From f332a97e1bf370b9ea15c0e18e76d3fe8cf92c26 Mon Sep 17 00:00:00 2001
From: Hanno Becker <hanno.becker@arm.com>
Date: Mon, 13 May 2019 11:56:21 +0100
Subject: [PATCH] Add ASN.1 API to free linked list representation of ASN.1
 sequences

---
 include/mbedtls/asn1.h | 37 +++++++++++++++++++++++++++++++------
 include/mbedtls/x509.h |  5 ++++-
 library/asn1parse.c    | 10 ++++++++++
 library/x509.c         | 11 -----------
 4 files changed, 45 insertions(+), 18 deletions(-)

diff --git a/include/mbedtls/asn1.h b/include/mbedtls/asn1.h
index 5b7b2b82d..b471a94b6 100644
--- a/include/mbedtls/asn1.h
+++ b/include/mbedtls/asn1.h
@@ -276,13 +276,38 @@ int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end
                              size_t *len );
 
 /**
- * \brief       Parses and splits an ASN.1 "SEQUENCE OF <tag>"
- *              Updated the pointer to immediately behind the full sequence tag.
+ * \brief          Free a heap-allocated linked list presentation of
+ *                 an ASN.1 sequence, including the first element.
  *
- * \param p     The position in the ASN.1 data
- * \param end   End of data
- * \param cur   First variable in the chain to fill
- * \param tag   Type of sequence
+ * \param seq      The address of the first sequence component. This may
+ *                 be \c NULL, in which case this functions returns
+ *                 immediately.
+ */
+void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq );
+
+/**
+ * \brief       This function parses and splits an ASN.1 "SEQUENCE OF <tag>"
+ *              and updates the source buffer pointer to immediately behind
+ *              the full sequence.
+ *
+ * \param p     The address of the pointer to the beginning of the
+ *              ASN.1 SEQUENCE OF structure, including ASN.1 tag+length header.
+ *              On success, `*p` is advanced to point to the first byte
+ *              following the parsed ASN.1 sequence.
+ * \param end   The end of the ASN.1 input buffer starting at \p p. This is
+ *              used for bounds checking.
+ * \param cur   The address at which to store the first entry in the parsed
+ *              sequence. Further entries are heap-allocated and referenced
+ *              from \p cur.
+ * \param tag   The common tag of the entries in the ASN.1 sequence.
+ *
+ * \note        Ownership for the heap-allocated elements \c cur->next,
+ *              \c cur->next->next, ..., is passed to the caller. It
+ *              is hence the caller's responsibility to free them when
+ *              no longer needed, and mbedtls_asn1_sequence_free() can
+ *              be used for that, passing \c cur->next as the \c seq
+ *              argument (or \p cur if \p cur itself was heap-allocated
+ *              by the caller).
  *
  * \return      0 if successful or a specific ASN.1 error code.
  */
diff --git a/include/mbedtls/x509.h b/include/mbedtls/x509.h
index 753019aac..5d091bc2d 100644
--- a/include/mbedtls/x509.h
+++ b/include/mbedtls/x509.h
@@ -296,7 +296,10 @@ void mbedtls_x509_name_free( mbedtls_x509_name *name );
  *                 be \c NULL, in which case this functions returns
  *                 immediately.
  */
-void mbedtls_x509_sequence_free( mbedtls_x509_sequence *seq );
+static inline void mbedtls_x509_sequence_free( mbedtls_x509_sequence *seq )
+{
+    mbedtls_asn1_sequence_free( (mbedtls_asn1_sequence*) seq );
+}
 
 #if defined(MBEDTLS_SELF_TEST)
 
diff --git a/library/asn1parse.c b/library/asn1parse.c
index f24fee69f..68a70e61f 100644
--- a/library/asn1parse.c
+++ b/library/asn1parse.c
@@ -229,6 +229,16 @@ int mbedtls_asn1_get_bitstring_null( unsigned char **p, const unsigned char *end
     return( 0 );
 }
 
+void mbedtls_asn1_sequence_free( mbedtls_asn1_sequence *seq )
+{
+    while( seq != NULL )
+    {
+        mbedtls_asn1_sequence *next = seq->next;
+        mbedtls_platform_zeroize( seq, sizeof( *seq ) );
+        mbedtls_free( seq );
+        seq = next;
+    }
+}
 
 /*
  * Traverse an ASN.1 "SEQUENCE OF <tag>"
diff --git a/library/x509.c b/library/x509.c
index 627a5a39b..f1c96a827 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -1220,17 +1220,6 @@ void mbedtls_x509_name_free( mbedtls_x509_name *name )
     }
 }
 
-void mbedtls_x509_sequence_free( mbedtls_x509_sequence *seq )
-{
-    while( seq != NULL )
-    {
-        mbedtls_x509_sequence *next = seq->next;
-        mbedtls_platform_zeroize( seq, sizeof( *seq ) );
-        mbedtls_free( seq );
-        seq = next;
-    }
-}
-
 #if defined(MBEDTLS_SELF_TEST)
 
 #include "mbedtls/x509_crt.h"