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ARSN-387: check for forwarded proto header #2210

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ARSN-387: check for forwarded proto header #2210

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9e3e723
ARSN-387: check for forwarded proto header
KazToozs Jan 19, 2024
8edd2f1
ARSN-387: update test
KazToozs Jan 19, 2024
0466eb4
fixup: update test
KazToozs Feb 9, 2024
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2 changes: 1 addition & 1 deletion lib/policyEvaluator/utils/conditions.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,7 @@ export function findConditionKey(
case 'aws:referer': return headers.referer;
// aws:SecureTransport – Used to check whether the request was sent
// using SSL (see Boolean Condition Operators).
case 'aws:SecureTransport': return requestContext.getSslEnabled() ? 'true' : 'false';
case 'aws:SecureTransport': return headers?.['x-forwarded-proto'] === 'https' ? 'true' : 'false';
// aws:SourceArn – Used check the source of the request,
// using the ARN of the source. N/A here.
case 'aws:SourceArn': return undefined;
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2 changes: 1 addition & 1 deletion lib/policyEvaluator/utils/variables.ts
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Expand Up @@ -38,7 +38,7 @@ function findVariable(variable: string, requestContext: RequestContext): string
// aws:SecureTransport is boolean value that represents whether the
// request was sent using SSL
map.set('aws:SecureTransport',
requestContext.getSslEnabled() ? 'true' : 'false');
headers?.['x-forwarded-proto'] === 'https' ? 'true' : 'false');
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Headers shouldn't be blindly trusted, as they could be forged if not explicitly overwritten by the http frontend - and since I'm not sure artesca is in scope for this PR, the forward port will automatically introduce the vulnerability.

This should be disabled by default and wrapped and enabled with explicit configuration, similar to how client IP conditions are handled.
https://github.com/scality/Arsenal/blob/development/7.10/lib/policyEvaluator/requestUtils.ts

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@KazToozs KazToozs Mar 12, 2024 •
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Supposing I revert this Arsenal change, would something like this in Cloudserver work according to you?:
scality/cloudserver@a66f293

function _checkBucketPolicyConditions(request, conditions, log) {
    const ip = request ? requestUtils.getClientIp(request, config) : undefined;
    if (!conditions) {
        return true;
    }
    const viaProxy = config.requests.viaProxy;

    const sslEnabled = (viaProxy ?
        request.headers['x-forwarded-proto'] === 'https' : request.connection.encrypted);
    // build request context from the request!
    const requestContext = new RequestContext(request.headers, request.query,
        request.bucketName, request.objectKey, ip,
        sslEnabled, request.resourceType, 's3', null, null,
        null, null, null, null, null, null, null, null, null,
        request.objectLockRetentionDays);
    return evaluators.meetConditions(requestContext, conditions, log);
}

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@rachedbenmustapha rachedbenmustapha Mar 12, 2024 •
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x-forwarded-proto should be a configurable, set by the same deployment infrastructure than the one that sets up the reverse proxy, so that no misguided cross-component assumptions are made. So for S3C that's Federation, and for artesca it's shared between artesca-installer and zenko-operator.

The reason I insist that we make it configurable and disabled by default even for RING is that I'm not sure 100% of customers go through the nginx we ship, some of them might use their own LB which may or may not overwrite x-forwarded-proto (or use a different header altogether). Or some might in the future and we don't want any surprises.

// aws:SourceIp is requester's IP address, for use with IP address
// conditions
map.set('aws:SourceIp', requestContext.getRequesterIp());
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8 changes: 6 additions & 2 deletions tests/unit/policyEvaluator.spec.js
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Expand Up @@ -906,7 +906,9 @@ describe('policyEvaluator', () => {
() => {
policy.Statement.Condition = { Bool:
{ 'aws:SecureTransport': 'true' } };
const rcModifiers = { _sslEnabled: false };
const rcModifiers = { _headers: {
'x-forwarded-proto': 'http',
} };
check(requestContext, rcModifiers, policy, 'Neutral');
});

Expand All @@ -915,7 +917,9 @@ describe('policyEvaluator', () => {
() => {
policy.Statement.Condition = { Bool:
{ 'aws:SecureTransport': 'true' } };
const rcModifiers = { _sslEnabled: true };
const rcModifiers = { _headers: {
'x-forwarded-proto': 'https',
} };
check(requestContext, rcModifiers, policy, 'Allow');
});

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