Use a common function for resolviong the user's editor in sudoedit

and visudo.  The find_path() function now returns a dynamically
allocated path instead of using a static string.

plugins/sudoers/editor.c

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2010-2015 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * 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 <config.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#ifdef STDC_HEADERS
+# include <stdlib.h>
+# include <stddef.h>
+#else
+# ifdef HAVE_STDLIB_H
+#  include <stdlib.h>
+# endif
+#endif /* STDC_HEADERS */
+#ifdef HAVE_STRING_H
+# if defined(HAVE_MEMORY_H) && !defined(STDC_HEADERS)
+#  include <memory.h>
+# endif
+# include <string.h>
+#endif /* HAVE_STRING_H */
+#ifdef HAVE_STRINGS_H
+# include <strings.h>
+#endif /* HAVE_STRINGS_H */
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif /* HAVE_UNISTD_H */
+#include <errno.h>
+
+#include "sudoers.h"
+
+/*
+ * Search for the specified editor in the user's PATH, checking
+ * the result against whitelist if non-NULL.  An argument vector
+ * suitable for execve() is allocated and stored in argv_out.
+ * If nfiles is non-zero, files[] is added to the end of argv_out.
+ * Returns the path to be executed on success, else NULL.
+ * The caller is responsible for freeing the returned editor path
+ * as well as the argument vector.
+ */
+char *
+resolve_editor(const char *ed, size_t edlen, int nfiles, char **files,
+    int *argc_out, char ***argv_out, char * const *whitelist)
+{
+    char **nargv, *editor, *editor_path = NULL;
+    const char *cp, *ep, *tmp;
+    const char *edend = ed + edlen;
+    struct stat user_editor_sb;
+    int nargc;
+    debug_decl(resolve_editor, SUDOERS_DEBUG_UTIL)
+
+    /*
+     * Split editor into an argument vector, including files to edit.
+     * The EDITOR and VISUAL environment variables may contain command
+     * line args so look for those and alloc space for them too.
+     */
+    cp = sudo_strsplit(ed, edend, " \t", &ep);
+    if (cp == NULL)
+	debug_return_str(NULL);
+    editor = strndup(cp, (size_t)(ep - cp));
+    if (editor == NULL) {
+	sudo_warnx(U_("unable to allocate memory"));
+	debug_return_str(NULL);
+    }
+
+    /* If we can't find the editor in the user's PATH, give up. */
+    if (find_path(editor, &editor_path, &user_editor_sb, getenv("PATH"), 0, whitelist) != FOUND) {
+	free(editor);
+	errno = ENOENT;
+	debug_return_str(NULL);
+    }
+
+    /* Count rest of arguments and allocate editor argv. */
+    for (nargc = 1, tmp = ep; sudo_strsplit(NULL, edend, " \t", &tmp) != NULL; )
+	nargc++;
+    if (nfiles != 0)
+	nargc += nfiles + 1;
+    nargv = reallocarray(NULL, nargc + 1, sizeof(char *));
+    if (nargv == NULL) {
+	sudo_warnx(U_("unable to allocate memory"));
+	free(editor);
+	debug_return_str(NULL);
+    }
+
+    /* Fill in editor argv (assumes files[] is NULL-terminated). */
+    nargv[0] = editor;
+    for (nargc = 1; (cp = sudo_strsplit(NULL, edend, " \t", &ep)) != NULL; nargc++) {
+	nargv[nargc] = strndup(cp, (size_t)(ep - cp));
+	if (nargv[nargc] == NULL) {
+	    sudo_warnx(U_("unable to allocate memory"));
+	    while (nargc--)
+		free(nargv[nargc]);
+	    debug_return_str(NULL);
+	}
+    }
+    if (nfiles != 0) {
+	nargv[nargc++] = "--";
+	while (nfiles--)
+	    nargv[nargc++] = *files++;
+    }
+    nargv[nargc] = NULL;
+
+    *argc_out = nargc;
+    *argv_out = nargv;
+    debug_return_str(editor_path);
+}