access_denied when accessing Gmail API with auth scope https://mail.google.com/ - gmail-api

Question

I am trying to read/write emails/folders inside Gmail mailboxes using the Gmail REST API. When adding the following Google auth scopes, emails can be read from Gmail REST API without any problem:
https://apps-apis.google.com/a/feeds/compliance/audit/,
https://www.googleapis.com/auth/admin.directory.user.readonly, https://www.googleapis.com/auth/gmail.readonly,
https://www.googleapis.com/auth/admin.directory.group.member.readonly, https://www.googleapis.com/auth/admin.directory.group.readonly
Note: The parameter https://www.googleapis.com/auth/gmail.readonly correctly allows one to read from mailboxes.
However, I need to be able to delete emails too. Thus, in line with the documentation at https://developers.google.com/gmail/api/auth/scopes?hl=ja, one simply needs to include https://mail.google.com/ in place of https://www.googleapis.com/auth/gmail.readonly. When adding the following auth scopes:
https://apps-apis.google.com/a/feeds/compliance/audit/,
https://www.googleapis.com/auth/admin.directory.user.readonly, https://mail.google.com/,
https://www.googleapis.com/auth/admin.directory.group.member.readonly, https://www.googleapis.com/auth/admin.directory.group.readonly
... the error outputted is as follows:
2015-07-27 10:27:59 i.c.s.a.cv [DEBUG] failed get labels for user
com.google.api.client.auth.oauth2.TokenResponseException: 403 Forbidden
{
"error" : "access_denied",
"error_description" : "Requested client not authorized."
}
Surely, this is incorrect on the part of Google? What am I missing? Is the documentation incorrect? What auth scope needs to be added?
I am interfacing with the Java Google API Client Library. See: https://developers.google.com/api-client-library/java/google-api-java-client/reference/1.20.0/overview-summary
The delete request is as follows:
public void deleteMessages(Queue<String> messages, GoogleUserAdapter user) throws Exception {
Gmail gmail = getService(user);
JsonBatchCallback<Void> voidCallBack = new JsonBatchCallback<Void>() {
#Override
public void onSuccess(Void t, HttpHeaders responseHeaders) throws IOException {
logger.debug("delete success");
}
#Override
public void onFailure(GoogleJsonError e, HttpHeaders responseHeaders) throws IOException {
logger.debug("failed to delete message:"+e.getMessage());
}
};
while (!messages.isEmpty()) {
if (Thread.currentThread().isInterrupted())
throw new InterruptedException();
BatchRequest batch = gmail.batch();
for (int i = 0; i < MAX_REQUESTS; i++) {
if (messages.isEmpty() || Thread.currentThread().isInterrupted())
break;
gmail.users().messages().delete(user.getId(), messages.poll()).queue(batch, voidCallBack);
}
batch.execute();
}
}
The credential is created as follows:
private GoogleCredential getCredentials(JsonFactory jsonFactory, HttpTransport httpTransport, String impersonateAccount) throws Exception {
Preconditions.checkNotNull(Strings.emptyToNull(impersonateAccount), "Google impersonate account is null");
Preconditions.checkNotNull(Strings.emptyToNull(connection.getServiceAccountId()), "Service Account Email address is null");
Preconditions.checkNotNull(connection.getServiceAccountPrivateKey(), "Service Account Private Key is null");
GoogleCredential credential = new GoogleCredential.Builder()
.setTransport(httpTransport)
.setJsonFactory(jsonFactory)
.setServiceAccountId(connection.getServiceAccountId())
.setServiceAccountScopes(
Arrays.asList(DirectoryScopes.ADMIN_DIRECTORY_USER_READONLY, GmailScopes.MAIL_GOOGLE_COM,
"https://apps-apis.google.com/a/feeds/compliance/audit/",
DirectoryScopes.ADMIN_DIRECTORY_GROUP_MEMBER_READONLY,
DirectoryScopes.ADMIN_DIRECTORY_GROUP_READONLY))
.setServiceAccountUser(impersonateAccount)
.setServiceAccountPrivateKey(connection.getServiceAccountPrivateKey().getPrivateKey())
.build();
setHttpTimeout(credential);
return credential;
}
The exact error that occurs on delete is:
failed to delete message:Insufficient Permission
Jamie

Answer 1

Access denied is caused by a typo in the constant GmailScopes.MAIL_GOOGLE_COM as defined by the Google Java Client API.
The constant returns "https://mail.google.com" and not "https://mail.google.com/" (as it ought to be). Omitting a backslash at the end of the string will result in access denied.
Thus, in the example above, the following service scopes must be set:
https://apps-apis.google.com/a/feeds/compliance/audit/","https://mail.google.com/",DirectoryScopes.ADMIN_DIRECTORY_GROUP_MEMBER_READONLY, DirectoryScopes.ADMIN_DIRECTORY_USER_READONLY, DirectoryScopes.ADMIN_DIRECTORY_GROUP_READONLY
(note: the hardcoded value of "https://mail.google.com/")
The following string must be added to Manage API client access page in Google Apps:
https://apps-apis.google.com/a/feeds/compliance/audit/,
https://www.googleapis.com/auth/admin.directory.user.readonly, https://mail.google.com/,
https://www.googleapis.com/auth/admin.directory.group.member.readonly, https://www.googleapis.com/auth/admin.directory.group.readonly
I hope this helps someone else!

Answer 2

private GoogleCredential getCredentials(JsonFactory jsonFactory, HttpTransport httpTransport, String impersonateAccount) throws Exception {
Preconditions.checkNotNull(Strings.emptyToNull(impersonateAccount), "Google impersonate account is null");
Preconditions.checkNotNull(Strings.emptyToNull(connection.getServiceAccountId()), "Service Account Email address is null");
Preconditions.checkNotNull(connection.getServiceAccountPrivateKey(), "Service Account Private Key is null");
GoogleCredential credential = new GoogleCredential.Builder()
.setTransport(httpTransport)
.setJsonFactory(jsonFactory)
.setServiceAccountId(connection.getServiceAccountId())
.setServiceAccountScopes(
Arrays.asList(DirectoryScopes.ADMIN_DIRECTORY_USER_READONLY, GmailScopes.MAIL_GOOGLE_COM,
"https://apps-apis.google.com/a/feeds/compliance/audit/",
DirectoryScopes.ADMIN_DIRECTORY_GROUP_MEMBER_READONLY,
DirectoryScopes.ADMIN_DIRECTORY_GROUP_READONLY))
.setServiceAccountUser(impersonateAccount)
.setServiceAccountPrivateKey(connection.getServiceAccountPrivateKey().getPrivateKey())
.build();
setHttpTimeout(credential);
return credential;
}