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Fix #5373: Handle unsupported rules for debouncing
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cuba committed Jul 12, 2022
1 parent 9b269a0 commit 9ad849b
Showing 1 changed file with 44 additions and 9 deletions.
53 changes: 44 additions & 9 deletions Client/WebFilters/DebouncingResourceDownloader.swift
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,11 @@ public class DebouncingResourceDownloader {
enum Action: String {
case base64
case redirect
case regexPath = "regex-path"
}

enum RuleError: Error {
case unsupportedAction(String)
}

/// A set of patterns that are include in this rule
Expand All @@ -38,9 +43,16 @@ public class DebouncingResourceDownloader {

/// Actions in a strictly typed format and split up into an array
/// - Note: Unrecognized actions will be filtered out
var actions: Set<Action> {
func makeActions() throws -> Set<Action> {
let actionStrings = action.split(separator: ",")
return Set(actionStrings.compactMap({ Action(rawValue: String($0)) }))

return Set(try actionStrings.map({
if let action = Action(rawValue: String($0)) {
return action
} else {
throw RuleError.unsupportedAction(String($0))
}
}))
}

/// Determines if this url is not excluded in the exclude list
Expand Down Expand Up @@ -154,6 +166,28 @@ public class DebouncingResourceDownloader {
/// 3. If any of the query params (the keys) in the map from #4 above are in URL we might navigate to, apply the corresponding rule
/// 4. Apply all the rules from bucket C
func redirectURLOnce(from url: URL) -> URL? {
do {
guard let pair = try matchingQueryItemAndActions(for: url) else {
return nil
}

return redirectURL(queryItem: pair.queryItem, actions: pair.actions)
} catch MatcherRule.RuleError.unsupportedAction(let rawRule) {
// We may add new rules in the future. If thats the case, this will throw but we don't want
// an error presented or anything to happen because ios is not ready to handle this new rule
// But since it's impossible to discriminate a programmer mistake from a new rule added
// we at least log this error.
log.error("Unsupported rule used for debouncing: `\(rawRule)`")
return nil
} catch {
assertionFailure(error.localizedDescription)
return nil
}
}

/// Attempts to find a valid query param and a set of actions for the given URL
/// - Throws: May throw `DebouncingResourceDownloader.MatcherRule.RuleError`
private func matchingQueryItemAndActions(for url: URL) throws -> (queryItem: URLQueryItem, actions: Set<MatcherRule.Action>)? {
// Extract the redirect URL
guard let components = URLComponents(url: url, resolvingAgainstBaseURL: false) else { return nil }
guard let queryItems = components.queryItems else { return nil }
Expand All @@ -168,15 +202,15 @@ public class DebouncingResourceDownloader {
return nil
}

return redirectURL(queryItem: queryItem, actions: entry.rule.actions)
} else if let pair = matchingQueryItemsAndActions(for: url, queryItems: queryItems) {
return redirectURL(queryItem: pair.queryItem, actions: pair.actions)
return (queryItem, try entry.rule.makeActions())
} else if let pair = try matchingQueryItemsAndActions(for: url, queryItems: queryItems) {
return (pair.queryItem, pair.actions)
} else if let rule = otherRules.first(where: { $0.handles(url: url) }) {
guard let queryItem = queryItems.first(where: { $0.name == rule.param }) else {
return nil
}

return redirectURL(queryItem: queryItem, actions: rule.actions)
return (queryItem, try rule.makeActions())
} else {
return nil
}
Expand All @@ -186,19 +220,20 @@ public class DebouncingResourceDownloader {
///
/// - Parameter queryItems: The query items to extract the value and actions from
/// - Returns: A raw query item and actions to perform on that query item
/// - Throws: May throw `DebouncingResourceDownloader.MatcherRule.RuleError`
private func matchingQueryItemsAndActions(
for url: URL,
queryItems: [URLQueryItem]
) -> (queryItem: URLQueryItem, actions: Set<MatcherRule.Action>)? {
) throws -> (queryItem: URLQueryItem, actions: Set<MatcherRule.Action>)? {
for queryItem in queryItems {
guard
let rule = queryToRule[queryItem.name],
!rule.isExcluded(url: url)
else {
continue
}

return (queryItem, rule.actions)
return (queryItem, try rule.makeActions())
}

return nil
Expand Down

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