Initial commit of twind - a small and simple gemini daemon

1 files changed, 161 insertions, 0 deletions

diff --git a/request.c b/request.c
new file mode 100644
index 0000000..609f368
--- /dev/null
+++ b/request.c
@@ -0,0 +1,161 @@
+/*
+ * Copyright (c) 2021 Matthias Schmidt <xhr@giessen.ccc.de>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <ctype.h>
+#include <limits.h>
+#include <string.h>
+
+#include "log.h"
+#include "twind.h"
+
+char hex_to_int(char);
+char* uridecode(const char *);
+
+/*
+ * The following two functions are from https://geekhideout.com/urlcode.shtml
+ * and provided without license restrictions
+ */
+char hex_to_int(char ch) {
+	return isdigit(ch) ? ch - '0' : tolower(ch) - 'a' + 10;
+}
+
+char *
+uridecode(const char *request)
+{
+	char *temp = xmalloc(strlen(request) + 1);
+	const char *p;
+	char *pt;
+
+	memset(temp, 0, strlen(request)+1);
+
+	p = request;
+	pt = temp;
+
+	while (*p) {
+		if (*p == '%') {
+			if (p[1] && p[2]) {
+				*pt++ = hex_to_int(p[1]) << 4 | hex_to_int(p[2]);
+				p += 2;
+			}
+		} else if (*p == '+') {
+			*pt++ = ' ';
+		} else {
+			*pt++ = *p;
+		}
+		p++;
+	}
+	*pt = '\0';
+
+	return temp;
+}
+
+int
+get_path_from_request(char *request, char *finalpath)
+{
+	char hostname[MAXREQLEN];
+	char localpath[MAXREQLEN];
+	char temp[MAXREQLEN];
+	char *p, *decoded_request;
+	int pos = 0, ret;
+
+	memset(hostname, 0, sizeof(hostname));
+	memset(localpath, 0, sizeof(localpath));
+	memset(temp, 0, sizeof(temp));
+
+	p = request;
+
+	if ((p = strchr(request, '\r')) == NULL) {
+		log_info("\\r missing from request, abort processing");
+		return -1;
+	}
+
+	*p = '\0';	/* Strip \r\n */
+	p = request;
+
+	if (strncmp(p, "gemini://", 9) != 0) {
+		log_info("Gemini scheme missing, abort processing");
+		return -1;
+	}
+	memmove(request, p + 9, strlen(request) + 1 - 9);
+
+	decoded_request = uridecode(request);
+
+	/* save hostname */
+	if ((p = strchr(decoded_request, '/')) != NULL)
+		snprintf(hostname, strlen(decoded_request) - strlen(p)+1, "%s",
+			decoded_request);
+	else
+		snprintf(hostname, strlen(decoded_request)+1, "%s", decoded_request);
+
+	/* Strip possible port (e.g. :1965) from hostname */
+	if ((p = strrchr(hostname, ':')) != NULL) {
+		pos = strlen(hostname) - strlen(p);
+		if (pos < 0 || pos > _POSIX_HOST_NAME_MAX)
+			fatalx("pos while shorten hostname out of range");
+		hostname[pos] = '\0';
+	}
+
+	/* Remove ../ for security reasons */
+	while ((p = strstr(decoded_request, "/..")) != NULL) {
+		memmove(decoded_request, p + 3, strlen(p) + 1 - 3);
+	}
+
+	if ((p = strchr(decoded_request, '/')) != NULL) {
+		/* Save all after the first / in localpath */
+		snprintf(localpath, strlen(decoded_request), "%s", p+1);
+		if (strlen(localpath) == 0) {
+			/*
+			 * If the request is 'example.com/', localpart will be empty. In this case
+			 * write the default to it.
+			 */
+			sprintf(localpath, "index.gmi");
+		}
+	} else {
+		/* There is no slash in the request, so assume index.gmi */
+		sprintf(localpath, "index.gmi");
+	}
+
+	/*
+	 *We do not need to take the base dir aka /var/db/gemini into account
+	 * since we already chroot() to _PATH_TWIND_CHROOT .
+	 *
+	 * Here, a string truncation could happen.  This can be implemented
+	 * better! XXX FIXME
+	 */
+	snprintf(finalpath, MAXREQLEN, "%s/%s", hostname, localpath);
+
+	/* Check if the wanted path exists and if it's a directory */
+	ret = check_gemini_file(finalpath);
+	if (ret < 0) {
+		log_debug("%s not found", finalpath);
+		free(decoded_request);
+		return -2;
+	} else if (ret == 1) {
+		log_debug("%s is a directory", finalpath);
+		/* Auto append index.gmi if destination is a directory */
+		snprintf(temp, MAXREQLEN, "%s", finalpath);
+		snprintf(finalpath, MAXREQLEN, "%s/index.gmi", temp);
+	}
+
+	log_debug("Got request for %s on server %s -> %s",
+		localpath, hostname, finalpath);
+
+	/* decoded_request is no longer used, so it can be freed */
+	free(decoded_request);
+
+	return 0;
+}
+