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Commit Diff

Commit:: 72342dc9606a0283490a3a9283d2ed2d31888eeb
From:: Omar Polo <op@omarpolo.com>
Date:: Fri Nov 6 12:01:31 2020 UTC
Message:: implementing CGI – NOT READY YET! This is a first try at implementing CGI scripting. The idea is that, if CGI is explicitly enabled by the user, when a user requires an executable file instead of serving it to the client, that file will be executed and its output fed to the client. There are various pieces that are still lacking, the firsts that comes to mind are: - performance: the handle_cgi just loops ignoring the WANT_POLLIN/POLLOUT and blocking if the child process hasn’t outputted anything. - we don’t parse query variable (yet) - we need to set more variables in the child environment side question: it’s better to set the variables using setenv() or by providing an explicit environment? - document what environment the CGI script will get - improve the horrible unveil/pledge(cgi ? …) but now I can serve “hello-world”-tier script from gmid!
Actions:: Patch | Tree

commit - 2c3a40faf850ad608abf87f928a11fb4fba3057b
commit + 72342dc9606a0283490a3a9283d2ed2d31888eeb
blob - fc2381fab34076f690fa3eacbef46081fdf20f66
blob + 2a0fea9ca8dcae76ff8702673f1a09e851c67bc1
--- README.md
+++ README.md
@@ -6,7 +6,7 @@
 # SYNOPSIS
 
 **gmid**
-\[**-h**]
+\[**-hx**]
 \[**-c**&nbsp;*cert.pem*]
 \[**-d**&nbsp;*docs*]
 \[**-k**&nbsp;*key.pem*]
@@ -78,6 +78,19 @@ The options are as follows:
 
 > log to the given file instead of the standard error.
 
+**-x**
+
+> Enable CGI scripts.
+
+# CGI
+
+If CGI scripts are enabled, when a file requested by a client is
+marked as executable it is executed and its output fed to the client.
+
+Note that since this give the chance to anybody to execute possibly
+**any file**
+in the served directory, this option is disabled by default.
+
 # EXAMPLES
 
 To quickly getting started
blob - a70e81714c7d397bfef19b484e31f03436ebbbe4
blob + 8f7a44eff28ba12b41299b7c46b11238458fb932
--- gmid.1
+++ gmid.1
@@ -20,7 +20,7 @@
 .Sh SYNOPSIS
 .Nm
 .Bk -words
-.Op Fl h
+.Op Fl hx
 .Op Fl c Ar cert.pem
 .Op Fl d Ar docs
 .Op Fl k Ar key.pem
@@ -81,7 +81,16 @@ The key for the certificate, by default is
 .Pa key.pem .
 .It Fl l Ar access.log
 log to the given file instead of the standard error.
+.It Fl x
+Enable CGI scripts.
 .El
+.Sh CGI
+If CGI scripts are enabled, when a file requested by a client is
+marked as executable it is executed and its output fed to the client.
+.Pp
+Note that since this give the chance to anybody to execute possibly
+.Sy any file
+in the served directory, this option is disabled by default.
 .Sh EXAMPLES
 To quickly getting started
 .Bd -literal -offset indent
blob - 4e03fc371fbc02c3b7c72efd0482d799cd527656
blob + 0a0ff2452bc0b320e96cb59ac92e3e0487ff5e53
--- gmid.c
+++ gmid.c
@@ -48,6 +48,7 @@
 #define PATHBUF		2048
 
 #define SUCCESS		20
+#define TEMP_FAILURE	40
 #define NOT_FOUND	51
 #define BAD_REQUEST	59
 
@@ -68,6 +69,7 @@ struct client {
 	int		 code;
 	const char	*meta;
 	int		 fd;
+	pid_t		 child;
 	void		*buf, *i;
 	ssize_t		 len, off;
 	int		 af;
@@ -104,7 +106,9 @@ struct etm {			/* file extension to mime */
 		dprintf(logfd, "[%s] " fmt "\n", buf, __VA_ARGS__);	\
 	} while (0)
 
+const char *dir;
 int dirfd, logfd;
+int cgi;
 
 char		*url_after_proto(char*);
 char		*url_start_of_request(char*);
@@ -114,10 +118,11 @@ int		 path_isdir(char*);
 ssize_t		 filesize(int);
 
 int		 start_reply(struct pollfd*, struct client*, int, const char*);
-int		 isdir(int);
 const char	*path_ext(const char*);
 const char	*mime(const char*);
 int		 open_file(char*, struct pollfd*, struct client*);
+void		 start_cgi(const char*, struct pollfd*, struct client*);
+void		 handle_cgi(struct pollfd*, struct client*);
 void		 send_file(char*, struct pollfd*, struct client*);
 void		 send_dir(char*, struct pollfd*, struct client*);
 void		 handle(struct pollfd*, struct client*);
@@ -247,19 +252,6 @@ start_reply(struct pollfd *pfd, struct client *client,
 	return 1;
 }
 
-int
-isdir(int fd)
-{
-	struct stat sb;
-
-	if (fstat(fd, &sb) == -1) {
-		warn("fstat");
-		return 1; 	/* we'll probably fail later on anyway */
-	}
-
-	return S_ISDIR(sb.st_mode);
-}
-
 ssize_t
 filesize(int fd)
 {
@@ -308,6 +300,7 @@ int
 open_file(char *path, struct pollfd *fds, struct client *c)
 {
 	char fpath[PATHBUF];
+	struct stat sb;
 
 	assert(path != NULL);
 
@@ -325,7 +318,15 @@ open_file(char *path, struct pollfd *fds, struct clien
 		return 0;
 	}
 
-	if (isdir(c->fd)) {
+	if (fstat(c->fd, &sb) == -1) {
+		LOG(c, "fstat failed for %s", fpath);
+		if (!start_reply(fds, c, TEMP_FAILURE, "internal server error"))
+			return 0;
+		goodbye(fds, c);
+		return 0;
+	}
+
+	if (S_ISDIR(sb.st_mode)) {
 		LOG(c, "%s is a directory, trying %s/index.gmi", fpath, fpath);
 		close(c->fd);
 		c->fd = -1;
@@ -333,6 +334,11 @@ open_file(char *path, struct pollfd *fds, struct clien
 		return 0;
 	}
 
+	if (cgi && (sb.st_mode & S_IXUSR)) {
+		start_cgi(fpath, fds, c);
+		return 0;
+	}
+
 	if ((c->len = filesize(c->fd)) == -1) {
 		LOG(c, "failed to get file size for %s", fpath);
 		goodbye(fds, c);
@@ -348,6 +354,120 @@ open_file(char *path, struct pollfd *fds, struct clien
 	c->i = c->buf;
 
 	return start_reply(fds, c, SUCCESS, mime(fpath));
+}
+
+void
+start_cgi(const char *path, struct pollfd *fds, struct client *c)
+{
+	pid_t pid;
+	int p[2];
+
+	if (pipe(p) == -1)
+		goto err;
+
+	switch (pid = fork()) {
+	case -1:
+		goto err;
+
+	case 0: {		/* child */
+                char *expath;
+		char addr[INET_ADDRSTRLEN];
+		char *argv[] = { NULL, NULL, NULL };
+		char *envp[] = {
+			/* inherited */
+			"PATH=",
+
+			/* CGI */
+			"SERVER_SOFTWARE=gmid",
+			/* "SERVER_NAME=example.com", */
+			/* "GATEWAY_INTERFACE=CGI/version" */
+			"SERVER_PROTOCOL=gemini",
+			"SERVER_PORT=1965",
+			/* "PATH_INFO=" */
+			/* "PATH_TRANSLATED=" */
+			/* "SCRIPT_NAME=" */
+			/* "QUERY_STRING=" */
+                        "REMOTE_ADDR=",
+			NULL,
+		};
+		size_t i;
+
+		close(p[0]);	/* close the read end */
+		if (dup2(p[1], 1) == -1)
+			goto childerr;
+
+		if (inet_ntop(c->af, &c->addr, addr, sizeof(addr)) == NULL)
+                        goto childerr;
+
+		/* skip the ./ at the start of path*/
+		if (asprintf(&expath, "%s%s", dir, path+2) == -1)
+			goto childerr;
+		argv[0] = argv[1] = expath;
+
+		/* fix the envp */
+		for (i = 0; envp[i] != NULL; ++i) {
+			if (!strcmp(envp[i], "PATH="))
+				envp[i] = getenv("PATH");
+			else if (!strcmp(envp[i], "REMOTE_ADDR="))
+				envp[i] = addr;
+			/* else if (!strcmp(envp[i], "PATH_INFO")) */
+			/* ... */
+		}
+
+		execvpe(expath, argv, envp);
+		goto childerr;
+	}
+
+	default:		/* parent */
+		close(p[1]);	/* close the write end */
+		close(c->fd);
+		c->fd = p[0];
+		c->child = pid;
+		handle_cgi(fds, c);
+		return;
+	}
+
+err:
+	if (!start_reply(fds, c, TEMP_FAILURE, "internal server error"))
+		return;
+	goodbye(fds, c);
+	return;
+
+childerr:
+	dprintf(p[1], "%d internal server error\r\n", TEMP_FAILURE);
+	close(p[1]);
+        _exit(1);
+}
+
+void
+handle_cgi(struct pollfd *fds, struct client *c)
+{
+	char buf[1024];
+	ssize_t r, todo;
+
+	while (1) {
+		r = read(c->fd, buf, sizeof(buf));
+		if (r == -1 || r == 0)
+			break;
+		todo = r;
+		while (todo > 0) {
+			switch (r = tls_write(c->ctx, buf, todo)) {
+			case -1:
+				goto end;
+
+			case TLS_WANT_POLLOUT:
+			case TLS_WANT_POLLIN:
+				/* evil! */
+				continue;
+
+			default:
+				todo -= r;
+			}
+		}
+	}
+
+end:
+	goodbye(fds, c);
 }
 
 void
@@ -581,6 +701,7 @@ do_accept(int sock, struct tls *ctx, struct pollfd *fd
 
 			clients[i].state = S_OPEN;
 			clients[i].fd = -1;
+			clients[i].child = -1;
 			clients[i].buf = MAP_FAILED;
 			clients[i].af = AF_INET;
 			clients[i].addr = addr.sin_addr;
@@ -678,16 +799,19 @@ usage(const char *me)
 int
 main(int argc, char **argv)
 {
-	const char *cert = "cert.pem", *key = "key.pem", *dir = "docs";
+	const char *cert = "cert.pem", *key = "key.pem";
 	struct tls *ctx = NULL;
 	struct tls_config *conf;
 	int sock, ch;
 
 	signal(SIGPIPE, SIG_IGN);
+	signal(SIGCHLD, SIG_IGN);
 
+	dir = "docs/";
 	logfd = 2;		/* stderr */
+	cgi = 0;
 
-	while ((ch = getopt(argc, argv, "c:d:hk:l:")) != -1) {
+	while ((ch = getopt(argc, argv, "c:d:hk:l:x")) != -1) {
 		switch (ch) {
 		case 'c':
 			cert = optarg;
@@ -712,6 +836,10 @@ main(int argc, char **argv)
 				err(1, "%s", optarg);
 			break;
 
+		case 'x':
+			cgi = 1;
+			break;
+
 		default:
 			usage(*argv);
 			return 1;
@@ -742,10 +870,10 @@ main(int argc, char **argv)
 	if ((dirfd = open(dir, O_RDONLY | O_DIRECTORY)) == -1)
 		err(1, "open: %s", dir);
 
-	if (unveil(dir, "r") == -1)
+	if (unveil(dir, cgi ? "rx" : "r") == -1)
 		err(1, "unveil");
 
-	if (pledge("stdio rpath inet", "") == -1)
+	if (pledge(cgi ? "stdio rpath inet proc exec" : "stdio rpath inet", NULL) == -1)
 		err(1, "pledge");
 
 	loop(ctx, sock);