<p>The issue was caused by not removing the space after <code>repo:</code> in the IAM Identity Provider Trust relationships' trust policy line that I had copied from the blog</p>
<pre><code>                    &quot;token.actions.githubusercontent.com:sub&quot;: &quot;repo: &lt;aws-samples/EXAMPLEREPO&gt;:ref:refs/heads/&lt;ExampleBranch&gt;&quot;,
</code></pre>

CC BY-SA 4.0
2023-06-02T14:35:33.747Z
2023-06-02T14:35:33.747Z
Edward Moffett
<p>I was unable to successfully authenticate when attempting to create a GitHub Actions workflow that would authenticate with an AWS IAM Identity Provider (IdP) using Open ID Connect (OIDC), based on this blog: <a href="https://aws.amazon.com/blogs/security/use-iam-roles-to-connect-github-actions-to-actions-in-aws/" rel="nofollow noreferrer">https://aws.amazon.com/blogs/security/use-iam-roles-to-connect-github-actions-to-actions-in-aws/</a></p>
<p>In GitHub Actions the error appeared as:</p>
<pre><code>Not authorized to perform sts:AssumeRoleWithWebIdentity
</code></pre>
<p>In AWS CloudTrail the error appeared as:</p>
<pre><code>    &quot;errorCode&quot;: &quot;AccessDenied&quot;,
    &quot;errorMessage&quot;: &quot;An unknown error occurred&quot;,
</code></pre>

<amazon-web-services><aws-iam><github-actions>
"An unknown error occurred" when authenticating between GitHub Actions and AWS using OIDC
Edward Moffett
# "An unknown error occurred" when authenticating between GitHub Actions and AWS using OIDC

(Asked by: username_0 on 2023-06-02)

I was unable to successfully authenticate when attempting to create a GitHub Actions workflow that would authenticate with an AWS IAM Identity Provider (IdP) using Open ID Connect (OIDC), based on this blog: https://aws.amazon.com/blogs/security/use-iam-roles-to-connect-github-actions-to-actions-in-aws/
In GitHub Actions the error appeared as:
Not authorized to perform sts:AssumeRoleWithWebIdentity

In AWS CloudTrail the error appeared as:
    "errorCode": "AccessDenied",
    "errorMessage": "An unknown error occurred",

**Tags:** amazon-web-services, aws-iam, github-actions


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## 1 answers

### Answer by username_0 on 2023-06-02. Score: 1

The issue was caused by not removing the space after repo: in the IAM Identity Provider Trust relationships' trust policy line that I had copied from the blog
                    "token.actions.githubusercontent.com:sub": "repo: :ref:refs/heads/",


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