Commit f7bf8e02 authored by Matt Caswell's avatar Matt Caswell Committed by Kurt Roeckx
Browse files

In certain situations the server provided certificate chain may no longer be... 


In certain situations the server provided certificate chain may no longer be valid. However the issuer of the leaf, or some intermediate cert is in fact in the trust store.

When building a trust chain if the first attempt fails, then try to see if
alternate chains could be constructed that are trusted.

RT3637
RT3621

Reviewed-by: default avatarKurt Roeckx <kurt@roeckx.be>
parent 3b509e8c

crypto/x509/x509_vfy.c

+98 −67
Original line number Diff line number Diff line
@@ -151,11 +151,11 @@ static int x509_subject_cmp(X509 **a, X509 **b) 


int X509_verify_cert(X509_STORE_CTX *ctx)

{

    X509 *x, *xtmp, *chain_ss = NULL;

    X509 *x, *xtmp, *xtmp2, *chain_ss = NULL;

    int bad_chain = 0;

    X509_VERIFY_PARAM *param = ctx->param;

    int depth, i, ok = 0;

    int num;

    int num, j, retry;

    int (*cb) (int xok, X509_STORE_CTX *xctx);

    STACK_OF(X509) *sktmp = NULL;

    if (ctx->cert == NULL) {
@@ -224,25 +224,27 @@ int X509_verify_cert(X509_STORE_CTX *ctx) 
        break;

    }



    /* Remember how many untrusted certs we have */

    j = num;

    /*

     * at this point, chain should contain a list of untrusted certificates.

     * We now need to add at least one trusted one, if possible, otherwise we

     * complain.

     */



    do {

        /*

         * Examine last certificate in chain and see if it is self signed.

         */



        i = sk_X509_num(ctx->chain);

        x = sk_X509_value(ctx->chain, i - 1);

        if (ctx->check_issued(ctx, x, x)) {

            /* we have a self signed certificate */

            if (sk_X509_num(ctx->chain) == 1) {

                /*

             * We have a single self signed certificate: see if we can find

             * it in the store. We must have an exact match to avoid possible

             * impersonation.

                 * We have a single self signed certificate: see if we can

                 * find it in the store. We must have an exact match to avoid

                 * possible impersonation.

                 */

                ok = ctx->get_issuer(&xtmp, ctx, x);

                if ((ok <= 0) || X509_cmp(x, xtmp)) {
@@ -257,8 +259,8 @@ int X509_verify_cert(X509_STORE_CTX *ctx) 
                        goto end;

                } else {

                    /*

                 * We have a match: replace certificate with store version so

                 * we get any trust settings.

                     * We have a match: replace certificate with store

                     * version so we get any trust settings.

                     */

                    X509_free(x);

                    x = xtmp;
@@ -272,27 +274,23 @@ int X509_verify_cert(X509_STORE_CTX *ctx) 
                chain_ss = sk_X509_pop(ctx->chain);

                ctx->last_untrusted--;

                num--;

                j--;

                x = sk_X509_value(ctx->chain, num - 1);

            }

        }



        /* We now lookup certs from the certificate store */

        for (;;) {

            /* If we have enough, we break */

            if (depth < num)

                break;



            /* If we are self signed, we break */

            if (ctx->check_issued(ctx, x, x))

                break;



            ok = ctx->get_issuer(&xtmp, ctx, x);



            if (ok < 0)

                return ok;

            if (ok == 0)

                break;



            x = xtmp;

            if (!sk_X509_push(ctx->chain, x)) {

                X509_free(xtmp);
@@ -302,7 +300,40 @@ int X509_verify_cert(X509_STORE_CTX *ctx) 
            num++;

        }



    /* we now have our chain, lets check it... */

        /*

         * If we haven't got a least one certificate from our store then check

         * if there is an alternative chain that could be used.

         */

        retry = 0;

        if (j == ctx->last_untrusted) {

            while (j-- > 1) {

                xtmp2 = sk_X509_value(ctx->chain, j - 1);

                ok = ctx->get_issuer(&xtmp, ctx, xtmp2);

                if (ok < 0)

                    goto end;

                /* Check if we found an alternate chain */

                if (ok > 0) {

                    /*

                     * Free up the found cert we'll add it again later

                     */

                    X509_free(xtmp);



                    /*

                     * Dump all the certs above this point - we've found an

                     * alternate chain

                     */

                    while (num > j) {

                        xtmp = sk_X509_pop(ctx->chain);

                        X509_free(xtmp);

                        num--;

                        ctx->last_untrusted--;

                    }

                    retry = 1;

                    break;

                }

            }

        }

    } while (retry);



    /* Is last certificate looked up self signed? */

    if (!ctx->check_issued(ctx, x, x)) {