b64: decode: add api tests and fix

Author: lws-team

lib/misc/base64-decode.c

@@ -173,16 +173,21 @@ lws_b64_decode_stateful(struct lws_b64state *s, const char *in, size_t *in_len,
 		s->i = 0;
 
 		/*
-		 * "The '==' sequence indicates that the last group contained
-		 * only one byte, and '=' indicates that it contained two
+		 * Normally we convert a group of 4 incoming symbols into 3 bytes.
+		 *
+		 * "The 'XX==' sequence indicates that the last group contained
+		 * only one byte, and 'XXX=' indicates that it contained two
 		 * bytes." (wikipedia)
+		 *
 		 */
 
-		if (s->len >= 2 || equals > 1)
+		if (s->len >= 2)
 			*out++ = (uint8_t)(s->quad[0] << 2 | s->quad[1] >> 4);
-		if (s->len >= 3 || equals)
+
+		if (s->len >= 3 && equals != 2)
 			*out++ = (uint8_t)(s->quad[1] << 4 | s->quad[2] >> 2);
-		if (s->len >= 4 && !equals)
+
+		if (s->len >= 4 && equals != 1)
 			*out++ = (uint8_t)(((s->quad[2] << 6) & 0xc0) | s->quad[3]);
 
 		s->done += s->len - 1;

minimal-examples-lowlevel/api-tests/api-test-lws_tokenize/main.c

@@ -776,6 +776,62 @@ int main(int argc, const char **argv)
 		}
 	}
 
+	/* sanity check base64 decode */
+
+	{
+		struct lws_b64state b64;
+		uint8_t result[16];
+		size_t in_len, out_len;
+
+		lws_b64_decode_state_init(&b64);
+		in_len = 8;
+		out_len = sizeof(result);
+		if (lws_b64_decode_stateful(&b64, "YWJjZA==", &in_len, result, &out_len, 1)) {
+			lwsl_err("%s: b64 test 1 decode failed\n", __func__);
+			return 1;
+		}
+		if (out_len != 4) {
+			lwsl_err("%s: b64 test 1 decode len not 4 (%d)\n", __func__, (int)out_len);
+			return 1;
+		}
+		if (memcmp(result, "abcd", out_len)) {
+			lwsl_err("%s: b64 test 1 decode value not 'abcde' (%.*s)\n", __func__, (int)out_len, result);
+			return 1;
+		}
+
+		lws_b64_decode_state_init(&b64);
+		in_len = 8;
+		out_len = sizeof(result);
+		if (lws_b64_decode_stateful(&b64, "YWJjZGU=", &in_len, result, &out_len, 1)) {
+			lwsl_err("%s: b64 test 2 decode failed\n", __func__);
+			return 1;
+		}
+		if (out_len != 5) {
+			lwsl_err("%s: b64 test 2 decode len not 5 (%d)\n", __func__, (int)out_len);
+			return 1;
+		}
+		if (memcmp(result, "abcde", out_len)) {
+			lwsl_err("%s: b64 test 2 decode value not 'abcd' (%.*s)\n", __func__, (int)out_len, result);
+			return 1;
+		}
+
+		lws_b64_decode_state_init(&b64);
+		in_len = 8;
+		out_len = sizeof(result);
+		if (lws_b64_decode_stateful(&b64, "YWJjZGVm", &in_len, result, &out_len, 1)) {
+			lwsl_err("%s: b64 test 3 decode failed\n", __func__);
+			return 1;
+		}
+		if (out_len != 6) {
+			lwsl_err("%s: b64 test 3 decode len not 6 (%d)\n", __func__, (int)out_len);
+			return 1;
+		}
+		if (memcmp(result, "abcdef", out_len)) {
+			lwsl_err("%s: b64 test 3 decode value not 'abcde' (%.*s)\n", __func__, (int)out_len, result);
+			return 1;
+		}
+	}
+
 	/* sanity check lws_strnncpy() */
 
 	lws_strnncpy(dotstar, "12345678", 4, sizeof(dotstar));