Add function parsing a TLS ECParameters record

include/polarssl/ecp.h

@@ -89,12 +89,14 @@ ecp_group;
  * \warning This library does not support validation of arbitrary domain
  * parameters. Therefore, only well-known domain parameters from trusted
  * sources should be used. See ecp_use_known_dp().
+ *
+ * \note The values are taken from RFC 4492's enum NamedCurve.
  */
-#define POLARSSL_ECP_DP_SECP192R1   0
+#define POLARSSL_ECP_DP_SECP192R1   19
-#define POLARSSL_ECP_DP_SECP224R1   1
+#define POLARSSL_ECP_DP_SECP224R1   21
-#define POLARSSL_ECP_DP_SECP256R1   2
+#define POLARSSL_ECP_DP_SECP256R1   23
-#define POLARSSL_ECP_DP_SECP384R1   3
+#define POLARSSL_ECP_DP_SECP384R1   24
-#define POLARSSL_ECP_DP_SECP521R1   4
+#define POLARSSL_ECP_DP_SECP521R1   25
 
 /**
  * Maximum bit size of the groups (that is, of N)
@@ -120,6 +122,12 @@ ecp_group;
 #define POLARSSL_ECP_PF_UNCOMPRESSED    0   /**< Uncompressed point format */
 #define POLARSSL_ECP_PF_COMPRESSED      1   /**< Compressed point format */
 
+/*
+ * Some constants from RFC 4492 (ECC for TLS)
+ */
+#define POLARSSL_ECP_TLS_NAMED_CURVE    3   /**< ECCurveType named_curve */
+
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -259,6 +267,7 @@ int ecp_write_binary( const ecp_group *grp, const ecp_point *P, int format,
  */
 int ecp_read_binary( const ecp_group *grp, ecp_point *P, int format,
                      const unsigned char *buf, size_t ilen );
+
 /**
  * \brief           Set a group using well-known domain parameters
  *
@@ -269,9 +278,23 @@ int ecp_read_binary( const ecp_group *grp, ecp_point *P, int format,
  *                  POLARSSL_ERR_MPI_XXX if initialization failed
  *                  POLARSSL_ERR_ECP_GENERIC if index is out of range
  *
- * \note            Index should be a POLARSSL_ECP_DP_XXX macro.
+ * \note            Index should be a value of RFC 4492's enum NamdeCurve,
+ *                  possibly in the form of a POLARSSL_ECP_DP_XXX macro.
  */
-int ecp_use_known_dp( ecp_group *grp, size_t index );
+int ecp_use_known_dp( ecp_group *grp, uint16_t index );
+
+/**
+ * \brief           Read a group from an ECParameters record
+ *
+ * \param grp       Destination group
+ * \param buf       Start of input buffer
+ * \param len       Buffer length
+ *
+ * \return          O if successful,
+ *                  POLARSSL_ERR_MPI_XXX if initialization failed
+ *                  POLARSSL_ERR_ECP_BAD_INPUT_DATA if input is invalid
+ */
+int ecp_tls_read_group( ecp_group *grp, const unsigned char *buf, size_t len );
 
 /**
  * \brief           Addition: R = P + Q

library/ecp.c

@@ -29,6 +29,7 @@
  * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
  * GECC = Guide to Elliptic Curve Cryptography - Hankerson, Menezes, Vanstone
  * FIPS 186-3 http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf
+ * RFC 4492 for the related TLS structures and constants
  */
 
 #include "polarssl/config.h"
@@ -493,7 +494,7 @@ cleanup:
 /*
  * Set a group using well-known domain parameters
  */
-int ecp_use_known_dp( ecp_group *grp, size_t index )
+int ecp_use_known_dp( ecp_group *grp, uint16_t index )
 {
     switch( index )
     {
@@ -525,7 +526,33 @@ int ecp_use_known_dp( ecp_group *grp, size_t index )
                         SECP521R1_GX, SECP521R1_GY, SECP521R1_N ) );
     }
 
-    return( POLARSSL_ERR_ECP_GENERIC );
+    return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
+}
+
+/*
+ * Set a group from an ECParameters record (RFC 4492)
+ */
+int ecp_tls_read_group( ecp_group *grp, const unsigned char *buf, size_t len )
+{
+    uint16_t namedcurve;
+
+    /*
+     * We expect at least three bytes (see below)
+     */
+    if( len < 3 )
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
+
+    /*
+     * First byte is curve_type; only named_curve is handled
+     */
+    if( *buf++ != POLARSSL_ECP_TLS_NAMED_CURVE )
+        return( POLARSSL_ERR_ECP_BAD_INPUT_DATA );
+
+    /*
+     * Next two bytes are the namedcurve
+     */
+    namedcurve = 256 * buf[0] + buf[1];
+    return ecp_use_known_dp( grp, namedcurve );
 }
 
 /*

tests/suites/test_suite_ecp.data

@@ -184,6 +184,21 @@ ecp_read_binary:SECP192R1:"0548d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc99336ce
 ECP read binary #6 (non-zero, OK)
 ecp_read_binary:SECP192R1:"0448d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc99336ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":UNCOMPRESSED:"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"6ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":"01":0
 
+ECP read params #1 (record too short)
+ecp_read_params:"0313":POLARSSL_ERR_ECP_BAD_INPUT_DATA:0
+
+ECP read params #2 (bad curve_type)
+ecp_read_params:"010013":POLARSSL_ERR_ECP_BAD_INPUT_DATA:0
+
+ECP read params #3 (unknown curve)
+ecp_read_params:"030010":POLARSSL_ERR_ECP_BAD_INPUT_DATA:0
+
+ECP read params #4 (OK, buffer just fits)
+ecp_read_params:"030017":0:256
+
+ECP read params #5 (OK, buffer continues)
+ecp_read_params:"030018DEAD":0:384
+
 ECP gen keypair
 ecp_gen_keypair:SECP192R1
 

tests/suites/test_suite_ecp.function

@@ -322,6 +322,28 @@ ecp_gen_keypair:id
 }
 END_CASE
 
+BEGIN_CASE
+ecp_read_params:record:ret:bits
+{
+    ecp_group grp;
+    unsigned char buf[10];
+    int len, ret;
+
+    ecp_group_init( &grp );
+    memset( buf, 0x00, sizeof( buf ) );
+
+    len = unhexify( buf, {record} );
+
+    ret = ecp_tls_read_group( &grp, buf, len );
+
+    TEST_ASSERT( ret == {ret} );
+    if( ret == 0)
+        TEST_ASSERT( mpi_msb( &grp.P ) == {bits} );
+
+    ecp_group_free( &grp );
+}
+END_CASE
+
 BEGIN_CASE
 ecp_selftest:
 {