Add entropy callbacks to HMAC_DRBG
diff --git a/include/polarssl/hmac_drbg.h b/include/polarssl/hmac_drbg.h
index b35d62b..54aa9a4 100644
--- a/include/polarssl/hmac_drbg.h
+++ b/include/polarssl/hmac_drbg.h
@@ -29,19 +29,40 @@
#include "md.h"
+/*
+ * ! Same values as ctr_drbg.h !
+ */
+#define POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
+#define POLARSSL_ERR_HMAC_DRBG_REQUEST_TOO_BIG -0x0036 /**< Too many random requested in single call. */
+#define POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG -0x0038 /**< Input too large (Entropy + additional). */
+#define POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR -0x003A /**< Read/write error in file. */
+
+#define HMAC_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */
+#define HMAC_DRBG_MAX_INPUT 256 /**< Maximum number of additional input bytes */
+#define HMAC_DRBG_MAX_REQUEST 1024 /**< Maximum number of requested bytes per call */
+#define HMAC_DRBG_MAX_SEED_INPUT 384 /**< Maximum size of (re)seed buffer */
+
#ifdef __cplusplus
extern "C" {
#endif
-/*
- * Simplified HMAC_DRBG context.
- * No reseed counter, no prediction resistance flag.
+/**
+ * HMAC_DRBG context.
+ * TODO: reseed counter, prediction resistance flag.
*/
typedef struct
{
md_context_t md_ctx;
unsigned char V[POLARSSL_MD_MAX_SIZE];
unsigned char K[POLARSSL_MD_MAX_SIZE];
+
+ size_t entropy_len; /*!< entropy bytes grabbed on each (re)seed */
+
+ /*
+ * Callbacks (Entropy)
+ */
+ int (*f_entropy)(void *, unsigned char *, size_t);
+ void *p_entropy; /*!< context for the entropy function */
} hmac_drbg_context;
/**
@@ -49,18 +70,47 @@
*
* \param ctx HMAC_DRBG context to be initialised
* \param md_info MD algorithm to use for HMAC_DRBG
- * \param data Concatenation of entropy string and additional data
- * \param data_len Length of data in bytes
+ * \param f_entropy Entropy callback (p_entropy, buffer to fill, buffer
+ * length)
+ * \param p_entropy Entropy context
+ * \param custom Personalization data (Device specific identifiers)
+ * (Can be NULL)
+ * \param len Length of personalization data
*
- * \todo Use entropy callback rather than buffer.
+ * \note The "security strength" as defined by NIST is set to:
+ * 128 bits if md_alg is SHA-1,
+ * 192 bits if md_alg is SHA-224,
+ * 256 bits if md_alg is SHA-256 or higher.
+ * Note that SHA-256 is just as efficient as SHA-224.
*
* \return 0 if successful, or
* POLARSSL_ERR_MD_BAD_INPUT_DATA, or
- * POLARSSL_ERR_MD_ALLOC_FAILED
+ * POLARSSL_ERR_MD_ALLOC_FAILED, or
+ * POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED.
*/
int hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
- const unsigned char *data, size_t data_len );
+ int (*f_entropy)(void *, unsigned char *, size_t),
+ void *p_entropy,
+ const unsigned char *custom,
+ size_t len );
+
+/**
+ * \brief Simplified HMAC_DRBG initialisation.
+ * (For use with deterministic ECDSA.)
+ *
+ * \param ctx HMAC_DRBG context to be initialised
+ * \param md_info MD algorithm to use for HMAC_DRBG
+ * \param data Concatenation of entropy string and additional data
+ * \param data_len Length of data in bytes
+ *
+ * \return 0 if successful, or
+ * POLARSSL_ERR_MD_BAD_INPUT_DATA, or
+ * POLARSSL_ERR_MD_ALLOC_FAILED.
+ */
+int hmac_drbg_init_buf( hmac_drbg_context *ctx,
+ const md_info_t * md_info,
+ const unsigned char *data, size_t data_len );
/**
* \brief HMAC_DRBG update state