Add buffer size and callback checks to wc_LmsKey_Sign

Fixes ZD#21439

Author: holtrop-wolfssl

wolfcrypt/src/wc_lms.c

@@ -987,6 +987,23 @@ int wc_LmsKey_Sign(LmsKey* key, byte* sig, word32* sigSz, const byte* msg,
         WOLFSSL_MSG("error: can't sign, LMS key not in good state");
         ret = BAD_STATE_E;
     }
+    /* Check signature buffer size. */
+    if ((ret == 0) && (*sigSz < key->params->sig_len)) {
+        /* Signature buffer too small. */
+        WOLFSSL_MSG("error: LMS sig buffer too small");
+        ret = BUFFER_E;
+    }
+    /* Check read and write callbacks available. */
+    if ((ret == 0) && ((key->write_private_key == NULL) ||
+            (key->read_private_key == NULL))) {
+        WOLFSSL_MSG("error: LmsKey write/read callbacks are not set");
+        ret = BAD_FUNC_ARG;
+    }
+    /* Check read/write callback context available. */
+    if ((ret == 0) && (key->context == NULL)) {
+        WOLFSSL_MSG("error: LmsKey context is not set");
+        ret = BAD_FUNC_ARG;
+    }
 
     if (ret == 0) {
         WC_DECLARE_VAR(state, LmsState, 1, 0);

wolfcrypt/test/test.c

@@ -51593,6 +51593,49 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t lms_test(void)
         ERROR_OUT(WC_TEST_RET_ENC_I(sigSz), out);
     }
 
+    /* Test wc_LmsKey_Sign input validation. */
+    {
+        word32 smallSz = 1;
+        wc_lms_write_private_key_cb saved_write_cb;
+        wc_lms_read_private_key_cb  saved_read_cb;
+        void*                       saved_ctx;
+
+        /* Undersized sig buffer should return BUFFER_E. */
+        ret = wc_LmsKey_Sign(&signingKey, sig, &smallSz, (byte *) msg, msgSz);
+        if (ret != WC_NO_ERR_TRACE(BUFFER_E)) {
+            ERROR_OUT(WC_TEST_RET_ENC_EC(ret), out);
+        }
+
+        /* NULL write callback should return BAD_FUNC_ARG. */
+        saved_write_cb = signingKey.write_private_key;
+        signingKey.write_private_key = NULL;
+        ret = wc_LmsKey_Sign(&signingKey, sig, &sigSz, (byte *) msg, msgSz);
+        signingKey.write_private_key = saved_write_cb;
+        if (ret != WC_NO_ERR_TRACE(BAD_FUNC_ARG)) {
+            ERROR_OUT(WC_TEST_RET_ENC_EC(ret), out);
+        }
+
+        /* NULL read callback should return BAD_FUNC_ARG. */
+        saved_read_cb = signingKey.read_private_key;
+        signingKey.read_private_key = NULL;
+        ret = wc_LmsKey_Sign(&signingKey, sig, &sigSz, (byte *) msg, msgSz);
+        signingKey.read_private_key = saved_read_cb;
+        if (ret != WC_NO_ERR_TRACE(BAD_FUNC_ARG)) {
+            ERROR_OUT(WC_TEST_RET_ENC_EC(ret), out);
+        }
+
+        /* NULL context should return BAD_FUNC_ARG. */
+        saved_ctx = signingKey.context;
+        signingKey.context = NULL;
+        ret = wc_LmsKey_Sign(&signingKey, sig, &sigSz, (byte *) msg, msgSz);
+        signingKey.context = saved_ctx;
+        if (ret != WC_NO_ERR_TRACE(BAD_FUNC_ARG)) {
+            ERROR_OUT(WC_TEST_RET_ENC_EC(ret), out);
+        }
+
+        ret = 0;
+    }
+
     /* 2 ** 5 should be the max number of signatures */
     for (i = 0; i < 32; ++i) {
         /* We should have remaining signstures. */