microg/GmsCore · error · UserVerificationRequirement.UnsupportedUserVerificationRequirementException

User verification requirement ${attachment} not supported

Error message

User verification requirement ${attachment} not supported

What it means

UserVerificationRequirement.fromString() maps a user-verification string ("required", "preferred", "discouraged") to the enum; other values throw UnsupportedUserVerificationRequirementException. (The parameter is confusingly named 'attachment' — copy-paste from Attachment.)

Source

Thrown at play-services-fido/src/main/java/com/google/android/gms/fido/fido2/api/common/UserVerificationRequirement.java:45

        return value;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(toString());
    }

    @Hide
    public static UserVerificationRequirement fromString(String attachment) throws UnsupportedUserVerificationRequirementException {
        for (UserVerificationRequirement value : values()) {
            if (value.value.equals(attachment)) return value;
        }
        throw new UnsupportedUserVerificationRequirementException("User verification requirement " + attachment + " not supported");
    }

    public static Creator<UserVerificationRequirement> CREATOR = new Creator<UserVerificationRequirement>() {
        @Override
        public UserVerificationRequirement createFromParcel(Parcel source) {
            try {
                return UserVerificationRequirement.fromString(source.readString());
            } catch (UnsupportedUserVerificationRequirementException e) {
                throw new RuntimeException(e);
            }
        }

        @Override
        public UserVerificationRequirement[] newArray(int size) {
            return new UserVerificationRequirement[size];
        }
    };

View on GitHub (pinned to 157c9d86ac)

Solutions

Pass exactly "required", "preferred", or "discouraged".
Default missing JSON fields to "preferred" instead of the empty string.
Validate against the enum's values() before calling fromString.

Example fix

// before
var uv = UserVerificationRequirement.fromString(json.optString("userVerification"));
// after
String uvStr = json.optString("userVerification", "preferred");
var uv = UserVerificationRequirement.fromString(uvStr);

Defensive patterns

Strategy: validation

Validate before calling

Set<String> valid = new HashSet<>(java.util.Arrays.asList("required", "preferred", "discouraged"));
if (!valid.contains(uvStr)) uvStr = "preferred";

Try / catch

try { uv = UserVerificationRequirement.fromString(s); } catch (UnsupportedUserVerificationRequirementException e) { uv = UserVerificationRequirement.fromString("preferred"); }

Prevention

Default missing userVerification JSON fields to "preferred" instead of an empty string.
Validate case-sensitive membership before parsing.
Use enum constants when building request options in code.

When it happens

Trigger: Calling fromString with a value outside {"required","preferred","discouraged"}: typos like "optional", case mismatches ("Required"), or empty strings from missing JSON keys (optString returns "").

Common situations: Relying-party JSON with userVerification values from a newer or nonstandard spec; JSON lacking the userVerification field so an empty/default string gets parsed.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of microg/GmsCore@157c9d86ac (2026-09-06). Data as JSON: /api/errors/d7ef504a2035af81. Report an issue: GitHub.