Instanciate the environment variables

Because it could be of interest to transmit the
port and the token in environment variables,
provision is made here to instanciate environment
variables before exec.

Change-Id: I65cc8e052ca9e2831520a19d2da2a96ada7f672e
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

1 files changed, 95 insertions, 50 deletions

diff --git a/src/main.c b/src/main.c
index f1ebd969..05805e2d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -265,52 +265,83 @@ static void on_sigchld(int signum, siginfo_t *info, void *uctx)
 #define SUBST_CHAR  '@'
 #define SUBST_STR   "@"
 
-static int instanciate_command_args()
+static char *instanciate_string(char *arg, const char *port, const char *token)
 {
-	char *orig, *repl, *sub, *val, port[20];
-	int i, rc, r;
-	size_t s, l;
-
-	rc = snprintf(port, sizeof port, "%d", config->httpdPort);
-	if (rc < 0 || rc >= (int)(sizeof port))
-		return -1;
-
-	for (i = 0 ; (orig = config->exec[i]) ; i++) {
-		repl = 0;
-		s = 0;
-		for(;;) {
-			sub = strchrnul(orig, SUBST_CHAR);
-			l = sub - orig;
-			if (repl)
-				repl = mempcpy(repl, orig, l);
-			else
-				s += l;
-			if (!*sub) {
-				/* at end */
-				if (repl || orig == config->exec[i])
-					break;
-				repl = malloc(1 + s);
-				if (!repl)
-					return -1;
-				orig = config->exec[i];
-				config->exec[i] = repl;
-				repl[s] = 0;
-			} else {
-				r = 2;
-				switch(sub[1]) {
-				case 'p': val = port;  break;
-				case 't': val = config->token ? : ""; break;
-				default: r = 1;
-				case SUBST_CHAR: val = SUBST_STR; break;
-				}
-				orig = &sub[r];
-				l = strlen(val);
-				if (repl)
-					repl = mempcpy(repl, val, l);
-				else
-					s += l;
-			}
+	char *resu, *it, *wr;
+	int chg, dif;
+
+	/* get the changes */
+	chg = 0;
+	dif = 0;
+	it = strchrnul(arg, SUBST_CHAR);
+	while (*it) {
+		switch(*++it) {
+		case 'p': chg++; dif += (int)strlen(port) - 2; break;
+		case 't': chg++; dif += (int)strlen(token) - 2; break;
+		case SUBST_CHAR: it++; chg++; dif--; break;
+		default: break;
 		}
+		it = strchrnul(it, SUBST_CHAR);
+	}
+
+	/* return arg when no change */
+	if (!chg)
+		return arg;
+
+	/* allocates the result */
+	resu = malloc((it - arg) + dif + 1);
+	if (!resu) {
+		ERROR("out of memory");
+		return NULL;
+	}
+
+	/* instanciate the arguments */
+	wr = resu;
+	for (;;) {
+		it = strchrnul(arg, SUBST_CHAR);
+		wr = mempcpy(wr, arg, it - arg);
+		if (!*it)
+			break;
+		switch(*++it) {
+		case 'p': wr = stpcpy(wr, port); break;
+		case 't': wr = stpcpy(wr, token); break;
+		default: *wr++ = SUBST_CHAR;
+		case SUBST_CHAR: *wr++ = *it;
+		}
+		arg = ++it;
+	}
+
+	*wr = 0;
+	return resu;
+}
+
+static int instanciate_environ(const char *port, const char *token)
+{
+	extern char **environ;
+	char *repl;
+	int i;
+
+	/* instanciate the environment */
+	for (i = 0 ; environ[i] ; i++) {
+		repl = instanciate_string(environ[i], port, token);
+		if (!repl)
+			return -1;
+		environ[i] = repl;
+	}
+	return 0;
+}
+
+static int instanciate_command_args(const char *port, const char *token)
+{
+	char *repl;
+	int i;
+
+	/* instanciate the arguments */
+	for (i = 0 ; config->exec[i] ; i++) {
+		repl = instanciate_string(config->exec[i], port, token);
+		if (!repl)
+			return -1;
+		config->exec[i] = repl;
 	}
 	return 0;
 }
@@ -318,6 +349,8 @@ static int instanciate_command_args()
 static int execute_command()
 {
 	struct sigaction siga;
+	char port[20];
+	int rc;
 
 	/* check whether a command is to execute or not */
 	if (!config->exec || !config->exec[0])
@@ -337,12 +370,24 @@ static int execute_command()
 	if (childpid)
 		return 0;
 
-	/* makes arguments */
-	if (instanciate_command_args() >= 0) {
-		if (!SELF_PGROUP)
-			setpgid(0, 0);
-		execv(config->exec[0], config->exec);
-		ERROR("can't launch %s: %m", config->exec[0]);
+	/* compute the string for port */
+	if (config->httpdPort)
+		rc = snprintf(port, sizeof port, "%d", config->httpdPort);
+	else
+		rc = snprintf(port, sizeof port, "%cp", SUBST_CHAR);
+	if (rc < 0 || rc >= (int)(sizeof port)) {
+		ERROR("port->txt failed");
+	}
+	else {
+		/* instanciate arguments and environment */
+		if (instanciate_command_args(port, config->token) >= 0
+		 && instanciate_environ(port, config->token) >= 0) {
+			/* run */
+			if (!SELF_PGROUP)
+				setpgid(0, 0);
+			execv(config->exec[0], config->exec);
+			ERROR("can't launch %s: %m", config->exec[0]);
+		}
 	}
 	exit(1);
 	return -1;