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Fixing CORS error #649

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merged 1 commit into from
Aug 8, 2018
Merged

Fixing CORS error #649

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21 changes: 19 additions & 2 deletions pbs_light.go
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Original file line number Diff line number Diff line change
Expand Up @@ -736,10 +736,27 @@ func serve(revision string, cfg *config.Configuration) error {

pbc.InitPrebidCache(cfg.CacheURL.GetBaseURL())

// Add CORS middleware
// Fixes #648
//
// These CORS options pose a security risk... but it's a calculated one.
// People _must_ call us with "withCredentials" set to "true" because that's how we use the cookie sync info.
// We also must allow all origins because every site on the internet _could_ call us.
//
// This is an inherent security risk. However, PBS doesn't use cookies for authorization--just identification.
// We only store the User's ID for each Bidder, and each Bidder has already exposed a public cookie sync endpoint
// which returns that data anyway.
//
// For more info, see:
//
// - https://github.com/rs/cors/issues/55
// - https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSNotSupportingCredentials
// - https://portswigger.net/blog/exploiting-cors-misconfigurations-for-bitcoins-and-bounties
c := cors.New(cors.Options{
AllowCredentials: true,
AllowedHeaders: []string{"Origin", "X-Requested-With", "Content-Type", "Accept"}})
AllowOriginFunc: func(origin string) bool {
return true
},
AllowedHeaders: []string{"Origin", "X-Requested-With", "Content-Type", "Accept"}})
corsRouter := c.Handler(router)

// Add no cache headers
Expand Down