First commit

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 224 insertions, 0 deletions

diff --git a/sshexec.c b/sshexec.c
new file mode 100644
index 0000000..b5eae7c
--- /dev/null
+++ b/sshexec.c
@@ -0,0 +1,224 @@
+/* See LICENSE file for copyright and license details. */
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+
+static const char *argv0 = "sshexec";
+
+
+#define exitf(...) (fprintf(stderr, __VA_ARGS__), exit(255))
+
+
+static void
+usage(void)
+{
+	exitf("usage: %s { %s } [ssh-option] ... destination command [argument] ...\n",
+	      argv0, "[ssh=command] [dir=directory]");
+}
+
+static const enum optclass {
+	NO_RECOGNISED = 0,
+	NO_ARGUMENT,
+	MANDATORY_ARGUMENT
+} sshopts[(size_t)1 << CHAR_BIT] = {
+#define X(F) [F] = NO_ARGUMENT
+	X('4'), X('6'), X('A'), X('a'), X('C'), X('f'), X('G'),
+	X('g'), X('K'), X('k'), X('M'), X('N'), X('n'), X('q'),
+	X('s'), X('T'), X('t'), X('V'), X('v'), X('X'), X('x'),
+	X('Y'), X('y'),
+#undef X
+#define X(F) [F] = MANDATORY_ARGUMENT
+	X('B'), X('b'), X('c'), X('D'), X('E'), X('e'), X('F'),
+	X('I'), X('i'), X('J'), X('L'), X('l'), X('m'), X('O'),
+	X('o'), X('P'), X('p'), X('Q'), X('R'), X('S'), X('W'),
+	X('w')
+#undef X
+};
+
+static char *command = NULL;
+static size_t command_size = 0;
+static size_t command_len = 0;
+
+
+#define build_command(DATA, N)\
+	do {\
+		build_command_reserve(N);\
+		memcpy(&command[command_len], (DATA), (N));\
+		command_len += (N);\
+	} while (0)
+
+#define build_command_asis(S)\
+	build_command(S, sizeof(S) - 1)
+
+#define finalise_command()\
+	build_command("", 1)
+
+
+static void
+build_command_reserve(size_t n)
+{
+	if (n > command_size - command_len) {
+		if (n < 512)
+			n = 512;
+		if (command_len + n > SIZE_MAX)
+			exitf("%s: could not allocate enough memory\n", argv0);
+		command_size = command_len + n;
+		command = realloc(command, command_size);
+		if (!command)
+			exitf("%s: could not allocate enough memory\n", argv0);
+	}
+}
+
+
+static void
+build_command_escape(const char *arg)
+{
+	size_t n = 0;
+	if (!*arg) {
+		build_command_asis("''");
+		return;
+	}
+	while (isalnum(arg[n]) || arg[n] == '_' || arg[n] == '/')
+		n += 1;
+	if (!arg[n]) {
+		build_command(arg, n);
+		return;
+	}
+	build_command_asis("\"$(printf '");
+	goto start;
+	while (*arg) {
+		build_command_reserve(4);
+		command[command_len++] = '\\';
+		command[command_len] = (((unsigned char)*arg >> 6) & 7) + '0';
+		command_len += (command[command_len] != '0');
+		command[command_len] = (((unsigned char)*arg >> 3) & 7) + '0';
+		command_len += (command[command_len] != '0');
+		command[command_len++] = ((unsigned char)*arg & 7) + '0';
+		arg = &arg[1];
+
+		n = 0;
+		while (isalpha(arg[n]) || arg[n] == '_' || arg[n] == '/')
+			n += 1;
+		if (n) {
+			while (isalnum(arg[n]) || arg[n] == '_' || arg[n] == '/')
+				n += 1;
+		start:
+			build_command(arg, n);
+			arg = &arg[n];
+		}
+	}
+	build_command_asis("\\n')\"");
+}
+
+
+int
+main(int argc_unused, char *argv[])
+{
+	const char *dir = NULL;
+	const char *ssh = NULL;
+	const char *destination;
+	char **opts;
+	size_t nopts;
+	enum optclass class;
+	const char *arg;
+	char opt;
+	const char **args;
+	size_t i;
+
+	(void) argc_unused;
+
+	if (*argv)
+		argv0 = *argv++;
+
+#define STORE_OPT(VARP, OPT)\
+	if (!strncmp(*argv, OPT"=", sizeof(OPT))) {\
+		if (*(VARP) || !*(*(VARP) = &(*argv)[sizeof(OPT)]))\
+			usage();\
+		continue;\
+	}
+	if (*argv && !strcmp(*argv, "{")) {
+		argv++;
+		for (; *argv && strcmp(*argv, "}"); argv++) {
+			STORE_OPT(&ssh, "ssh")
+			STORE_OPT(&dir, "dir")
+			usage();
+		}
+		if (!*argv)
+			usage();
+		argv++;
+	}
+#undef STORE_OPT
+
+	if (!ssh)
+		ssh = "ssh";
+
+	opts = argv;
+	nopts = 0;
+	while (*argv) {
+		if (!strcmp(*argv, "--")) {
+			argv++;
+			break;
+		} else if ((*argv)[0] != '-' || !(*argv)[1]) {
+			break;
+		}
+		arg = &(*argv++)[1];
+		nopts++;
+		while (*arg) {
+			opt = *arg++;
+			class = sshopts[(unsigned char)opt];
+			if (class == MANDATORY_ARGUMENT) {
+				if (*arg) {
+					break;
+				} else if (*argv) {
+					argv++;
+					nopts++;
+					break;
+				} else {
+					exitf("%s: argument missing for option -%c\n", argv0, opt);
+				}
+			} else if (class == NO_RECOGNISED) {
+				exitf("%s: unrecognised option -%c\n", argv0, opt);
+			}
+		}
+	}
+
+	destination = *argv++;
+	if (!destination && !*argv)
+		usage();
+
+	if (dir) {
+		build_command_asis("cd -- ");
+		build_command_escape(dir);
+		build_command_asis(" && ");
+	}
+	build_command_asis("exec --");
+	for (; *argv; argv++) {
+		build_command_asis(" ");
+		build_command_escape(*argv);
+	}
+	finalise_command();
+
+	i = 0;
+	args = calloc(5 + nopts, sizeof(*args));
+	if (!args)
+		exitf("%s: could not allocate enough memory\n", argv0);
+	args[i++] = ssh;
+	memcpy(&args[i], opts, nopts * sizeof(*opts));
+	i += nopts;
+	args[i++] = "--";
+	args[i++] = destination;
+	args[i++] = command;
+	args[i++] = NULL;
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic ignored "-Wcast-qual"
+#endif
+	execvp(ssh, (char **)args);
+	exitf("%s: failed to execute %s: %s\n", argv0, ssh, strerror(errno));
+}