Respect outputSz in PKCS7 decode methods

Reported by: Nicholas Carlini <npc@anthropic.com>

Author: Frauschi

tests/api.c

@@ -34749,6 +34749,89 @@ static int test_ed448_rejects_identity_key(void)
     return EXPECT_RESULT();
 }
 
+/* Test: wc_PKCS7_DecodeEncryptedData must respect outputSz.
+ * 588-byte EncryptedData blob: 496 bytes of 'A' encrypted with
+ * AES-256-CBC under all-zero key/IV. Decrypted content is 496 bytes,
+ * but we pass a 128-byte output buffer. Must return BUFFER_E. */
+static int test_pkcs7_decode_encrypted_outputsz(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_PKCS7) && !defined(NO_AES) && defined(HAVE_AES_CBC) && \
+    !defined(WOLFSSL_NO_MALLOC) && defined(WOLFSSL_AES_256)
+    wc_PKCS7* p7 = NULL;
+    byte key[32];
+    byte out[128]; /* smaller than 496-byte decrypted content */
+
+    static const byte encBlob[] = {
+        0x30,0x82,0x02,0x48,0x06,0x09,0x2a,0x86,0x48,0x86,0xf7,0x0d,
+        0x01,0x07,0x06,0xa0,0x82,0x02,0x39,0x30,0x82,0x02,0x35,0x02,
+        0x01,0x00,0x30,0x82,0x02,0x2e,0x06,0x09,0x2a,0x86,0x48,0x86,
+        0xf7,0x0d,0x01,0x07,0x01,0x30,0x1d,0x06,0x09,0x60,0x86,0x48,
+        0x01,0x65,0x03,0x04,0x01,0x2a,0x04,0x10,0x00,0x00,0x00,0x00,
+        0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
+        0x80,0x82,0x02,0x00,0x7e,0x0e,0x75,0x77,0xef,0x9c,0x30,0xa6,
+        0xbf,0x0b,0x25,0xe0,0x62,0x1e,0x82,0x7e,0x76,0xf7,0x57,0xef,
+        0x12,0x71,0xc5,0x74,0x0e,0x60,0xc3,0x3c,0x8e,0xc3,0xce,0x70,
+        0xbd,0x3c,0xb4,0x60,0x76,0xb1,0xea,0xb5,0x4b,0xc1,0xfe,0x5b,
+        0x88,0xfa,0x43,0x46,0x03,0x28,0x9d,0xab,0x3d,0xb5,0x88,0x50,
+        0x07,0xfc,0x3c,0xc9,0x49,0x4d,0x68,0x97,0xb1,0x59,0xb6,0x35,
+        0xa1,0x68,0x80,0xb0,0x8f,0xb2,0x21,0x9b,0xfc,0xd8,0xf0,0x67,
+        0xbc,0x4b,0x9b,0x28,0x1c,0x3b,0xa0,0x40,0x76,0x8f,0x1f,0x9f,
+        0x87,0xe6,0xe4,0xa5,0xdc,0x9a,0x9a,0x84,0x86,0xff,0x43,0x8a,
+        0x57,0x8d,0x97,0xd2,0x8f,0x67,0x90,0xd8,0x4f,0x0f,0x0d,0xac,
+        0x56,0x6d,0x51,0x33,0xa3,0x37,0x9e,0xe9,0xbf,0x07,0xab,0x93,
+        0xbc,0xbe,0xc1,0x64,0x07,0x30,0xf0,0xff,0x89,0x0a,0x36,0x1c,
+        0xc8,0xe9,0xae,0x24,0x1f,0x95,0x5c,0xa1,0x8a,0x3e,0x15,0x86,
+        0x49,0x70,0x55,0xc2,0xa5,0x90,0xb9,0xda,0x2b,0x97,0x6f,0x5f,
+        0x60,0x61,0xc9,0xcf,0x4d,0x3a,0xb1,0xe4,0x9f,0x37,0x0f,0xf3,
+        0xba,0x85,0x04,0x52,0x68,0x00,0x47,0x3d,0x83,0xc1,0x3f,0xc6,
+        0x70,0x97,0xc1,0x0c,0xc0,0x0b,0xa2,0xcb,0x8c,0x88,0xb5,0x01,
+        0x29,0x7f,0x7e,0xd2,0x46,0x24,0x82,0x92,0x28,0xdd,0x49,0x53,
+        0x0f,0x76,0xad,0x4b,0x81,0x85,0x3a,0x9f,0xda,0x0d,0x69,0xe2,
+        0x57,0xb9,0xe9,0xfa,0x53,0xed,0x20,0x6f,0x62,0x43,0x1d,0x21,
+        0xa9,0x53,0x3d,0xd5,0xb9,0x1a,0x4b,0x3e,0xb7,0x05,0x87,0xb6,
+        0xe3,0xfe,0x03,0x09,0xe1,0x74,0x34,0x42,0x84,0xb1,0x06,0xf9,
+        0xfe,0x64,0xc1,0xd2,0xce,0x3d,0x29,0xf4,0x94,0xb8,0xfc,0xbe,
+        0xb1,0x90,0xd6,0x38,0x61,0x4e,0x43,0x36,0x4e,0x27,0x87,0xd3,
+        0x24,0xdc,0x34,0xf0,0x28,0x2d,0xc8,0xff,0x89,0x9f,0xeb,0xee,
+        0x0d,0x45,0xfb,0xc5,0x53,0xd3,0xdf,0xcb,0xf8,0xeb,0x7e,0xcb,
+        0x2a,0xd7,0xa2,0xd6,0x6a,0xf1,0xb8,0x24,0xa1,0x05,0x16,0x56,
+        0x2e,0x03,0xfe,0x21,0x19,0x36,0x8a,0xeb,0x50,0x8d,0x42,0x31,
+        0x1d,0xb3,0x0a,0x13,0x1d,0x16,0x09,0x0b,0x40,0x4e,0x90,0x78,
+        0xbf,0x41,0x5f,0x4d,0xd9,0xce,0x91,0xaa,0xd0,0x38,0x5c,0xfb,
+        0xc4,0x9f,0x55,0x4e,0x04,0x9d,0xd0,0xca,0x74,0x3c,0x6c,0x01,
+        0x1b,0x84,0x76,0xfa,0xba,0x5d,0x2d,0x35,0x7e,0xe3,0x37,0x8b,
+        0x72,0x0a,0xbb,0xa4,0x4d,0x56,0x2b,0x3b,0x9f,0x5a,0xa0,0xe3,
+        0x60,0x26,0x65,0x09,0xed,0xfc,0x10,0x0c,0xa1,0x4f,0x12,0x76,
+        0xe2,0x4c,0xbd,0x1b,0x67,0xb4,0xb4,0x54,0x5c,0x38,0x47,0x8b,
+        0x7e,0x35,0x8e,0x4d,0x4e,0xef,0x91,0x3f,0xff,0x16,0x0a,0x42,
+        0x0b,0xe5,0x28,0x26,0x24,0x9f,0x6f,0xb4,0x63,0x8a,0xa1,0x52,
+        0x22,0x3a,0xdb,0xd9,0x8e,0x76,0x6e,0x6a,0xa9,0xa1,0xec,0xf2,
+        0x9c,0x58,0xf8,0x6b,0xdd,0xf2,0xf8,0x2d,0xcb,0x8c,0x96,0xda,
+        0xb4,0x9c,0x44,0xdc,0xab,0x43,0x2c,0x22,0xf3,0xfe,0x1a,0xb9,
+        0x3b,0x82,0x30,0xa2,0xc7,0xef,0x52,0x08,0x7b,0x4f,0x3f,0x7a,
+        0x7e,0x28,0xd7,0x67,0xb9,0xb1,0x69,0x9b,0x96,0x3e,0xc5,0xe4,
+        0x45,0xb0,0x23,0x75,0x00,0xda,0xee,0xdb,0x6d,0xa9,0xe7,0x98
+    };
+
+    XMEMSET(key, 0, sizeof(key));
+
+    p7 = wc_PKCS7_New(NULL, INVALID_DEVID);
+    ExpectNotNull(p7);
+    if (p7 != NULL) {
+        p7->encryptionKey = key;
+        p7->encryptionKeySz = sizeof(key);
+
+        /* 496-byte content into 128-byte buffer must return BUFFER_E */
+        ExpectIntLT(wc_PKCS7_DecodeEncryptedData(p7, (byte*)encBlob,
+                    (word32)sizeof(encBlob), out, sizeof(out)), 0);
+
+        wc_PKCS7_Free(p7);
+    }
+#endif
+    return EXPECT_RESULT();
+}
+
 TEST_CASE testCases[] = {
     TEST_DECL(test_fileAccess),
 
@@ -35564,6 +35647,7 @@ TEST_CASE testCases[] = {
     TEST_DECL(test_wc_DhSetNamedKey),
     TEST_DECL(test_DhAgree_rejects_p_minus_1),
     TEST_DECL(test_ed448_rejects_identity_key),
+    TEST_DECL(test_pkcs7_decode_encrypted_outputsz),
 
 #if defined(WOLFSSL_SNIFFER) && defined(WOLFSSL_SNIFFER_CHAIN_INPUT)
     TEST_DECL(test_sniffer_chain_input_overflow),

wolfcrypt/src/pkcs7.c

@@ -14606,6 +14606,10 @@ int wc_PKCS7_DecodeAuthEnvelopedData(wc_PKCS7* pkcs7, byte* in,
             }
 
             /* copy plaintext to output */
+            if ((word32)encryptedContentSz > outputSz) {
+                ret = BUFFER_E;
+                break;
+            }
             XMEMCPY(output, encryptedContent, (word32)encryptedContentSz);
 
             /* free memory, zero out keys */
@@ -15290,6 +15294,11 @@ int wc_PKCS7_DecodeEncryptedData(wc_PKCS7* pkcs7, byte* in, word32 inSz,
                 }
 
                 /* copy plaintext to output */
+                if ((word32)(encryptedContentSz - padLen) > outputSz) {
+                    XFREE(encryptedContent, pkcs7->heap, DYNAMIC_TYPE_PKCS7);
+                    ret = BUFFER_E;
+                    break;
+                }
                 XMEMCPY(output, encryptedContent,
                     (unsigned int)(encryptedContentSz - padLen));