diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index c2c270881..2def1ee96 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -957,6 +957,20 @@
  */
 //#define POLARSSL_X509_ALLOW_UNSUPPORTED_CRITICAL_EXTENSION
 
+/**
+ * \def POLARSSL_X509_CHECK_KEY_USAGE
+ *
+ * Enable verification of the keyUsage extension (CA and leaf certificates).
+ *
+ * Disabling this avoids problems with mis-issued and/or misused
+ * (intermediate) CA and leaf certificates.
+ *
+ * \warning Depending on your PKI use, disabling this can be a security risk!
+ *
+ * Comment to skip keyUsage checking for both CA and leaf certificates.
+ */
+#define POLARSSL_X509_CHECK_KEY_USAGE
+
 /**
  * \def POLARSSL_ZLIB_SUPPORT
  *
diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index 95859e861..cb3280505 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -1657,6 +1657,19 @@ static inline x509_crt *ssl_own_cert( ssl_context *ssl )
     return( ssl->handshake->key_cert == NULL ? NULL
             : ssl->handshake->key_cert->cert );
 }
+
+/*
+ * Check usage of a certificate wrt extensions:
+ * keyUsage, extendedKeyUsage (later), and nSCertType (later).
+ *
+ * Warning: cert_endpoint is the endpoint of the cert (ie, of our peer when we
+ * check a cert we received from them)!
+ *
+ * Return 0 if everything is OK, -1 if not.
+ */
+int ssl_check_cert_usage( const x509_crt *cert,
+                          const ssl_ciphersuite_t *ciphersuite,
+                          int cert_endpoint );
 #endif /* POLARSSL_X509_CRT_PARSE_C */
 
 /* constant-time buffer comparison */
diff --git a/include/polarssl/x509_crt.h b/include/polarssl/x509_crt.h
index e3c8b1877..93340eccd 100644
--- a/include/polarssl/x509_crt.h
+++ b/include/polarssl/x509_crt.h
@@ -244,6 +244,26 @@ int x509_crt_verify( x509_crt *crt,
                      int (*f_vrfy)(void *, x509_crt *, int, int *),
                      void *p_vrfy );
 
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+/**
+ * \brief          Check usage of certificate against keyUsage extension.
+ *
+ * \param crt      Leaf certificate used.
+ * \param usage    Intended usage(s) (eg KU_KEY_ENCIPHERMENT before using the
+ *                 certificate to perform an RSA key exchange).
+ *
+ * \return         0 is these uses of the certificate are allowed,
+ *                 POLARSSL_ERR_X509_BAD_INPUT_DATA if the keyUsage extension
+ *                 is present but does not contain all the bits set in the
+ *                 usage argument.
+ *
+ * \note           You should only call this function on leaf certificates, on
+ *                 (intermediate) CAs the keyUsage extension is automatically
+ *                 checked by \c x509_crt_verify().
+ */
+int x509_crt_check_key_usage( const x509_crt *crt, int usage );
+#endif /* POLARSSL_X509_CHECK_KEY_USAGE) */
+
 #if defined(POLARSSL_X509_CRL_PARSE_C)
 /**
  * \brief          Verify the certificate revocation status
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 08f6eea67..8bdf237d9 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -797,6 +797,20 @@ static int ssl_pick_cert( ssl_context *ssl,
         if( ! pk_can_do( cur->key, pk_alg ) )
             continue;
 
+        /*
+         * This avoids sending the client a cert it'll reject based on
+         * keyUsage or other extensions.
+         *
+         * It also allows the user to provision different certificates for
+         * different uses based on keyUsage, eg if they want to avoid signing
+         * and decrypting with the same RSA key.
+         */
+        if( ssl_check_cert_usage( cur->cert, ciphersuite_info,
+                                  SSL_IS_SERVER ) != 0 )
+        {
+            continue;
+        }
+
 #if defined(POLARSSL_ECDSA_C)
         if( pk_alg == POLARSSL_PK_ECDSA )
         {
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 38843a3cd..588cbc4a2 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2699,6 +2699,9 @@ int ssl_parse_certificate( ssl_context *ssl )
             return( POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED );
         }
 
+        /*
+         * Main check: verify certificate
+         */
         ret = x509_crt_verify( ssl->session_negotiate->peer_cert,
                                ssl->ca_chain, ssl->ca_crl, ssl->peer_cn,
                               &ssl->session_negotiate->verify_result,
@@ -2708,21 +2711,35 @@ int ssl_parse_certificate( ssl_context *ssl )
         {
             SSL_DEBUG_RET( 1, "x509_verify_cert", ret );
         }
+
+        /*
+         * Secondary checks: always done, but change 'ret' only if it was 0
+         */
+
 #if defined(POLARSSL_SSL_SET_CURVES)
-        else
         {
-            pk_context *pk = &ssl->session_negotiate->peer_cert->pk;
+            const pk_context *pk = &ssl->session_negotiate->peer_cert->pk;
 
             /* If certificate uses an EC key, make sure the curve is OK */
             if( pk_can_do( pk, POLARSSL_PK_ECKEY ) &&
                 ! ssl_curve_is_acceptable( ssl, pk_ec( *pk )->grp.id ) )
             {
-                SSL_DEBUG_MSG( 1, ( "bad server certificate (EC key curve)" ) );
-                ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
+                SSL_DEBUG_MSG( 1, ( "bad certificate (EC key curve)" ) );
+                if( ret == 0 )
+                    ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
             }
         }
 #endif
 
+        if( ssl_check_cert_usage( ssl->session_negotiate->peer_cert,
+                                  ciphersuite_info,
+                                  ! ssl->endpoint ) != 0 )
+        {
+            SSL_DEBUG_MSG( 1, ( "bad certificate (usage extensions)" ) );
+            if( ret == 0 )
+                ret = POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE;
+        }
+
         if( ssl->authmode != SSL_VERIFY_REQUIRED )
             ret = 0;
     }
@@ -4747,3 +4764,54 @@ int ssl_curve_is_acceptable( const ssl_context *ssl, ecp_group_id grp_id )
     return( 0 );
 }
 #endif
+
+int ssl_check_cert_usage( const x509_crt *cert,
+                          const ssl_ciphersuite_t *ciphersuite,
+                          int cert_endpoint )
+{
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+    int usage = 0;
+#endif
+
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+    if( cert_endpoint == SSL_IS_SERVER )
+    {
+        /* Server part of the key exchange */
+        switch( ciphersuite->key_exchange )
+        {
+            case POLARSSL_KEY_EXCHANGE_RSA:
+            case POLARSSL_KEY_EXCHANGE_RSA_PSK:
+                usage = KU_KEY_ENCIPHERMENT;
+                break;
+
+            case POLARSSL_KEY_EXCHANGE_DHE_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_ECDSA:
+                usage = KU_DIGITAL_SIGNATURE;
+                break;
+
+            case POLARSSL_KEY_EXCHANGE_ECDH_RSA:
+            case POLARSSL_KEY_EXCHANGE_ECDH_ECDSA:
+                usage = KU_KEY_AGREEMENT;
+                break;
+
+            /* Don't use default: we want warnings when adding new values */
+            case POLARSSL_KEY_EXCHANGE_NONE:
+            case POLARSSL_KEY_EXCHANGE_PSK:
+            case POLARSSL_KEY_EXCHANGE_DHE_PSK:
+            case POLARSSL_KEY_EXCHANGE_ECDHE_PSK:
+                usage = 0;
+        }
+    }
+    else
+    {
+        /* Client auth: we only implement rsa_sign and ecdsa_sign for now */
+        usage = KU_DIGITAL_SIGNATURE;
+    }
+
+    if( x509_crt_check_key_usage( cert, usage ) != 0 )
+        return( -1 );
+#endif /* POLARSSL_X509_CHECK_KEY_USAGE */
+
+    return( 0 );
+}
diff --git a/library/x509_crt.c b/library/x509_crt.c
index d9f25edf1..42fbfab20 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1360,6 +1360,17 @@ int x509_crt_info( char *buf, size_t size, const char *prefix,
     return( (int) ( size - n ) );
 }
 
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+int x509_crt_check_key_usage( const x509_crt *crt, int usage )
+{
+    if( ( crt->ext_types & EXT_KEY_USAGE ) != 0 &&
+        ( crt->key_usage & usage ) != usage )
+        return( POLARSSL_ERR_X509_BAD_INPUT_DATA );
+
+    return( 0 );
+}
+#endif
+
 #if defined(POLARSSL_X509_CRL_PARSE_C)
 /*
  * Return 1 if the certificate is revoked, or 0 otherwise.
@@ -1413,6 +1424,17 @@ static int x509_crt_verifycrl( x509_crt *crt, x509_crt *ca,
             continue;
         }
 
+        /*
+         * Check if the CA is configured to sign CRLs
+         */
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+        if( x509_crt_check_key_usage( ca, KU_CRL_SIGN ) != 0 )
+        {
+            flags |= BADCRL_NOT_TRUSTED;
+            break;
+        }
+#endif
+
         /*
          * Check if CRL is correctly signed by the trusted CA
          */
@@ -1516,6 +1538,30 @@ static int x509_wildcard_verify( const char *cn, x509_buf *name )
     return( 0 );
 }
 
+/*
+ * Check if 'parent' is a suitable parent (signing CA) for 'child'.
+ * Return 0 if yes, -1 if not.
+ */
+static int x509_crt_check_parent( const x509_crt *child,
+                                  const x509_crt *parent )
+{
+    if( parent->version == 0 ||
+        parent->ca_istrue == 0 ||
+        child->issuer_raw.len != parent->subject_raw.len ||
+        memcmp( child->issuer_raw.p, parent->subject_raw.p,
+                child->issuer_raw.len ) != 0 )
+    {
+        return( -1 );
+    }
+
+#if defined(POLARSSL_X509_CHECK_KEY_USAGE)
+    if( x509_crt_check_key_usage( parent, KU_KEY_CERT_SIGN ) != 0 )
+        return( -1 );
+#endif
+
+    return( 0 );
+}
+
 static int x509_crt_verify_top(
                 x509_crt *child, x509_crt *trust_ca,
                 x509_crl *ca_crl, int path_cnt, int *flags,
@@ -1549,16 +1595,10 @@ static int x509_crt_verify_top(
     else
         md( md_info, child->tbs.p, child->tbs.len, hash );
 
-    while( trust_ca != NULL )
+    for( /* trust_ca */ ; trust_ca != NULL; trust_ca = trust_ca->next )
     {
-        if( trust_ca->version == 0 ||
-            child->issuer_raw.len != trust_ca->subject_raw.len ||
-            memcmp( child->issuer_raw.p, trust_ca->subject_raw.p,
-                    child->issuer_raw.len ) != 0 )
-        {
-            trust_ca = trust_ca->next;
+        if( x509_crt_check_parent( child, trust_ca ) != 0 )
             continue;
-        }
 
         /*
          * Reduce path_len to check against if top of the chain is
@@ -1574,7 +1614,6 @@ static int x509_crt_verify_top(
         if( trust_ca->max_pathlen > 0 &&
             trust_ca->max_pathlen < check_path_cnt )
         {
-            trust_ca = trust_ca->next;
             continue;
         }
 
@@ -1582,7 +1621,6 @@ static int x509_crt_verify_top(
             pk_verify( &trust_ca->pk, child->sig_md, hash, md_info->size,
                        child->sig.p, child->sig.len ) != 0 )
         {
-            trust_ca = trust_ca->next;
             continue;
         }
 
@@ -1678,34 +1716,27 @@ static int x509_crt_verify_child(
     *flags |= x509_crt_verifycrl(child, parent, ca_crl);
 #endif
 
-    grandparent = parent->next;
-
-    while( grandparent != NULL )
+    /* Look for a grandparent upwards the chain */
+    for( grandparent = parent->next;
+         grandparent != NULL;
+         grandparent = grandparent->next )
     {
-        if( grandparent->version == 0 ||
-            grandparent->ca_istrue == 0 ||
-            parent->issuer_raw.len != grandparent->subject_raw.len ||
-            memcmp( parent->issuer_raw.p, grandparent->subject_raw.p,
-                    parent->issuer_raw.len ) != 0 )
-        {
-            grandparent = grandparent->next;
-            continue;
-        }
-        break;
+        if( x509_crt_check_parent( parent, grandparent ) == 0 )
+            break;
     }
 
+    /* Is our parent part of the chain or at the top? */
     if( grandparent != NULL )
     {
-        /*
-         * Part of the chain
-         */
-        ret = x509_crt_verify_child( parent, grandparent, trust_ca, ca_crl, path_cnt + 1, &parent_flags, f_vrfy, p_vrfy );
+        ret = x509_crt_verify_child( parent, grandparent, trust_ca, ca_crl,
+                                path_cnt + 1, &parent_flags, f_vrfy, p_vrfy );
         if( ret != 0 )
             return( ret );
     }
     else
     {
-        ret = x509_crt_verify_top( parent, trust_ca, ca_crl, path_cnt + 1, &parent_flags, f_vrfy, p_vrfy );
+        ret = x509_crt_verify_top( parent, trust_ca, ca_crl,
+                                path_cnt + 1, &parent_flags, f_vrfy, p_vrfy );
         if( ret != 0 )
             return( ret );
     }
@@ -1789,37 +1820,25 @@ int x509_crt_verify( x509_crt *crt,
         }
     }
 
-    /*
-     * Iterate upwards in the given cert chain, to find our crt parent.
-     * Ignore any upper cert with CA != TRUE.
-     */
-    parent = crt->next;
-
-    while( parent != NULL && parent->version != 0 )
+    /* Look for a parent upwards the chain */
+    for( parent = crt->next; parent != NULL; parent = parent->next )
     {
-        if( parent->ca_istrue == 0 ||
-            crt->issuer_raw.len != parent->subject_raw.len ||
-            memcmp( crt->issuer_raw.p, parent->subject_raw.p,
-                    crt->issuer_raw.len ) != 0 )
-        {
-            parent = parent->next;
-            continue;
-        }
-        break;
+        if( x509_crt_check_parent( crt, parent ) == 0 )
+            break;
     }
 
+    /* Are we part of the chain or at the top? */
     if( parent != NULL )
     {
-        /*
-         * Part of the chain
-         */
-        ret = x509_crt_verify_child( crt, parent, trust_ca, ca_crl, pathlen, flags, f_vrfy, p_vrfy );
+        ret = x509_crt_verify_child( crt, parent, trust_ca, ca_crl,
+                                     pathlen, flags, f_vrfy, p_vrfy );
         if( ret != 0 )
             return( ret );
     }
     else
     {
-        ret = x509_crt_verify_top( crt, trust_ca, ca_crl, pathlen, flags, f_vrfy, p_vrfy );
+        ret = x509_crt_verify_top( crt, trust_ca, ca_crl,
+                                   pathlen, flags, f_vrfy, p_vrfy );
         if( ret != 0 )
             return( ret );
     }
diff --git a/tests/data_files/server2.ku-ds.crt b/tests/data_files/server2.ku-ds.crt
new file mode 100644
index 000000000..3bd07d0fb
--- /dev/null
+++ b/tests/data_files/server2.ku-ds.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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==
+-----END CERTIFICATE-----
diff --git a/tests/data_files/server2.ku-ds_ke.crt b/tests/data_files/server2.ku-ds_ke.crt
new file mode 100644
index 000000000..ebee7e1c3
--- /dev/null
+++ b/tests/data_files/server2.ku-ds_ke.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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==
+-----END CERTIFICATE-----
diff --git a/tests/data_files/server2.ku-ka.crt b/tests/data_files/server2.ku-ka.crt
new file mode 100644
index 000000000..90f7c4a99
--- /dev/null
+++ b/tests/data_files/server2.ku-ka.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIDijCCAnKgAwIBAgIBKjANBgkqhkiG9w0BAQUFADA7MQswCQYDVQQGEwJOTDER
+MA8GA1UEChMIUG9sYXJTU0wxGTAXBgNVBAMTEFBvbGFyU1NMIFRlc3QgQ0EwHhcN
+MTQwNDA5MDg0NDIzWhcNMjQwNDA2MDg0NDIzWjA0MQswCQYDVQQGEwJOTDERMA8G
+A1UEChMIUG9sYXJTU0wxEjAQBgNVBAMTCWxvY2FsaG9zdDCCASIwDQYJKoZIhvcN
+AQEBBQADggEPADCCAQoCggEBAMFNo93nzR3RBNdJcriZrA545Do8Ss86ExbQWuTN
+owCIp+4ea5anUrSQ7y1yej4kmvy2NKwk9XfgJmSMnLAofaHa6ozmyRyWvP7BBFKz
+NtSj+uGxdtiQwWG0ZlI2oiZTqqt0Xgd9GYLbKtgfoNkNHC1JZvdbJXNG6AuKT2kM
+tQCQ4dqCEGZ9rlQri2V5kaHiYcPNQEkI7mgM8YuG0ka/0LiqEQMef1aoGh5EGA8P
+hYvai0Re4hjGYi/HZo36Xdh98yeJKQHFkA4/J/EwyEoO79bex8cna8cFPXrEAjya
+HT4P6DSYW8tzS1KW2BGiLICIaTla0w+w3lkvEcf36hIBMJcCAwEAAaOBnzCBnDAJ
+BgNVHRMEAjAAMB0GA1UdDgQWBBSlBehkuNzfYA9QEk1gqGSvTYtDkzBjBgNVHSME
+XDBagBS0WuSls97SUva51aaVD+s+vMf9/6E/pD0wOzELMAkGA1UEBhMCTkwxETAP
+BgNVBAoTCFBvbGFyU1NMMRkwFwYDVQQDExBQb2xhclNTTCBUZXN0IENBggEAMAsG
+A1UdDwQEAwIDCDANBgkqhkiG9w0BAQUFAAOCAQEAriPloIWfu7U8d1hls97C7OBI
+OiE2xFh2UmuN/9hTK2CyW6MtBf8aG3l4jQDrsutHO0gUyoR67ug4yj+s+0S/zETZ
+q6mPo7cBbVwjhGciQRiYgufFpdnbXR05HDgOVPK7qqjL6UOZnbu5caIEvIJgdwXn
+n8WB9x/Ii4/2S9ysmRdRhDBYekzgH3Ac2UnHJTMh1XaSL817MW6B9BDKHt4xa7pW
+cplDzrFKYbmxSSxzALE4Dr+zRvmDx4bcYpBkRRfOhnnR1caQBgaZzPcX/Vu+vw8e
+qs2nyBW5RBu8MBCBU1DpqOSo6jl0QTpuq3NzQZIouG9fyckqDJS5ibrxQTutPw==
+-----END CERTIFICATE-----
diff --git a/tests/data_files/server2.ku-ke.crt b/tests/data_files/server2.ku-ke.crt
new file mode 100644
index 000000000..8daa0c13d
--- /dev/null
+++ b/tests/data_files/server2.ku-ke.crt
@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----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==
+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.ku-ds.crt b/tests/data_files/server5.ku-ds.crt
new file mode 100644
index 000000000..58dd0714b
--- /dev/null
+++ b/tests/data_files/server5.ku-ds.crt
@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.ku-ka.crt b/tests/data_files/server5.ku-ka.crt
new file mode 100644
index 000000000..2447326c2
--- /dev/null
+++ b/tests/data_files/server5.ku-ka.crt
@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.ku-ke.crt b/tests/data_files/server5.ku-ke.crt
new file mode 100644
index 000000000..41ae5ada3
--- /dev/null
+++ b/tests/data_files/server5.ku-ke.crt
@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/test-ca2.ku-crl.crt b/tests/data_files/test-ca2.ku-crl.crt
new file mode 100644
index 000000000..4fb40838c
--- /dev/null
+++ b/tests/data_files/test-ca2.ku-crl.crt
@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/test-ca2.ku-crt.crt b/tests/data_files/test-ca2.ku-crt.crt
new file mode 100644
index 000000000..edacc64c9
--- /dev/null
+++ b/tests/data_files/test-ca2.ku-crt.crt
@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/test-ca2.ku-crt_crl.crt b/tests/data_files/test-ca2.ku-crt_crl.crt
new file mode 100644
index 000000000..ac74e402a
--- /dev/null
+++ b/tests/data_files/test-ca2.ku-crt_crl.crt
@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/test-ca2.ku-ds.crt b/tests/data_files/test-ca2.ku-ds.crt
new file mode 100644
index 000000000..c28e17b22
--- /dev/null
+++ b/tests/data_files/test-ca2.ku-ds.crt
@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index b35a9e4a8..16748b07c 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -151,8 +151,9 @@ run_test() {
     CLI_EXIT=$?
     echo "EXIT: $CLI_EXIT" >> cli_out
 
+    # psk is usefull when server only has bad certs
     if is_polar "$SRV_CMD"; then
-        "$P_CLI" request_page=SERVERQUIT tickets=0 auth_mode=none \
+        "$P_CLI" request_page=SERVERQUIT tickets=0 auth_mode=none psk=abc123 \
             crt_file=data_files/cli2.crt key_file=data_files/cli2.key \
             >/dev/null
     else
@@ -980,6 +981,161 @@ run_test    "ALPN #6 (both, no common)" \
 
 fi
 
+# Tests for keyUsage in leaf certificates, part 1:
+# server-side certificate/suite selection
+
+run_test    "keyUsage srv #1 (RSA, digitalSignature -> ECDHE-RSA)" \
+            "$P_SRV key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ds.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDHE-RSA-WITH-"
+
+
+run_test    "keyUsage srv #2 (RSA, keyEncipherment -> RSA)" \
+            "$P_SRV key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ke.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-RSA-WITH-"
+
+# add psk to leave an option for client to send SERVERQUIT
+run_test    "keyUsage srv #3 (RSA, keyAgreement -> fail)" \
+            "$P_SRV psk=abc123 key_file=data_files/server2.key \
+             crt_file=data_files/server2.ku-ka.crt" \
+            "$P_CLI psk=badbad" \
+            1 \
+            -C "Ciphersuite is "
+
+run_test    "keyUsage srv #4 (ECDSA, digitalSignature -> ECDHE-ECDSA)" \
+            "$P_SRV key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ds.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDHE-ECDSA-WITH-"
+
+
+run_test    "keyUsage srv #5 (ECDSA, keyAgreement -> ECDH-)" \
+            "$P_SRV key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ka.crt" \
+            "$P_CLI" \
+            0 \
+            -c "Ciphersuite is TLS-ECDH-"
+
+# add psk to leave an option for client to send SERVERQUIT
+run_test    "keyUsage srv #6 (ECDSA, keyEncipherment -> fail)" \
+            "$P_SRV psk=abc123 key_file=data_files/server5.key \
+             crt_file=data_files/server5.ku-ke.crt" \
+            "$P_CLI psk=badbad" \
+            1 \
+            -C "Ciphersuite is "
+
+# Tests for keyUsage in leaf certificates, part 2:
+# client-side checking of server cert
+
+run_test    "keyUsage cli #1 (DigitalSignature+KeyEncipherment, RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds_ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad certificate (usage extensions)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #2 (DigitalSignature+KeyEncipherment, DHE-RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds_ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad certificate (usage extensions)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #3 (KeyEncipherment, RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad certificate (usage extensions)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #4 (KeyEncipherment, DHE-RSA: fail)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            1 \
+            -c "bad certificate (usage extensions)" \
+            -c "Processing of the Certificate handshake message failed" \
+            -C "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #5 (DigitalSignature, DHE-RSA: OK)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-DHE-RSA-WITH-AES-128-CBC-SHA" \
+            0 \
+            -C "bad certificate (usage extensions)" \
+            -C "Processing of the Certificate handshake message failed" \
+            -c "Ciphersuite is TLS-"
+
+run_test    "keyUsage cli #5 (DigitalSignature, RSA: fail)" \
+            "$O_SRV -key data_files/server2.key \
+             -cert data_files/server2.ku-ds.crt" \
+            "$P_CLI debug_level=2 \
+             force_ciphersuite=TLS-RSA-WITH-AES-128-CBC-SHA" \
+            1 \
+            -c "bad certificate (usage extensions)" \
+            -c "Processing of the Certificate handshake message failed" \
+            -C "Ciphersuite is TLS-"
+
+# Tests for keyUsage in leaf certificates, part 3:
+# server-side checking of client cert
+
+run_test    "keyUsage cli-auth #1 (RSA, DigitalSignature: OK)" \
+            "$P_SRV debug_level=2 auth_mode=optional" \
+            "$O_CLI -key data_files/server2.key \
+             -cert data_files/server2.ku-ds.crt" \
+            0 \
+            -S "bad certificate (usage extensions)" \
+            -S "Processing of the Certificate handshake message failed"
+
+run_test    "keyUsage cli-auth #2 (RSA, KeyEncipherment: fail (soft))" \
+            "$P_SRV debug_level=2 auth_mode=optional" \
+            "$O_CLI -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            0 \
+            -s "bad certificate (usage extensions)" \
+            -S "Processing of the Certificate handshake message failed"
+
+run_test    "keyUsage cli-auth #3 (RSA, KeyEncipherment: fail (hard))" \
+            "$P_SRV debug_level=2 auth_mode=required" \
+            "$O_CLI -key data_files/server2.key \
+             -cert data_files/server2.ku-ke.crt" \
+            1 \
+            -s "bad certificate (usage extensions)" \
+            -s "Processing of the Certificate handshake message failed"
+
+run_test    "keyUsage cli-auth #4 (ECDSA, DigitalSignature: OK)" \
+            "$P_SRV debug_level=2 auth_mode=optional" \
+            "$O_CLI -key data_files/server5.key \
+             -cert data_files/server5.ku-ds.crt" \
+            0 \
+            -S "bad certificate (usage extensions)" \
+            -S "Processing of the Certificate handshake message failed"
+
+run_test    "keyUsage cli-auth #5 (ECDSA, KeyAgreement: fail (soft))" \
+            "$P_SRV debug_level=2 auth_mode=optional" \
+            "$O_CLI -key data_files/server5.key \
+             -cert data_files/server5.ku-ka.crt" \
+            0 \
+            -s "bad certificate (usage extensions)" \
+            -S "Processing of the Certificate handshake message failed"
+
 # Final report
 
 echo "------------------------------------------------------------------------"
diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index ef9a331f5..8b1df44a4 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -442,6 +442,26 @@ X509 Certificate verification #51 (Valid, multiple CAs, reverse order)
 depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_RSA_C:POLARSSL_ECP_DP_SECP192R1_ENABLED:POLARSSL_PKCS1_V15
 x509_verify:"data_files/server2.crt":"data_files/test-ca_cat21.crt":"data_files/crl.pem":"NULL":0:0:"NULL"
 
+X509 Certificate verification #52 (CA keyUsage valid)
+depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_SHA256_C
+x509_verify:"data_files/server5.crt":"data_files/test-ca2.ku-crt_crl.crt":"data_files/crl-ec-sha256.pem":"NULL":0:0:"NULL"
+
+X509 Certificate verification #53 (CA keyUsage missing cRLSign)
+depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_SHA256_C
+x509_verify:"data_files/server5.crt":"data_files/test-ca2.ku-crt.crt":"data_files/crl-ec-sha256.pem":"NULL":POLARSSL_ERR_X509_CERT_VERIFY_FAILED:BADCRL_NOT_TRUSTED:"NULL"
+
+X509 Certificate verification #54 (CA keyUsage missing cRLSign, no CRL)
+depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_SHA256_C
+x509_verify:"data_files/server5.crt":"data_files/test-ca2.ku-crt.crt":"data_files/crl.pem":"NULL":0:0:"NULL"
+
+X509 Certificate verification #55 (CA keyUsage missing keyCertSign)
+depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_SHA256_C
+x509_verify:"data_files/server5.crt":"data_files/test-ca2.ku-crl.crt":"data_files/crl-ec-sha256.pem":"NULL":POLARSSL_ERR_X509_CERT_VERIFY_FAILED:BADCERT_NOT_TRUSTED:"NULL"
+
+X509 Certificate verification #55 (CA keyUsage plain wrong)
+depends_on:POLARSSL_PEM_PARSE_C:POLARSSL_ECDSA_C:POLARSSL_SHA256_C
+x509_verify:"data_files/server5.crt":"data_files/test-ca2.ku-ds.crt":"data_files/crl-ec-sha256.pem":"NULL":POLARSSL_ERR_X509_CERT_VERIFY_FAILED:BADCERT_NOT_TRUSTED:"NULL"
+
 X509 Parse Selftest
 depends_on:POLARSSL_MD5_C:POLARSSL_PEM_PARSE_C
 x509_selftest:
@@ -826,3 +846,28 @@ x509_oid_numstr:"2A864886F70D":"1.2.840.113549":15:14
 
 X509 OID numstring #5 (arithmetic overflow)
 x509_oid_numstr:"2A8648F9F8F7F6F5F4F3F2F1F001":"":100:POLARSSL_ERR_OID_BUF_TOO_SMALL
+
+X509 crt keyUsage #1 (no extension, expected KU)
+x509_check_key_usage:"data_files/server1.crt":KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT:0
+
+X509 crt keyUsage #2 (no extension, suprising KU)
+x509_check_key_usage:"data_files/server1.crt":KU_KEY_CERT_SIGN:0
+
+X509 crt keyUsage #3 (extension present, no KU)
+x509_check_key_usage:"data_files/server1.key_usage.crt":0:0
+
+X509 crt keyUsage #4 (extension present, single KU present)
+x509_check_key_usage:"data_files/server1.key_usage.crt":KU_DIGITAL_SIGNATURE:0
+
+X509 crt keyUsage #5 (extension present, single KU absent)
+x509_check_key_usage:"data_files/server1.key_usage.crt":KU_KEY_CERT_SIGN:POLARSSL_ERR_X509_BAD_INPUT_DATA
+
+X509 crt keyUsage #6 (extension present, combined KU present)
+x509_check_key_usage:"data_files/server1.key_usage.crt":KU_DIGITAL_SIGNATURE|KU_KEY_ENCIPHERMENT:0
+
+X509 crt keyUsage #7 (extension present, combined KU both absent)
+x509_check_key_usage:"data_files/server1.key_usage.crt":KU_KEY_CERT_SIGN|KU_CRL_SIGN:POLARSSL_ERR_X509_BAD_INPUT_DATA
+
+X509 crt keyUsage #8 (extension present, combined KU one absent)
+x509_check_key_usage:"data_files/server1.key_usage.crt":KU_KEY_ENCIPHERMENT|KU_KEY_AGREEMENT:POLARSSL_ERR_X509_BAD_INPUT_DATA
+
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index effa4cc30..a4b2cf3a4 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -316,6 +316,21 @@ void x509_oid_numstr( char *oid_str, char *numstr, int blen, int ret )
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:POLARSSL_X509_CRT_PARSE_C */
+void x509_check_key_usage( char *crt_file, int usage, int ret )
+{
+    x509_crt crt;
+
+    x509_crt_init( &crt );
+
+    TEST_ASSERT( x509_crt_parse_file( &crt, crt_file ) == 0 );
+
+    TEST_ASSERT( x509_crt_check_key_usage( &crt, usage ) == ret );
+
+    x509_crt_free( &crt );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:POLARSSL_X509_CRT_PARSE_C:POLARSSL_SELF_TEST */
 void x509_selftest()
 {