Add ecdsa_{read,write}_signature()
diff --git a/library/ecdsa.c b/library/ecdsa.c
index e87bc65..cf5355c 100644
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -34,6 +34,7 @@
#if defined(POLARSSL_ECDSA_C)
#include "polarssl/ecdsa.h"
+#include "polarssl/asn1write.h"
/*
* Derive a suitable integer for group grp from a buffer of length len
@@ -188,6 +189,91 @@
}
/*
+ * RFC 4492 page 20:
+ *
+ * Ecdsa-Sig-Value ::= SEQUENCE {
+ * r INTEGER,
+ * s INTEGER
+ * }
+ *
+ * Size is at most
+ * 1 (tag) + 1 (len) + 1 (initial 0) + ECP_MAX_BYTES for each of r and s,
+ * twice that + 1 (tag) + 2 (len) for the sequence
+ * (assuming ECP_MAX_BYTES is less than 126 for r and s,
+ * and less than 124 (total len <= 255) for the sequence)
+ */
+#if POLARSSL_ECP_MAX_BYTES > 124
+#error "POLARSSL_ECP_MAX_BYTES bigger than expected, please fix MAX_SIG_LEN"
+#endif
+#define MAX_SIG_LEN ( 3 + 2 * ( 2 + POLARSSL_ECP_MAX_BYTES ) )
+
+/*
+ * Compute and write signature
+ */
+int ecdsa_write_signature( ecdsa_context *ctx,
+ const unsigned char *hash, size_t hlen,
+ unsigned char *sig, size_t *slen,
+ int (*f_rng)(void *, unsigned char *, size_t),
+ void *p_rng )
+{
+ int ret;
+ unsigned char buf[MAX_SIG_LEN];
+ unsigned char *p = buf + MAX_SIG_LEN - 1;
+ size_t len = 0;
+
+ if( ( ret = ecdsa_sign( &ctx->grp, &ctx->r, &ctx->s, &ctx->d,
+ hash, hlen, f_rng, p_rng ) ) != 0 )
+ {
+ return( ret );
+ }
+
+ ASN1_CHK_ADD( len, asn1_write_mpi( &p, buf, &ctx->s ) );
+ ASN1_CHK_ADD( len, asn1_write_mpi( &p, buf, &ctx->r ) );
+
+ ASN1_CHK_ADD( len, asn1_write_len( &p, buf, len ) );
+ ASN1_CHK_ADD( len, asn1_write_tag( &p, buf,
+ ASN1_CONSTRUCTED | ASN1_SEQUENCE ) );
+
+ memcpy( sig, p, len );
+ *slen = len;
+
+ return( 0 );
+}
+
+/*
+ * Read and check signature
+ */
+int ecdsa_read_signature( ecdsa_context *ctx,
+ const unsigned char *hash, size_t hlen,
+ const unsigned char *sig, size_t slen )
+{
+ int ret;
+ unsigned char *p = (unsigned char *) sig;
+ const unsigned char *end = sig + slen;
+ size_t len;
+
+ if( ( ret = asn1_get_tag( &p, end, &len,
+ ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
+ {
+ return( POLARSSL_ERR_ECP_BAD_INPUT_DATA + ret );
+ }
+
+ if( p + len != end )
+ return( POLARSSL_ERR_ECP_BAD_INPUT_DATA +
+ POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+ if( ( ret = asn1_get_mpi( &p, end, &ctx->r ) ) != 0 ||
+ ( ret = asn1_get_mpi( &p, end, &ctx->s ) ) != 0 )
+ return( POLARSSL_ERR_ECP_BAD_INPUT_DATA + ret );
+
+ if( p != end )
+ return( POLARSSL_ERR_ECP_BAD_INPUT_DATA +
+ POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
+
+ return( ecdsa_verify( &ctx->grp, hash, hlen, &ctx->Q, &ctx->r, &ctx->s ) );
+}
+
+/*
* Initialize context
*/
void ecdsa_init( ecdsa_context *ctx )