commit 19c10e9984acaef5a5fb4c15965b982fc1728d1f
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Thu May 11 12:49:51 2017 +0200
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Thu May 11 13:37:45 2017 +0200
tree 71abe45658829c1493450fbdd98835b4b722f5dd
parent 98864d5c0b154eda7aeb2c2bffe7e7e1c97424bc

RSA PKCS1v1.5 verification: check padding length

The test case was generated by modifying our signature code so that it
produces a 7-byte long padding (which also means garbage at the end, so it is
essential to check that the error that is detected first is indeed the
padding rather than the final length check).

ChangeLog

diff --git a/ChangeLog b/ChangeLog
index b46c728..832810b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS 1.3.x branch released xxxx-xx-xx
+
+Security
+   * Tighten parsing of RSA PKCS#1 v1.5 signatures, to avoid a
+     potential Bleichenbacher/BERserk-style attack.
+
 = mbed TLS 1.3.19 branch released 2017-03-08
 
 Security

library/rsa.c

diff --git a/library/rsa.c b/library/rsa.c
index 79726c1..9a4134c 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1376,7 +1376,11 @@
             return( POLARSSL_ERR_RSA_INVALID_PADDING );
         p++;
     }
-    p++;
+    p++; /* skip 00 byte */
+
+    /* We've read: 00 01 PS 00 where PS must be at least 8 bytes */
+    if( p - buf < 11 )
+        return( POLARSSL_ERR_RSA_INVALID_PADDING );
 
     len = siglen - ( p - buf );
 

tests/suites/test_suite_rsa.data

diff --git a/tests/suites/test_suite_rsa.data b/tests/suites/test_suite_rsa.data
index e4bc89e..2c62990 100644
--- a/tests/suites/test_suite_rsa.data
+++ b/tests/suites/test_suite_rsa.data
@@ -134,6 +134,10 @@
 depends_on:POLARSSL_SHA512_C:POLARSSL_PKCS1_V15
 rsa_pkcs1_verify:"59779fd2a39e56640c4fc1e67b60aeffcecd78aed7ad2bdfa464e93d04198d48466b8da7445f25bfa19db2844edd5c8f539cf772cc132b483169d390db28a43bc4ee0f038f6568ffc87447746cb72fefac2d6d90ee3143a915ac4688028805905a68eb8f8a96674b093c495eddd8704461eaa2b345efbb2ad6930acd8023f870":RSA_PKCS_V15:POLARSSL_MD_SHA512:1536:16:"a59d9b7269b102b7be684ec5e28db79992e6d3231e77c90b78960c2638b35ef6dbdac1ac59e7249d96d426e7f99397eabc6b8903fe1942da580322b98bafacd81bb911c29666f83886a2a2864f3552044300e60cedd5a8c321c43e280413dc41673c39a11b98a885486f8187a70f270185c4c12bc48a1968305269776c070ef69d4913589a887c4d0f5e7dd58bd806d0d49a14a1762c38665cef4646ff13a0cd29c3a60460703c3d051d5b28c660bffb5f8bd43d495ffa64175f72b8abe5fddd":16:"11":"0b4d96f411c727a262d6d0ade34195b78603551061917d060f89add47b09dfe8715f4f9147d327dc25e91fe457e5d1a2f22cd8fe6fe8e29d2060658307c87a40640650fef3d4b289a6c3febc5a100b29a8b56623afb29fd3c13ea372bf3c638c1db25f8bd8c74c821beec7b5affcace1d05d056a6c2d3035926c7a268df4751a54bc20a6b8cfd729a7cba309ae817daccbef9950a482cf23950a8ca1d3a13ddb7d8d0f87ad5587d4d9ebe19fe93457597a7bdd056c2fd4cea7d31e4a0e595a7b":0
 
+RSA PKCS1 Verify v1.5 padding too short
+depends_on:MBEDTLS_SHA1_C:MBEDTLS_PKCS1_V15
+mbedtls_rsa_pkcs1_verify:"AABBCC03020100FFFFFFFFFF1122330A0B0CCCDDDDDDDDDD":MBEDTLS_RSA_PKCS_V15:MBEDTLS_MD_SHA1:1024:16:"9292758453063D803DD603D5E777D7888ED1D5BF35786190FA2F23EBC0848AEADDA92CA6C3D80B32C4D109BE0F36D6AE7130B9CED7ACDF54CFC7555AC14EEBAB93A89813FBF3C4F8066D2D800F7C38A81AE31942917403FF4946B0A83D3D3E05EE57C6F5F5606FB5D4BC6CD34EE0801A5E94BB77B07507233A0BC7BAC8F90F79":16:"10001":"6edd56f397d9bc6d176bbe3d80946fc352ad6127b85b1d67d849c0a38cbde7222c5fafbb18dcef791178a8e15f5c8cd91869f8ca4b758c46ce3e229bf666d2e3e296544351bcb5db7e0004f6c0800f76a432071297e405759d4324d1cf1c412758be93a39f834e03dee59e28ac571ce2b0b3c8fe639979f516223b54027340a5":MBEDTLS_ERR_RSA_INVALID_PADDING
+
 RSA PKCS1 Sign #1 (SHA512, 1536 bits RSA)
 depends_on:POLARSSL_SHA512_C:POLARSSL_PKCS1_V15
 rsa_pkcs1_sign:"59779fd2a39e56640c4fc1e67b60aeffcecd78aed7ad2bdfa464e93d04198d48466b8da7445f25bfa19db2844edd5c8f539cf772cc132b483169d390db28a43bc4ee0f038f6568ffc87447746cb72fefac2d6d90ee3143a915ac4688028805905a68eb8f8a96674b093c495eddd8704461eaa2b345efbb2ad6930acd8023f870":RSA_PKCS_V15:POLARSSL_MD_SHA512:1536:16:"c8c67df894c882045ede26a9008ab09ea0672077d7bc71d412511cd93981ddde8f91b967da404056c39f105f7f239abdaff92923859920f6299e82b95bd5b8c959948f4a035cbd693ad83014294d349813d1ad57911a6355d0731fe3a034e9db":16:"f15147d0e7c04a1e3f37adde802cdc610999bf7ab0088434aaeda0c0ab3910b14d2ce56cb66bffd97552195fae8b061077e03920814d8b9cfb5a3958b3a82c2a7fc97e55db5978b47a922156eb8a3e55c06a54a45d1670abdfb995489c4d0051":16:"bd429bb7c3b00bbea19ba664c0f8172d1a73c3cfa05e2ed656d570c1590918bb7e372ed25e2cd71395ba0a9b1a30f3ee012ffb0546cab8e3581fe3e23f44ab57a8aee9717e71a936a580fa8572d450fb00339a6f6704b717df0c149a465bab768c61500cd93b61113ff3e4389167f7b2c8e3c0da2d4765286bee555b0bcb4998f59b14fad03180a17c8b4f69bcd1234f4ae85950137665ac2ba80b55cc9b1aafb454b83771aa755acd2a00e93ddb65e696dbed8bdca69fb5e0c5c2097b9cfe4b":16:"3":"93b6fa99485c116ca6efdd4202ea1cf49f4c6345fae692584413743ce5b65510e8e4690aee9a19ea1ff10d57f22aa3548d839f28a8525a34354e9e58e0f3947e056ce2554e21bf287e220b98db3b551258cd42b495e5d1a3bbc83c9d1a02f2a300ef6d866ea75108e44ebb3e16b47df2f6de28feb2be3874dbbf21599451082d86e9f2f462575a8185c69aa1f1fcb6a363c5d71aeba2103449eaf3845285291148d5f78d1646b8dc95cbcc4082f987d948b0e7d4e80b60595f8a7517584e1643":0