diff --git a/Dockerfile b/Dockerfile
index 53065ff..1a2d0a1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -13,11 +13,11 @@ LABEL org.opencontainers.image.source https://github.com/rpardini/docker-registr
 RUN apk add --no-cache --update bash ca-certificates-bundle coreutils openssl
 
 # If set to 1, enables building mitmproxy, which helps a lot in debugging, but is super heavy to build.
-ARG DEBUG_BUILD="1"
+ARG DEBUG_BUILD="0"
 ENV DO_DEBUG_BUILD="$DEBUG_BUILD"
 
 # Build mitmproxy via pip. This is heavy, takes minutes do build and creates a 90mb+ layer. Oh well.
-RUN [[ "a$DO_DEBUG_BUILD" == "a1" ]] && { echo "Debug build ENABLED." \
+RUN [ "$DO_DEBUG_BUILD" = "1" ] && { echo "Debug build ENABLED." \
  && apk add --no-cache --update su-exec git g++ libffi libffi-dev libstdc++ openssl-dev python3 python3-dev py3-pip py3-wheel py3-six py3-idna py3-certifi py3-setuptools \
  && LDFLAGS=-L/lib pip install mitmproxy==5.2 \
  && apk del --purge git g++ libffi-dev openssl-dev python3-dev py3-pip py3-wheel \
@@ -28,7 +28,7 @@ RUN [[ "a$DO_DEBUG_BUILD" == "a1" ]] && { echo "Debug build ENABLED." \
 ENV LANG=en_US.UTF-8
 
 # Check the installed mitmproxy version, if built.
-RUN [[ "a$DO_DEBUG_BUILD" == "a1" ]] && { mitmproxy --version && mitmweb --version ; } || { echo "Debug build disabled."; }
+RUN [ "$DO_DEBUG_BUILD" = "1" ] && { mitmproxy --version && mitmweb --version ; } || { echo "Debug build disabled."; }
 
 # Create the cache directory and CA directory
 RUN mkdir -p /docker_mirror_cache /ca
@@ -60,17 +60,24 @@ EXPOSE 8082
 
 ## Default envs.
 # A space delimited list of registries we should proxy and cache; this is in addition to the central DockerHub.
-ENV REGISTRIES="k8s.gcr.io gcr.io quay.io"
+ENV REGISTRIES="auth.docker.io registry-1.docker.io docker.caching.proxy.internal k8s.gcr.io gcr.io quay.io gitlab.com registry.gitlab.com"
 # A space delimited list of registry:user:password to inject authentication for
-ENV AUTH_REGISTRIES="some.authenticated.registry:oneuser:onepassword another.registry:user:password"
+# (e.g. AUTH_REGISTRIES="auth.docker.io:dhuser:dhpass gitlab.com:gluser:glpass")
+ENV AUTH_REGISTRIES=""
 # Should we verify upstream's certificates? Default to true.
 ENV VERIFY_SSL="true"
+
 # Enable debugging mode; this inserts mitmproxy/mitmweb between the CONNECT proxy and the caching layer
 ENV DEBUG="false"
 # Enable debugging mode; this inserts mitmproxy/mitmweb between the caching layer and DockerHub's registry
 ENV DEBUG_HUB="false"
 # Enable nginx debugging mode; this uses nginx-debug binary and enabled debug logging, which is VERY verbose so separate setting
 ENV DEBUG_NGINX="false"
+# Enable debugging mode for creating CA certificate
+ENV DEBUG_CA_CERT="false"
+
+# Set Docker Registry cache size, by default, 32 GB ('32g')
+ENV CACHE_MAX_SIZE="32g"
 
 # Manifest caching tiers. Disabled by default, to mimick 0.4/0.5 behaviour.
 # Setting it to true enables the processing of the ENVs below.
@@ -94,8 +101,13 @@ ENV MANIFEST_CACHE_SECONDARY_TIME="60d"
 # In the default config, :latest and other frequently-used tags will get this value.
 ENV MANIFEST_CACHE_DEFAULT_TIME="1h"
 
+# Should we allow overridding with own authentication, default to false.
+ENV ALLOW_OWN_AUTH="false"
+
 # Should we allow actions different than pull, default to false.
 ENV ALLOW_PUSH="false"
+# Should we allow push only with own authentication, default to false.
+ENV ALLOW_PUSH_WITH_OWN_AUTH="false"
 
 # Timeouts
 # ngx_http_core_module
diff --git a/README.md b/README.md
index a419e99..e92f911 100644
--- a/README.md
+++ b/README.md
@@ -79,7 +79,9 @@ for this to work it requires inserting a root CA certificate into system trusted
 - Expose port 3128 to the network
 - Map volume `/docker_mirror_cache` for up to `CACHE_MAX_SIZE` (32gb by default) of cached images across all cached registries
 - Map volume `/ca`, the proxy will store the CA certificate here across restarts. **Important** this is security sensitive.
-- Env `ALLOW_PUSH` : This bypasses the proxy when pushing, default to false - if kept to false, pushing will not work. For more info see this [commit](https://github.com/rpardini/docker-registry-proxy/commit/536f0fc8a078d03755f1ae8edc19a86fc4b37fcf).
+- Env `ALLOW_OWN_AUTH` (default `false`): Allow overridding the `AUTH_REGISTRIES` authentication with own Docker credentials if provided (to support `docker login` as another user).
+- Env `ALLOW_PUSH` (default `false`): This bypasses the proxy when pushing, default to false - if kept to false, pushing will not work. For more info see this [commit](https://github.com/rpardini/docker-registry-proxy/commit/536f0fc8a078d03755f1ae8edc19a86fc4b37fcf).
+- Env `ALLOW_PUSH_WITH_OWN_AUTH` (default `false`): Allow bypassing the proxy when pushing only if own authentication is provided.
 - Env `CACHE_MAX_SIZE` (default `32g`): set the max size to be used for caching local Docker image layers. Use [Nginx sizes](http://nginx.org/en/docs/syntax.html).
 - Env `ENABLE_MANIFEST_CACHE`, see the section on pull rate limiting.
 - Env `REGISTRIES`: space separated list of registries to cache; no need to include DockerHub, its already done internally.
diff --git a/create_ca_cert.sh b/create_ca_cert.sh
index b7c9352..c27099b 100644
--- a/create_ca_cert.sh
+++ b/create_ca_cert.sh
@@ -2,8 +2,6 @@
 
 set -Eeuo pipefail
 
-declare -i DEBUG=0
-
 logInfo() {
     echo "INFO: $@"
 }
@@ -53,10 +51,10 @@ subjectKeyIdentifier = hash
 EOF
 )
 
-    [[ ${DEBUG} -gt 0 ]] && logInfo "show the CA cert details"
-    [[ ${DEBUG} -gt 0 ]] && openssl x509 -noout -text -in ${CA_CRT_FILE}
+    [ "${DEBUG_CA_CERT}" = "true" ] && logInfo "show the CA cert details"
+    [ "${DEBUG_CA_CERT}" = "true" ] && openssl x509 -noout -text -in ${CA_CRT_FILE}
 
-    echo 01 > ${CA_SRL_FILE}
+    echo "01" > ${CA_SRL_FILE}
 
 fi
 
@@ -78,8 +76,8 @@ subjectKeyIdentifier = hash
 EOF
 )
 
-[[ ${DEBUG} -gt 0 ]] && logInfo "Show the singing request, to make sure extensions are there"
-[[ ${DEBUG} -gt 0 ]] && openssl req -in ia.csr -noout -text
+[ "${DEBUG_CA_CERT}" = "true" ] && logInfo "Show the singing request, to make sure extensions are there"
+[ "${DEBUG_CA_CERT}" = "true" ] && openssl req -in ia.csr -noout -text
 
 logInfo "Sign the IA request with the CA cert and key, producing the IA cert"
 openssl x509 -req -days 730 -in ia.csr -CA ${CA_CRT_FILE} -CAkey ${CA_KEY_FILE} -CAserial ${CA_SRL_FILE} -out ia.crt -passin pass:foobar -extensions IA -extfile <(
@@ -95,8 +93,8 @@ EOF
 ) &> /dev/null
 
 
-[[ ${DEBUG} -gt 0 ]] && logInfo "show the IA cert details"
-[[ ${DEBUG} -gt 0 ]] && openssl x509 -noout -text -in ia.crt
+[ "${DEBUG_CA_CERT}" = "true" ] && logInfo "show the IA cert details"
+[ "${DEBUG_CA_CERT}" = "true" ] && openssl x509 -noout -text -in ia.crt
 
 logInfo "Initialize the serial number for signed certificates"
 echo 01 > ia.srl
@@ -108,14 +106,14 @@ openssl rsa -passin pass:foobar -in web.orig.key -out web.key  &> /dev/null
 logInfo "Create the signing request, using extensions"
 openssl req -new -key web.key -sha256 -out web.csr -passin pass:foobar -subj "/C=NL/ST=Noord Holland/L=Amsterdam/O=ME/OU=IT/CN=${CN_WEB}" -reqexts SAN -config <(cat <(printf "[req]\ndistinguished_name = dn\n[dn]\n[SAN]\nsubjectAltName=${ALLDOMAINS}"))
 
-[[ ${DEBUG} -gt 0 ]] && logInfo "Show the singing request, to make sure extensions are there"
-[[ ${DEBUG} -gt 0 ]] && openssl req -in web.csr -noout -text
+[ "${DEBUG_CA_CERT}" = "true" ] && logInfo "Show the singing request, to make sure extensions are there"
+[ "${DEBUG_CA_CERT}" = "true" ] && openssl req -in web.csr -noout -text
 
 logInfo "Sign the request, using the intermediate cert and key"
 openssl x509 -req -days 365 -in web.csr -CA ia.crt -CAkey ia.key -out web.crt -passin pass:foobar -extensions SAN -extfile <(cat <(printf "[req]\ndistinguished_name = dn\n[dn]\n[SAN]\nsubjectAltName=${ALLDOMAINS}"))  &> /dev/null
 
-[[ ${DEBUG} -gt 0 ]] && logInfo "Show the final cert details"
-[[ ${DEBUG} -gt 0 ]] && openssl x509 -noout -text -in web.crt
+[ "${DEBUG_CA_CERT}" = "true" ] && logInfo "Show the final cert details"
+[ "${DEBUG_CA_CERT}" = "true" ] && openssl x509 -noout -text -in web.crt
 
 logInfo "Concatenating fullchain.pem..."
 cat web.crt ia.crt ${CA_CRT_FILE}  > fullchain.pem
diff --git a/entrypoint.sh b/entrypoint.sh
index 7a7aa2c..2c3e596 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -5,7 +5,7 @@ trap "echo TRAPed signal" HUP INT QUIT TERM
 
 #configure nginx DNS settings to match host, why must we do that nginx?
 export RESOLVERS=$(awk '$1 == "nameserver" {print ($2 ~ ":")? "["$2"]": $2}' ORS=' ' /etc/resolv.conf | sed 's/ *$//g')
-if [ "x$RESOLVERS" = "x" ]; then
+if [ -z "$RESOLVERS" ]; then
     echo "Warning: unable to determine DNS resolvers for nginx" >&2
     exit 66
 fi
@@ -20,7 +20,7 @@ done
 
 echo "Final chosen resolver: $conf"
 confpath=/etc/nginx/resolvers.conf
-if [ ! -e $confpath ] || [ "$conf" != "$(cat $confpath)" ]
+if [ ! -e "$confpath" ] || [ "$conf" != "$(cat "$confpath")" ]
 then
     echo "Using auto-determined resolver '$conf' via '$confpath'"
     echo "$conf" > $confpath
@@ -36,7 +36,7 @@ ALLDOMAINS=""
 echo -n "" > /etc/nginx/docker.intercept.map
 
 # Some hosts/registries are always needed, but others can be configured in env var REGISTRIES
-for ONEREGISTRYIN in docker.caching.proxy.internal registry-1.docker.io auth.docker.io ${REGISTRIES}; do
+for ONEREGISTRYIN in ${REGISTRIES}; do
     ONEREGISTRY=$(echo ${ONEREGISTRYIN} | xargs) # Remove whitespace
     echo "Adding certificate for registry: $ONEREGISTRY"
     ALLDOMAINS="${ALLDOMAINS},DNS:${ONEREGISTRY}"
@@ -55,7 +55,7 @@ echo -n "" > /etc/nginx/docker.targetHost.map
 echo -n "" > /etc/nginx/docker.auth.map
 
 # Only configure auth registries if the env var contains values
-if [ "$AUTH_REGISTRIES" ]; then
+if [ -n "$AUTH_REGISTRIES" ]; then
     # Ref: https://stackoverflow.com/a/47633817/219530
     AUTH_REGISTRIES_DELIMITER=${AUTH_REGISTRIES_DELIMITER:-" "}
     s=$AUTH_REGISTRIES$AUTH_REGISTRIES_DELIMITER
@@ -87,9 +87,6 @@ fi
 echo "        listen 443 ssl default_server;" > /etc/nginx/caching.layer.listen
 echo "error_log  /var/log/nginx/error.log warn;" > /etc/nginx/error.log.debug.warn
 
-# Set Docker Registry cache size, by default, 32 GB ('32g')
-CACHE_MAX_SIZE=${CACHE_MAX_SIZE:-32g}
-
 # The cache directory. This can get huge. Better to use a Docker volume pointing here!
 # Set to 32gb which should be enough
 echo "proxy_cache_path /docker_mirror_cache levels=1:2 max_size=$CACHE_MAX_SIZE inactive=60d keys_zone=cache:10m use_temp_path=off;" > /etc/nginx/conf.d/cache_max_size.conf
@@ -97,47 +94,57 @@ echo "proxy_cache_path /docker_mirror_cache levels=1:2 max_size=$CACHE_MAX_SIZE
 # Manifest caching configuration. We generate config based on the environment vars.
 echo -n "" >/etc/nginx/nginx.manifest.caching.config.conf
 
-[[ "a${ENABLE_MANIFEST_CACHE}" == "atrue" ]] && [[ "a${MANIFEST_CACHE_PRIMARY_REGEX}" != "a" ]] && cat <<EOD >>/etc/nginx/nginx.manifest.caching.config.conf
+if [ "${ENABLE_MANIFEST_CACHE}" = "true" ]; then
+    [ -n "${MANIFEST_CACHE_PRIMARY_REGEX}" ] && cat <<EOF >>/etc/nginx/nginx.manifest.caching.config.conf
     # First tier caching of manifests; configure via MANIFEST_CACHE_PRIMARY_REGEX and MANIFEST_CACHE_PRIMARY_TIME
     location ~ ^/v2/(.*)/manifests/${MANIFEST_CACHE_PRIMARY_REGEX} {
         set \$docker_proxy_request_type "manifest-primary";
         proxy_cache_valid ${MANIFEST_CACHE_PRIMARY_TIME};
         include "/etc/nginx/nginx.manifest.stale.conf";
     }
-EOD
-
-[[ "a${ENABLE_MANIFEST_CACHE}" == "atrue" ]] && [[ "a${MANIFEST_CACHE_SECONDARY_REGEX}" != "a" ]] && cat <<EOD >>/etc/nginx/nginx.manifest.caching.config.conf
+EOF
+    [ -n "${MANIFEST_CACHE_SECONDARY_REGEX}" ] && cat <<EOF >>/etc/nginx/nginx.manifest.caching.config.conf
     # Secondary tier caching of manifests; configure via MANIFEST_CACHE_SECONDARY_REGEX and MANIFEST_CACHE_SECONDARY_TIME
     location ~ ^/v2/(.*)/manifests/${MANIFEST_CACHE_SECONDARY_REGEX} {
         set \$docker_proxy_request_type "manifest-secondary";
         proxy_cache_valid ${MANIFEST_CACHE_SECONDARY_TIME};
         include "/etc/nginx/nginx.manifest.stale.conf";
     }
-EOD
-
-[[ "a${ENABLE_MANIFEST_CACHE}" == "atrue" ]] && cat <<EOD >>/etc/nginx/nginx.manifest.caching.config.conf
+EOF
+    cat <<EOF >>/etc/nginx/nginx.manifest.caching.config.conf
     # Default tier caching for manifests. Caches for ${MANIFEST_CACHE_DEFAULT_TIME} (from MANIFEST_CACHE_DEFAULT_TIME)
     location ~ ^/v2/(.*)/manifests/ {
         set \$docker_proxy_request_type "manifest-default";
         proxy_cache_valid ${MANIFEST_CACHE_DEFAULT_TIME};
         include "/etc/nginx/nginx.manifest.stale.conf";
     }
-EOD
-
-[[ "a${ENABLE_MANIFEST_CACHE}" != "atrue" ]] && cat <<EOD >>/etc/nginx/nginx.manifest.caching.config.conf
+EOF
+else
+    cat <<EOF >>/etc/nginx/nginx.manifest.caching.config.conf
     # Manifest caching is disabled. Enable it with ENABLE_MANIFEST_CACHE=true
     location ~ ^/v2/(.*)/manifests/ {
         set \$docker_proxy_request_type "manifest-default-disabled";
         proxy_cache_valid 0s;
         include "/etc/nginx/nginx.manifest.stale.conf";
     }
-EOD
+EOF
+fi
 
 echo -e "\nManifest caching config: ---\n"
 cat /etc/nginx/nginx.manifest.caching.config.conf
 echo "---"
 
-if [[ "a${ALLOW_PUSH}" == "atrue" ]]; then
+echo -n "" > /etc/nginx/conf.d/allowed_override_auth.conf
+if [ "${ALLOW_OWN_AUTH}" = "true" ]; then
+    cat <<'EOF' > /etc/nginx/conf.d/allowed_override_auth.conf
+    if ($http_authorization != "") {
+        # override with own authentication if provided
+        set $finalAuth $http_authorization;
+    }
+EOF
+fi
+
+if [ "${ALLOW_PUSH}" = "true" ]; then
     cat <<EOF > /etc/nginx/conf.d/allowed.methods.conf
     # allow to upload big layers
     client_max_body_size 0;
@@ -145,6 +152,31 @@ if [[ "a${ALLOW_PUSH}" == "atrue" ]]; then
     # only cache GET requests
     proxy_cache_methods GET;
 EOF
+elif [ "${ALLOW_PUSH_WITH_OWN_AUTH}" = "true" ]; then
+    cat <<'EOF' > /etc/nginx/conf.d/allowed.methods.conf
+    # Block POST/PUT/DELETE if own authentication is not provided.
+    set $combined_ha_rm "$http_authorization$request_method";
+    if ($combined_ha_rm = POST) {
+        return 405 "POST method is not allowed";
+    }
+    if ($combined_ha_rm = PUT) {
+        return 405 "PUT method is not allowed";
+    }
+    if ($combined_ha_rm = DELETE) {
+        return 405  "DELETE method is not allowed";
+    }
+
+    if ($http_authorization != "") {
+        # override with own authentication if provided
+        set $finalAuth $http_authorization;
+    }
+
+    # allow to upload big layers
+    client_max_body_size 0;
+
+    # only cache GET requests
+    proxy_cache_methods GET;
+EOF
 else
     cat << 'EOF' > /etc/nginx/conf.d/allowed.methods.conf
     # Block POST/PUT/DELETE. Don't use this proxy for pushing.
@@ -163,8 +195,8 @@ fi
 # normally use non-debug version of nginx
 NGINX_BIN="/usr/sbin/nginx"
 
-if [[ "a${DEBUG}" == "atrue" ]]; then
-  if [[ ! -f /usr/bin/mitmweb ]]; then
+if [ "${DEBUG}" = "true" ]; then
+  if [ ! -f /usr/bin/mitmweb ]; then
     echo "To debug, you need the -debug version of this image, eg: :latest-debug"
     exit 3
   fi
@@ -182,8 +214,8 @@ if [[ "a${DEBUG}" == "atrue" ]]; then
   echo "Access mitmweb via http://127.0.0.1:8081/ "
 fi
 
-if [[ "a${DEBUG_HUB}" == "atrue" ]]; then
-  if [[ ! -f /usr/bin/mitmweb ]]; then
+if [ "${DEBUG_HUB}" = "true" ]; then
+  if [ ! -f /usr/bin/mitmweb ]; then
     echo "To debug, you need the -debug version of this image, eg: :latest-debug"
     exit 3
   fi
@@ -205,8 +237,8 @@ if [[ "a${DEBUG_HUB}" == "atrue" ]]; then
   echo "Access mitmweb for outgoing DockerHub requests via http://127.0.0.1:8082/ "
 fi
 
-if [[ "a${DEBUG_NGINX}" == "atrue" ]]; then
-  if [[ ! -f /usr/sbin/nginx-debug ]]; then
+if [ "${DEBUG_NGINX}" = "true" ]; then
+  if [ ! -f /usr/sbin/nginx-debug ]; then
     echo "To debug, you need the -debug version of this image, eg: :latest-debug"
     exit 4
   fi
@@ -219,8 +251,8 @@ fi
 
 
 # Timeout configurations
-echo "" > /etc/nginx/nginx.timeouts.config.conf
-cat <<EOD >>/etc/nginx/nginx.timeouts.config.conf
+echo -n "" > /etc/nginx/nginx.timeouts.config.conf
+cat <<EOF >>/etc/nginx/nginx.timeouts.config.conf
   # Timeouts
 
   # ngx_http_core_module
@@ -238,23 +270,23 @@ cat <<EOD >>/etc/nginx/nginx.timeouts.config.conf
   proxy_connect_read_timeout ${PROXY_CONNECT_READ_TIMEOUT};
   proxy_connect_connect_timeout ${PROXY_CONNECT_CONNECT_TIMEOUT};
   proxy_connect_send_timeout ${PROXY_CONNECT_SEND_TIMEOUT};
-EOD
+EOF
 
 echo -e "\nTimeout configs: ---"
 cat /etc/nginx/nginx.timeouts.config.conf
 echo -e "---\n"
 
 # Upstream SSL verification.
-echo "" > /etc/nginx/docker.verify.ssl.conf
-if [[ "a${VERIFY_SSL}" == "atrue" ]]; then
-    cat << EOD > /etc/nginx/docker.verify.ssl.conf
+echo -n "" > /etc/nginx/docker.verify.ssl.conf
+if [ "${VERIFY_SSL}" = "true" ]; then
+    cat <<EOF > /etc/nginx/docker.verify.ssl.conf
     # We actually wanna be secure and avoid mitm attacks.
     # Fitting, since this whole thing is a mitm...
     # We'll accept any cert signed by a CA trusted by Mozilla (ca-certificates-bundle in alpine)
     proxy_ssl_verify on;
     proxy_ssl_trusted_certificate /etc/ssl/certs/ca-certificates.crt;
     proxy_ssl_verify_depth 2;
-EOD
+EOF
     echo "Upstream SSL certificate verification enabled."
 else
     echo "Upstream SSL certificate verification is DISABLED."
diff --git a/nginx.conf b/nginx.conf
index 897628e..054b187 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -245,6 +245,7 @@ echo "Docker configured with HTTPS_PROXY=$scheme://$http_host/"
         proxy_ignore_headers   X-Accel-Expires Expires Cache-Control Set-Cookie;
 
         # Add the authentication info, if the map matched the target domain.
+        include "/etc/nginx/conf.d/allowed_override_auth.conf";
         proxy_set_header Authorization $finalAuth;
 
         # Use SNI during the TLS handshake with the upstream.