fix memory corruption caused by use-after-free

[oweals/ucert.git] / usign-exec.c

diff --git a/usign-exec.c b/usign-exec.c
index bed3db7ee059ba14af797452eea609a4cfc3de5b..687cb7dcfeaaf98203a31e3f40846ba46842229e 100644 (file)
--- a/usign-exec.c
+++ b/usign-exec.c
@@ -1,54 +1,46 @@
+/*
+ * wrapper functions around the usign executable
+ * Copyright (C) 2018 Daniel Golle <daniel@makrotopia.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
 #include <stdbool.h>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/wait.h>
 
 #include "usign.h"
 
-int usign_v(const char *msgfile, const char *pubkeyfile,
-           const char *pubkeydir, const char *sigfile, bool quiet) {
-       pid_t pid;
-       int status;
-       const char *usign_argv[16] = {0};
-       unsigned int usign_argc = 0;
-
-       usign_argv[usign_argc++] = "/usr/bin/usign";
-       usign_argv[usign_argc++] = "-V";
-       usign_argv[usign_argc++] = "-m";
-       usign_argv[usign_argc++] = msgfile;
-
-       if (quiet)
-               usign_argv[usign_argc++] = "-q";
-
-       if (pubkeyfile) {
-               usign_argv[usign_argc++] = "-p";
-               usign_argv[usign_argc++] = pubkeyfile;
-       }
-
-       if (pubkeydir) {
-               usign_argv[usign_argc++] = "-P";
-               usign_argv[usign_argc++] = pubkeydir;
-       }
-
-       pid = fork();
-       switch (pid) {
-       case -1:
-               return -1;
-
-       case 0:
-               if (execv(usign_argv[0], usign_argv))
-                       return -1;
-
-               break;
-
-       default:
-               waitpid(pid, &status, 0);
-               return WEXITSTATUS(status);
-       }
-
-       return -1;
+/*
+ * check for revoker deadlink in pubkeydir
+ * return true if a revoker exists, false otherwise
+ */
+int _usign_key_is_revoked(const char *fingerprint, const char *pubkeydir) {
+       char tml[64] = {0};
+       char rfname[256] = {0};
+
+       snprintf(rfname, sizeof(rfname)-1, "%s/%s", pubkeydir, fingerprint);
+       if (readlink(rfname, tml, sizeof(tml)) > 0 &&
+           !strcmp(tml, ".revoked.")) {
+               return true;
+       };
+
+       return false;
 }
 
+/*
+ * call usign -S ...
+ * return WEXITSTATUS or -1 if fork or execv fails
+ */
 int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bool quiet) {
        pid_t pid;
        int status;
@@ -86,6 +78,10 @@ int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bo
        return -1;
 }
 
+/*
+ * call usign -F ... and set fingerprint returned
+ * return WEXITSTATUS or -1 if fork or execv fails
+ */
 static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckeyfile, const char *sigfile) {
        int fds[2];
        pid_t pid;
@@ -147,14 +143,89 @@ static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckey
        return -1;
 }
 
+/*
+ * call usign -F -p ...
+ */
 int usign_f_pubkey(char *fingerprint, const char *pubkeyfile) {
        return usign_f(fingerprint, pubkeyfile, NULL, NULL);
 }
 
+/*
+ * call usign -F -s ...
+ */
 int usign_f_seckey(char *fingerprint, const char *seckeyfile) {
        return usign_f(fingerprint, NULL, seckeyfile, NULL);
 }
 
+/*
+ * call usign -F -x ...
+ */
 int usign_f_sig(char *fingerprint, const char *sigfile) {
        return usign_f(fingerprint, NULL, NULL, sigfile);
 }
+
+
+/*
+ * call usign -V ...
+ * return WEXITSTATUS or -1 if fork or execv fails
+ */
+int usign_v(const char *msgfile, const char *pubkeyfile,
+           const char *pubkeydir, const char *sigfile, bool quiet) {
+       pid_t pid;
+       int status;
+       const char *usign_argv[16] = {0};
+       unsigned int usign_argc = 0;
+       char fingerprint[17];
+
+       if (usign_f_sig(fingerprint, sigfile)) {
+               if (!quiet)
+                       fprintf(stdout, "cannot get signing key fingerprint\n");
+               return 1;
+       }
+
+       if (pubkeydir && _usign_key_is_revoked(fingerprint, pubkeydir)) {
+               if (!quiet)
+                       fprintf(stdout, "key %s has been revoked!\n", fingerprint);
+               return 1;
+       }
+       usign_argv[usign_argc++] = "/usr/bin/usign";
+       usign_argv[usign_argc++] = "-V";
+       usign_argv[usign_argc++] = "-m";
+       usign_argv[usign_argc++] = msgfile;
+
+       if (quiet)
+               usign_argv[usign_argc++] = "-q";
+
+       if (pubkeyfile) {
+               usign_argv[usign_argc++] = "-p";
+               usign_argv[usign_argc++] = pubkeyfile;
+       }
+
+       if (pubkeydir) {
+               usign_argv[usign_argc++] = "-P";
+               usign_argv[usign_argc++] = pubkeydir;
+       }
+
+       if (sigfile) {
+               usign_argv[usign_argc++] = "-x";
+               usign_argv[usign_argc++] = sigfile;
+       }
+
+       pid = fork();
+       switch (pid) {
+       case -1:
+               return -1;
+
+       case 0:
+               if (execv(usign_argv[0], usign_argv))
+                       return -1;
+
+               break;
+
+       default:
+               waitpid(pid, &status, 0);
+               return WEXITSTATUS(status);
+       }
+
+       return -1;
+}