Commit 55a6250f authored by Viktor Dukhovni's avatar Viktor Dukhovni
Browse files

Skip CN DNS name constraint checks when not needed 



Only check the CN against DNS name contraints if the
`X509_CHECK_FLAG_NEVER_CHECK_SUBJECT` flag is not set, and either the
certificate has no DNS subject alternative names or the
`X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT` flag is set.

Add pertinent documentation, and touch up some stale text about
name checks and DANE.

Reviewed-by: default avatarMatt Caswell <matt@openssl.org>
Reviewed-by: default avatarTim Hudson <tjh@openssl.org>
parent d02d80b2

crypto/x509/x509_vfy.c

+27 −1
Original line number Diff line number Diff line
@@ -560,6 +560,27 @@ static int check_chain_extensions(X509_STORE_CTX *ctx) 
    return 1;

}



static int has_san_id(X509 *x, int gtype)

{

    int i;

    int ret = 0;

    GENERAL_NAMES *gs = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);



    if (gs == NULL)

        return 0;



    for (i = 0; i < sk_GENERAL_NAME_num(gs); i++) {

        GENERAL_NAME *g = sk_GENERAL_NAME_value(gs, i);



        if (g->type == gtype) {

            ret = 1;

            break;

        }

    }

    GENERAL_NAMES_free(gs);

    return ret;

}



static int check_name_constraints(X509_STORE_CTX *ctx)

{

    int i;
@@ -658,7 +679,12 @@ static int check_name_constraints(X509_STORE_CTX *ctx) 
                int rv = NAME_CONSTRAINTS_check(x, nc);



                /* If EE certificate check commonName too */

                if (rv == X509_V_OK && i == 0)

                if (rv == X509_V_OK && i == 0

                    && (ctx->param->hostflags

                        & X509_CHECK_FLAG_NEVER_CHECK_SUBJECT) == 0

                    && ((ctx->param->hostflags

                         & X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT) != 0

                        || !has_san_id(x, GEN_DNS)))

                    rv = NAME_CONSTRAINTS_check_CN(x, nc);



                switch (rv) {

crypto/x509v3/v3_ncons.c

+8 −23
Original line number Diff line number Diff line
@@ -299,9 +299,9 @@ int NAME_CONSTRAINTS_check(X509 *x, NAME_CONSTRAINTS *nc) 


static int cn2dnsid(ASN1_STRING *cn, unsigned char **dnsid, size_t *idlen)

{

    int utf8_length;    /* Return type of ASN1_STRING_to_UTF8 */

    int i;

    int utf8_length;

    unsigned char *utf8_value;

    int i;

    int isdnsname = 0;



    /* Don't leave outputs uninitialized */
@@ -337,8 +337,10 @@ static int cn2dnsid(ASN1_STRING *cn, unsigned char **dnsid, size_t *idlen) 
        --utf8_length;



    /* Reject *embedded* NULs */

    if ((size_t)utf8_length != strlen((char *)utf8_value))

        return X509_V_ERR_UNSPECIFIED;

    if ((size_t)utf8_length != strlen((char *)utf8_value)) {

        OPENSSL_free(utf8_value);

        return X509_V_ERR_UNSUPPORTED_NAME_SYNTAX;

    }



    /*

     * XXX: Deviation from strict DNS name syntax, also check names with '_'
@@ -389,14 +391,12 @@ static int cn2dnsid(ASN1_STRING *cn, unsigned char **dnsid, size_t *idlen) 
}



/*

 * Check CN against DNS-ID name constraints, provided no DNS-ID

 * subjectAlternativeName values are present in the certificate.

 * Check CN against DNS-ID name constraints.

 */

int NAME_CONSTRAINTS_check_CN(X509 *x, NAME_CONSTRAINTS *nc)

{

    int r, i;

    GENERAL_NAMES *gens = NULL;

    X509_NAME *nm;

    X509_NAME *nm = X509_get_subject_name(x);

    ASN1_STRING stmp;

    GENERAL_NAME gntmp;
@@ -405,21 +405,6 @@ int NAME_CONSTRAINTS_check_CN(X509 *x, NAME_CONSTRAINTS *nc) 
    gntmp.type = GEN_DNS;

    gntmp.d.dNSName = &stmp;



    gens = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL);

    if (gens != NULL) {

        for (i = 0; i < sk_GENERAL_NAME_num(gens); i++) {

            GENERAL_NAME *gen = sk_GENERAL_NAME_value(gens, i);



            if (gen->type == GEN_DNS) {

                GENERAL_NAMES_free(gens);

                return X509_V_OK;

            }

        }

        GENERAL_NAMES_free(gens);

    }



    nm = X509_get_subject_name(x);



    /* Process any commonName attributes in subject name */



    for (i = -1;;) {

doc/man3/SSL_set1_host.pod

+1 −1
Original line number Diff line number Diff line
@@ -56,7 +56,7 @@ is cleared or freed, or a renegotiation takes place. Applications 
must not free the return value.



SSL clients are advised to use these functions in preference to

explicitly calling L<X509_check_host(3)>.  Hostname checks are out

explicitly calling L<X509_check_host(3)>.  Hostname checks may be out

of scope with the RFC7671 DANE-EE(3) certificate usage, and the

internal check will be suppressed as appropriate when DANE is

enabled.

doc/man3/X509_VERIFY_PARAM_set_flags.pod

+18 −3
Original line number Diff line number Diff line
@@ -133,14 +133,29 @@ B<name> clearing any previously specified host name or names. If 
B<name> is NULL, or empty the list of hostnames is cleared, and

name checks are not performed on the peer certificate.  If B<name>

is NUL-terminated, B<namelen> may be zero, otherwise B<namelen>

must be set to the length of B<name>.  When a hostname is specified,

must be set to the length of B<name>.



When a hostname is specified,

certificate verification automatically invokes L<X509_check_host(3)>

with flags equal to the B<flags> argument given to

X509_VERIFY_PARAM_set_hostflags() (default zero).  Applications

are strongly advised to use this interface in preference to explicitly

calling L<X509_check_host(3)>, hostname checks are out of scope

calling L<X509_check_host(3)>, hostname checks may be out of scope

with the DANE-EE(3) certificate usage, and the internal check will

be suppressed as appropriate when DANE support is added to OpenSSL.

be suppressed as appropriate when DANE verification is enabled.



When the subject CommonName will not be ignored, whether as a result of the

B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> host flag, or because no DNS subject

alternative names are present in the certificate, any DNS name constraints in

issuer certificates apply to the subject CommonName as well as the subject

alternative name extension.



When the subject CommonName will be ignored, whether as a result of the

B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> host flag, or because some DNS subject

alternative names are present in the certificate, DNS name constraints in

issuer certificates will not be applied to the subject DN.

As described in X509_check_host(3) the B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>

flag takes precendence over the B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag.



X509_VERIFY_PARAM_get_hostflags() returns any host flags previously set via a

call to X509_VERIFY_PARAM_set_hostflags().

doc/man3/X509_check_host.pod

+5 −2
Original line number Diff line number Diff line
@@ -93,6 +93,9 @@ consider the subject DN even if the certificate contains no subject alternative 
names of the right type (DNS name or email address as appropriate); the default

is to use the subject DN when no corresponding subject alternative names are

present.

If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and

B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes

precedence and the subject DN is not checked for matching names.



If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard

expansion; this only applies to B<X509_check_host>.
@@ -128,9 +131,9 @@ NULs. 


Applications are encouraged to use X509_VERIFY_PARAM_set1_host()

rather than explicitly calling L<X509_check_host(3)>. Host name

checks are out of scope with the DANE-EE(3) certificate usage,

checks may be out of scope with the DANE-EE(3) certificate usage,

and the internal checks will be suppressed as appropriate when

DANE support is added to OpenSSL.

DANE support is enabled.



=head1 SEE ALSO