release: rc-1.4

1 files changed, 114 insertions, 0 deletions

diff --git a/which.c b/which.c
new file mode 100644
index 0000000..a9e2f65
--- /dev/null
+++ b/which.c
@@ -0,0 +1,114 @@
+/* which.c: check to see if a file is executable.
+
+   This function was originally written with Maarten Litmaath's which.c as
+   a template, but was changed in order to accomodate the possibility of
+   rc's running setuid or the possibility of executing files not in the
+   primary group. Much of this file has been re-vamped by Paul Haahr.
+   I re-re-vamped the functions that Paul supplied to correct minor bugs
+   and to strip out unneeded functionality.
+*/
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/param.h>
+#include <errno.h>
+#include "rc.h"
+
+#define X_USR 0100
+#define X_GRP 0010
+#define X_OTH 0001
+#define X_ALL (X_USR|X_GRP|X_OTH)
+
+extern int stat(const char *, struct stat *);
+
+static bool initialized = FALSE;
+static int uid, gid;
+
+#ifdef NGROUPS
+static int ngroups, gidset[NGROUPS];
+
+/* determine whether gid lies in gidset */
+
+static int ingidset(int g) {
+	int i;
+	for (i = 0; i < ngroups; i++)
+		if (g == gidset[i])
+			return 1;
+	return 0;
+}
+#endif
+
+/*
+   A home-grown access/stat. Does the right thing for group-executable files.
+   Returns a bool instead of this -1 nonsense.
+*/
+
+static bool rc_access(char *path, bool verbose) {
+	struct stat st;
+	int mask;
+	if (stat(path, &st) != 0) {
+		if (verbose) /* verbose flag only set for absolute pathname */
+			uerror(path);
+		return FALSE;
+	}
+	if (uid == 0)
+		mask = X_ALL;
+	else if (uid == st.st_uid)
+		mask = X_USR;
+#ifdef NGROUPS
+	else if (gid == st.st_gid || ingidset(st.st_gid))
+#else
+	else if (gid == st.st_gid)
+#endif
+		mask = X_GRP;
+	else
+		mask = X_OTH;
+	if (((st.st_mode & S_IFMT) == S_IFREG) && (st.st_mode & mask))
+		return TRUE;
+	errno = EACCES;
+	if (verbose)
+		uerror(path);
+	return FALSE;
+}
+
+/* return a full pathname by searching $path, and by checking the status of the file */
+
+extern char *which(char *name, bool verbose) {
+	static char *test = NULL;
+	static SIZE_T testlen = 0;
+	List *path;
+	int len;
+	if (name == NULL)	/* no filename? can happen with "> foo" as a command */
+		return NULL;
+	if (!initialized) {
+		initialized = TRUE;
+		uid = geteuid();
+		gid = getegid();
+#ifdef NGROUPS
+		ngroups = getgroups(NGROUPS, gidset);
+#endif
+	}
+	if (isabsolute(name)) /* absolute pathname? */
+		return rc_access(name, verbose) ? name : NULL;
+	len = strlen(name);
+	for (path = varlookup("path"); path != NULL; path = path->n) {
+		SIZE_T need = strlen(path->w) + len + 2; /* one for null terminator, one for the '/' */
+		if (testlen < need) {
+			efree(test);
+			test = ealloc(testlen = need);
+		}
+		if (*path->w == '\0') {
+			strcpy(test, name);
+		} else {
+			strcpy(test, path->w);
+			if (!streq(test, "/")) /* "//" is special to POSIX */
+				strcat(test, "/");
+			strcat(test, name);
+		}
+		if (rc_access(test, FALSE))
+			return test;
+	}
+	if (verbose)
+		fprint(2, "%s not found\n", name);
+	return NULL;
+}