Update following initial review

CHANGELOG.md

@@ -17,7 +17,7 @@ All notable changes to this project will be documented in this file.
 - Fixed `HostPortWaitStrategy` throws `NumberFormatException` when port is exposed but not mapped ([\#640](https://github.com/testcontainers/testcontainers-java/issues/640))
 - Fixed log processing: multibyte unicode, linebreaks and ASCII color codes. Color codes can be turned on with `withRemoveAnsiCodes(false)` ([\#643](https://github.com/testcontainers/testcontainers-java/pull/643))
 - Fixed Docker host IP detection within docker container (detect only if not explicitly set) ([\#648](https://github.com/testcontainers/testcontainers-java/pull/648))
-- Add support for private repositories using docker credential stores/helpers (fixes [\#567](https://github.com/testcontainers/testcontainers-java/issues/567))
+- Add support for private repositories using docker credential stores/helpers ([PR \#647](https://github.com/testcontainers/testcontainers-java/pull/647), fixes [\#567](https://github.com/testcontainers/testcontainers-java/issues/567))
 
 ### Changed
 - Support multiple HTTP status codes for HttpWaitStrategy ([\#630](https://github.com/testcontainers/testcontainers-java/issues/630))

core/src/main/java/org/testcontainers/utility/RegistryAuthLocator.java

@@ -4,7 +4,6 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.github.dockerjava.api.model.AuthConfig;
 import com.google.common.annotations.VisibleForTesting;
-import org.apache.commons.lang.StringUtils;
 import org.slf4j.Logger;
 import org.zeroturnaround.exec.ProcessExecutor;
 
@@ -39,7 +38,9 @@ public class RegistryAuthLocator {
      */
     public RegistryAuthLocator(AuthConfig defaultAuthConfig) {
         this.defaultAuthConfig = defaultAuthConfig;
-        this.configFile = new File(System.getProperty("user.home") + "/.docker/config.json");
+        final String dockerConfigLocation = System.getenv().getOrDefault("DOCKER_CONFIG",
+            System.getProperty("user.home") + "/.docker");
+        this.configFile = new File(dockerConfigLocation + "/config.json");
         this.commandPathPrefix = "";
     }
 
@@ -62,6 +63,7 @@ public AuthConfig lookupAuthConfig(DockerImageName dockerImageName) {
                 // auths/<registry> is an empty dict - use a credential helper
                 return authConfigUsingCredentialsStoreOrHelper(reposName, config);
             }
+            // otherwise, defaultAuthConfig should already contain any credentials available
         } catch (Exception e) {
             log.error("Failure when attempting to lookup auth config. Falling back to docker-java default behaviour", e);
         }
@@ -70,13 +72,13 @@ public AuthConfig lookupAuthConfig(DockerImageName dockerImageName) {
 
     private AuthConfig authConfigUsingCredentialsStoreOrHelper(String hostName, JsonNode config) throws Exception {
 
-        final String credsStoreName = config.at("/credsStore").asText();
-        final String credHelper = config.at("/credHelpers/" + hostName).asText();
+        final JsonNode credsStoreName = config.at("/credsStore");
+        final JsonNode credHelper = config.at("/credHelpers/" + hostName);
 
-        if (StringUtils.isNotBlank(credHelper)) {
-            return runCredentialProvider(hostName, credHelper);
-        } else if (StringUtils.isNotBlank(credsStoreName)) {
-            return runCredentialProvider(hostName, credsStoreName);
+        if (!credHelper.isMissingNode()) {
+            return runCredentialProvider(hostName, credHelper.asText());
+        } else if (!credsStoreName.isMissingNode()) {
+            return runCredentialProvider(hostName, credsStoreName.asText());
         } else {
             throw new UnsupportedOperationException();
         }