X509 time: tighten validation per RFC 5280

- Reject fractional seconds
- Reject offsets
- Check that the date/time digits are in valid range.
- Add documentation for X509_cmp_time

GH issue 2620

Backported from 80770da

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from openssl#6182)

CHANGES

@@ -9,7 +9,10 @@
 
  Changes between 1.0.2o and 1.0.2p [xx XXX xxxx]
 
-  *)
+  *) Certificate time validation (X509_cmp_time) enforces stricter
+     compliance with RFC 5280. Fractional seconds and timezone offsets
+     are no longer allowed.
+     [Emilia Käsper]
 
  Changes between 1.0.2n and 1.0.2o [27 Mar 2018]
 

crypto/x509/x509_vfy.c

@@ -56,6 +56,7 @@
  * [including the GNU Public Licence.]
  */
 
+#include <ctype.h>
 #include <stdio.h>
 #include <time.h>
 #include <errno.h>
@@ -1937,120 +1938,67 @@ int X509_cmp_current_time(const ASN1_TIME *ctm)
 
 int X509_cmp_time(const ASN1_TIME *ctm, time_t *cmp_time)
 {
-    char *str;
-    ASN1_TIME atm;
-    long offset;
-    char buff1[24], buff2[24], *p;
-    int i, j, remaining;
+    static const size_t utctime_length = sizeof("YYMMDDHHMMSSZ") - 1;
+    static const size_t generalizedtime_length = sizeof("YYYYMMDDHHMMSSZ") - 1;
+    ASN1_TIME *asn1_cmp_time = NULL;
+    int i, day, sec, ret = 0;
 
-    p = buff1;
-    remaining = ctm->length;
-    str = (char *)ctm->data;
     /*
-     * Note that the following (historical) code allows much more slack in the
-     * time format than RFC5280. In RFC5280, the representation is fixed:
+     * Note that ASN.1 allows much more slack in the time format than RFC5280.
+     * In RFC5280, the representation is fixed:
      * UTCTime: YYMMDDHHMMSSZ
      * GeneralizedTime: YYYYMMDDHHMMSSZ
+     *
+     * We do NOT currently enforce the following RFC 5280 requirement:
+     * "CAs conforming to this profile MUST always encode certificate
+     *  validity dates through the year 2049 as UTCTime; certificate validity
+     *  dates in 2050 or later MUST be encoded as GeneralizedTime."
      */
-    if (ctm->type == V_ASN1_UTCTIME) {
-        /* YYMMDDHHMM[SS]Z or YYMMDDHHMM[SS](+-)hhmm */
-        int min_length = sizeof("YYMMDDHHMMZ") - 1;
-        int max_length = sizeof("YYMMDDHHMMSS+hhmm") - 1;
-        if (remaining < min_length || remaining > max_length)
+    switch (ctm->type) {
+    case V_ASN1_UTCTIME:
+        if (ctm->length != (int)(utctime_length))
             return 0;
-        memcpy(p, str, 10);
-        p += 10;
-        str += 10;
-        remaining -= 10;
-    } else {
-        /* YYYYMMDDHHMM[SS[.fff]]Z or YYYYMMDDHHMM[SS[.f[f[f]]]](+-)hhmm */
-        int min_length = sizeof("YYYYMMDDHHMMZ") - 1;
-        int max_length = sizeof("YYYYMMDDHHMMSS.fff+hhmm") - 1;
-        if (remaining < min_length || remaining > max_length)
+        break;
+    case V_ASN1_GENERALIZEDTIME:
+        if (ctm->length != (int)(generalizedtime_length))
             return 0;
-        memcpy(p, str, 12);
-        p += 12;
-        str += 12;
-        remaining -= 12;
+        break;
+    default:
+        return 0;
     }
 
-    if ((*str == 'Z') || (*str == '-') || (*str == '+')) {
-        *(p++) = '0';
-        *(p++) = '0';
-    } else {
-        /* SS (seconds) */
-        if (remaining < 2)
+    /**
+     * Verify the format: the ASN.1 functions we use below allow a more
+     * flexible format than what's mandated by RFC 5280.
+     * Digit and date ranges will be verified in the conversion methods.
+     */
+    for (i = 0; i < ctm->length - 1; i++) {
+        if (!isdigit(ctm->data[i]))
             return 0;
-        *(p++) = *(str++);
-        *(p++) = *(str++);
-        remaining -= 2;
-        /*
-         * Skip any (up to three) fractional seconds...
-         * TODO(emilia): in RFC5280, fractional seconds are forbidden.
-         * Can we just kill them altogether?
-         */
-        if (remaining && *str == '.') {
-            str++;
-            remaining--;
-            for (i = 0; i < 3 && remaining; i++, str++, remaining--) {
-                if (*str < '0' || *str > '9')
-                    break;
-            }
-        }
-
     }
-    *(p++) = 'Z';
-    *(p++) = '\0';
-
-    /* We now need either a terminating 'Z' or an offset. */
-    if (!remaining)
+    if (ctm->data[ctm->length - 1] != 'Z')
         return 0;
-    if (*str == 'Z') {
-        if (remaining != 1)
-            return 0;
-        offset = 0;
-    } else {
-        /* (+-)HHMM */
-        if ((*str != '+') && (*str != '-'))
-            return 0;
-        /* Historical behaviour: the (+-)hhmm offset is forbidden in RFC5280. */
-        if (remaining != 5)
-            return 0;
-        if (str[1] < '0' || str[1] > '9' || str[2] < '0' || str[2] > '9' ||
-            str[3] < '0' || str[3] > '9' || str[4] < '0' || str[4] > '9')
-            return 0;
-        offset = ((str[1] - '0') * 10 + (str[2] - '0')) * 60;
-        offset += (str[3] - '0') * 10 + (str[4] - '0');
-        if (*str == '-')
-            offset = -offset;
-    }
-    atm.type = ctm->type;
-    atm.flags = 0;
-    atm.length = sizeof(buff2);
-    atm.data = (unsigned char *)buff2;
 
-    if (X509_time_adj(&atm, offset * 60, cmp_time) == NULL)
-        return 0;
+    /*
+     * There is ASN1_UTCTIME_cmp_time_t but no
+     * ASN1_GENERALIZEDTIME_cmp_time_t or ASN1_TIME_cmp_time_t,
+     * so we go through ASN.1
+     */
+    asn1_cmp_time = X509_time_adj(NULL, 0, cmp_time);
+    if (asn1_cmp_time == NULL)
+        goto err;
+    if (!ASN1_TIME_diff(&day, &sec, ctm, asn1_cmp_time))
+        goto err;
 
-    if (ctm->type == V_ASN1_UTCTIME) {
-        i = (buff1[0] - '0') * 10 + (buff1[1] - '0');
-        if (i < 50)
-            i += 100;           /* cf. RFC 2459 */
-        j = (buff2[0] - '0') * 10 + (buff2[1] - '0');
-        if (j < 50)
-            j += 100;
-
-        if (i < j)
-            return -1;
-        if (i > j)
-            return 1;
-    }
-    i = strcmp(buff1, buff2);
     /*
      * X509_cmp_time comparison is <=.
      * The return value 0 is reserved for errors.
      */
-    return i > 0 ? 1 : -1;
+    ret = (day >= 0 && sec >= 0) ? -1 : 1;
+
+ err:
+    ASN1_TIME_free(asn1_cmp_time);
+    return ret;
 }
 
 ASN1_TIME *X509_gmtime_adj(ASN1_TIME *s, long adj)

doc/man3/X509_cmp_time.pod

@@ -0,0 +1,39 @@
+=pod
+
+=head1 NAME
+
+X509_cmp_time - X509 time functions
+
+=head1 SYNOPSIS
+
+ X509_cmp_time(const ASN1_TIME *asn1_time, time_t *cmp_time);
+
+=head1 DESCRIPTION
+
+X509_cmp_time() compares the ASN1_TIME in B<asn1_time> with the time in
+<cmp_time>.
+
+B<asn1_time> must satisfy the ASN1_TIME format mandated by RFC 5280, i.e.,
+its format must be either YYMMDDHHMMSSZ or YYYYMMDDHHMMSSZ.
+
+If B<cmp_time> is NULL the current time is used.
+
+=head1 BUGS
+
+Unlike many standard comparison functions, X509_cmp_time returns 0 on error.
+
+=head1 RETURN VALUES
+
+X509_cmp_time() returns -1 if B<asn1_time> is earlier than, or equal to,
+B<cmp_time>, and 1 otherwise. It returns 0 on error.
+
+=head1 COPYRIGHT
+
+Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut

test/Makefile

@@ -74,7 +74,7 @@ BADDTLSTEST=	bad_dtls_test
 SSLV2CONFTEST = 	sslv2conftest
 DTLSTEST =	dtlstest
 FATALERRTEST =	fatalerrtest
-
+X509TIMETEST = x509_time_test
 TESTS=		alltests
 
 EXE=	$(BNTEST)$(EXE_EXT) $(ECTEST)$(EXE_EXT)  $(ECDSATEST)$(EXE_EXT) $(ECDHTEST)$(EXE_EXT) $(IDEATEST)$(EXE_EXT) \
@@ -88,7 +88,7 @@ EXE=	$(BNTEST)$(EXE_EXT) $(ECTEST)$(EXE_EXT)  $(ECDSATEST)$(EXE_EXT) $(ECDHTEST)
 	$(ASN1TEST)$(EXE_EXT) $(V3NAMETEST)$(EXE_EXT) $(HEARTBEATTEST)$(EXE_EXT) \
 	$(CONSTTIMETEST)$(EXE_EXT) $(VERIFYEXTRATEST)$(EXE_EXT) \
 	$(CLIENTHELLOTEST)$(EXE_EXT) $(SSLV2CONFTEST)$(EXE_EXT) $(DTLSTEST)$(EXE_EXT) \
-	$(BADDTLSTEST)$(EXE_EXT) $(FATALERRTEST)$(EXE_EXT)
+	$(BADDTLSTEST)$(EXE_EXT) $(FATALERRTEST)$(EXE_EXT) $(X509TIMETEST)$(EXE_EXT)
 
 # $(METHTEST)$(EXE_EXT)
 
@@ -103,7 +103,7 @@ OBJ=	$(BNTEST).o $(ECTEST).o  $(ECDSATEST).o $(ECDHTEST).o $(IDEATEST).o \
 	$(EVPTEST).o $(EVPEXTRATEST).o $(IGETEST).o $(JPAKETEST).o $(ASN1TEST).o $(V3NAMETEST).o \
 	$(HEARTBEATTEST).o $(CONSTTIMETEST).o $(VERIFYEXTRATEST).o \
 	$(CLIENTHELLOTEST).o  $(SSLV2CONFTEST).o $(DTLSTEST).o ssltestlib.o \
-	$(BADDTLSTEST).o $(FATALERRTEST).o
+	$(BADDTLSTEST).o $(FATALERRTEST).o $(X509TIMETEST).o
 
 SRC=	$(BNTEST).c $(ECTEST).c  $(ECDSATEST).c $(ECDHTEST).c $(IDEATEST).c \
 	$(MD2TEST).c  $(MD4TEST).c $(MD5TEST).c \
@@ -115,7 +115,7 @@ SRC=	$(BNTEST).c $(ECTEST).c  $(ECDSATEST).c $(ECDHTEST).c $(IDEATEST).c \
 	$(EVPTEST).c $(EVPEXTRATEST).c $(IGETEST).c $(JPAKETEST).c $(SRPTEST).c $(ASN1TEST).c \
 	$(V3NAMETEST).c $(HEARTBEATTEST).c $(CONSTTIMETEST).c $(VERIFYEXTRATEST).c \
 	$(CLIENTHELLOTEST).c  $(SSLV2CONFTEST).c $(DTLSTEST).c ssltestlib.c \
-	$(BADDTLSTEST).c $(FATALERRTEST).c
+	$(BADDTLSTEST).c $(FATALERRTEST).c $(X509TIMETEST).c
 
 EXHEADER= 
 HEADER=	testutil.h ssltestlib.h $(EXHEADER)
@@ -160,7 +160,7 @@ alltests: \
 	test_ss test_ca test_engine test_evp test_evp_extra test_ssl test_tsa test_ige \
 	test_jpake test_srp test_cms test_ocsp test_v3name test_heartbeat \
 	test_constant_time test_verify_extra test_clienthello test_sslv2conftest \
-	test_dtls test_bad_dtls test_fatalerr
+	test_dtls test_bad_dtls test_fatalerr test_x509_time
 
 test_evp: $(EVPTEST)$(EXE_EXT) evptests.txt
 	../util/shlib_wrap.sh ./$(EVPTEST) evptests.txt
@@ -378,6 +378,10 @@ test_fatalerr: $(FATALERRTEST)$(EXE_EXT)
 	@echo $(START) $@
 	../util/shlib_wrap.sh ./$(FATALERRTEST) ../apps/server.pem ../apps/server.pem
 
+test_x509_time: $(X509TIMETEST)$(EXE_EXT)
+	@echo $(START) $@
+	../util/shlib_wrap.sh ./$(X509TIMETEST)
+
 test_sslv2conftest: $(SSLV2CONFTEST)$(EXE_EXT)
 	@echo $(START) $@
 	../util/shlib_wrap.sh ./$(SSLV2CONFTEST)
@@ -569,6 +573,9 @@ $(BADDTLSTEST)$(EXE_EXT): $(BADDTLSTEST).o
 $(FATALERRTEST)$(EXE_EXT): $(FATALERRTEST).o ssltestlib.o $(DLIBSSL) $(DLIBCRYPTO)
 	@target=$(FATALERRTEST); exobj=ssltestlib.o; $(BUILD_CMD)
 
+$(X509TIMETEST)$(EXE_EXT): $(X509TIMETEST).o
+	@target=$(X509TIMETEST) $(BUILD_CMD)
+
 $(SSLV2CONFTEST)$(EXE_EXT): $(SSLV2CONFTEST).o
 	@target=$(SSLV2CONFTEST) $(BUILD_CMD)
 
@@ -832,8 +839,11 @@ hmactest.o: ../include/openssl/objects.h ../include/openssl/opensslconf.h
 hmactest.o: ../include/openssl/opensslv.h ../include/openssl/ossl_typ.h
 hmactest.o: ../include/openssl/safestack.h ../include/openssl/stack.h
 hmactest.o: ../include/openssl/symhacks.h hmactest.c
-ideatest.o: ../e_os.h ../include/openssl/e_os2.h ../include/openssl/idea.h
-ideatest.o: ../include/openssl/opensslconf.h ideatest.c
+ideatest.o: ../include/openssl/buffer.h ../include/openssl/crypto.h
+ideatest.o: ../include/openssl/e_os2.h ../include/openssl/opensslconf.h
+ideatest.o: ../include/openssl/opensslv.h ../include/openssl/ossl_typ.h
+ideatest.o: ../include/openssl/safestack.h ../include/openssl/stack.h
+ideatest.o: ../include/openssl/symhacks.h ideatest.c
 igetest.o: ../include/openssl/aes.h ../include/openssl/e_os2.h
 igetest.o: ../include/openssl/opensslconf.h ../include/openssl/ossl_typ.h
 igetest.o: ../include/openssl/rand.h igetest.c
@@ -1012,3 +1022,15 @@ wp_test.o: ../include/openssl/opensslconf.h ../include/openssl/opensslv.h
 wp_test.o: ../include/openssl/ossl_typ.h ../include/openssl/safestack.h
 wp_test.o: ../include/openssl/stack.h ../include/openssl/symhacks.h
 wp_test.o: ../include/openssl/whrlpool.h wp_test.c
+x509_time_test.o: ../e_os.h ../include/openssl/asn1.h ../include/openssl/bio.h
+x509_time_test.o: ../include/openssl/buffer.h ../include/openssl/crypto.h
+x509_time_test.o: ../include/openssl/e_os2.h ../include/openssl/ec.h
+x509_time_test.o: ../include/openssl/ecdh.h ../include/openssl/ecdsa.h
+x509_time_test.o: ../include/openssl/evp.h ../include/openssl/lhash.h
+x509_time_test.o: ../include/openssl/obj_mac.h ../include/openssl/objects.h
+x509_time_test.o: ../include/openssl/opensslconf.h
+x509_time_test.o: ../include/openssl/opensslv.h ../include/openssl/ossl_typ.h
+x509_time_test.o: ../include/openssl/pkcs7.h ../include/openssl/safestack.h
+x509_time_test.o: ../include/openssl/sha.h ../include/openssl/stack.h
+x509_time_test.o: ../include/openssl/symhacks.h ../include/openssl/x509.h
+x509_time_test.o: ../include/openssl/x509_vfy.h testutil.h x509_time_test.c

test/recipes/60-test_x509_time.t

@@ -0,0 +1,12 @@
+#! /usr/bin/env perl
+# Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+
+use OpenSSL::Test::Simple;
+
+simple_test("test_x509_time", "x509_time_test");