harden reading fingerprint from usign process

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

diff --git a/usign-exec.c b/usign-exec.c
index d88f750fb43f39e75be98fa1bc45fd6369889acd..2ab2cd3c434bee4f5f8110feaa3feabab4591c82 100644 (file)
--- a/usign-exec.c
+++ b/usign-exec.c
@@ -1,3 +1,17 @@
+/*
+ * 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>
@@ -6,13 +20,37 @@
 
 #include "usign.h"
 
+#define USIGN_EXEC "/usr/bin/usign"
+
+/*
+ * 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;
+}
+
+#ifdef UCERT_FULL
+/*
+ * 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;
        const char *usign_argv[16] = {0};
        unsigned int usign_argc = 0;
 
-       usign_argv[usign_argc++] = "/usr/bin/usign";
+       usign_argv[usign_argc++] = USIGN_EXEC;
        usign_argv[usign_argc++] = "-S";
        usign_argv[usign_argc++] = "-m";
        usign_argv[usign_argc++] = msgfile;
@@ -42,7 +80,16 @@ int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bo
 
        return -1;
 }
+#else
+int usign_s(const char *msgfile, const char *seckeyfile, const char *sigfile, bool quiet) {
+       return -1;
+};
+#endif
 
+/*
+ * 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;
@@ -53,7 +100,7 @@ static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckey
        if (pipe(fds))
                return -1;
 
-       usign_argv[usign_argc++] = "/usr/bin/usign";
+       usign_argv[usign_argc++] = USIGN_EXEC;
        usign_argv[usign_argc++] = "-F";
 
        if (pubkeyfile) {
@@ -91,44 +138,50 @@ static int usign_f(char *fingerprint, const char *pubkeyfile, const char *seckey
 
        default:
                waitpid(pid, &status, 0);
+               status = WEXITSTATUS(status);
                if (fingerprint && !WEXITSTATUS(status)) {
-                       memset(fingerprint, 0, 16);
-                       read(fds[0], fingerprint, 16);
+                       memset(fingerprint, 0, 17);
+                       read(fds[0], fingerprint, 17);
+                       if (fingerprint[16] != '\n')
+                               status = -1;
+
                        fingerprint[16] = '\0';
+
                }
                close(fds[0]);
                close(fds[1]);
-               return WEXITSTATUS(status);
+               return status;
        }
 
        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);
 }
 
-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 -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;
@@ -137,13 +190,18 @@ int usign_v(const char *msgfile, const char *pubkeyfile,
        unsigned int usign_argc = 0;
        char fingerprint[17];
 
-       if (usign_f_sig(fingerprint, sigfile))
+       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 (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++] = USIGN_EXEC;
        usign_argv[usign_argc++] = "-V";
        usign_argv[usign_argc++] = "-m";
        usign_argv[usign_argc++] = msgfile;