Canonization of header values does not convert all sequential spaces into one.

[xjewer]

https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_sigv-create-signed-request.html

According to signature guide, for header values you must:

• ...
• convert sequential spaces to a single space.
• ...

Rusoto signature::canonical_values only replaces double spaces, but it's not recursive, causing 3+ spaces signature mismatch.

st.push_str(s.replace("  ", " ").trim());

Source