Added ecp_read_binary().

include/polarssl/ecp.h

@@ -218,7 +218,7 @@ int ecp_group_read_string( ecp_group *grp, int radix,
 /**
  * \brief           Export a point into unsigned binary data
  *
- * \param grp       Group the point belongs to
+ * \param grp       Group to which the point should belong
  * \param P         Point to export
  * \param format    Point format, should be a POLARSSL_ECP_PF_XXX macro
  * \param olen      Length of the actual ouput
@@ -230,6 +230,25 @@ int ecp_group_read_string( ecp_group *grp, int radix,
 int ecp_write_binary( const ecp_group *grp, const ecp_point *P, int format,
                       size_t *olen, unsigned char *buf, size_t buflen );
 
+/**
+ * \brief           Import a point from unsigned binary data
+ *
+ * \param grp       Group to which the point should belong
+ * \param P         Point to import
+ * \param format    Point format, must be POLARSSL_ECP_PF_UNCOMPRESSED for now
+ * \param buf       Input buffer
+ * \param ilen      Actual length of input
+ *
+ * \return          0 if successful,
+ *                  POLARSSL_ERR_ECP_GENERIC if input is invalid
+ *                  POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed
+ *
+ * \note            This function does NOT check that the point actually
+ *                  belongs to the given group, see ecp_check_pubkey() for
+ *                  that.
+ */
+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
  *

library/ecp.c

@@ -228,6 +228,33 @@ cleanup:
     return( ret );
 }
 
+/*
+ * Import a point from unsigned binary data (SEC1 2.3.4)
+ */
+int ecp_read_binary( const ecp_group *grp, ecp_point *P, int format,
+                     const unsigned char *buf, size_t ilen ) {
+    int ret;
+    size_t plen;
+
+    if( format != POLARSSL_ECP_PF_UNCOMPRESSED )
+        return( POLARSSL_ERR_ECP_GENERIC );
+
+    if( ilen == 1 && buf[0] == 0x00 )
+        return( ecp_set_zero( P ) );
+
+    plen = mpi_size( &grp-> P );
+
+    if( ilen != 2 * plen + 1 || buf[0] != 0x04 )
+        return( POLARSSL_ERR_ECP_GENERIC );
+
+    MPI_CHK( mpi_read_binary( &P->X, buf + 1, plen ) );
+    MPI_CHK( mpi_read_binary( &P->Y, buf + 1 + plen, plen ) );
+    MPI_CHK( mpi_lset( &P->Z, 1 ) );
+
+cleanup:
+    return( ret );
+}
+
 /*
  * Wrapper around fast quasi-modp functions, with fall-back to mpi_mod_mpi.
  * See the documentation of struct ecp_group.

tests/suites/test_suite_ecp.data

@@ -163,6 +163,27 @@ ecp_write_binary:SECP192R1:"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"6
 ECP write binary #7 (odd, compressed, buffer just fits)
 ecp_write_binary:SECP192R1:"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"93112b28345b7d1d7799611e49bea9d8290cb2d7afe1f9f3":"01":COMPRESSED:"0348d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":25:0
 
+ECP read binary #0 (invalid format)
+ecp_read_binary:SECP192R1:"00":UNKNOWN:"01":"01":"00":POLARSSL_ERR_ECP_GENERIC
+
+ECP read binary #1 (zero, invalid ilen)
+ecp_read_binary:SECP192R1:"0000":UNCOMPRESSED:"01":"01":"00":POLARSSL_ERR_ECP_GENERIC
+
+ECP read binary #2 (zero, invalid first byte)
+ecp_read_binary:SECP192R1:"01":UNCOMPRESSED:"01":"01":"00":POLARSSL_ERR_ECP_GENERIC
+
+ECP read binary #3 (zero, OK)
+ecp_read_binary:SECP192R1:"00":UNCOMPRESSED:"01":"01":"00":0
+
+ECP read binary #4 (non-zero, invalid ilen)
+ecp_read_binary:SECP192R1:"04001122":UNCOMPRESSED:"01":"01":"00":POLARSSL_ERR_ECP_GENERIC
+
+ECP read binary #5 (non-zero, invalid first byte)
+ecp_read_binary:SECP192R1:"0548d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc99336ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":UNCOMPRESSED:"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"6ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":"01":POLARSSL_ERR_ECP_GENERIC
+
+ECP read binary #6 (non-zero, OK)
+ecp_read_binary:SECP192R1:"0448d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc99336ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":UNCOMPRESSED:"48d8082a3a1e3112bc03a8ef2f6d40d0a77a6f8e00cc9933":"6ceed4d7cba482e288669ee1b6415626d6f34d28501e060c":"01":0
+
 ECP mod p192 readable
 ecp_fast_mod:SECP192R1:"000000000000010500000000000001040000000000000103000000000000010200000000000001010000000000000100"
 

tests/suites/test_suite_ecp.function

@@ -257,6 +257,44 @@ ecp_write_binary:id:x:y:z:format:out:blen:ret
 }
 END_CASE
 
+BEGIN_CASE
+ecp_read_binary:id:input:format:x:y:z:ret
+{
+    ecp_group grp;
+    ecp_point P;
+    mpi X, Y, Z;
+    int ilen;
+    unsigned char buf[256];
+
+    memset( buf, 0, sizeof( buf ) );
+
+    ecp_group_init( &grp ); ecp_point_init( &P );
+    mpi_init( &X ); mpi_init( &Y ); mpi_init( &Z );
+
+    TEST_ASSERT( ecp_use_known_dp( &grp, POLARSSL_ECP_DP_{id} ) == 0 );
+
+    TEST_ASSERT( mpi_read_string( &X, 16, {x} ) == 0 );
+    TEST_ASSERT( mpi_read_string( &Y, 16, {y} ) == 0 );
+    TEST_ASSERT( mpi_read_string( &Z, 16, {z} ) == 0 );
+
+    ilen = unhexify( buf, {input} );
+
+#define POLARSSL_ECP_PF_UNKNOWN     -1
+    TEST_ASSERT( ecp_read_binary( &grp, &P, POLARSSL_ECP_PF_{format},
+                                  buf, ilen ) == {ret} );
+
+    if( {ret} == 0 )
+    {
+        TEST_ASSERT( mpi_cmp_mpi( &P.X, &X ) == 0 );
+        TEST_ASSERT( mpi_cmp_mpi( &P.Y, &Y ) == 0 );
+        TEST_ASSERT( mpi_cmp_mpi( &P.Z, &Z ) == 0 );
+    }
+
+    ecp_group_free( &grp ); ecp_point_free( &P );
+    mpi_free( &X ); mpi_free( &Y ); mpi_free( &Z );
+}
+END_CASE
+
 BEGIN_CASE
 ecp_selftest:
 {