Commit c8223538 authored by Richard Levitte's avatar Richard Levitte
Browse files

Check that the subject name in a proxy cert complies to RFC 3820 



The subject name MUST be the same as the issuer name, with a single CN
entry added.

RT#1852

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
Reviewed-by: default avatarStephen Henson <steve@openssl.org>
parent 54f24e3e

crypto/x509/x509_txt.c

+2 −0
Original line number Diff line number Diff line
@@ -167,6 +167,8 @@ const char *X509_verify_cert_error_string(long n) 
        return ("Issuer certificate lookup error");

    case X509_V_ERR_NO_VALID_SCTS:

        return ("Certificate Transparency required, but no valid SCTs found");

    case X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION:

        return ("proxy subject name violation");



    default:

        /* Printing an error number into a static buffer is not thread-safe */

crypto/x509/x509_vfy.c

+73 −0
Original line number Diff line number Diff line
@@ -558,6 +558,79 @@ static int check_name_constraints(X509_STORE_CTX *ctx) 
        /* Ignore self issued certs unless last in chain */

        if (i && (x->ex_flags & EXFLAG_SI))

            continue;



        /*

         * Proxy certificates policy has an extra constraint, where the

         * certificate subject MUST be the issuer with a single CN entry

         * added.

         * (RFC 3820: 3.4, 4.1.3 (a)(4))

         */

        if (x->ex_flags & EXFLAG_PROXY) {

            X509_NAME *tmpsubject = X509_get_subject_name(x);

            X509_NAME *tmpissuer = X509_get_issuer_name(x);

            X509_NAME_ENTRY *tmpentry = NULL;

            int last_object_nid = 0;

            int err = X509_V_OK;

            int last_object_loc = X509_NAME_entry_count(tmpsubject) - 1;



            /* Check that there are at least two RDNs */

            if (last_object_loc < 1) {

                err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;

                goto proxy_name_done;

            }



            /*

             * Check that there is exactly one more RDN in subject as

             * there is in issuer.

             */

            if (X509_NAME_entry_count(tmpsubject)

                != X509_NAME_entry_count(tmpissuer) + 1) {

                err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;

                goto proxy_name_done;

            }



            /*

             * Check that the last subject component isn't part of a

             * multivalued RDN

             */

            if (X509_NAME_ENTRY_set(X509_NAME_get_entry(tmpsubject,

                                                        last_object_loc))

                == X509_NAME_ENTRY_set(X509_NAME_get_entry(tmpsubject,

                                                           last_object_loc - 1))) {

                err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;

                goto proxy_name_done;

            }



            /*

             * Check that the last subject RDN is a commonName, and that

             * all the previous RDNs match the issuer exactly

             */

            tmpsubject = X509_NAME_dup(tmpsubject);

            if (tmpsubject == NULL) {

                X509err(X509_F_CHECK_NAME_CONSTRAINTS, ERR_R_MALLOC_FAILURE);

                ctx->error = X509_V_ERR_OUT_OF_MEM;

                return 0;

            }



            tmpentry =

                X509_NAME_delete_entry(tmpsubject, last_object_loc);

            last_object_nid =

                OBJ_obj2nid(X509_NAME_ENTRY_get_object(tmpentry));



            if (last_object_nid != NID_commonName

                || X509_NAME_cmp(tmpsubject, tmpissuer) != 0) {

                err = X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION;

            }



            X509_NAME_ENTRY_free(tmpentry);

            X509_NAME_free(tmpsubject);



         proxy_name_done:

            if (err != X509_V_OK

                && !verify_cb_cert(ctx, x, i, err))

                return 0;

        }



        /*

         * Check against constraints for all certificates higher in chain

         * including trust anchor. Trust anchor not strictly speaking needed

include/openssl/x509_vfy.h

+2 −0
Original line number Diff line number Diff line
@@ -165,6 +165,8 @@ void X509_STORE_CTX_set_depth(X509_STORE_CTX *ctx, int depth); 
/* Certificate transparency */

# define         X509_V_ERR_NO_VALID_SCTS                        71



# define         X509_V_ERR_PROXY_SUBJECT_NAME_VIOLATION         72



/* Certificate verify flags */



# if OPENSSL_API_COMPAT < 0x10100000L