Understanding DNS with ActionDispatch::HostAuthorization

2020 年 10 月 3 日開催の、Kaigi on Rails で発表した内容です。（発表時間 20 分）

## 2020/10/12 追記
このスライドの説明だけですと攻撃の特性がわかりづらかったので、個人ブログの以下の記事にて追加の説明を行いました。
https://yucao24hours.me/blog/2020/10/12/dns-rebindig-basics-revised/

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   ZVDBPIPVST ActionDispatch::HostAuthorization DNS ͱֶͿ ͷ͠ ͘ Έ Photo by Gauravdeep Singh Bansal on Unsplash
2. 2 Ӭ࿨γεςϜϚωδϝϯτ
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6. 6 ਆాਢాொํ໘͔Β͖·ͨ͠ ʁ ˞
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7. 7 ຊ೔͓࿩͢͠Δ͜ͱ  %/4
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8. 8 %/4
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9. 9 DNS … Domain Name System %/4ͱ͸ͳʹ͔
10. 10 Πϯλʔωοτ্Ͱϗετͷಛఆ
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11. 11 ਓ͕ؒѻ͍΍͍ࣝ͢ผࢠʜ໊લ %/4ͱ͸ͳʹ͔ هԱ͠΍͍͢ɺղऍ͠΍͍͢
    ʮ෼ࢄ؅ཧʯͷߟ͑ํʹରԠͰ͖ΔʢυϝΠϯͱ%/4ͷ୉ޣຯ ͚ͩΕͲࠓ೔͸͓࿩͠·ͤΜʣ
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12. 12 %/4ͷجຊతͳ໾ׂ %/4ͱ͸ͳʹ͔ υϝΠϯ໊ͱ
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13. 13 υϝΠϯ໊͝ͱʹ؅ཧΛҕ೚͢Δ ໰͍߹Θͤޮ཰ԽͷͨΊʹ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 agile.esm.co.jp 13.33.9.96 ͷ
    *1
    ΞυϨε͸ TTL 60 kaigionrails.org 185.199.109.153 ͷ
    *1
    ΞυϨε͸ TTL 3600
14. 14 υϝΠϯ໊͝ͱʹ؅ཧΛҕ೚͢Δ ໰͍߹Θͤޮ཰ԽͷͨΊʹ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 agile.esm.co.jp 13.33.9.96 ͷ
    *1
    ΞυϨε͸ TTL 60 kaigionrails.org 185.199.109.153 ͷ
    *1
    ΞυϨε͸ TTL 3600
15. 15 υϝΠϯ໊͝ͱʹ؅ཧΛҕ೚͢Δ ໰͍߹Θͤޮ཰ԽͷͨΊʹ yucao24hours.me 99.84.130.27 ͷ
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    ΞυϨε͸ TTL 60 agile.esm.co.jp 13.33.9.96 ͷ
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    *1
    ΞυϨε͸ TTL 3600
16. 16 υϝΠϯ໊͝ͱʹ؅ཧΛҕ೚͢Δ ໰͍߹Θͤޮ཰ԽͷͨΊʹ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 agile.esm.co.jp 13.33.9.96 ͷ
    *1
    ΞυϨε͸ TTL 60 kaigionrails.org 185.199.109.153 ͷ
    *1
    ΞυϨε͸ TTL 3600
17. 17 ར༻ऀ yucao24hours.me ͷ
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 ஌Γ͍ͨ ϑϧϦκϧό ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ໊લղܾͷ͘͠Έ
18. 18 ར༻ऀ yucao24hours.me ͷ
    *1
    ΞυϨεΛ
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19. 19 ར༻ऀ yucao24hours.me ͷ
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 ஌Γ͍ͨ yucao24hours.me ͷ
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    ΞυϨε͸ʁ ϑϧϦκϧό 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
20. 20 ར༻ऀ ϑϧϦκϧό yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
21. 21 ར༻ऀ ϑϧϦκϧό yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
22. 22 ར༻ऀ ϑϧϦκϧό 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
23. 23 ϑϧϦκϧό ར༻ऀ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
24. 24 ϑϧϦκϧό ར༻ऀ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
25. 25 ར༻ऀ yucao24hours.me ͷ
    *1
    ΞυϨεΛ
 ஌Γ͍ͨ ϑϧϦκϧό ݖҖαʔό yucao24hours.me. 99.84.130.27 ໰͍߹Θͤޮ཰ԽͷͨΊʹ yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
26. 26 ར༻ऀ ϑϧϦκϧό 99.84.130.27 yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ TTL 60 yucao24hours.me 99.84.130.27 ͷ
    *1
    ΞυϨε͸ ໰͍߹Θͤޮ཰ԽͷͨΊʹ ݖҖαʔό yucao24hours.me. ໊લղܾͷ୅ߦ໾ ໊લղܾͷ͘͠Έ
27. 27 %/4
    ·ͱΊ υϝΠϯ໊ͱ*1ΞυϨεͷରԠ͚ͮΛ؅ཧ͠ɺ໊લղܾΛߦ͏ͨΊͷ͘͠Έ
    ϑϧϦκϧό໊͕લղܾΛ୅ߦ͢Δ
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    ϑϧϦκϧό͸ɺҎલͷ໰͍߹Θͤ݁ՌͷΩϟογϡ͕͋Ε͹ͦΕΛ࢖ͬͯ Ϣʔβ΁Ԡ౴͠ɺݖҖαʔό΁͸৽ͨʹ໰͍߹ΘͤΛൃߦ͠ͳ͍
    ϑϧϦκϧό͕Ԡ౴಺༰ΛΩϟογϡͯ͠Α͍࣌ؒ 55- ͸֤κʔϯͷ؅ཧ ऀ͕ܾΊΒΕΔ
28. 28 ΋ͬͱ%/4Λֶͼ͍ͨͳΒʜ %/4͕Α͘Θ͔ΔڭՊॻʛ4#ΫϦΤΠςΟϒ https://www.sbcr.jp/product/4797394481/
29. 29 %/4
    ϦόΠϯσΟϯά • ߈ܸͷͨΊͷ४උ
    • ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ 5PQJD
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30. 30 ߈ܸͷͨΊͷ४උ Piyostagram piyostagram.com 133.127.254.9 ߈ܸऀ
31. 31 ߈ܸͷͨΊͷ४උ ߈ܸऀ kougeki.com
32. 243.102.110.103 32 ߈ܸͷͨΊͷ४උ ߈ܸऀ ᠘αΠτ kougeki.com
33. 33 ߈ܸͷͨΊͷ४උ ߈ܸऀ ᠘αΠτ ݖҖαʔό kougeki.com 243.102.110.103 ͷ
    *1
    ΞυϨε͸ TTL 3 243.102.110.103
34. 34 ߈ܸͷͨΊͷ४උ ߈ܸऀ ᠘αΠτ kougeki.com 243.102.110.103 ͷ
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35. 35 ߈ܸͷͨΊͷ४උ ߈ܸऀ ᠘αΠτ kougeki.com 243.102.110.103 ͷ
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36. 36 ߈ܸ։࢝ ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔
37. 37 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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 ΫϦοΫ ϝʔϧ಺ͷ
38. 38 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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39. 39 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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40. 40 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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41. 41 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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42. 42 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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43. 43 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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    *1
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44. 44 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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    *1
    ΞυϨε͸ TTL 3 ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
45. 45 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
    :͞Μ ϑϧϦκϧό 243.102.110.103 133.127.254.9 kougeki.com 243.102.110.103 ͷ
    *1
    ΞυϨε͸ 133.127.254.9 ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
46. 46 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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    *1
    ΞυϨεΛ
 ஌Γ͍ͨ ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
47. 47 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
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    ΞυϨε͸ʁ ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
48. 48 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
    :͞Μ ϑϧϦκϧό 243.102.110.103 133.127.254.9 kougeki.com ͷ
    *1
    ΞυϨε͸ kougeki.com 133.127.254.9 ͷ
    *1
    ΞυϨε͸ TTL 86400 133.127.254.9 ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
49. 49 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ߈ܸऀ ߈ܸର৅ऀ
    :͞Μ ϑϧϦκϧό 243.102.110.103 133.127.254.9 ݸਓ৘ใΛ
 ൈ͖औΔFUDʜ ݖҖαʔό kougeki.com. ໊લղܾͷ୅ߦ໾
50. 50 ͲͷΑ͏ʹ߈ܸ͞ΕΔͷ͔ ͋͘·Ͱ΋
    %/4
    ͷ࢓༷Ͳ͓ΓͰ͋Δ %/4
    ͷ੬ऑੑΛͭ͘Α͏ͳ߈ܸͰ͸ͳ͍
    ʜͰ͸ɺͲ͏ͨ͠Βʁ
51. 51 %/4ϦόΠϯσΟϯά
    ·ͱΊ %/4
    ͷ࢓༷Λѱ༻ͨ͠߈ܸख๏Ͱ͢
    ϗετ໊͸ม͑ͣɺ*1ΞυϨεΛ࠮শ͞ΕΔ߈ܸͰ͢
    ϦόΠϯσΟϯάޙʹϓϥΠϕʔτωοτϫʔΫͷ*1ΞυϨε౳Λࢦఆ͞ΕΔ ͜ͱͰɺϑΝΠΞ΢Υʔϧ಺ͷϓϥΠϕʔτωοτϫʔΫ΋߈ܸର৅ͱͳΓ· ͢ʢࠓճͷΑ͏ʹΠϯλʔωοτ্ͷαʔόΛ߈ܸ͞ΕΔͱ͍͏ͷ͸͋͘·Ͱ ΋Ұྫʣ
52. 52 5PQJD
     ActionDispatch:: HostAuthorization • %/4ϦόΠϯσΟϯάͷݟഁΓํ
    • 3BJMT
    ͷ
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    ͱ͸Ͳ͏͍͏΋ͷʁ Photo by Wolfgang Hasselmann on Unsplash
53. 53 %/4ϦόΠϯσΟϯάͷݟഁΓํ GET /login.html HTTP/1.1 User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT) Host: kougeki.com Accept-Language: ja-JP ߈ܸͷಛੑ্ɺ
54. 54 GET /login.html HTTP/1.1 User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT) Host: kougeki.com Accept-Language: ja-JP ໊લղܾͷࡍʹ࢖ΘΕͨυϝΠϯ໊͕
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    ʹهࡌ͞ΕΔ ߈ܸͷಛੑ্ɺ %/4ϦόΠϯσΟϯάͷݟഁΓํ ˞
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    ϔομͷมߋ͸Ͱ͖ͳ͍
55. 55 ϦΫΤετͷ
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56. 56 GET /login.html HTTP/1.1 User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT) Host: piyostragram.com Accept-Language: ja-JP GET /login.html HTTP/1.1 User-Agent: Mozilla/4.0 (compatible; MSIE5.01; Windows NT) Host: kougeki.com Accept-Language: ja-JP Valid Request Invalid Request %/4ϦόΠϯσΟϯάͷݟഁΓํ
57. 57 ͦͷͨΊʹ࣮૷͞Εͨͷ͕ɺ %/4ϦόΠϯσΟϯάͷݟഁΓํ
58. 58 https://github.com/rails/rails/blob/6-0-stable/actionpack/CHANGELOG.md#rails-600beta1-january-18-2019 ͜Ε͸ɺϦΫΤετ͕Ͱ͖ΔϗετΛ໌ࣔతʹڐՄ͢Δ͜ͱͰɺ%/4ϦόΠϯσΟϯά߈ܸΛ๷ޚ͢Δɺ ৽͍͠ϛυϧ΢ΣΞͰ͢ɻ
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59. 59 3BJMT
    ͷ
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    ͱ͸Ͳ͏͍͏΋ͷʁ Rails.application.config.hosts = [ IPAddr.new(“0.0.0.0/0”), # All IPv4 addresses. IPAddr.new(“::/0"), # All IPv6 addresses. “localhost” # The localhost reserved domain. ] )PTU
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60. 60 3BJMT
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    ͱ͸Ͳ͏͍͏΋ͷʁ σϑΥϧτͰ͸ɺڐՄϦετʹ஋͕͋Δͷ͸ https://github.com/rails/rails/blob/6-0-stable/railties/lib/rails/application/ configuration.rb#L34 EFWFMPQNFOU
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61. 61 EFWFMPQNFOU
    ؀ڥҎ֎Ͱ΋ݕূΛ༗ޮʹ͍ͨ͠৔߹͸ʜ # config/environments/#{environment}.rb Rails.application.config.hosts = [ “yucao24hours.me" # Add hostname you’d like to pass ] 3BJMT
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62. 62 3BJMT
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    ͱ͸Ͳ͏͍͏΋ͷʁ https://github.com/rails/rails/blob/6-0-stable/actionpack/lib/action_dispatch/ middleware/host_authorization.rb#L22-L30 ڐՄϦετ ϦΫΤετϔομͷ஋
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63. 63 3BJMT
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    ͱ͸Ͳ͏͍͏΋ͷʁ https://github.com/rails/rails/blob/6-0-stable/actionpack/lib/action_dispatch/ middleware/host_authorization.rb#L56-L67 
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64. 64 3BJMT
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    ͱ͸Ͳ͏͍͏΋ͷʁ Rails.application.config.hosts << IPAddr.new(“10.0.0.1/8”) IPAddr Rails.application.config.hosts << /.*\.example\.com/ RegExp Rails.application.config.hosts << "yucao24hours.me" String
65. 65 3BJMT
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66. 66 3BJMT
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67. 67 3BJMT
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68. 68 3BJMT
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69. 69 )PTU"VUIPSJ[BUJPO
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70. 75 参考文献 DNS がよくわかる教科書 (SB クリエイティブ) https://www.sbcr.jp/product/4797394481/ 【インターネットとは】 1-2. ドメイン名とIPアドレス ～ドメイン名～ (JPNIC) https://youtu.be/l2XZBjOEK2w ドメイン名のしくみ - JPNIC https://www.nic.ad.jp/ja/dom/system.html 浸透いうな! http://www.e-ontap.com/dns/propagation/ DNS浸透の都市伝説を斬る ～ランチのおともにDNS～ https://jprs.jp/tech/material/iw2011-lunch-L1-01.pdf DNS のきほん
71. 76 参考文献 DNS rebinding attack の対策と考察 https://dnsops.jp/bof/20071119/dnsrebinding-20071119.pdf Protecting Browsers from DNS Rebinding Attacks https://crypto.stanford.edu/dns/ DNS Rebinding ～今日の用語特別版～ | 徳丸浩の日記 https://blog.tokumaru.org/2007/11/dns-rebinding.html DNS リバインディング
72. 77 参考文献 Guard against DNS rebinding attacks by permitting hosts by gsamokovarov · Pull Request #33145 · rails/rails https://github.com/rails/rails/pull/33145/ #3397 ([PATCH] CgiRequest returns incorrect host name in event of multiple proxies) - Rails Trac - Trac https://web.archive.org/web/20100618053001/http://dev.rubyonrails.org/ticket/3397 X-Forwarded-Host - HTTP | MDN https://developer.mozilla.org/ja/docs/Web/HTTP/Headers/X-Forwarded-Host ターゲットグループのヘルスチェック - Elastic Load Balancing https://docs.aws.amazon.com/ja_jp/elasticloadbalancing/latest/network/target-group-health- checks.html Application Load Balancer のヘルスチェック失敗のトラブルシューティング https://aws.amazon.com/jp/premiumsupport/knowledge-center/elb-fix-failing-health-checks-alb/ ActionDispatch::HostAuthorization(1/2)
73. 78 参考文献 Practical Web Cache Poisoning | PortSwigger Research https://portswigger.net/research/practical-web-cache-poisoning How to Configure Symfony to Work behind a Load Balancer or a Reverse Proxy (Symfony Docs) https://symfony.com/doc/current/deployment/proxies.html ActionDispatch::HostAuthorization(2/2)