From 9ddfe93c434470f578a69674b1e0e16ccdee960f Mon Sep 17 00:00:00 2001
From: David Garske <david@wolfssl.com>
Date: Tue, 2 Aug 2016 16:47:21 -0700
Subject: [PATCH] Fixed issue with CRL check and zero pad (the GetRevoked
 function was not trimming pad). Added new ASN "GetSerialNumber" function and
 implemented it in three places in asn.c.

---
 wolfcrypt/src/asn.c     | 126 +++++++++++++++++-----------------------
 wolfssl/wolfcrypt/asn.h |   2 +
 2 files changed, 55 insertions(+), 73 deletions(-)

diff --git a/wolfcrypt/src/asn.c b/wolfcrypt/src/asn.c
index b151f16a9..4a75f5e6f 100644
--- a/wolfcrypt/src/asn.c
+++ b/wolfcrypt/src/asn.c
@@ -2318,13 +2318,6 @@ void FreeDecodedCert(DecodedCert* cert)
 static int GetCertHeader(DecodedCert* cert)
 {
     int ret = 0, len;
-    byte serialTmp[EXTERNAL_SERIAL_SIZE];
-#if defined(WOLFSSL_SMALL_STACK) && defined(USE_FAST_MATH)
-    mp_int* mpi = NULL;
-#else
-    mp_int stack_mpi;
-    mp_int* mpi = &stack_mpi;
-#endif
 
     if (GetSequence(cert->source, &cert->srcIdx, &len, cert->maxIdx) < 0)
         return ASN_PARSE_E;
@@ -2338,31 +2331,9 @@ static int GetCertHeader(DecodedCert* cert)
     if (GetExplicitVersion(cert->source, &cert->srcIdx, &cert->version) < 0)
         return ASN_PARSE_E;
 
-#if defined(WOLFSSL_SMALL_STACK) && defined(USE_FAST_MATH)
-    mpi = (mp_int*)XMALLOC(sizeof(mp_int), NULL, DYNAMIC_TYPE_TMP_BUFFER);
-    if (mpi == NULL)
-        return MEMORY_E;
-#endif
-
-    if (GetInt(mpi, cert->source, &cert->srcIdx, cert->maxIdx) < 0) {
-#if defined(WOLFSSL_SMALL_STACK) && defined(USE_FAST_MATH)
-        XFREE(mpi, NULL, DYNAMIC_TYPE_TMP_BUFFER);
-#endif
+    if (GetSerialNumber(cert->source, &cert->srcIdx, cert->serial,
+                                        &cert->serialSz, cert->maxIdx) < 0)
         return ASN_PARSE_E;
-    }
-
-    len = mp_unsigned_bin_size(mpi);
-    if (len < (int)sizeof(serialTmp)) {
-        if ( (ret = mp_to_unsigned_bin(mpi, serialTmp)) == MP_OKAY) {
-            XMEMCPY(cert->serial, serialTmp, len);
-            cert->serialSz = len;
-        }
-    }
-    mp_clear(mpi);
-
-#if defined(WOLFSSL_SMALL_STACK) && defined(USE_FAST_MATH)
-    XFREE(mpi, NULL, DYNAMIC_TYPE_TMP_BUFFER);
-#endif
 
     return ret;
 }
@@ -5307,6 +5278,49 @@ WOLFSSL_LOCAL int SetSerialNumber(const byte* sn, word32 snSz, byte* output)
     return result;
 }
 
+WOLFSSL_LOCAL int GetSerialNumber(const byte* input, word32* inOutIdx,
+    byte* serial, int* serialSz, word32 maxIdx)
+{
+    int result = 0;
+    byte b;
+
+    WOLFSSL_ENTER("GetSerialNumber");
+
+    if (serial == NULL || input == NULL || serialSz == NULL) {
+        return BAD_FUNC_ARG;
+    }
+
+    /* First byte is ASN type */
+    b = input[*inOutIdx];
+    *inOutIdx += 1;
+
+    if (b != ASN_INTEGER) {
+        WOLFSSL_MSG("Expecting Integer");
+        return ASN_PARSE_E;
+    }
+
+    if (GetLength(input, inOutIdx, serialSz, maxIdx) < 0) {
+        return ASN_PARSE_E;
+    }
+
+    if (*serialSz > EXTERNAL_SERIAL_SIZE) {
+        WOLFSSL_MSG("Serial Size too big");
+        return ASN_PARSE_E;
+    }
+
+    /* skip padding */
+    if (input[*inOutIdx] == 0x00) {
+        *serialSz -= 1;
+        *inOutIdx += 1;
+    }
+
+    /* return serial */
+    XMEMCPY(serial, &input[*inOutIdx], *serialSz);
+    *inOutIdx += *serialSz;
+
+    return result;
+}
+
 
 
 const char* BEGIN_CERT         = "-----BEGIN CERTIFICATE-----";
@@ -8922,28 +8936,9 @@ static int DecodeSingleResponse(byte* source,
     resp->issuerKeyHash = source + idx;
     idx += length;
 
-    /* Read the serial number, it is handled as a string, not as a
-     * proper number. Just XMEMCPY the data over, rather than load it
-     * as an mp_int. */
-    if (source[idx++] != ASN_INTEGER)
+    /* Get serial number */
+    if (GetSerialNumber(source, &idx, cs->serial, &cs->serialSz, size) < 0)
         return ASN_PARSE_E;
-    if (GetLength(source, &idx, &length, size) < 0)
-        return ASN_PARSE_E;
-    if (length <= EXTERNAL_SERIAL_SIZE)
-    {
-        if (source[idx] == 0)
-        {
-            idx++;
-            length--;
-        }
-        XMEMCPY(cs->serial, source + idx, length);
-        cs->serialSz = length;
-    }
-    else
-    {
-        return ASN_GETINT_E;
-    }
-    idx += length;
 
     /* CertStatus */
     switch (source[idx++])
@@ -9655,39 +9650,24 @@ static int GetRevoked(const byte* buff, word32* idx, DecodedCRL* dcrl,
 
     end = *idx + len;
 
-    /* get serial number */
-    b = buff[*idx];
-    *idx += 1;
-
-    if (b != ASN_INTEGER) {
-        WOLFSSL_MSG("Expecting Integer");
-        return ASN_PARSE_E;
-    }
-
-    if (GetLength(buff, idx, &len, maxIdx) < 0)
-        return ASN_PARSE_E;
-
-    if (len > EXTERNAL_SERIAL_SIZE) {
-        WOLFSSL_MSG("Serial Size too big");
-        return ASN_PARSE_E;
-    }
-
     rc = (RevokedCert*)XMALLOC(sizeof(RevokedCert), dcrl->heap,
-                                                              DYNAMIC_TYPE_CRL);
+                                                          DYNAMIC_TYPE_CRL);
     if (rc == NULL) {
         WOLFSSL_MSG("Alloc Revoked Cert failed");
         return MEMORY_E;
     }
 
-    XMEMCPY(rc->serialNumber, &buff[*idx], len);
-    rc->serialSz = len;
+    if (GetSerialNumber(buff, idx, rc->serialNumber, &rc->serialSz,
+                                                                maxIdx) < 0) {
+        XFREE(rc, dcrl->heap, DYNAMIC_TYPE_CRL);
+        return ASN_PARSE_E;
+    }
 
     /* add to list */
     rc->next = dcrl->certs;
     dcrl->certs = rc;
     dcrl->totalCerts++;
 
-    *idx += len;
 
     /* get date */
     b = buff[*idx];
diff --git a/wolfssl/wolfcrypt/asn.h b/wolfssl/wolfcrypt/asn.h
index 293adfd4d..366a652d2 100644
--- a/wolfssl/wolfcrypt/asn.h
+++ b/wolfssl/wolfcrypt/asn.h
@@ -670,6 +670,8 @@ WOLFSSL_LOCAL word32 SetSet(word32 len, byte* output);
 WOLFSSL_LOCAL word32 SetAlgoID(int algoOID,byte* output,int type,int curveSz);
 WOLFSSL_LOCAL int SetMyVersion(word32 version, byte* output, int header);
 WOLFSSL_LOCAL int SetSerialNumber(const byte* sn, word32 snSz, byte* output);
+WOLFSSL_LOCAL int GetSerialNumber(const byte* input, word32* inOutIdx,
+    byte* serial, int* serialSz, word32 maxIdx);
 WOLFSSL_LOCAL int GetNameHash(const byte* source, word32* idx, byte* hash,
                              int maxIdx);