GHSA-jgvc-jfgh-rjvv

Summary

RSA15 in jose4j is susceptible to chosen ciphertext attacks. The attack allows to decrypt RSA15 or RSA_OAEP encrypted ciphertexts. It may be feasible to sign with affected keys.

Severity

Moderate - exploiting this ciphertext attack could result in the ability to decrypt RSA15 or RSAOAEP encrypted ciphertexts.

Proof of Concept

A test case that can reproduce the padding oracle uses the following private key:

{
        "kty": "RSA",
        "alg": "RSA1_5",
        "use": "enc",
        "n": "w2A4cbwOAK4ATnwXkGWereqv9dkEcgAGHc9g-cjo1HFeilYirvfD2Un2vQxW_6g2OKRPmmo46vMZFMYv_V57174j411y-NQlZGb7iFqMQADzo60VZ7vpvAX_NuxNGxYR-N2cBgvgqDiGAoO9ouNdhuHhxipTjGVfrPUpxmJtNPZpxsgxQWSpYCYMl304DD_5wWrnumNNIKOaVsAYmjFPV_wqxFCHbitPd1BG9SwXPk7wAHtXT6rYaUImS_OKaHkTO1OO0PNhd3-wJRNMCh_EGUwAghfWgFyAd20pQLZamamxgHvfL4-0hwuzndhHt0ye-gRVTtXDFEwABB--zwvlCw",
        "e": "AQAB",
        "kid": "rsa1_5",
        "d": "EjMvbuDeyQ9sdeM3arscqgTXuWYq9Netui8sUHh3v_qDnQ1jE7t-4gny0y-IFy67RlGAHNlSTgixSG8h309i5_kNbMuyvx08EntJaS1OLVQpXhDskoo9vscsPBiNIj3PFMjIFQQcPG9vhGJzUu4tMzhtiME-oTB8VidMae-XTryPvozTu4rgfb4U7uauvLqESLz3A5xtzPnwNwqXAIlrdxU-MT_iln08on_QIF8afWUqCbsWWjEck_QDKLVpzh8VV9kkEVWwYfCFhHBwS-fgGJJTE3gK4HwOokydMtH95Dzj47MA2pLe600l7ioyGSPltcv967NtOpxMPM5ro751KQ",
        "p": "-F1u3NAMWPu1TIuvIywIjh5fuiA3AVKLgS6Fw_hAi3M9c3T7E1zNJZuHgQExJEu06ZPfzye9m7taDzh-Vw4VGDED_MZedsE2jEsWa9EKeq3bZVf5j81FLCHH8BicFqrPjvoVUC35wrl9SGJzaOa7KXxD2jW22umYjJS_kcopvf0",
        "q": "yWHG7jHqvfqT8gfhIlxpMbeJ02FrWIkgJC-zOJ26wXC6oxPeqhqEO7ulGqZPngNDdSGgWcQ7noGEU8O4MA9V3yhl91TFZy8unox0sGe0jDMwtxm3saXtTsjTE7FBxzcR0PubfyGiS0fJqQcj8oJSWzZPkUshzZ8rF3jTLc8UWac",
        "dp": "Va9WWhPkzqY4TCo8x_OfF_jeqcYHdAtYWb8FIzD4g6PEZZrMLEft9rWLsDQLEiyUQ6lio4NgZOPkFDA3Vi1jla8DYyfE20-ZVBlrqNK7vMtST8pkLPpyjOEyq2CyKRfQ99DLnZfe_RElad2dV2mS1KMsfZHeffPtT0LaPJ_0erk",
        "dq": "M8rA1cviun9yg0HBhgvMRiwU91dLu1Zw_L2D02DFgjCS35QhpQ_yyEYHPWZefZ4LQFmoms2cI7TdqolgmoOnKyCBsO2NY29AByjKbgAN8CzOL5kepEKvWJ7PonXpG-ou29eJ81VcHw5Ub_NVLG6V7b13E0AGbpKsC3pYnaRvcGs",
        "qi": "8zIqISvddJYC93hP0sKkdHuVd-Mes_gsbi8xqSFYGqc-wSU12KjzHnZmBuJl_VTGy9CO9W4K2gejr588a3Ozf9U5hx9qCVkV0_ttxHcTRem5sFPe9z-HkQE5IMW3SdmL1sEcvkzD7z8QhcHRpp5aMptfuwnxBPY8U449_iNgXd4"
      },

jose4j has distinguishable behvaior for the following test cases:

The first ciphertext below contains an invalid PKCS #1 padding. Because of hte invalid padding a random AES key is generated during decryption. This leads to an authentication error.

"eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4R0NNIn0.ksmeZ6dBbP0UfDEaLXlqPl2XDaAA29kGlKtDb89x-4xN5-A6bx2umI_ToHK2GadzxUOgKROCACYb6rmKsqsQCOZaBsnq_4mDII1W0pja7Lz4zTnr7R3O4kALg4zXqG-gSlcDA7k1NgkpMDS15PjMmADqyqxbxQsXdfjstN324iqdvYGh6NsckkfTSWxDVAqiSR9fW8PsIbo3uSMokNaC-f64CDWIB9AsCxhF-3mnFbxXNxw7JE0upOgG4enQ8kZkwi_v54HBqAau1YNW7gPhFV8ElTQ71J6aHB3dja23lbWdaJmrK6PJE7gEeZmUbFkSYmuyzRUS-NGfXA23fYv5JQ.46AsIpPgnJCLH0Xm.u2rG.LyEHEGCWM8CXDEEHiaqhiQ"

The second ciphertext below ontains valid PKCS #1 padding, but the size of the encoded key is incorrect. Because of this, trying to dcrypt the symmetric part of the ciphertext immediately fails with org.jose4j.lang.JoseException: Invalid key for AES/GCM/NoPadding.

"eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4R0NNIn0.oyVTmkyoChxFtyCtiKhv8OpBJcV6C6s_gMFSSRJBNStpdHPzq2YmroTfXGj1J1plFG4BBQwIZtdt6rIS6YkCvTLGqP1hds9CAO1a_bgRyoAVuOVvH2vmz5U2r74_SRbAzD35M7yZ_tSnnEdMFlHMFbf5uNwmgArrtPgh0V5OLn5i4XIc154FLTiQlvAEhUxiPuYBkm_1GBiYEH4JjP2RKXAUx_TxAVwPsOfIPAVrO0Ev_nvdtVLCE-uOn8WQbxh4wwOztaXOV1HIaPrl7HN-YtDOA840QUHm97ZZLAPRgLzGlkMI0ZS8QkYdb9_FT3KMbNu60nBKEniv2uhBdIhM9g.46AsIpPgnJCLH0Xm.u2rG.LyEHEGCWM8CXDEEHiaqhiQ"

A correct implementation would not have distinguishable behavior. A test case for the missing algorithm checks uses the key:

{
        "alg": "RSA-OAEP",
        "use": "enc",
        "n": "kqGboBfAWttWPCA-0cGRgsY6SaYoIARt0B_PkaEcIq9HPYNdu9n6UuWHuuTHrjF_ZoQW97r5HaAorNvrMEGTGdxCHZdEtkHvNVVmrtxTBLiQCbCozXhFoIrVcr3qUBrdGnNn_M3jJi7Wg7p_-x62nS5gNG875oyheRkutHsQXikFZwsN3q_TsPNOVlCiHy8mxzaFTUQGm-X8UYexFyAivlDSjgDJLAZSWfxd7k9Gxuwa3AUfQqQcVcegmgKGCaErQ3qQbh1x7WB6iopE3_-GZ8HMAVtR9AmrVscqYsnjhaCehfAI0iKKs8zXr8tISc0ORbaalrkk03H1ZrsEnDKEWQ",
        "e": "AQAB",
        "d": "YsfIRYN6rDqSz5KRf1E9q7HK1o6-_UK-j7S-asb0Y1FdVs1GuiRQhMPoOjmhY3Io93EI3_7vj8uzWzAUMsAaTxOY3sJnIbktYuqTcD0xGD8VmdGPBkx963db8B6M2UYfqZARf7dbzP9EuB1N1miMcTsqyGgfHGOk7CXQ1vkIv8Uww38KMtEdJ3iB8r-f3qcu-UJjE7Egw9CxKOMjArOXxZEr4VnoIXrImrcTxBfjdY8GbzXGATiPQLur5GT99ZDW78falsir-b5Ean6HNyOeuaJuceT-yjgCXn57Rd3oIHD94CrjNtjBusoLdjbr489L8K9ksCh1gynzLGkeeWgVGQ",
        "p": "0xalbl1PJbSBGD4XOjIYJLwMYyHMiM06SBauMGzBfCask5DN5jH68Kw1yPS4wkLpx4ltGLuy0X5mMaZzrSOkBGb27-NizBgB2-L279XotznWeh2jbF05Kqzkoz3VaX_7dRhCHEhOopMQh619hA1bwaJyW1k8aNlLPTl3BotkP4M",
        "q": "sdQsQVz3tI7hmisAgiIjppOssEnZaZO0ONeRRDxBHGLe3BCo1FJoMMQryOAlglayjQnnWjQ-BpwUpa0r9YQhVLweoNEIig6Beph7iYRZgOHEiiTTgUIGgXAL6xhsby1PueUfT0xsN1Y7qt5f5EwOfu7tnFqNyJXIp9W1NQgU6fM",
        "dp": "kEpEnuJNfdqa-_VFb1RayJF6bjDmXQTcN_a47wUIZVMSWHR9KkMz41v0D_-oY7HVl73Kw0NagnVCaeH75HgeX5v6ZBQsrpIigynr3hl8T_LLNwIXebVnpFI2n5de0BTZ0DraxfZvOhYJEJV43NE8zWm7fdHLx2fxVFJ5mBGkXv0",
        "dq": "U_xJCnXF51iz5AP7MXq-K6YDIR8_t0UzEMV-riNm_OkVKAoWMnDZFG8R3sU98djQaxwKT-fsg2KjvbuTz1igBUzzijAvQESpkiUB82i2fNAj6rqJybpNKESq3FWkoL1dsgYsS19knJ31gDWWRFRHZFujjPyXiexz4BBmjK1Mc1E",
        "qi": "Uvb84tWiJF3fB-U9wZSPi7juGgrzeXS_LYtf5fcdV0fZg_h_5nSVpXyYyQ-PK218qEC5MlDkaHKRD9wBOe_eU_zJTNoXzB2oAcgl2MapBWUMytbiF84ghP_2K9UD63ZVsyrorSZhmsJIBBuqQjrmk0tIdpMdlMxLYhrbYwFxUqc",
        "kid": "kid-rsa-enc-oaep",
        "kty": "RSA"
      }

and the cipher text

"eyJhbGciOiJSU0ExXzUiLCJlbmMiOiJBMTI4R0NNIn0.CuUuY9PH2wWjuLXd5O9LLFanwyt5-y-NzEpy9rC3A63tFsvdp8GWP1kRt1d3zd0bGqakwls623VQxzxqQ25j5gdHh8dKMl67xTLHt1Qlg36nI9Ukn7syq25VrzfrRRwy0k7isqMncHpzuBQlmfzPrszW7d13z7_ex0Uha869RaP-W2NNBfHYw26xIXcCSVIPg8jTLA7h6QmOetEej-NXXcWrRKQgBRapYy4iWrij9Vr3JzAGSHVtIID74tFOm01FdJj4s1M4IXegDbvAdQb6Vao1Ln5GolnTki4IGvH5FDssDHz6MS2JG5QBcITzfuXU81vDC00xzNEuMat0AngmOw.UjPQbnakkZYUdoDa.vcbS.WQ_bOPiGKjPSq-qyGOIfjA"

The header of this ciphertext is: {"alg":"RSA1_5","enc":"A128GCM"} Hence the algorithm in the header does not match the algorithm in the key. Such ciphertexts should be rejected. The wrapped key is a valid RSA15 encrypted key. jose4j currently decrypts the ciphertext above without an exception. The problem with this behavior is that jose4j also allows chosen ciphertext attacks when the key uses RSAOAEP. The attacker simply has to modify the header to and replace the algorithm with RSA1_5. Attempts to decrypt modified ciphertexts will then leak whether the decrypted message has valid PKCS #1 padding.

Further Analysis

Fix Commit - https://bitbucket.org/b_c/jose4j/commits/63b86581e7bfcc2d9d04ee15caea4b5bfb911f59

Timeline

Date reported: 01/27/2023 Date fixed: 02/09/2023 Date disclosed: 04/27/2023