Update openssl to 1.0.2d

Also update Cryptlib to edk2 r17731

Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>

1 files changed, 1219 insertions, 257 deletions

diff --git a/Cryptlib/OpenSSL/crypto/x509/x509_vfy.c b/Cryptlib/OpenSSL/crypto/x509/x509_vfy.c
index 3249ff82..c085c134 100644
--- a/Cryptlib/OpenSSL/crypto/x509/x509_vfy.c
+++ b/Cryptlib/OpenSSL/crypto/x509/x509_vfy.c
@@ -69,15 +69,73 @@
 #include <openssl/x509.h>
 #include <openssl/x509v3.h>
 #include <openssl/objects.h>
+#include "vpm_int.h"
+
+/* CRL score values */
+
+/* No unhandled critical extensions */
+
+#define CRL_SCORE_NOCRITICAL    0x100
+
+/* certificate is within CRL scope */
+
+#define CRL_SCORE_SCOPE         0x080
+
+/* CRL times valid */
+
+#define CRL_SCORE_TIME          0x040
+
+/* Issuer name matches certificate */
+
+#define CRL_SCORE_ISSUER_NAME   0x020
+
+/* If this score or above CRL is probably valid */
+
+#define CRL_SCORE_VALID (CRL_SCORE_NOCRITICAL|CRL_SCORE_TIME|CRL_SCORE_SCOPE)
+
+/* CRL issuer is certificate issuer */
+
+#define CRL_SCORE_ISSUER_CERT   0x018
+
+/* CRL issuer is on certificate path */
+
+#define CRL_SCORE_SAME_PATH     0x008
+
+/* CRL issuer matches CRL AKID */
+
+#define CRL_SCORE_AKID          0x004
+
+/* Have a delta CRL with valid times */
+
+#define CRL_SCORE_TIME_DELTA    0x002
 
 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_id(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);
 static int check_policy(X509_STORE_CTX *ctx);
+
+static int get_crl_score(X509_STORE_CTX *ctx, X509 **pissuer,
+                         unsigned int *preasons, X509_CRL *crl, X509 *x);
+static int get_crl_delta(X509_STORE_CTX *ctx,
+                         X509_CRL **pcrl, X509_CRL **pdcrl, X509 *x);
+static void get_delta_sk(X509_STORE_CTX *ctx, X509_CRL **dcrl,
+                         int *pcrl_score, X509_CRL *base,
+                         STACK_OF(X509_CRL) *crls);
+static void crl_akid_check(X509_STORE_CTX *ctx, X509_CRL *crl, X509 **pissuer,
+                           int *pcrl_score);
+static int crl_crldp_check(X509 *x, X509_CRL *crl, int crl_score,
+                           unsigned int *preasons);
+static int check_crl_path(X509_STORE_CTX *ctx, X509 *x);
+static int check_crl_chain(X509_STORE_CTX *ctx,
+                           STACK_OF(X509) *cert_path,
+                           STACK_OF(X509) *crl_path);
+
 static int internal_verify(X509_STORE_CTX *ctx);
 const char X509_version[] = "X.509" OPENSSL_VERSION_PTEXT;
 
@@ -92,20 +150,62 @@ static int x509_subject_cmp(X509 **a, X509 **b)
     return X509_subject_name_cmp(*a, *b);
 }
 #endif
+/* Return 1 is a certificate is self signed */
+static int cert_self_signed(X509 *x)
+{
+    X509_check_purpose(x, -1, 0);
+    if (x->ex_flags & EXFLAG_SS)
+        return 1;
+    else
+        return 0;
+}
+
+/* Given a certificate try and find an exact match in the store */
+
+static X509 *lookup_cert_match(X509_STORE_CTX *ctx, X509 *x)
+{
+    STACK_OF(X509) *certs;
+    X509 *xtmp = NULL;
+    int i;
+    /* Lookup all certs with matching subject name */
+    certs = ctx->lookup_certs(ctx, X509_get_subject_name(x));
+    if (certs == NULL)
+        return NULL;
+    /* Look for exact match */
+    for (i = 0; i < sk_X509_num(certs); i++) {
+        xtmp = sk_X509_value(certs, i);
+        if (!X509_cmp(xtmp, x))
+            break;
+    }
+    if (i < sk_X509_num(certs))
+        CRYPTO_add(&xtmp->references, 1, CRYPTO_LOCK_X509);
+    else
+        xtmp = NULL;
+    sk_X509_pop_free(certs, X509_free);
+    return xtmp;
+}
 
 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) {
         X509err(X509_F_X509_VERIFY_CERT, X509_R_NO_CERT_SET_FOR_US_TO_VERIFY);
         return -1;
     }
+    if (ctx->chain != NULL) {
+        /*
+         * This X509_STORE_CTX has already been used to verify a cert. We
+         * cannot do another one.
+         */
+        X509err(X509_F_X509_VERIFY_CERT, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
+        return -1;
+    }
 
     cb = ctx->verify_cb;
 
@@ -113,15 +213,13 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
      * first we make sure the chain we are going to build is present and that
      * the first entry is in place
      */
-    if (ctx->chain == NULL) {
-        if (((ctx->chain = sk_X509_new_null()) == NULL) ||
-            (!sk_X509_push(ctx->chain, ctx->cert))) {
-            X509err(X509_F_X509_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
-            goto end;
-        }
-        CRYPTO_add(&ctx->cert->references, 1, CRYPTO_LOCK_X509);
-        ctx->last_untrusted = 1;
+    if (((ctx->chain = sk_X509_new_null()) == NULL) ||
+        (!sk_X509_push(ctx->chain, ctx->cert))) {
+        X509err(X509_F_X509_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
+        goto end;
     }
+    CRYPTO_add(&ctx->cert->references, 1, CRYPTO_LOCK_X509);
+    ctx->last_untrusted = 1;
 
     /* We use a temporary STACK so we can chop and hack at it */
     if (ctx->untrusted != NULL
@@ -143,8 +241,24 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
                                  * later. */
 
         /* If we are self signed, we break */
-        if (ctx->check_issued(ctx, x, x))
+        if (cert_self_signed(x))
             break;
+        /*
+         * If asked see if we can find issuer in trusted store first
+         */
+        if (ctx->param->flags & X509_V_FLAG_TRUSTED_FIRST) {
+            ok = ctx->get_issuer(&xtmp, ctx, x);
+            if (ok < 0)
+                return ok;
+            /*
+             * If successful for now free up cert so it will be picked up
+             * again later.
+             */
+            if (ok > 0) {
+                X509_free(xtmp);
+                break;
+            }
+        }
 
         /* If we were passed a cert chain, use it first */
         if (ctx->untrusted != NULL) {
@@ -168,88 +282,134 @@ 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.
      */
 
-    /*
-     * 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.
-             */
-            ok = ctx->get_issuer(&xtmp, ctx, x);
-            if ((ok <= 0) || X509_cmp(x, xtmp)) {
-                ctx->error = X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT;
-                ctx->current_cert = x;
-                ctx->error_depth = i - 1;
-                if (ok == 1)
-                    X509_free(xtmp);
-                bad_chain = 1;
-                ok = cb(0, ctx);
-                if (!ok)
-                    goto end;
+    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 (cert_self_signed(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.
+                 */
+                ok = ctx->get_issuer(&xtmp, ctx, x);
+                if ((ok <= 0) || X509_cmp(x, xtmp)) {
+                    ctx->error = X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT;
+                    ctx->current_cert = x;
+                    ctx->error_depth = i - 1;
+                    if (ok == 1)
+                        X509_free(xtmp);
+                    bad_chain = 1;
+                    ok = cb(0, ctx);
+                    if (!ok)
+                        goto end;
+                } else {
+                    /*
+                     * We have a match: replace certificate with store
+                     * version so we get any trust settings.
+                     */
+                    X509_free(x);
+                    x = xtmp;
+                    (void)sk_X509_set(ctx->chain, i - 1, x);
+                    ctx->last_untrusted = 0;
+                }
             } else {
                 /*
-                 * We have a match: replace certificate with store version so
-                 * we get any trust settings.
+                 * extract and save self signed certificate for later use
                  */
-                X509_free(x);
-                x = xtmp;
-                (void)sk_X509_set(ctx->chain, i - 1, x);
-                ctx->last_untrusted = 0;
+                chain_ss = sk_X509_pop(ctx->chain);
+                ctx->last_untrusted--;
+                num--;
+                j--;
+                x = sk_X509_value(ctx->chain, num - 1);
             }
-        } else {
-            /*
-             * extract and save self signed certificate for later use
-             */
-            chain_ss = sk_X509_pop(ctx->chain);
-            ctx->last_untrusted--;
-            num--;
-            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;
+        /* 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 (cert_self_signed(x))
+                break;
+            ok = ctx->get_issuer(&xtmp, ctx, x);
 
-        /* If we are self signed, we break */
-        if (ctx->check_issued(ctx, x, x))
-            break;
+            if (ok < 0)
+                return ok;
+            if (ok == 0)
+                break;
+            x = xtmp;
+            if (!sk_X509_push(ctx->chain, x)) {
+                X509_free(xtmp);
+                X509err(X509_F_X509_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
+                return 0;
+            }
+            num++;
+        }
 
-        ok = ctx->get_issuer(&xtmp, ctx, x);
+        /* we now have our chain, lets check it... */
+        i = check_trust(ctx);
 
-        if (ok < 0)
-            return ok;
-        if (ok == 0)
-            break;
+        /* If explicitly rejected error */
+        if (i == X509_TRUST_REJECTED)
+            goto end;
+        /*
+         * If it's not explicitly trusted then check if there is an alternative
+         * chain that could be used. We only do this if we haven't already
+         * checked via TRUSTED_FIRST and the user hasn't switched off alternate
+         * chain checking
+         */
+        retry = 0;
+        if (i != X509_TRUST_TRUSTED
+            && !(ctx->param->flags & X509_V_FLAG_TRUSTED_FIRST)
+            && !(ctx->param->flags & X509_V_FLAG_NO_ALT_CHAINS)) {
+            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);
 
-        x = xtmp;
-        if (!sk_X509_push(ctx->chain, x)) {
-            X509_free(xtmp);
-            X509err(X509_F_X509_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
-            return 0;
+                    /*
+                     * 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 = sk_X509_num(ctx->chain);
+                    retry = 1;
+                    break;
+                }
+            }
         }
-        num++;
-    }
-
-    /* we now have our chain, lets check it... */
+    } while (retry);
 
-    /* Is last certificate looked up self signed? */
-    if (!ctx->check_issued(ctx, x, x)) {
+    /*
+     * If not explicitly trusted then indicate error unless it's a single
+     * self signed certificate in which case we've indicated an error already
+     * and set bad_chain == 1
+     */
+    if (i != X509_TRUST_TRUSTED && !bad_chain) {
         if ((chain_ss == NULL) || !ctx->check_issued(ctx, x, chain_ss)) {
             if (ctx->last_untrusted >= num)
                 ctx->error = X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY;
@@ -279,10 +439,14 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
     if (!ok)
         goto end;
 
-    /* The chain extensions are OK: check trust */
+    /* Check name constraints */
+
+    ok = check_name_constraints(ctx);
+
+    if (!ok)
+        goto end;
 
-    if (param->trust > 0)
-        ok = check_trust(ctx);
+    ok = check_id(ctx);
 
     if (!ok)
         goto end;
@@ -299,6 +463,16 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
     if (!ok)
         goto end;
 
+    i = X509_chain_check_suiteb(&ctx->error_depth, NULL, ctx->chain,
+                                ctx->param->flags);
+    if (i != X509_V_OK) {
+        ctx->error = i;
+        ctx->current_cert = sk_X509_value(ctx->chain, ctx->error_depth);
+        ok = cb(0, ctx);
+        if (!ok)
+            goto end;
+    }
+
     /* At this point, we have a chain and need to verify it */
     if (ctx->verify != NULL)
         ok = ctx->verify(ctx);
@@ -365,7 +539,6 @@ static int check_issued(X509_STORE_CTX *ctx, X509 *x, X509 *issuer)
     ctx->current_cert = x;
     ctx->current_issuer = issuer;
     return ctx->verify_cb(0, ctx);
-    return 0;
 }
 
 /* Alternative lookup method: look from a STACK stored in other_ctx */
@@ -394,8 +567,8 @@ static int check_chain_extensions(X509_STORE_CTX *ctx)
     X509 *x;
     int (*cb) (int xok, X509_STORE_CTX *xctx);
     int proxy_path_length = 0;
-    int allow_proxy_certs =
-        ! !(ctx->param->flags & X509_V_FLAG_ALLOW_PROXY_CERTS);
+    int purpose;
+    int allow_proxy_certs;
     cb = ctx->verify_cb;
 
     /*-
@@ -409,11 +582,21 @@ static int check_chain_extensions(X509_STORE_CTX *ctx)
      */
     must_be_ca = -1;
 
-    /*
-     * A hack to keep people who don't want to modify their software happy
-     */
-    if (getenv("OPENSSL_ALLOW_PROXY_CERTS"))
-        allow_proxy_certs = 1;
+    /* CRL path validation */
+    if (ctx->parent) {
+        allow_proxy_certs = 0;
+        purpose = X509_PURPOSE_CRL_SIGN;
+    } else {
+        allow_proxy_certs =
+            ! !(ctx->param->flags & X509_V_FLAG_ALLOW_PROXY_CERTS);
+        /*
+         * A hack to keep people who don't want to modify their software
+         * happy
+         */
+        if (getenv("OPENSSL_ALLOW_PROXY_CERTS"))
+            allow_proxy_certs = 1;
+        purpose = ctx->param->purpose;
+    }
 
     /* Check all untrusted certificates */
     for (i = 0; i < ctx->last_untrusted; i++) {
@@ -471,7 +654,7 @@ static int check_chain_extensions(X509_STORE_CTX *ctx)
                 goto end;
         }
         if (ctx->param->purpose > 0) {
-            ret = X509_check_purpose(x, ctx->param->purpose, must_be_ca > 0);
+            ret = X509_check_purpose(x, purpose, must_be_ca > 0);
             if ((ret == 0)
                 || ((ctx->param->flags & X509_V_FLAG_X509_STRICT)
                     && (ret != 1))) {
@@ -522,30 +705,130 @@ static int check_chain_extensions(X509_STORE_CTX *ctx)
 #endif
 }
 
-static int check_trust(X509_STORE_CTX *ctx)
+static int check_name_constraints(X509_STORE_CTX *ctx)
 {
-#ifdef OPENSSL_NO_CHAIN_VERIFY
+    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;
-#else
+}
+
+static int check_id_error(X509_STORE_CTX *ctx, int errcode)
+{
+    ctx->error = errcode;
+    ctx->current_cert = ctx->cert;
+    ctx->error_depth = 0;
+    return ctx->verify_cb(0, ctx);
+}
+
+static int check_hosts(X509 *x, X509_VERIFY_PARAM_ID *id)
+{
+    int i;
+    int n = sk_OPENSSL_STRING_num(id->hosts);
+    char *name;
+
+    for (i = 0; i < n; ++i) {
+        name = sk_OPENSSL_STRING_value(id->hosts, i);
+        if (X509_check_host(x, name, 0, id->hostflags, &id->peername) > 0)
+            return 1;
+    }
+    return n == 0;
+}
+
+static int check_id(X509_STORE_CTX *ctx)
+{
+    X509_VERIFY_PARAM *vpm = ctx->param;
+    X509_VERIFY_PARAM_ID *id = vpm->id;
+    X509 *x = ctx->cert;
+    if (id->hosts && check_hosts(x, id) <= 0) {
+        if (!check_id_error(ctx, X509_V_ERR_HOSTNAME_MISMATCH))
+            return 0;
+    }
+    if (id->email && X509_check_email(x, id->email, id->emaillen, 0) <= 0) {
+        if (!check_id_error(ctx, X509_V_ERR_EMAIL_MISMATCH))
+            return 0;
+    }
+    if (id->ip && X509_check_ip(x, id->ip, id->iplen, 0) <= 0) {
+        if (!check_id_error(ctx, X509_V_ERR_IP_ADDRESS_MISMATCH))
+            return 0;
+    }
+    return 1;
+}
+
+static int check_trust(X509_STORE_CTX *ctx)
+{
     int i, ok;
-    X509 *x;
+    X509 *x = NULL;
     int (*cb) (int xok, X509_STORE_CTX *xctx);
     cb = ctx->verify_cb;
-/* For now just check the last certificate in the chain */
-    i = sk_X509_num(ctx->chain) - 1;
-    x = sk_X509_value(ctx->chain, i);
-    ok = X509_check_trust(x, ctx->param->trust, 0);
-    if (ok == X509_TRUST_TRUSTED)
-        return 1;
-    ctx->error_depth = i;
-    ctx->current_cert = x;
-    if (ok == X509_TRUST_REJECTED)
-        ctx->error = X509_V_ERR_CERT_REJECTED;
-    else
-        ctx->error = X509_V_ERR_CERT_UNTRUSTED;
-    ok = cb(0, ctx);
-    return ok;
-#endif
+    /* Check all trusted certificates in chain */
+    for (i = ctx->last_untrusted; i < sk_X509_num(ctx->chain); i++) {
+        x = sk_X509_value(ctx->chain, i);
+        ok = X509_check_trust(x, ctx->param->trust, 0);
+        /* If explicitly trusted return trusted */
+        if (ok == X509_TRUST_TRUSTED)
+            return X509_TRUST_TRUSTED;
+        /*
+         * If explicitly rejected notify callback and reject if not
+         * overridden.
+         */
+        if (ok == X509_TRUST_REJECTED) {
+            ctx->error_depth = i;
+            ctx->current_cert = x;
+            ctx->error = X509_V_ERR_CERT_REJECTED;
+            ok = cb(0, ctx);
+            if (!ok)
+                return X509_TRUST_REJECTED;
+        }
+    }
+    /*
+     * If we accept partial chains and have at least one trusted certificate
+     * return success.
+     */
+    if (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN) {
+        X509 *mx;
+        if (ctx->last_untrusted < sk_X509_num(ctx->chain))
+            return X509_TRUST_TRUSTED;
+        x = sk_X509_value(ctx->chain, 0);
+        mx = lookup_cert_match(ctx, x);
+        if (mx) {
+            (void)sk_X509_set(ctx->chain, 0, mx);
+            X509_free(x);
+            ctx->last_untrusted = 0;
+            return X509_TRUST_TRUSTED;
+        }
+    }
+
+    /*
+     * If no trusted certs in chain at all return untrusted and allow
+     * standard (no issuer cert) etc errors to be indicated.
+     */
+    return X509_TRUST_UNTRUSTED;
 }
 
 static int check_revocation(X509_STORE_CTX *ctx)
@@ -555,8 +838,12 @@ static int check_revocation(X509_STORE_CTX *ctx)
         return 1;
     if (ctx->param->flags & X509_V_FLAG_CRL_CHECK_ALL)
         last = sk_X509_num(ctx->chain) - 1;
-    else
+    else {
+        /* If checking CRL paths this isn't the EE certificate */
+        if (ctx->parent)
+            return 1;
         last = 0;
+    }
     for (i = 0; i <= last; i++) {
         ctx->error_depth = i;
         ok = check_cert(ctx);
@@ -568,30 +855,72 @@ static int check_revocation(X509_STORE_CTX *ctx)
 
 static int check_cert(X509_STORE_CTX *ctx)
 {
-    X509_CRL *crl = NULL;
+    X509_CRL *crl = NULL, *dcrl = NULL;
     X509 *x;
     int ok, cnum;
+    unsigned int last_reasons;
     cnum = ctx->error_depth;
     x = sk_X509_value(ctx->chain, cnum);
     ctx->current_cert = x;
-    /* Try to retrieve relevant CRL */
-    ok = ctx->get_crl(ctx, &crl, x);
-    /*
-     * If error looking up CRL, nothing we can do except notify callback
-     */
-    if (!ok) {
-        ctx->error = X509_V_ERR_UNABLE_TO_GET_CRL;
-        ok = ctx->verify_cb(0, ctx);
-        goto err;
+    ctx->current_issuer = NULL;
+    ctx->current_crl_score = 0;
+    ctx->current_reasons = 0;
+    while (ctx->current_reasons != CRLDP_ALL_REASONS) {
+        last_reasons = ctx->current_reasons;
+        /* Try to retrieve relevant CRL */
+        if (ctx->get_crl)
+            ok = ctx->get_crl(ctx, &crl, x);
+        else
+            ok = get_crl_delta(ctx, &crl, &dcrl, x);
+        /*
+         * If error looking up CRL, nothing we can do except notify callback
+         */
+        if (!ok) {
+            ctx->error = X509_V_ERR_UNABLE_TO_GET_CRL;
+            ok = ctx->verify_cb(0, ctx);
+            goto err;
+        }
+        ctx->current_crl = crl;
+        ok = ctx->check_crl(ctx, crl);
+        if (!ok)
+            goto err;
+
+        if (dcrl) {
+            ok = ctx->check_crl(ctx, dcrl);
+            if (!ok)
+                goto err;
+            ok = ctx->cert_crl(ctx, dcrl, x);
+            if (!ok)
+                goto err;
+        } else
+            ok = 1;
+
+        /* Don't look in full CRL if delta reason is removefromCRL */
+        if (ok != 2) {
+            ok = ctx->cert_crl(ctx, crl, x);
+            if (!ok)
+                goto err;
+        }
+
+        X509_CRL_free(crl);
+        X509_CRL_free(dcrl);
+        crl = NULL;
+        dcrl = NULL;
+        /*
+         * If reasons not updated we wont get anywhere by another iteration,
+         * so exit loop.
+         */
+        if (last_reasons == ctx->current_reasons) {
+            ctx->error = X509_V_ERR_UNABLE_TO_GET_CRL;
+            ok = ctx->verify_cb(0, ctx);
+            goto err;
+        }
     }
-    ctx->current_crl = crl;
-    ok = ctx->check_crl(ctx, crl);
-    if (!ok)
-        goto err;
-    ok = ctx->cert_crl(ctx, crl, x);
  err:
-    ctx->current_crl = NULL;
     X509_CRL_free(crl);
+    X509_CRL_free(dcrl);
+
+    ctx->current_crl = NULL;
     return ok;
 
 }
@@ -602,7 +931,8 @@ static int check_crl_time(X509_STORE_CTX *ctx, X509_CRL *crl, int notify)
 {
     time_t *ptime;
     int i;
-    ctx->current_crl = crl;
+    if (notify)
+        ctx->current_crl = crl;
     if (ctx->param->flags & X509_V_FLAG_USE_CHECK_TIME)
         ptime = &ctx->param->check_time;
     else
@@ -610,14 +940,18 @@ static int check_crl_time(X509_STORE_CTX *ctx, X509_CRL *crl, int notify)
 
     i = X509_cmp_time(X509_CRL_get_lastUpdate(crl), ptime);
     if (i == 0) {
+        if (!notify)
+            return 0;
         ctx->error = X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD;
-        if (!notify || !ctx->verify_cb(0, ctx))
+        if (!ctx->verify_cb(0, ctx))
             return 0;
     }
 
     if (i > 0) {
+        if (!notify)
+            return 0;
         ctx->error = X509_V_ERR_CRL_NOT_YET_VALID;
-        if (!notify || !ctx->verify_cb(0, ctx))
+        if (!ctx->verify_cb(0, ctx))
             return 0;
     }
 
@@ -625,86 +959,509 @@ static int check_crl_time(X509_STORE_CTX *ctx, X509_CRL *crl, int notify)
         i = X509_cmp_time(X509_CRL_get_nextUpdate(crl), ptime);
 
         if (i == 0) {
+            if (!notify)
+                return 0;
             ctx->error = X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD;
-            if (!notify || !ctx->verify_cb(0, ctx))
+            if (!ctx->verify_cb(0, ctx))
                 return 0;
         }
-
-        if (i < 0) {
+        /* Ignore expiry of base CRL is delta is valid */
+        if ((i < 0) && !(ctx->current_crl_score & CRL_SCORE_TIME_DELTA)) {
+            if (!notify)
+                return 0;
             ctx->error = X509_V_ERR_CRL_HAS_EXPIRED;
-            if (!notify || !ctx->verify_cb(0, ctx))
+            if (!ctx->verify_cb(0, ctx))
                 return 0;
         }
     }
 
-    ctx->current_crl = NULL;
+    if (notify)
+        ctx->current_crl = NULL;
 
     return 1;
 }
 
-/*
- * Lookup CRLs from the supplied list. Look for matching isser name and
- * validity. If we can't find a valid CRL return the last one with matching
- * name. This gives more meaningful error codes. Otherwise we'd get a CRL not
- * found error if a CRL existed with matching name but was invalid.
- */
-
-static int get_crl_sk(X509_STORE_CTX *ctx, X509_CRL **pcrl,
-                      X509_NAME *nm, STACK_OF(X509_CRL) *crls)
+static int get_crl_sk(X509_STORE_CTX *ctx, X509_CRL **pcrl, X509_CRL **pdcrl,
+                      X509 **pissuer, int *pscore, unsigned int *preasons,
+                      STACK_OF(X509_CRL) *crls)
 {
-    int i;
+    int i, crl_score, best_score = *pscore;
+    unsigned int reasons, best_reasons = 0;
+    X509 *x = ctx->current_cert;
     X509_CRL *crl, *best_crl = NULL;
+    X509 *crl_issuer = NULL, *best_crl_issuer = NULL;
+
     for (i = 0; i < sk_X509_CRL_num(crls); i++) {
         crl = sk_X509_CRL_value(crls, i);
-        if (X509_NAME_cmp(nm, X509_CRL_get_issuer(crl)))
-            continue;
-        if (check_crl_time(ctx, crl, 0)) {
-            *pcrl = crl;
-            CRYPTO_add(&crl->references, 1, CRYPTO_LOCK_X509);
-            return 1;
+        reasons = *preasons;
+        crl_score = get_crl_score(ctx, &crl_issuer, &reasons, crl, x);
+
+        if (crl_score > best_score) {
+            best_crl = crl;
+            best_crl_issuer = crl_issuer;
+            best_score = crl_score;
+            best_reasons = reasons;
         }
-        best_crl = crl;
     }
+
     if (best_crl) {
+        if (*pcrl)
+            X509_CRL_free(*pcrl);
         *pcrl = best_crl;
-        CRYPTO_add(&best_crl->references, 1, CRYPTO_LOCK_X509);
+        *pissuer = best_crl_issuer;
+        *pscore = best_score;
+        *preasons = best_reasons;
+        CRYPTO_add(&best_crl->references, 1, CRYPTO_LOCK_X509_CRL);
+        if (*pdcrl) {
+            X509_CRL_free(*pdcrl);
+            *pdcrl = NULL;
+        }
+        get_delta_sk(ctx, pdcrl, pscore, best_crl, crls);
     }
 
+    if (best_score >= CRL_SCORE_VALID)
+        return 1;
+
     return 0;
 }
 
 /*
- * Retrieve CRL corresponding to certificate: currently just a subject
- * lookup: maybe use AKID later...
+ * Compare two CRL extensions for delta checking purposes. They should be
+ * both present or both absent. If both present all fields must be identical.
  */
-static int get_crl(X509_STORE_CTX *ctx, X509_CRL **pcrl, X509 *x)
+
+static int crl_extension_match(X509_CRL *a, X509_CRL *b, int nid)
 {
-    int ok;
-    X509_CRL *crl = NULL;
-    X509_OBJECT xobj;
-    X509_NAME *nm;
-    nm = X509_get_issuer_name(x);
-    ok = get_crl_sk(ctx, &crl, nm, ctx->crls);
-    if (ok) {
-        *pcrl = crl;
+    ASN1_OCTET_STRING *exta, *extb;
+    int i;
+    i = X509_CRL_get_ext_by_NID(a, nid, -1);
+    if (i >= 0) {
+        /* Can't have multiple occurrences */
+        if (X509_CRL_get_ext_by_NID(a, nid, i) != -1)
+            return 0;
+        exta = X509_EXTENSION_get_data(X509_CRL_get_ext(a, i));
+    } else
+        exta = NULL;
+
+    i = X509_CRL_get_ext_by_NID(b, nid, -1);
+
+    if (i >= 0) {
+
+        if (X509_CRL_get_ext_by_NID(b, nid, i) != -1)
+            return 0;
+        extb = X509_EXTENSION_get_data(X509_CRL_get_ext(b, i));
+    } else
+        extb = NULL;
+
+    if (!exta && !extb)
         return 1;
+
+    if (!exta || !extb)
+        return 0;
+
+    if (ASN1_OCTET_STRING_cmp(exta, extb))
+        return 0;
+
+    return 1;
+}
+
+/* See if a base and delta are compatible */
+
+static int check_delta_base(X509_CRL *delta, X509_CRL *base)
+{
+    /* Delta CRL must be a delta */
+    if (!delta->base_crl_number)
+        return 0;
+    /* Base must have a CRL number */
+    if (!base->crl_number)
+        return 0;
+    /* Issuer names must match */
+    if (X509_NAME_cmp(X509_CRL_get_issuer(base), X509_CRL_get_issuer(delta)))
+        return 0;
+    /* AKID and IDP must match */
+    if (!crl_extension_match(delta, base, NID_authority_key_identifier))
+        return 0;
+    if (!crl_extension_match(delta, base, NID_issuing_distribution_point))
+        return 0;
+    /* Delta CRL base number must not exceed Full CRL number. */
+    if (ASN1_INTEGER_cmp(delta->base_crl_number, base->crl_number) > 0)
+        return 0;
+    /* Delta CRL number must exceed full CRL number */
+    if (ASN1_INTEGER_cmp(delta->crl_number, base->crl_number) > 0)
+        return 1;
+    return 0;
+}
+
+/*
+ * For a given base CRL find a delta... maybe extend to delta scoring or
+ * retrieve a chain of deltas...
+ */
+
+static void get_delta_sk(X509_STORE_CTX *ctx, X509_CRL **dcrl, int *pscore,
+                         X509_CRL *base, STACK_OF(X509_CRL) *crls)
+{
+    X509_CRL *delta;
+    int i;
+    if (!(ctx->param->flags & X509_V_FLAG_USE_DELTAS))
+        return;
+    if (!((ctx->current_cert->ex_flags | base->flags) & EXFLAG_FRESHEST))
+        return;
+    for (i = 0; i < sk_X509_CRL_num(crls); i++) {
+        delta = sk_X509_CRL_value(crls, i);
+        if (check_delta_base(delta, base)) {
+            if (check_crl_time(ctx, delta, 0))
+                *pscore |= CRL_SCORE_TIME_DELTA;
+            CRYPTO_add(&delta->references, 1, CRYPTO_LOCK_X509_CRL);
+            *dcrl = delta;
+            return;
+        }
     }
+    *dcrl = NULL;
+}
 
-    ok = X509_STORE_get_by_subject(ctx, X509_LU_CRL, nm, &xobj);
+/*
+ * For a given CRL return how suitable it is for the supplied certificate
+ * 'x'. The return value is a mask of several criteria. If the issuer is not
+ * the certificate issuer this is returned in *pissuer. The reasons mask is
+ * also used to determine if the CRL is suitable: if no new reasons the CRL
+ * is rejected, otherwise reasons is updated.
+ */
 
-    if (!ok) {
-        /* If we got a near match from get_crl_sk use that */
-        if (crl) {
-            *pcrl = crl;
-            return 1;
+static int get_crl_score(X509_STORE_CTX *ctx, X509 **pissuer,
+                         unsigned int *preasons, X509_CRL *crl, X509 *x)
+{
+
+    int crl_score = 0;
+    unsigned int tmp_reasons = *preasons, crl_reasons;
+
+    /* First see if we can reject CRL straight away */
+
+    /* Invalid IDP cannot be processed */
+    if (crl->idp_flags & IDP_INVALID)
+        return 0;
+    /* Reason codes or indirect CRLs need extended CRL support */
+    if (!(ctx->param->flags & X509_V_FLAG_EXTENDED_CRL_SUPPORT)) {
+        if (crl->idp_flags & (IDP_INDIRECT | IDP_REASONS))
+            return 0;
+    } else if (crl->idp_flags & IDP_REASONS) {
+        /* If no new reasons reject */
+        if (!(crl->idp_reasons & ~tmp_reasons))
+            return 0;
+    }
+    /* Don't process deltas at this stage */
+    else if (crl->base_crl_number)
+        return 0;
+    /* If issuer name doesn't match certificate need indirect CRL */
+    if (X509_NAME_cmp(X509_get_issuer_name(x), X509_CRL_get_issuer(crl))) {
+        if (!(crl->idp_flags & IDP_INDIRECT))
+            return 0;
+    } else
+        crl_score |= CRL_SCORE_ISSUER_NAME;
+
+    if (!(crl->flags & EXFLAG_CRITICAL))
+        crl_score |= CRL_SCORE_NOCRITICAL;
+
+    /* Check expiry */
+    if (check_crl_time(ctx, crl, 0))
+        crl_score |= CRL_SCORE_TIME;
+
+    /* Check authority key ID and locate certificate issuer */
+    crl_akid_check(ctx, crl, pissuer, &crl_score);
+
+    /* If we can't locate certificate issuer at this point forget it */
+
+    if (!(crl_score & CRL_SCORE_AKID))
+        return 0;
+
+    /* Check cert for matching CRL distribution points */
+
+    if (crl_crldp_check(x, crl, crl_score, &crl_reasons)) {
+        /* If no new reasons reject */
+        if (!(crl_reasons & ~tmp_reasons))
+            return 0;
+        tmp_reasons |= crl_reasons;
+        crl_score |= CRL_SCORE_SCOPE;
+    }
+
+    *preasons = tmp_reasons;
+
+    return crl_score;
+
+}
+
+static void crl_akid_check(X509_STORE_CTX *ctx, X509_CRL *crl,
+                           X509 **pissuer, int *pcrl_score)
+{
+    X509 *crl_issuer = NULL;
+    X509_NAME *cnm = X509_CRL_get_issuer(crl);
+    int cidx = ctx->error_depth;
+    int i;
+
+    if (cidx != sk_X509_num(ctx->chain) - 1)
+        cidx++;
+
+    crl_issuer = sk_X509_value(ctx->chain, cidx);
+
+    if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
+        if (*pcrl_score & CRL_SCORE_ISSUER_NAME) {
+            *pcrl_score |= CRL_SCORE_AKID | CRL_SCORE_ISSUER_CERT;
+            *pissuer = crl_issuer;
+            return;
+        }
+    }
+
+    for (cidx++; cidx < sk_X509_num(ctx->chain); cidx++) {
+        crl_issuer = sk_X509_value(ctx->chain, cidx);
+        if (X509_NAME_cmp(X509_get_subject_name(crl_issuer), cnm))
+            continue;
+        if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
+            *pcrl_score |= CRL_SCORE_AKID | CRL_SCORE_SAME_PATH;
+            *pissuer = crl_issuer;
+            return;
         }
+    }
+
+    /* Anything else needs extended CRL support */
+
+    if (!(ctx->param->flags & X509_V_FLAG_EXTENDED_CRL_SUPPORT))
+        return;
+
+    /*
+     * Otherwise the CRL issuer is not on the path. Look for it in the set of
+     * untrusted certificates.
+     */
+    for (i = 0; i < sk_X509_num(ctx->untrusted); i++) {
+        crl_issuer = sk_X509_value(ctx->untrusted, i);
+        if (X509_NAME_cmp(X509_get_subject_name(crl_issuer), cnm))
+            continue;
+        if (X509_check_akid(crl_issuer, crl->akid) == X509_V_OK) {
+            *pissuer = crl_issuer;
+            *pcrl_score |= CRL_SCORE_AKID;
+            return;
+        }
+    }
+}
+
+/*
+ * Check the path of a CRL issuer certificate. This creates a new
+ * X509_STORE_CTX and populates it with most of the parameters from the
+ * parent. This could be optimised somewhat since a lot of path checking will
+ * be duplicated by the parent, but this will rarely be used in practice.
+ */
+
+static int check_crl_path(X509_STORE_CTX *ctx, X509 *x)
+{
+    X509_STORE_CTX crl_ctx;
+    int ret;
+    /* Don't allow recursive CRL path validation */
+    if (ctx->parent)
         return 0;
+    if (!X509_STORE_CTX_init(&crl_ctx, ctx->ctx, x, ctx->untrusted))
+        return -1;
+
+    crl_ctx.crls = ctx->crls;
+    /* Copy verify params across */
+    X509_STORE_CTX_set0_param(&crl_ctx, ctx->param);
+
+    crl_ctx.parent = ctx;
+    crl_ctx.verify_cb = ctx->verify_cb;
+
+    /* Verify CRL issuer */
+    ret = X509_verify_cert(&crl_ctx);
+
+    if (ret <= 0)
+        goto err;
+
+    /* Check chain is acceptable */
+
+    ret = check_crl_chain(ctx, ctx->chain, crl_ctx.chain);
+ err:
+    X509_STORE_CTX_cleanup(&crl_ctx);
+    return ret;
+}
+
+/*
+ * RFC3280 says nothing about the relationship between CRL path and
+ * certificate path, which could lead to situations where a certificate could
+ * be revoked or validated by a CA not authorised to do so. RFC5280 is more
+ * strict and states that the two paths must end in the same trust anchor,
+ * though some discussions remain... until this is resolved we use the
+ * RFC5280 version
+ */
+
+static int check_crl_chain(X509_STORE_CTX *ctx,
+                           STACK_OF(X509) *cert_path,
+                           STACK_OF(X509) *crl_path)
+{
+    X509 *cert_ta, *crl_ta;
+    cert_ta = sk_X509_value(cert_path, sk_X509_num(cert_path) - 1);
+    crl_ta = sk_X509_value(crl_path, sk_X509_num(crl_path) - 1);
+    if (!X509_cmp(cert_ta, crl_ta))
+        return 1;
+    return 0;
+}
+
+/*-
+ * Check for match between two dist point names: three separate cases.
+ * 1. Both are relative names and compare X509_NAME types.
+ * 2. One full, one relative. Compare X509_NAME to GENERAL_NAMES.
+ * 3. Both are full names and compare two GENERAL_NAMES.
+ * 4. One is NULL: automatic match.
+ */
+
+static int idp_check_dp(DIST_POINT_NAME *a, DIST_POINT_NAME *b)
+{
+    X509_NAME *nm = NULL;
+    GENERAL_NAMES *gens = NULL;
+    GENERAL_NAME *gena, *genb;
+    int i, j;
+    if (!a || !b)
+        return 1;
+    if (a->type == 1) {
+        if (!a->dpname)
+            return 0;
+        /* Case 1: two X509_NAME */
+        if (b->type == 1) {
+            if (!b->dpname)
+                return 0;
+            if (!X509_NAME_cmp(a->dpname, b->dpname))
+                return 1;
+            else
+                return 0;
+        }
+        /* Case 2: set name and GENERAL_NAMES appropriately */
+        nm = a->dpname;
+        gens = b->name.fullname;
+    } else if (b->type == 1) {
+        if (!b->dpname)
+            return 0;
+        /* Case 2: set name and GENERAL_NAMES appropriately */
+        gens = a->name.fullname;
+        nm = b->dpname;
     }
 
-    *pcrl = xobj.data.crl;
-    if (crl)
-        X509_CRL_free(crl);
-    return 1;
+    /* Handle case 2 with one GENERAL_NAMES and one X509_NAME */
+    if (nm) {
+        for (i = 0; i < sk_GENERAL_NAME_num(gens); i++) {
+            gena = sk_GENERAL_NAME_value(gens, i);
+            if (gena->type != GEN_DIRNAME)
+                continue;
+            if (!X509_NAME_cmp(nm, gena->d.directoryName))
+                return 1;
+        }
+        return 0;
+    }
+
+    /* Else case 3: two GENERAL_NAMES */
+
+    for (i = 0; i < sk_GENERAL_NAME_num(a->name.fullname); i++) {
+        gena = sk_GENERAL_NAME_value(a->name.fullname, i);
+        for (j = 0; j < sk_GENERAL_NAME_num(b->name.fullname); j++) {
+            genb = sk_GENERAL_NAME_value(b->name.fullname, j);
+            if (!GENERAL_NAME_cmp(gena, genb))
+                return 1;
+        }
+    }
+
+    return 0;
+
+}
+
+static int crldp_check_crlissuer(DIST_POINT *dp, X509_CRL *crl, int crl_score)
+{
+    int i;
+    X509_NAME *nm = X509_CRL_get_issuer(crl);
+    /* If no CRLissuer return is successful iff don't need a match */
+    if (!dp->CRLissuer)
+        return ! !(crl_score & CRL_SCORE_ISSUER_NAME);
+    for (i = 0; i < sk_GENERAL_NAME_num(dp->CRLissuer); i++) {
+        GENERAL_NAME *gen = sk_GENERAL_NAME_value(dp->CRLissuer, i);
+        if (gen->type != GEN_DIRNAME)
+            continue;
+        if (!X509_NAME_cmp(gen->d.directoryName, nm))
+            return 1;
+    }
+    return 0;
+}
+
+/* Check CRLDP and IDP */
+
+static int crl_crldp_check(X509 *x, X509_CRL *crl, int crl_score,
+                           unsigned int *preasons)
+{
+    int i;
+    if (crl->idp_flags & IDP_ONLYATTR)
+        return 0;
+    if (x->ex_flags & EXFLAG_CA) {
+        if (crl->idp_flags & IDP_ONLYUSER)
+            return 0;
+    } else {
+        if (crl->idp_flags & IDP_ONLYCA)
+            return 0;
+    }
+    *preasons = crl->idp_reasons;
+    for (i = 0; i < sk_DIST_POINT_num(x->crldp); i++) {
+        DIST_POINT *dp = sk_DIST_POINT_value(x->crldp, i);
+        if (crldp_check_crlissuer(dp, crl, crl_score)) {
+            if (!crl->idp || idp_check_dp(dp->distpoint, crl->idp->distpoint)) {
+                *preasons &= dp->dp_reasons;
+                return 1;
+            }
+        }
+    }
+    if ((!crl->idp || !crl->idp->distpoint)
+        && (crl_score & CRL_SCORE_ISSUER_NAME))
+        return 1;
+    return 0;
+}
+
+/*
+ * Retrieve CRL corresponding to current certificate. If deltas enabled try
+ * to find a delta CRL too
+ */
+
+static int get_crl_delta(X509_STORE_CTX *ctx,
+                         X509_CRL **pcrl, X509_CRL **pdcrl, X509 *x)
+{
+    int ok;
+    X509 *issuer = NULL;
+    int crl_score = 0;
+    unsigned int reasons;
+    X509_CRL *crl = NULL, *dcrl = NULL;
+    STACK_OF(X509_CRL) *skcrl;
+    X509_NAME *nm = X509_get_issuer_name(x);
+    reasons = ctx->current_reasons;
+    ok = get_crl_sk(ctx, &crl, &dcrl,
+                    &issuer, &crl_score, &reasons, ctx->crls);
+
+    if (ok)
+        goto done;
+
+    /* Lookup CRLs from store */
+
+    skcrl = ctx->lookup_crls(ctx, nm);
+
+    /* If no CRLs found and a near match from get_crl_sk use that */
+    if (!skcrl && crl)
+        goto done;
+
+    get_crl_sk(ctx, &crl, &dcrl, &issuer, &crl_score, &reasons, skcrl);
+
+    sk_X509_CRL_pop_free(skcrl, X509_CRL_free);
+
+ done:
+
+    /* If we got any kind of CRL use it and return success */
+    if (crl) {
+        ctx->current_issuer = issuer;
+        ctx->current_crl_score = crl_score;
+        ctx->current_reasons = reasons;
+        *pcrl = crl;
+        *pdcrl = dcrl;
+        return 1;
+    }
+
+    return 0;
 }
 
 /* Check CRL validity */
@@ -715,11 +1472,15 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
     int ok = 0, chnum, cnum;
     cnum = ctx->error_depth;
     chnum = sk_X509_num(ctx->chain) - 1;
+    /* if we have an alternative CRL issuer cert use that */
+    if (ctx->current_issuer)
+        issuer = ctx->current_issuer;
+
     /*
-     * Find CRL issuer: if not last certificate then issuer is next
+     * Else find CRL issuer: if not last certificate then issuer is next
      * certificate in chain.
      */
-    if (cnum < chnum)
+    else if (cnum < chnum)
         issuer = sk_X509_value(ctx->chain, cnum + 1);
     else {
         issuer = sk_X509_value(ctx->chain, chnum);
@@ -733,11 +1494,46 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
     }
 
     if (issuer) {
-        /* Check for cRLSign bit if keyUsage present */
-        if ((issuer->ex_flags & EXFLAG_KUSAGE) &&
-            !(issuer->ex_kusage & KU_CRL_SIGN)) {
-            ctx->error = X509_V_ERR_KEYUSAGE_NO_CRL_SIGN;
-            ok = ctx->verify_cb(0, ctx);
+        /*
+         * Skip most tests for deltas because they have already been done
+         */
+        if (!crl->base_crl_number) {
+            /* Check for cRLSign bit if keyUsage present */
+            if ((issuer->ex_flags & EXFLAG_KUSAGE) &&
+                !(issuer->ex_kusage & KU_CRL_SIGN)) {
+                ctx->error = X509_V_ERR_KEYUSAGE_NO_CRL_SIGN;
+                ok = ctx->verify_cb(0, ctx);
+                if (!ok)
+                    goto err;
+            }
+
+            if (!(ctx->current_crl_score & CRL_SCORE_SCOPE)) {
+                ctx->error = X509_V_ERR_DIFFERENT_CRL_SCOPE;
+                ok = ctx->verify_cb(0, ctx);
+                if (!ok)
+                    goto err;
+            }
+
+            if (!(ctx->current_crl_score & CRL_SCORE_SAME_PATH)) {
+                if (check_crl_path(ctx, ctx->current_issuer) <= 0) {
+                    ctx->error = X509_V_ERR_CRL_PATH_VALIDATION_ERROR;
+                    ok = ctx->verify_cb(0, ctx);
+                    if (!ok)
+                        goto err;
+                }
+            }
+
+            if (crl->idp_flags & IDP_INVALID) {
+                ctx->error = X509_V_ERR_INVALID_EXTENSION;
+                ok = ctx->verify_cb(0, ctx);
+                if (!ok)
+                    goto err;
+            }
+
+        }
+
+        if (!(ctx->current_crl_score & CRL_SCORE_TIME)) {
+            ok = check_crl_time(ctx, crl, 1);
             if (!ok)
                 goto err;
         }
@@ -751,6 +1547,14 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
             if (!ok)
                 goto err;
         } else {
+            int rv;
+            rv = X509_CRL_check_suiteb(crl, ikey, ctx->param->flags);
+            if (rv != X509_V_OK) {
+                ctx->error = rv;
+                ok = ctx->verify_cb(0, ctx);
+                if (!ok)
+                    goto err;
+            }
             /* Verify CRL signature */
             if (X509_CRL_verify(crl, ikey) <= 0) {
                 ctx->error = X509_V_ERR_CRL_SIGNATURE_FAILURE;
@@ -761,10 +1565,6 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
         }
     }
 
-    ok = check_crl_time(ctx, crl, 1);
-    if (!ok)
-        goto err;
-
     ok = 1;
 
  err:
@@ -775,61 +1575,42 @@ static int check_crl(X509_STORE_CTX *ctx, X509_CRL *crl)
 /* Check certificate against CRL */
 static int cert_crl(X509_STORE_CTX *ctx, X509_CRL *crl, X509 *x)
 {
-    int idx, ok;
-    X509_REVOKED rtmp;
-    STACK_OF(X509_EXTENSION) *exts;
-    X509_EXTENSION *ext;
-    /* Look for serial number of certificate in CRL */
-    rtmp.serialNumber = X509_get_serialNumber(x);
+    int ok;
+    X509_REVOKED *rev;
     /*
-     * Sort revoked into serial number order if not already sorted. Do this
-     * under a lock to avoid race condition.
+     * The rules changed for this... previously if a CRL contained unhandled
+     * critical extensions it could still be used to indicate a certificate
+     * was revoked. This has since been changed since critical extension can
+     * change the meaning of CRL entries.
      */
-    if (!sk_X509_REVOKED_is_sorted(crl->crl->revoked)) {
-        CRYPTO_w_lock(CRYPTO_LOCK_X509_CRL);
-        sk_X509_REVOKED_sort(crl->crl->revoked);
-        CRYPTO_w_unlock(CRYPTO_LOCK_X509_CRL);
+    if (!(ctx->param->flags & X509_V_FLAG_IGNORE_CRITICAL)
+        && (crl->flags & EXFLAG_CRITICAL)) {
+        ctx->error = X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION;
+        ok = ctx->verify_cb(0, ctx);
+        if (!ok)
+            return 0;
     }
-    idx = sk_X509_REVOKED_find(crl->crl->revoked, &rtmp);
     /*
-     * If found assume revoked: want something cleverer than this to handle
-     * entry extensions in V2 CRLs.
+     * Look for serial number of certificate in CRL If found make sure reason
+     * is not removeFromCRL.
      */
-    if (idx >= 0) {
+    if (X509_CRL_get0_by_cert(crl, &rev, x)) {
+        if (rev->reason == CRL_REASON_REMOVE_FROM_CRL)
+            return 2;
         ctx->error = X509_V_ERR_CERT_REVOKED;
         ok = ctx->verify_cb(0, ctx);
         if (!ok)
             return 0;
     }
 
-    if (ctx->param->flags & X509_V_FLAG_IGNORE_CRITICAL)
-        return 1;
-
-    /*
-     * See if we have any critical CRL extensions: since we currently don't
-     * handle any CRL extensions the CRL must be rejected. This code
-     * accesses the X509_CRL structure directly: applications shouldn't do
-     * this.
-     */
-
-    exts = crl->crl->extensions;
-
-    for (idx = 0; idx < sk_X509_EXTENSION_num(exts); idx++) {
-        ext = sk_X509_EXTENSION_value(exts, idx);
-        if (ext->critical > 0) {
-            ctx->error = X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION;
-            ok = ctx->verify_cb(0, ctx);
-            if (!ok)
-                return 0;
-            break;
-        }
-    }
     return 1;
 }
 
 static int check_policy(X509_STORE_CTX *ctx)
 {
     int ret;
+    if (ctx->parent)
+        return 1;
     ret = X509_policy_check(&ctx->tree, &ctx->explicit_policy, ctx->chain,
                             ctx->param->policies, ctx->param->flags);
     if (ret == 0) {
@@ -849,7 +1630,8 @@ static int check_policy(X509_STORE_CTX *ctx)
                 continue;
             ctx->current_cert = x;
             ctx->error = X509_V_ERR_INVALID_POLICY_EXTENSION;
-            ret = ctx->verify_cb(0, ctx);
+            if (!ctx->verify_cb(0, ctx))
+                return 0;
         }
         return 1;
     }
@@ -871,9 +1653,9 @@ static int check_policy(X509_STORE_CTX *ctx)
 
 static int check_cert_time(X509_STORE_CTX *ctx, X509 *x)
 {
-#if defined(OPENSSL_SYS_UEFI)
-  /* Bypass Certificate Time Checking for UEFI version. */
-  return 1;
+#ifdef OPENSSL_SYS_UEFI
+    /* Bypass Certificate Time Checking for UEFI version. */
+    return 1;
 #else
     time_t *ptime;
     int i;
@@ -934,6 +1716,10 @@ static int internal_verify(X509_STORE_CTX *ctx)
     if (ctx->check_issued(ctx, xi, xi))
         xs = xi;
     else {
+        if (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN) {
+            xs = xi;
+            goto check_cert;
+        }
         if (n <= 0) {
             ctx->error = X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE;
             ctx->current_cert = xi;
@@ -979,6 +1765,7 @@ static int internal_verify(X509_STORE_CTX *ctx)
 
         xs->valid = 1;
 
+ check_cert:
         ok = check_cert_time(ctx, xs);
         if (!ok)
             goto end;
@@ -1001,64 +1788,102 @@ static int internal_verify(X509_STORE_CTX *ctx)
     return ok;
 }
 
-int X509_cmp_current_time(ASN1_TIME *ctm)
+int X509_cmp_current_time(const ASN1_TIME *ctm)
 {
     return X509_cmp_time(ctm, NULL);
 }
 
-int X509_cmp_time(ASN1_TIME *ctm, time_t *cmp_time)
+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;
+    int i, j, remaining;
 
     p = buff1;
-    i = ctm->length;
+    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:
+     * UTCTime: YYMMDDHHMMSSZ
+     * GeneralizedTime: YYYYMMDDHHMMSSZ
+     */
     if (ctm->type == V_ASN1_UTCTIME) {
-        if ((i < 11) || (i > 17))
+        /* 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)
             return 0;
         memcpy(p, str, 10);
         p += 10;
         str += 10;
+        remaining -= 10;
     } else {
-        if (i < 13)
+        /* 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)
             return 0;
         memcpy(p, str, 12);
         p += 12;
         str += 12;
+        remaining -= 12;
     }
 
     if ((*str == 'Z') || (*str == '-') || (*str == '+')) {
         *(p++) = '0';
         *(p++) = '0';
     } else {
+        /* SS (seconds) */
+        if (remaining < 2)
+            return 0;
         *(p++) = *(str++);
         *(p++) = *(str++);
-        /* Skip any fractional seconds... */
-        if (*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++;
-            while ((*str >= '0') && (*str <= '9'))
-                str++;
+            remaining--;
+            for (i = 0; i < 3 && remaining; i++, str++, remaining--) {
+                if (*str < '0' || *str > '9')
+                    break;
+            }
         }
 
     }
     *(p++) = 'Z';
     *(p++) = '\0';
 
-    if (*str == 'Z')
+    /* We now need either a terminating 'Z' or an offset. */
+    if (!remaining)
+        return 0;
+    if (*str == 'Z') {
+        if (remaining != 1)
+            return 0;
         offset = 0;
-    else {
+    } 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;
 
@@ -1090,24 +1915,28 @@ ASN1_TIME *X509_gmtime_adj(ASN1_TIME *s, long adj)
     return X509_time_adj(s, adj, NULL);
 }
 
-ASN1_TIME *X509_time_adj(ASN1_TIME *s, long adj, time_t *in_tm)
+ASN1_TIME *X509_time_adj(ASN1_TIME *s, long offset_sec, time_t *in_tm)
+{
+    return X509_time_adj_ex(s, 0, offset_sec, in_tm);
+}
+
+ASN1_TIME *X509_time_adj_ex(ASN1_TIME *s,
+                            int offset_day, long offset_sec, time_t *in_tm)
 {
     time_t t;
-    int type = -1;
 
     if (in_tm)
         t = *in_tm;
     else
         time(&t);
 
-    t += adj;
-    if (s)
-        type = s->type;
-    if (type == V_ASN1_UTCTIME)
-        return ASN1_UTCTIME_set(s, t);
-    if (type == V_ASN1_GENERALIZEDTIME)
-        return ASN1_GENERALIZEDTIME_set(s, t);
-    return ASN1_TIME_set(s, t);
+    if (s && !(s->flags & ASN1_STRING_FLAG_MSTRING)) {
+        if (s->type == V_ASN1_UTCTIME)
+            return ASN1_UTCTIME_adj(s, t, offset_day, offset_sec);
+        if (s->type == V_ASN1_GENERALIZEDTIME)
+            return ASN1_GENERALIZEDTIME_adj(s, t, offset_day, offset_sec);
+    }
+    return ASN1_TIME_adj(s, t, offset_day, offset_sec);
 }
 
 int X509_get_pubkey_parameters(EVP_PKEY *pkey, STACK_OF(X509) *chain)
@@ -1151,6 +1980,114 @@ int X509_get_pubkey_parameters(EVP_PKEY *pkey, STACK_OF(X509) *chain)
     return 1;
 }
 
+/* Make a delta CRL as the diff between two full CRLs */
+
+X509_CRL *X509_CRL_diff(X509_CRL *base, X509_CRL *newer,
+                        EVP_PKEY *skey, const EVP_MD *md, unsigned int flags)
+{
+    X509_CRL *crl = NULL;
+    int i;
+    STACK_OF(X509_REVOKED) *revs = NULL;
+    /* CRLs can't be delta already */
+    if (base->base_crl_number || newer->base_crl_number) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_CRL_ALREADY_DELTA);
+        return NULL;
+    }
+    /* Base and new CRL must have a CRL number */
+    if (!base->crl_number || !newer->crl_number) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_NO_CRL_NUMBER);
+        return NULL;
+    }
+    /* Issuer names must match */
+    if (X509_NAME_cmp(X509_CRL_get_issuer(base), X509_CRL_get_issuer(newer))) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_ISSUER_MISMATCH);
+        return NULL;
+    }
+    /* AKID and IDP must match */
+    if (!crl_extension_match(base, newer, NID_authority_key_identifier)) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_AKID_MISMATCH);
+        return NULL;
+    }
+    if (!crl_extension_match(base, newer, NID_issuing_distribution_point)) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_IDP_MISMATCH);
+        return NULL;
+    }
+    /* Newer CRL number must exceed full CRL number */
+    if (ASN1_INTEGER_cmp(newer->crl_number, base->crl_number) <= 0) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_NEWER_CRL_NOT_NEWER);
+        return NULL;
+    }
+    /* CRLs must verify */
+    if (skey && (X509_CRL_verify(base, skey) <= 0 ||
+                 X509_CRL_verify(newer, skey) <= 0)) {
+        X509err(X509_F_X509_CRL_DIFF, X509_R_CRL_VERIFY_FAILURE);
+        return NULL;
+    }
+    /* Create new CRL */
+    crl = X509_CRL_new();
+    if (!crl || !X509_CRL_set_version(crl, 1))
+        goto memerr;
+    /* Set issuer name */
+    if (!X509_CRL_set_issuer_name(crl, X509_CRL_get_issuer(newer)))
+        goto memerr;
+
+    if (!X509_CRL_set_lastUpdate(crl, X509_CRL_get_lastUpdate(newer)))
+        goto memerr;
+    if (!X509_CRL_set_nextUpdate(crl, X509_CRL_get_nextUpdate(newer)))
+        goto memerr;
+
+    /* Set base CRL number: must be critical */
+
+    if (!X509_CRL_add1_ext_i2d(crl, NID_delta_crl, base->crl_number, 1, 0))
+        goto memerr;
+
+    /*
+     * Copy extensions across from newest CRL to delta: this will set CRL
+     * number to correct value too.
+     */
+
+    for (i = 0; i < X509_CRL_get_ext_count(newer); i++) {
+        X509_EXTENSION *ext;
+        ext = X509_CRL_get_ext(newer, i);
+        if (!X509_CRL_add_ext(crl, ext, -1))
+            goto memerr;
+    }
+
+    /* Go through revoked entries, copying as needed */
+
+    revs = X509_CRL_get_REVOKED(newer);
+
+    for (i = 0; i < sk_X509_REVOKED_num(revs); i++) {
+        X509_REVOKED *rvn, *rvtmp;
+        rvn = sk_X509_REVOKED_value(revs, i);
+        /*
+         * Add only if not also in base. TODO: need something cleverer here
+         * for some more complex CRLs covering multiple CAs.
+         */
+        if (!X509_CRL_get0_by_serial(base, &rvtmp, rvn->serialNumber)) {
+            rvtmp = X509_REVOKED_dup(rvn);
+            if (!rvtmp)
+                goto memerr;
+            if (!X509_CRL_add0_revoked(crl, rvtmp)) {
+                X509_REVOKED_free(rvtmp);
+                goto memerr;
+            }
+        }
+    }
+    /* TODO: optionally prune deleted entries */
+
+    if (skey && md && !X509_CRL_sign(crl, skey, md))
+        goto memerr;
+
+    return crl;
+
+ memerr:
+    X509err(X509_F_X509_CRL_DIFF, ERR_R_MALLOC_FAILURE);
+    if (crl)
+        X509_CRL_free(crl);
+    return NULL;
+}
+
 int X509_STORE_CTX_get_ex_new_index(long argl, void *argp,
                                     CRYPTO_EX_new *new_func,
                                     CRYPTO_EX_dup *dup_func,
@@ -1201,16 +2138,24 @@ STACK_OF(X509) *X509_STORE_CTX_get_chain(X509_STORE_CTX *ctx)
 
 STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx)
 {
-    int i;
-    X509 *x;
-    STACK_OF(X509) *chain;
-    if (!ctx->chain || !(chain = sk_X509_dup(ctx->chain)))
+    if (!ctx->chain)
         return NULL;
-    for (i = 0; i < sk_X509_num(chain); i++) {
-        x = sk_X509_value(chain, i);
-        CRYPTO_add(&x->references, 1, CRYPTO_LOCK_X509);
-    }
-    return chain;
+    return X509_chain_up_ref(ctx->chain);
+}
+
+X509 *X509_STORE_CTX_get0_current_issuer(X509_STORE_CTX *ctx)
+{
+    return ctx->current_issuer;
+}
+
+X509_CRL *X509_STORE_CTX_get0_current_crl(X509_STORE_CTX *ctx)
+{
+    return ctx->current_crl;
+}
+
+X509_STORE_CTX *X509_STORE_CTX_get0_parent_ctx(X509_STORE_CTX *ctx)
+{
+    return ctx->parent;
 }
 
 void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx, X509 *x)
@@ -1309,6 +2254,8 @@ X509_STORE_CTX *X509_STORE_CTX_new(void)
 
 void X509_STORE_CTX_free(X509_STORE_CTX *ctx)
 {
+    if (!ctx)
+        return;
     X509_STORE_CTX_cleanup(ctx);
     OPENSSL_free(ctx);
 }
@@ -1331,7 +2278,11 @@ int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store, X509 *x509,
     ctx->error_depth = 0;
     ctx->current_cert = NULL;
     ctx->current_issuer = NULL;
+    ctx->current_crl = NULL;
+    ctx->current_crl_score = 0;
+    ctx->current_reasons = 0;
     ctx->tree = NULL;
+    ctx->parent = NULL;
 
     ctx->param = X509_VERIFY_PARAM_new();
 
@@ -1392,7 +2343,7 @@ int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store, X509 *x509,
     if (store && store->get_crl)
         ctx->get_crl = store->get_crl;
     else
-        ctx->get_crl = get_crl;
+        ctx->get_crl = NULL;
 
     if (store && store->check_crl)
         ctx->check_crl = store->check_crl;
@@ -1404,6 +2355,16 @@ int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store, X509 *x509,
     else
         ctx->cert_crl = cert_crl;
 
+    if (store && store->lookup_certs)
+        ctx->lookup_certs = store->lookup_certs;
+    else
+        ctx->lookup_certs = X509_STORE_get1_certs;
+
+    if (store && store->lookup_crls)
+        ctx->lookup_crls = store->lookup_crls;
+    else
+        ctx->lookup_crls = X509_STORE_get1_crls;
+
     ctx->check_policy = check_policy;
 
     /*
@@ -1437,7 +2398,8 @@ void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx)
     if (ctx->cleanup)
         ctx->cleanup(ctx);
     if (ctx->param != NULL) {
-        X509_VERIFY_PARAM_free(ctx->param);
+        if (ctx->parent == NULL)
+            X509_VERIFY_PARAM_free(ctx->param);
         ctx->param = NULL;
     }
     if (ctx->tree != NULL) {