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simbrowser.go
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simbrowser.go
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// Package simbrowser provides facilities for simulating aspects of web browsers.
package simbrowser
import (
"context"
"time"
tls "github.com/refraction-networking/utls"
"github.com/getlantern/flashlight/v7/common"
"github.com/getlantern/flashlight/v7/deterministic"
"github.com/getlantern/flashlight/v7/geolookup"
"github.com/getlantern/golog"
)
// This timeout should be longer than anything a caller might pass to us. We use this to avoid
// goroutine leaks.
const longTimeout = 10 * time.Minute
var log = golog.LoggerFor("simbrowser")
// Browser represents a specific web browser, e.g. Chrome or Firefox.
type Browser struct {
Type BrowserType
SessionTicketLifetime time.Duration
ClientHelloID tls.ClientHelloID
}
var (
// Session ticket lifetime data can be found here:
// https://github.com/getlantern/lantern-internal/issues/3315#issue-560602994
chrome = Browser{Chrome, 30 * time.Minute, tls.HelloChrome_Auto}
firefox = Browser{Firefox, 24 * time.Hour, tls.HelloFirefox_Auto}
edge = Browser{Edge, 10 * time.Hour, tls.HelloEdge_Auto}
threeSixty = Browser{ThreeSixtySecureBrowser, 9 * time.Hour, tls.Hello360_Auto}
qq = Browser{QQBrowser, 30 * time.Minute, tls.HelloQQ_Auto}
safari = Browser{Safari, 24 * time.Hour, tls.HelloSafari_Auto}
)
// ChooseForUser chooses a web browser for the input user. If it is possible to determine the
// system's default web browser, a corresponding Browser instance will be returned. If not, this
// function chooses a browser to mimic. This choice is deterministic for a given user ID, and the
// distribution of choices across user IDs will reflect the market share of the top 4 browsers.
//
// If necessary, we use region-specific market share figures. This is based on the client's
// geolocation and thus this function may block for a period while geolocation is determined. If the
// context expires before the client's geolocation can be determined, global market shares will be
// used.
func ChooseForUser(ctx context.Context, uc common.UserConfig) Browser {
type browserResult struct {
b *Browser
err error
}
geolookupTimeout := longTimeout
if deadline, ok := ctx.Deadline(); ok {
// A timeout of 0 tells geolookup to return immediately.
geolookupTimeout = max(deadline.Sub(time.Now()), 0)
}
defaultBrowserC := make(chan browserResult, 1)
go func() {
b, err := mimicDefaultBrowser(ctx)
defaultBrowserC <- browserResult{b, err}
}()
countryCodeC := make(chan CountryCode, 1)
go func() {
if cc := geolookup.GetCountry(geolookupTimeout); cc != "" {
countryCodeC <- CountryCode(cc)
}
}()
select {
case res := <-defaultBrowserC:
if res.err == nil {
return *res.b
}
log.Debugf("failed to mimic default browser: %v; falling back to weighted choice", res.err)
case <-ctx.Done():
log.Debugf("context expired determining default browser, falling back to weighted choice")
}
marketShareLock.RLock()
choices := marketShareData[globally]
select {
case countryCode := <-countryCodeC:
if countryChoices, ok := marketShareData[countryCode]; ok {
choices = countryChoices
}
default:
log.Debug("context expired retrieving country code, falling back to global browser choices")
}
marketShareLock.RUnlock()
weightedChoices := []deterministic.WeightedChoice{}
for _, c := range choices {
if c.Browser.Type == Firefox {
// Using utls.HelloFirefox_65 results in an error, so we're disabling it for now.
// Possibly related to https://github.com/getlantern/lantern-internal/issues/3850
continue
}
weightedChoices = append(weightedChoices, c)
}
choice := deterministic.MakeWeightedChoice(uc.GetUserID(), weightedChoices)
browser := choice.(browserChoice).Browser
return browser
}
func max(a, b time.Duration) time.Duration {
if a > b {
return a
}
return b
}