diff --git a/library/pkcs7.c b/library/pkcs7.c
index 65dc83a..2299cfd 100644
--- a/library/pkcs7.c
+++ b/library/pkcs7.c
@@ -24,6 +24,7 @@
 #include "mbedtls/x509_crt.h"
 #include "mbedtls/x509_crl.h"
 #include "mbedtls/oid.h"
+#include "mbedtls/error.h"
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -64,15 +65,16 @@
 static int pkcs7_get_next_content_len( unsigned char **p, unsigned char *end,
                                        size_t *len )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
-    if( ( ret = mbedtls_asn1_get_tag( p, end, len, MBEDTLS_ASN1_CONSTRUCTED
-                    | MBEDTLS_ASN1_CONTEXT_SPECIFIC ) ) != 0 )
+    ret = mbedtls_asn1_get_tag( p, end, len, MBEDTLS_ASN1_CONSTRUCTED
+            | MBEDTLS_ASN1_CONTEXT_SPECIFIC );
+    if( ret != 0 )
     {
-        return( MBEDTLS_ERR_PKCS7_INVALID_FORMAT + ret );
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_FORMAT, ret );
     }
 
-    return( 0 );
+    return( ret );
 }
 
 /**
@@ -81,16 +83,17 @@
  **/
 static int pkcs7_get_version( unsigned char **p, unsigned char *end, int *ver )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
-    if( ( ret = mbedtls_asn1_get_int( p, end, ver ) ) != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_VERSION + ret );
+    ret = mbedtls_asn1_get_int( p, end, ver );
+    if( ret != 0 )
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_VERSION, ret );
 
     /* If version != 1, return invalid version */
     if( *ver != MBEDTLS_PKCS7_SUPPORTED_VERSION )
-        return( MBEDTLS_ERR_PKCS7_INVALID_VERSION );
+        ret = MBEDTLS_ERR_PKCS7_INVALID_VERSION;
 
-    return( 0 );
+    return( ret );
 }
 
 /**
@@ -103,26 +106,29 @@
                                         mbedtls_pkcs7_buf *pkcs7 )
 {
     size_t len = 0;
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     unsigned char *start = *p;
 
     ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
                                             | MBEDTLS_ASN1_SEQUENCE );
     if( ret != 0 ) {
         *p = start;
-        return( MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO + ret );
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO, ret );
+        goto out;
     }
 
     ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_OID );
     if( ret != 0 ) {
         *p = start;
-        return( MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO + ret );
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO, ret );
+        goto out;
     }
 
     pkcs7->tag = MBEDTLS_ASN1_OID;
     pkcs7->len = len;
     pkcs7->p = *p;
 
+out:
     return( ret );
 }
 
@@ -134,12 +140,12 @@
 static int pkcs7_get_digest_algorithm( unsigned char **p, unsigned char *end,
                                        mbedtls_x509_buf *alg )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
     if( ( ret = mbedtls_asn1_get_alg_null( p, end, alg ) ) != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_ALG );
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_ALG, ret );
 
-    return( 0 );
+    return( ret );
 }
 
 /**
@@ -150,24 +156,31 @@
                                            mbedtls_x509_buf *alg )
 {
     size_t len = 0;
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
     ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
                                             | MBEDTLS_ASN1_SET );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_ALG + ret );
+    {
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_ALG, ret );
+        goto out;
+    }
 
     end = *p + len;
 
     /** For now, it assumes there is only one digest algorithm specified **/
     ret = mbedtls_asn1_get_alg_null( p, end, alg );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_ALG + ret );
+    {
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_ALG, ret );
+        goto out;
+    }
 
     if ( *p != end )
-        return ( MBEDTLS_ERR_PKCS7_INVALID_FORMAT );
+        ret = MBEDTLS_ERR_PKCS7_INVALID_FORMAT;
 
-    return( 0 );
+out:
+    return( ret );
 }
 
 /**
@@ -182,7 +195,7 @@
 static int pkcs7_get_certificates( unsigned char **p, unsigned char *end,
                                    mbedtls_x509_crt *certs )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len1 = 0;
     size_t len2 = 0;
     unsigned char *end_set, *end_cert;
@@ -192,9 +205,10 @@
                     | MBEDTLS_ASN1_CONTEXT_SPECIFIC ) ) != 0 )
     {
         if( ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG )
-            return( 0 );
-
-        return( MBEDTLS_ERR_PKCS7_INVALID_FORMAT + ret );
+            ret = 0;
+        else
+            ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_FORMAT, ret );
+        goto out;
     }
     start = *p;
     end_set = *p + len1;
@@ -202,7 +216,10 @@
     ret = mbedtls_asn1_get_tag( p, end_set, &len2, MBEDTLS_ASN1_CONSTRUCTED
             | MBEDTLS_ASN1_SEQUENCE );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_CERT + ret );
+    {
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_CERT, ret );
+        goto out;
+    }
 
     end_cert = *p + len2;
 
@@ -213,18 +230,28 @@
      * The behaviour would be improved with addition of multiple signer support.
      */
     if (end_cert != end_set)
-        return ( MBEDTLS_ERR_PKCS7_INVALID_CERT );
+    {
+        ret = MBEDTLS_ERR_PKCS7_INVALID_CERT;
+        goto out;
+    }
 
     *p = start;
     if( ( ret = mbedtls_x509_crt_parse( certs, *p, len1 ) ) < 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_CERT );
+    {
+        ret = MBEDTLS_ERR_PKCS7_INVALID_CERT;
+        goto out;
+    }
 
     *p = *p + len1;
 
-    /* Since in this version we strictly support single certificate, and reaching
-     * here implies we have parsed successfully, we return 1. */
+    /* 
+     * Since in this version we strictly support single certificate, and reaching
+     * here implies we have parsed successfully, we return 1. 
+     */
+    ret = 1;
 
-    return( 1 );
+out:
+    return( ret );
 }
 
 /**
@@ -233,12 +260,12 @@
 static int pkcs7_get_signature( unsigned char **p, unsigned char *end,
                                 mbedtls_pkcs7_buf *signature )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len = 0;
 
     ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_OCTET_STRING );
     if( ret != 0 )
-        return( ret );
+        goto out;
 
     signature->tag = MBEDTLS_ASN1_OCTET_STRING;
     signature->len = len;
@@ -246,7 +273,8 @@
 
     *p = *p + len;
 
-    return( 0 );
+out:
+    return( ret );
 }
 
 /**
@@ -267,60 +295,67 @@
                                   mbedtls_pkcs7_signer_info *signer )
 {
     unsigned char *end_signer;
-    int ret;
+    int asn1_ret = 0, ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t len = 0;
 
-    ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
+    asn1_ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
                                 | MBEDTLS_ASN1_SEQUENCE );
-    if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO + ret );
+    if( asn1_ret != 0 )
+        goto out;
 
     end_signer = *p + len;
 
     ret = pkcs7_get_version( p, end_signer, &signer->version );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
-    ret = mbedtls_asn1_get_tag( p, end_signer, &len, MBEDTLS_ASN1_CONSTRUCTED
-                                | MBEDTLS_ASN1_SEQUENCE );
-    if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO + ret );
+    asn1_ret = mbedtls_asn1_get_tag( p, end_signer, &len,
+                MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE );
+    if( asn1_ret != 0 )
+        goto out;
 
     /* Parsing IssuerAndSerialNumber */
     signer->issuer_raw.p = *p;
 
-    ret = mbedtls_asn1_get_tag( p, end_signer, &len, MBEDTLS_ASN1_CONSTRUCTED
-                                | MBEDTLS_ASN1_SEQUENCE );
-    if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO + ret );
+    asn1_ret = mbedtls_asn1_get_tag( p, end_signer, &len,
+                MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE );
+    if( asn1_ret != 0 )
+        goto out;
 
     ret  = mbedtls_x509_get_name( p, *p + len, &signer->issuer );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
     signer->issuer_raw.len =  *p - signer->issuer_raw.p;
 
     ret = mbedtls_x509_get_serial( p, end_signer, &signer->serial );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
     ret = pkcs7_get_digest_algorithm( p, end_signer, &signer->alg_identifier );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
     ret = pkcs7_get_digest_algorithm( p, end_signer, &signer->sig_alg_identifier );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
     ret = pkcs7_get_signature( p, end_signer, &signer->sig );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        goto out;
 
     /* Do not permit any unauthenticated attributes */
     if( *p != end_signer )
-        return ( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO );
+        ret = MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO;
 
-    return( 0 );
+out:
+    if( asn1_ret != 0 )
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO,
+                                    asn1_ret );
+    else if( ret != 0 )
+        ret = MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO;
+
+    return( ret );
 }
 
 static void pkcs7_free_signer_info( mbedtls_pkcs7_signer_info *signer )
@@ -350,7 +385,7 @@
                                        mbedtls_pkcs7_signer_info *signers_set )
 {
     unsigned char *end_set;
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     int count = 0;
     size_t len = 0;
     mbedtls_pkcs7_signer_info *signer, *prev;
@@ -358,17 +393,23 @@
     ret = mbedtls_asn1_get_tag( p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
                                 | MBEDTLS_ASN1_SET );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO + ret );
+    {
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_SIGNER_INFO, ret );
+        goto out;
+    }
 
     /* Detect zero signers */
     if( len == 0 )
-        return( 0 );
+    {
+        ret = 0;
+        goto out;
+    }
 
     end_set = *p + len;
 
     ret = pkcs7_get_signer_info( p, end_set, signers_set );
     if( ret != 0 )
-        return( ret );
+        goto out;
     count++;
 
     prev = signers_set;
@@ -391,7 +432,8 @@
         count++;
     }
 
-    return( count );
+    ret = count;
+    goto out;
 
 cleanup:
     signer = signers_set->next;
@@ -403,6 +445,8 @@
         pkcs7_free_signer_info( prev );
         mbedtls_free( prev );
     }
+
+out:
     return( ret );
 }
 
@@ -425,39 +469,46 @@
     unsigned char *end = buf + buflen;
     unsigned char *end_set;
     size_t len = 0;
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     mbedtls_md_type_t md_alg;
 
     ret = mbedtls_asn1_get_tag( &p, end, &len, MBEDTLS_ASN1_CONSTRUCTED
                                 | MBEDTLS_ASN1_SEQUENCE );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_FORMAT + ret );
+    {
+        ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_PKCS7_INVALID_FORMAT, ret );
+        goto out;
+    }
 
     end_set = p + len;
 
     /* Get version of signed data */
     ret = pkcs7_get_version( &p, end_set, &signed_data->version );
     if( ret != 0 )
-        return( ret );
+        goto out;
 
     /* Get digest algorithm */
     ret = pkcs7_get_digest_algorithm_set( &p, end_set,
             &signed_data->digest_alg_identifiers );
     if( ret != 0 )
-        return( ret );
+        goto out;
 
     ret = mbedtls_oid_get_md_alg( &signed_data->digest_alg_identifiers, &md_alg );
     if( ret != 0 )
-        return( MBEDTLS_ERR_PKCS7_INVALID_ALG );
+    {
+        ret = MBEDTLS_ERR_PKCS7_INVALID_ALG;
+        goto out;
+    }
 
     /* Do not expect any content */
     ret = pkcs7_get_content_info_type( &p, end_set, &signed_data->content.oid );
     if( ret != 0 )
-        return( ret );
+        goto out;
 
     if( MBEDTLS_OID_CMP( MBEDTLS_OID_PKCS7_DATA, &signed_data->content.oid ) )
     {
-        return( MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO ) ;
+        ret = MBEDTLS_ERR_PKCS7_INVALID_CONTENT_INFO;
+        goto out;
     }
 
     p = p + signed_data->content.oid.len;
@@ -466,7 +517,7 @@
     mbedtls_x509_crt_init( &signed_data->certs );
     ret = pkcs7_get_certificates( &p, end_set, &signed_data->certs );
     if( ret < 0 )
-        return( ret ) ;
+        goto out;
 
     signed_data->no_of_certs = ret;
 
@@ -481,15 +532,17 @@
     /* Get signers info */
     ret = pkcs7_get_signers_info_set( &p, end_set, &signed_data->signers );
     if( ret < 0 )
-        return( ret );
+        goto out;
 
     signed_data->no_of_signers = ret;
 
     /* Don't permit trailing data */
     if ( p != end )
         ret = MBEDTLS_ERR_PKCS7_INVALID_FORMAT;
+    else
+        ret = 0;
 
-    ret = 0;
+out:
     return( ret );
 }
 
@@ -499,17 +552,21 @@
     unsigned char *start;
     unsigned char *end;
     size_t len = 0;
-    int ret;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     int isoidset = 0;
 
     if( !pkcs7 )
-        return( MBEDTLS_ERR_PKCS7_BAD_INPUT_DATA );
+    {
+        ret = MBEDTLS_ERR_PKCS7_BAD_INPUT_DATA;
+        goto out;
+    }
 
     /* make an internal copy of the buffer for parsing */
     pkcs7->raw.p = start = mbedtls_calloc( 1, buflen );
     if( pkcs7->raw.p == NULL )
     {
-        return( MBEDTLS_ERR_PKCS7_ALLOC_FAILED );
+        ret = MBEDTLS_ERR_PKCS7_ALLOC_FAILED;
+        goto out;
     }
     memcpy( start, buf, buflen );
     pkcs7->raw.len = buflen;
@@ -573,7 +630,7 @@
                                       size_t datalen )
 {
 
-    int ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     unsigned char *hash;
     mbedtls_pk_context pk_cxt = cert->pk;
     const mbedtls_md_info_t *md_info;
@@ -581,8 +638,10 @@
     mbedtls_pkcs7_signer_info *signer;
 
     if( pkcs7->signed_data.no_of_signers == 0 )
-        return( MBEDTLS_ERR_PKCS7_VERIFY_FAIL );
-
+    {
+        ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+        goto out;
+    }
 
     /*
      * Potential TODOs
@@ -602,20 +661,24 @@
     {
         ret = mbedtls_oid_get_md_alg( &signer->alg_identifier, &md_alg );
         if( ret != 0 )
-            return( MBEDTLS_ERR_PKCS7_VERIFY_FAIL );
+        {
+            ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+            goto out;
+        }
 
         md_info = mbedtls_md_info_from_type( md_alg );
 
         hash = mbedtls_calloc( mbedtls_md_get_size( md_info ), 1 );
         if( hash == NULL ) {
-            return( MBEDTLS_ERR_PKCS7_ALLOC_FAILED );
+            ret = MBEDTLS_ERR_PKCS7_ALLOC_FAILED;
+            goto out;
         }
 
         ret = mbedtls_md( md_info, data, datalen, hash );
         if( ret != 0 )
         {
             mbedtls_free( hash );
-            return( ret );
+            goto out;
         }
 
         ret = mbedtls_pk_verify( &pk_cxt, md_alg, hash,
@@ -630,6 +693,7 @@
         signer = signer->next;
     }
 
+out:
     return( ret );
 }
 
@@ -637,7 +701,7 @@
                                       const mbedtls_x509_crt *cert,
                                       const unsigned char *hash, size_t hashlen)
 {
-    int ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     const mbedtls_md_info_t *md_info;
     mbedtls_md_type_t md_alg;
     mbedtls_pk_context pk_cxt;
@@ -646,14 +710,20 @@
     pk_cxt = cert->pk;
 
     if( pkcs7->signed_data.no_of_signers == 0 )
-        return( MBEDTLS_ERR_PKCS7_VERIFY_FAIL );
+    {
+        ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+        goto out;
+    }
 
     signer = &pkcs7->signed_data.signers;
     while( signer )
     {
         ret = mbedtls_oid_get_md_alg( &signer->alg_identifier, &md_alg );
         if( ret != 0 )
-            return( MBEDTLS_ERR_PKCS7_VERIFY_FAIL );
+        {
+            ret = MBEDTLS_ERR_PKCS7_VERIFY_FAIL;
+            goto out;
+        }
 
         md_info = mbedtls_md_info_from_type( md_alg );
 
@@ -673,6 +743,7 @@
         signer = signer->next;
     }
 
+out:
     return ( ret );
 }