1 files changed, 84 insertions, 0 deletions

diff --git a/src/firejail/output.c b/src/firejail/output.c
new file mode 100644
index 000000000..32adac108
--- /dev/null
+++ b/src/firejail/output.c
@@ -0,0 +1,84 @@
+#include "firejail.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+void check_output(int argc, char **argv) {
+        int i;
+        char *outfile = NULL;
+//      drop_privs(0);
+
+        int found = 0;
+        for (i = 1; i < argc; i++) {
+                if (strncmp(argv[i], "--output=", 9) == 0) {
+                        found = 1;
+                        outfile = argv[i] + 9;
+
+                        // do not accept directories, links, and files with ".."
+                        if (strstr(outfile, "..") || is_link(outfile) || is_dir(outfile)) {
+                                fprintf(stderr, "Error: invalid output file. Links, directories and files with \"..\" are not allowed.\n");
+                                exit(1);
+                        }
+                        
+                        struct stat s;
+                        if (stat(outfile, &s) == 0) {
+                                // check permissions
+                                if (s.st_uid != getuid() || s.st_gid != getgid()) {
+                                        fprintf(stderr, "Error: the output file needs to be owned by the current user.\n");
+                                        exit(1);
+                                }
+                                
+                                // check hard links
+                                if (s.st_nlink != 1) {
+                                        fprintf(stderr, "Error: no hard links allowed.\n");
+                                        exit(1);
+                                }
+                        }
+
+                        // drop privileges and try to open the file for writing
+                        drop_privs(0);
+                        /* coverity[toctou] */
+                        FILE *fp = fopen(outfile, "a");
+                        if (!fp) {
+                                fprintf(stderr, "Error: cannot open output file %s\n", outfile);
+                                exit(1);
+                        }
+                        fclose(fp);
+                        break;
+                }
+        }
+        if (!found)
+                return;
+
+
+        // build the new command line
+        int len = 0;
+        for (i = 0; i < argc; i++) {
+                len += strlen(argv[i]) + 1; // + ' '
+        }
+        len += 50 + strlen(outfile); // tee command
+        
+        char *cmd = malloc(len + 1); // + '\0'
+        if (!cmd)
+                errExit("malloc");
+        
+        char *ptr = cmd;
+        for (i = 0; i < argc; i++) {
+                if (strncmp(argv[i], "--output=", 9) == 0)
+                        continue;
+                ptr += sprintf(ptr, "%s ", argv[i]);
+        }
+        sprintf(ptr, "| %s/lib/firejail/ftee %s", PREFIX, outfile);
+
+        // run command
+        char *a[4];
+        a[0] = "/bin/bash";
+        a[1] = "-c";
+        a[2] = cmd;
+        a[3] = NULL;
+
+        execvp(a[0], a); 
+
+        perror("execvp");
+        exit(1);
+}