeyuj8vj6Q8j4l17VzZwmJl0gN\n"
+	"bCGoKMl0J/0NiN/fQRIsdbwQDh0RUN/RN3I6DTtB20ER6f3VdnzAh8nXkQ4=\n"
+	"-----END CERTIFICATE-----\n",
+	NULL
+};
+
+static const char *cross_signed_ca[] = {
+	/* A (self-signed) */
+	"-----BEGIN CERTIFICATE-----\n"
+	"MIIBJzCB2qADAgECAhQs1Ur+gzPs1ISxs3Tbs700q0CZcjAFBgMrZXAwETEPMA0G\n"
+	"A1UEAxMGUm9vdCBBMCAXDTI0MDExMTA2MTYwMFoYDzk5OTkxMjMxMjM1OTU5WjAR\n"
+	"MQ8wDQYDVQQDEwZSb290IEEwKjAFBgMrZXADIQA0vDYyg3tgotSETL1Wq2hBs32p\n"
+	"WbnINkmOSNmOiZlGHKNCMEAwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8BAf8EBAMC\n"
+	"AgQwHQYDVR0OBBYEFFtiA6REax3dnvj4Jq5fiG3MuDSXMAUGAytlcANBAHrVv7E9\n"
+	"5scuOVCH9gNRRm8Z9SUoLakRHAPnySdg6z/kI3vOgA/OM7reArpnW8l1H2FapgpL\n"
+	"bDeZ2XJH+BdVFwg=\n"
+	"-----END CERTIFICATE-----\n",
+	NULL
+};
+
 #if defined __clang__ || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5)
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wunused-variable"
@@ -4442,6 +4565,7 @@ static struct
     rsa_sha1_not_in_trusted, rsa_sha1_not_in_trusted_ca,
     GNUTLS_PROFILE_TO_VFLAGS(GNUTLS_PROFILE_MEDIUM),
     GNUTLS_CERT_INSECURE_ALGORITHM | GNUTLS_CERT_INVALID, NULL, 1620118136, 1},
+  { "cross signed - ok", cross_signed, cross_signed_ca, 0, 0, 0, 1704955300},
   { NULL, NULL, NULL, 0, 0}
 };
 
-- 
2.33.0