+/*
+ * Restart |drbg|, using the specified entropy or additional input
+ *
+ * Tries its best to get the drbg instantiated by all means,
+ * regardless of its current state.
+ *
+ * Optionally, a |buffer| of |len| random bytes can be passed,
+ * which is assumed to contain at least |entropy| bits of entropy.
+ *
+ * If |entropy| > 0, the buffer content is used as entropy input.
+ *
+ * If |entropy| == 0, the buffer content is used as additional input
+ *
+ * Returns 1 on success, 0 on failure.
+ *
+ * This function is used internally only.
+ */
+int rand_drbg_restart(RAND_DRBG *drbg,
+ const unsigned char *buffer, size_t len, size_t entropy)
+{
+ int reseeded = 0;
+ const unsigned char *adin = NULL;
+ size_t adinlen = 0;
+
+ if (drbg->pool != NULL) {
+ RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
+ RAND_POOL_free(drbg->pool);
+ drbg->pool = NULL;
+ }
+
+ if (buffer != NULL) {
+ if (entropy > 0) {
+ if (drbg->max_entropylen < len) {
+ RANDerr(RAND_F_RAND_DRBG_RESTART,
+ RAND_R_ENTROPY_INPUT_TOO_LONG);
+ return 0;
+ }
+
+ if (entropy > 8 * len) {
+ RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
+ return 0;
+ }
+
+ /* will be picked up by the rand_drbg_get_entropy() callback */
+ drbg->pool = RAND_POOL_new(entropy, len, len);
+ if (drbg->pool == NULL)
+ return 0;
+
+ RAND_POOL_add(drbg->pool, buffer, len, entropy);
+ } else {
+ if (drbg->max_adinlen < len) {
+ RANDerr(RAND_F_RAND_DRBG_RESTART,
+ RAND_R_ADDITIONAL_INPUT_TOO_LONG);
+ return 0;
+ }
+ adin = buffer;
+ adinlen = len;
+ }
+ }
+
+ /* repair error state */
+ if (drbg->state == DRBG_ERROR)
+ RAND_DRBG_uninstantiate(drbg);
+
+ /* repair uninitialized state */
+ if (drbg->state == DRBG_UNINITIALISED) {
+ /* reinstantiate drbg */
+ RAND_DRBG_instantiate(drbg,
+ (const unsigned char *) ossl_pers_string,
+ sizeof(ossl_pers_string) - 1);
+ /* already reseeded. prevent second reseeding below */
+ reseeded = (drbg->state == DRBG_READY);
+ }
+
+ /* refresh current state if entropy or additional input has been provided */
+ if (drbg->state == DRBG_READY) {
+ if (adin != NULL) {
+ /*
+ * mix in additional input without reseeding
+ *
+ * Similar to RAND_DRBG_reseed(), but the provided additional
+ * data |adin| is mixed into the current state without pulling
+ * entropy from the trusted entropy source using get_entropy().
+ * This is not a reseeding in the strict sense of NIST SP 800-90A.
+ */
+ drbg->meth->reseed(drbg, adin, adinlen, NULL, 0);
+ } else if (reseeded == 0) {
+ /* do a full reseeding if it has not been done yet above */
+ RAND_DRBG_reseed(drbg, NULL, 0);
+ }
+ }
+
+ /* check whether a given entropy pool was cleared properly during reseed */
+ if (drbg->pool != NULL) {
+ drbg->state = DRBG_ERROR;
+ RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
+ RAND_POOL_free(drbg->pool);
+ drbg->pool = NULL;
+ return 0;
+ }
+
+ return drbg->state == DRBG_READY;
+}
+