Initial support for name constraints certificate extension.

TODO: robustness checking on name forms.

CHANGES

@@ -4,6 +4,18 @@
 
  Changes between 0.9.8i and 0.9.9  [xx XXX xxxx]
 
+  *) Fixes to pathlength constraint, self issued certificate handling,
+     policy processing to align with RFC3280 and PKITS tests.
+
+     This work was sponsored by Google.
+     [Steve Henson]
+
+  *) Support for name constraints certificate extension. DN, email, DNS
+     and URI types are currently supported.
+
+     This work was sponsored by Google.
+     [Steve Henson]
+
   *) To cater for systems that provide a pointer-based thread ID rather
      than numeric, deprecate the current numeric thread ID mechanism and
      replace it with a structure and associated callback type. This
@@ -31,6 +43,8 @@
   *) Initial support for different CRL issuing certificates. This covers a
      simple case where the self issued certificates in the chain exist and
      the real CRL issuer is higher in the existing chain.
+
+     This work was sponsored by Google.
      [Steve Henson]
 
   *) Removed effectively defunct crypto/store from the build.

crypto/asn1/x_x509.c

@@ -116,6 +116,8 @@ static int x509_cb(int operation, ASN1_VALUE **pval, const ASN1_ITEM *it,
 		AUTHORITY_KEYID_free(ret->akid);
 		CRL_DIST_POINTS_free(ret->crldp);
 		policy_cache_free(ret->policy_cache);
+		GENERAL_NAMES_free(ret->altname);
+		NAME_CONSTRAINTS_free(ret->nc);
 #ifndef OPENSSL_NO_RFC3779
 		sk_IPAddressFamily_pop_free(ret->rfc3779_addr, IPAddressFamily_free);
 		ASIdentifiers_free(ret->rfc3779_asid);

crypto/ossl_typ.h

@@ -177,6 +177,7 @@ typedef struct X509_POLICY_CACHE_st X509_POLICY_CACHE;
 typedef struct AUTHORITY_KEYID_st AUTHORITY_KEYID;
 typedef struct DIST_POINT_st DIST_POINT;
 typedef struct ISSUING_DIST_POINT_st ISSUING_DIST_POINT;
+typedef struct NAME_CONSTRAINTS_st NAME_CONSTRAINTS;
 
   /* If placed in pkcs12.h, we end up with a circular depency with pkcs7.h */
 #define DECLARE_PKCS12_STACK_OF(type) /* Nothing */

crypto/x509/x509.h

@@ -294,6 +294,8 @@ struct x509_st
 	AUTHORITY_KEYID *akid;
 	X509_POLICY_CACHE *policy_cache;
 	STACK_OF(DIST_POINT) *crldp;
+	STACK_OF(GENERAL_NAME) *altname;
+	NAME_CONSTRAINTS *nc;
 #ifndef OPENSSL_NO_RFC3779
 	STACK_OF(IPAddressFamily) *rfc3779_addr;
 	struct ASIdentifiers_st *rfc3779_asid;

crypto/x509/x509_txt.c

@@ -168,6 +168,20 @@ const char *X509_verify_cert_error_string(long n)
 	return("Unsupported extension feature");
  	case X509_V_ERR_UNNESTED_RESOURCE:
  		return("RFC 3779 resource not subset of parent's resources");
+
+	case X509_V_ERR_PERMITTED_VIOLATION:
+		return("permitted subtree violation");
+	case X509_V_ERR_EXCLUDED_VIOLATION:
+		return("excluded subtree violation");
+	case X509_V_ERR_SUBTREE_MINMAX:
+		return("name constraints minimum and maximum not supported");
+	case X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE:
+		return("unsupported name constraint type");
+	case X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX:
+		return("unsupported or invalid name constraint syntax");
+	case X509_V_ERR_UNSUPPORTED_NAME_SYNTAX:
+		return("unsupported or invalid name syntax");
+
 	default:
 		BIO_snprintf(buf,sizeof buf,"error number %ld",n);
 		return(buf);

crypto/x509/x509_vfy.c

@@ -74,6 +74,7 @@ static int null_callback(int ok,X509_STORE_CTX *e);
 static int check_issued(X509_STORE_CTX *ctx, X509 *x, X509 *issuer);
 static X509 *find_issuer(X509_STORE_CTX *ctx, STACK_OF(X509) *sk, X509 *x);
 static int check_chain_extensions(X509_STORE_CTX *ctx);
+static int check_name_constraints(X509_STORE_CTX *ctx);
 static int check_trust(X509_STORE_CTX *ctx);
 static int check_revocation(X509_STORE_CTX *ctx);
 static int check_cert(X509_STORE_CTX *ctx);
@@ -291,6 +292,12 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
 
 	if (!ok) goto end;
 
+	/* Check name constraints */
+
+	ok = check_name_constraints(ctx);
+	
+	if (!ok) goto end;
+
 	/* The chain extensions are OK: check trust */
 
 	if (param->trust > 0) ok = check_trust(ctx);
@@ -538,6 +545,42 @@ static int check_chain_extensions(X509_STORE_CTX *ctx)
 #endif
 }
 
+static int check_name_constraints(X509_STORE_CTX *ctx)
+	{
+	X509 *x;
+	int i, j, rv;
+	/* Check name constraints for all certificates */
+	for (i = sk_X509_num(ctx->chain) - 1; i >= 0; i--)
+		{
+		x = sk_X509_value(ctx->chain, i);
+		/* Ignore self issued certs unless last in chain */
+		if (i && (x->ex_flags & EXFLAG_SI))
+			continue;
+		/* Check against constraints for all certificates higher in
+		 * chain including trust anchor. Trust anchor not strictly
+		 * speaking needed but if it includes constraints it is to be
+		 * assumed it expects them to be obeyed.
+		 */
+		for (j = sk_X509_num(ctx->chain) - 1; j > i; j--)
+			{
+			NAME_CONSTRAINTS *nc = sk_X509_value(ctx->chain, j)->nc;
+			if (nc)
+				{
+				rv = NAME_CONSTRAINTS_check(x, nc);
+				if (rv != X509_V_OK)
+					{
+					ctx->error = rv;
+					ctx->error_depth = i;
+					ctx->current_cert = x;
+					if (!ctx->verify_cb(0,ctx))
+						return 0;
+					}
+				}
+			}
+		}
+	return 1;
+	}
+
 static int check_trust(X509_STORE_CTX *ctx)
 {
 #ifdef OPENSSL_NO_CHAIN_VERIFY

crypto/x509/x509_vfy.h

@@ -341,6 +341,13 @@ void X509_STORE_CTX_set_depth(X509_STORE_CTX *ctx, int depth);
 
 #define		X509_V_ERR_UNNESTED_RESOURCE			46
 
+#define		X509_V_ERR_PERMITTED_VIOLATION			47
+#define		X509_V_ERR_EXCLUDED_VIOLATION			48
+#define		X509_V_ERR_SUBTREE_MINMAX			49
+#define		X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE		51
+#define		X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX	52
+#define		X509_V_ERR_UNSUPPORTED_NAME_SYNTAX		53
+
 /* The application is not happy */
 #define		X509_V_ERR_APPLICATION_VERIFICATION		50
 

crypto/x509v3/v3_ncons.c

@@ -72,6 +72,13 @@ static int do_i2r_name_constraints(X509V3_EXT_METHOD *method,
 					BIO *bp, int ind, char *name);
 static int print_nc_ipadd(BIO *bp, ASN1_OCTET_STRING *ip);
 
+static int nc_match(GENERAL_NAME *gen, NAME_CONSTRAINTS *nc);
+static int nc_match_single(GENERAL_NAME *sub, GENERAL_NAME *gen);
+static int nc_dn(X509_NAME *sub, X509_NAME *nm);
+static int nc_dns(ASN1_IA5STRING *sub, ASN1_IA5STRING *dns);
+static int nc_email(ASN1_IA5STRING *sub, ASN1_IA5STRING *eml);
+static int nc_uri(ASN1_IA5STRING *uri, ASN1_IA5STRING *base);
+
 const X509V3_EXT_METHOD v3_name_constraints = {
 	NID_name_constraints, 0,
 	ASN1_ITEM_ref(NAME_CONSTRAINTS),
@@ -218,3 +225,277 @@ static int print_nc_ipadd(BIO *bp, ASN1_OCTET_STRING *ip)
 	return 1;
 	}
 
+/* Check a certificate conforms to a specified set of constraints.
+ * Return values:
+ *  X509_V_OK: All constraints obeyed.
+ *  X509_V_ERR_PERMITTED_VIOLATION: Permitted subtree violation.
+ *  X509_V_ERR_EXCLUDED_VIOLATION: Excluded subtree violation.
+ *  X509_V_ERR_SUBTREE_MINMAX: Min or max values present and matching type.
+ *  X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE:  Unsupported constraint type.
+ *  X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX: bad unsupported constraint syntax.
+ *  X509_V_ERR_UNSUPPORTED_NAME_SYNTAX: bad or unsupported syntax of name
+
+ */
+
+int NAME_CONSTRAINTS_check(X509 *x, NAME_CONSTRAINTS *nc)
+	{
+	int r, i;
+	X509_NAME *nm;
+
+	nm = X509_get_subject_name(x);
+
+	if (X509_NAME_entry_count(nm) > 0)
+		{
+		GENERAL_NAME gntmp;
+		gntmp.type = GEN_DIRNAME;
+		gntmp.d.directoryName = nm;
+
+		r = nc_match(&gntmp, nc);
+
+		if (r != X509_V_OK)
+			return r;
+
+		gntmp.type = GEN_EMAIL;
+
+
+		/* Process any email address attributes in subject name */
+
+		for (i = -1;;)
+			{
+			X509_NAME_ENTRY *ne;
+			i = X509_NAME_get_index_by_NID(nm,
+						       NID_pkcs9_emailAddress,
+						       i);
+			if (i == -1)
+				break;
+			ne = X509_NAME_get_entry(nm, i);
+			gntmp.d.rfc822Name = X509_NAME_ENTRY_get_data(ne);
+			if (gntmp.d.rfc822Name->type != V_ASN1_IA5STRING)
+				return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+
+			r = nc_match(&gntmp, nc);
+
+			if (r != X509_V_OK)
+				return r;
+			}
+		
+		}
+
+	for (i = 0; i < sk_GENERAL_NAME_num(x->altname); i++)
+		{
+		GENERAL_NAME *gen = sk_GENERAL_NAME_value(x->altname, i);
+		r = nc_match(gen, nc);
+		if (r != X509_V_OK)
+			return r;
+		}
+
+	return X509_V_OK;
+
+	}
+
+static int nc_match(GENERAL_NAME *gen, NAME_CONSTRAINTS *nc)
+	{
+	GENERAL_SUBTREE *sub;
+	int i, r, match = 0;
+
+	/* Permitted subtrees: if any subtrees exist of matching the type
+	 * at least one subtree must match.
+	 */
+
+	for (i = 0; i < sk_GENERAL_SUBTREE_num(nc->permittedSubtrees); i++)
+		{
+		sub = sk_GENERAL_SUBTREE_value(nc->permittedSubtrees, i);
+		if (gen->type != sub->base->type)
+			continue;
+		if (sub->minimum || sub->maximum)
+			return X509_V_ERR_SUBTREE_MINMAX;
+		/* If we already have a match don't bother trying any more */
+		if (match == 2)
+			continue;
+		if (match == 0)
+			match = 1;
+		r = nc_match_single(gen, sub->base);
+		if (r == X509_V_OK)
+			match = 2;
+		else if (r != X509_V_ERR_PERMITTED_VIOLATION)
+			return r;
+		}
+
+	if (match == 1)
+		return X509_V_ERR_PERMITTED_VIOLATION;
+
+	/* Excluded subtrees: must not match any of these */
+
+	for (i = 0; i < sk_GENERAL_SUBTREE_num(nc->excludedSubtrees); i++)
+		{
+		sub = sk_GENERAL_SUBTREE_value(nc->excludedSubtrees, i);
+		if (gen->type != sub->base->type)
+			continue;
+		if (sub->minimum || sub->maximum)
+			return X509_V_ERR_SUBTREE_MINMAX;
+
+		r = nc_match_single(gen, sub->base);
+		if (r == X509_V_OK)
+			return X509_V_ERR_EXCLUDED_VIOLATION;
+		else if (r != X509_V_ERR_PERMITTED_VIOLATION)
+			return r;
+
+		}
+
+	return X509_V_OK;
+
+	}
+
+static int nc_match_single(GENERAL_NAME *gen, GENERAL_NAME *base)
+	{
+	switch(base->type)
+		{
+		case GEN_DIRNAME:
+		return nc_dn(gen->d.directoryName, base->d.directoryName);
+
+		case GEN_DNS:
+		return nc_dns(gen->d.dNSName, base->d.dNSName);
+
+		case GEN_EMAIL:
+		return nc_email(gen->d.rfc822Name, base->d.rfc822Name);
+
+		case GEN_URI:
+		return nc_uri(gen->d.uniformResourceIdentifier,
+					base->d.uniformResourceIdentifier);
+
+		default:
+		return X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE;
+		}
+
+	}
+
+/* directoryName name constraint matching.
+ * The canonical encoding of X509_NAME makes this comparison easy. It is
+ * matched if the subtree is a subset of the name.
+ */
+
+static int nc_dn(X509_NAME *nm, X509_NAME *base)
+	{
+	if (base->canon_enclen > nm->canon_enclen)
+		return X509_V_ERR_PERMITTED_VIOLATION;
+	if (memcmp(base->canon_enc, nm->canon_enc, base->canon_enclen))
+		return X509_V_ERR_PERMITTED_VIOLATION;
+	return X509_V_OK;
+	}
+
+static int nc_dns(ASN1_IA5STRING *dns, ASN1_IA5STRING *base)
+	{
+	char *baseptr = (char *)base->data;
+	char *dnsptr = (char *)dns->data;
+	/* Empty matches everything */
+	if (!*baseptr)
+		return X509_V_OK;
+	/* Otherwise can add zero or more components on the left so
+	 * compare RHS and if dns is longer and expect '.' as preceding
+	 * character.
+	 */
+	if (dns->length > base->length)
+		{
+		dnsptr += dns->length - base->length;
+		if (dnsptr[-1] != '.')
+			return X509_V_ERR_PERMITTED_VIOLATION;
+		}
+
+	if (strcasecmp(baseptr, dnsptr))
+			return X509_V_ERR_PERMITTED_VIOLATION;
+
+	return X509_V_OK;
+
+	}
+
+static int nc_email(ASN1_IA5STRING *eml, ASN1_IA5STRING *base)
+	{
+	const char *baseptr = (char *)base->data;
+	const char *emlptr = (char *)eml->data;
+
+	const char *baseat = strchr(baseptr, '@');
+	const char *emlat = strchr(emlptr, '@');
+	if (!emlat)
+		return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+	/* Special case: inital '.' is RHS match */
+	if (!baseat && (*baseptr == '.'))
+		{
+		if (eml->length > base->length)
+			{
+			emlptr += eml->length - base->length;
+			if (!strcasecmp(baseptr, emlptr))
+				return X509_V_OK;
+			}
+		return X509_V_ERR_PERMITTED_VIOLATION;
+		}
+
+	/* If we have anything before '@' match local part */
+
+	if (baseat)
+		{
+		if (baseat != baseptr)
+			{
+			if ((baseat - baseptr) != (emlat - emlptr))
+				return X509_V_ERR_PERMITTED_VIOLATION;
+			/* Case sensitive match of local part */
+			if (strncmp(baseptr, emlptr, emlat - emlptr))
+				return X509_V_ERR_PERMITTED_VIOLATION;
+			}
+		/* Position base after '@' */
+		baseptr = baseat + 1;
+		}
+	emlptr = emlat + 1;
+	/* Just have hostname left to match: case insensitive */
+	if (strcasecmp(baseptr, emlptr))
+		return X509_V_ERR_PERMITTED_VIOLATION;
+
+	return X509_V_OK;
+
+	}
+
+static int nc_uri(ASN1_IA5STRING *uri, ASN1_IA5STRING *base)
+	{
+	const char *baseptr = (char *)base->data;
+	const char *hostptr = (char *)uri->data;
+	const char *p = strchr(hostptr, ':');
+	size_t hostlen;
+	/* Check for foo:// and skip past it */
+	if (!p || (p[1] != '/') || (p[2] != '/'))
+		return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+	hostptr = p + 3;
+
+	/* Determine length of hostname part of URI */
+
+	/* Look for a port indicator as end of hostname first */
+
+	p = strchr(hostptr, ':');
+	/* Otherwise look for trailing slash */
+	if (!p)
+		p = strchr(hostptr, '/');
+
+	if (!p)
+		hostlen = strlen(hostptr);
+	else
+		hostlen = p - hostptr;
+
+	if (hostlen == 0)
+		return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;
+
+	/* Special case: inital '.' is RHS match */
+	if (*baseptr == '.')
+		{
+		if (hostlen > base->length)
+			{
+			p = hostptr + hostlen - base->length;
+			if (!strncasecmp(p, baseptr, base->length))
+				return X509_V_OK;
+			}
+		return X509_V_ERR_PERMITTED_VIOLATION;
+		}
+
+	if ((base->length != hostlen) || strncasecmp(hostptr, baseptr, hostlen))
+		return X509_V_ERR_PERMITTED_VIOLATION;
+
+	return X509_V_OK;
+
+	}

crypto/x509v3/v3_purp.c

@@ -295,6 +295,7 @@ int X509_supported_extension(X509_EXTENSION *ex)
 #endif
 		NID_policy_constraints,	/* 401 */
 		NID_proxyCertInfo,	/* 663 */
+		NID_name_constraints,	/* 666 */
 		NID_inhibit_any_policy	/* 748 */
 	};
 
@@ -448,6 +449,10 @@ static void x509v3_cache_extensions(X509 *x)
 	}
 	x->skid =X509_get_ext_d2i(x, NID_subject_key_identifier, NULL, NULL);
 	x->akid =X509_get_ext_d2i(x, NID_authority_key_identifier, NULL, NULL);
+	x->altname = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);
+	x->nc = X509_get_ext_d2i(x, NID_name_constraints, &i, NULL);
+	if (!x->nc && (i != -1))
+		x->ex_flags |= EXFLAG_INVALID;
 	setup_crldp(x);
 			
 			

crypto/x509v3/x509v3.h

@@ -305,10 +305,10 @@ typedef struct GENERAL_SUBTREE_st {
 
 DECLARE_STACK_OF(GENERAL_SUBTREE)
 
-typedef struct NAME_CONSTRAINTS_st {
+struct NAME_CONSTRAINTS_st {
 	STACK_OF(GENERAL_SUBTREE) *permittedSubtrees;
 	STACK_OF(GENERAL_SUBTREE) *excludedSubtrees;
-} NAME_CONSTRAINTS;
+};
 
 typedef struct POLICY_CONSTRAINTS_st {
 	ASN1_INTEGER *requireExplicitPolicy;
@@ -549,6 +549,8 @@ DECLARE_ASN1_FUNCTIONS(ISSUING_DIST_POINT)
 
 int DIST_POINT_set_dpname(DIST_POINT_NAME *dpn, X509_NAME *iname);
 
+int NAME_CONSTRAINTS_check(X509 *x, NAME_CONSTRAINTS *nc);
+
 DECLARE_ASN1_FUNCTIONS(ACCESS_DESCRIPTION)
 DECLARE_ASN1_FUNCTIONS(AUTHORITY_INFO_ACCESS)