diff options
Diffstat (limited to 'fuzz/preload-snoop.c')
| -rw-r--r-- | fuzz/preload-snoop.c | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/fuzz/preload-snoop.c b/fuzz/preload-snoop.c new file mode 100644 index 0000000..34d57ad --- /dev/null +++ b/fuzz/preload-snoop.c @@ -0,0 +1,218 @@ +/* + * Copyright (c) 2019 Yubico AB. All rights reserved. + * Use of this source code is governed by a BSD-style + * license that can be found in the LICENSE file. + * SPDX-License-Identifier: BSD-2-Clause + */ + +/* + * cc -fPIC -D_GNU_SOURCE -shared -o preload-snoop.so preload-snoop.c + * LD_PRELOAD=$(realpath preload-snoop.so) + */ + +#include <sys/types.h> +#include <sys/stat.h> + +#include <dlfcn.h> +#include <err.h> +#include <errno.h> +#include <fcntl.h> +#include <limits.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#define SNOOP_DEV_PREFIX "/dev/hidraw" + +struct fd_tuple { + int snoop_in; + int snoop_out; + int real_dev; +}; + +static struct fd_tuple *fd_tuple; +static int (*open_f)(const char *, int, mode_t); +static int (*close_f)(int); +static ssize_t (*read_f)(int, void *, size_t); +static ssize_t (*write_f)(int, const void *, size_t); + +static int +get_fd(const char *hid_path, const char *suffix) +{ + char *s = NULL; + char path[PATH_MAX]; + int fd; + int r; + + if ((s = strdup(hid_path)) == NULL) { + warnx("%s: strdup", __func__); + return (-1); + } + + for (size_t i = 0; i < strlen(s); i++) + if (s[i] == '/') + s[i] = '_'; + + if ((r = snprintf(path, sizeof(path), "%s-%s", s, suffix)) < 0 || + (size_t)r >= sizeof(path)) { + warnx("%s: snprintf", __func__); + free(s); + return (-1); + } + + free(s); + s = NULL; + + if ((fd = open_f(path, O_CREAT | O_WRONLY, 0644)) < 0) { + warn("%s: open", __func__); + return (-1); + } + + return (fd); +} + +int +open(const char *path, int flags, ...) +{ + va_list ap; + mode_t mode; + + va_start(ap, flags); + mode = va_arg(ap, mode_t); + va_end(ap); + + if (open_f == NULL) { + open_f = dlsym(RTLD_NEXT, "open"); + if (open_f == NULL) { + warnx("%s: dlsym", __func__); + errno = EACCES; + return (-1); + } + } + + if (strncmp(path, SNOOP_DEV_PREFIX, strlen(SNOOP_DEV_PREFIX)) != 0) + return (open_f(path, flags, mode)); + + if (fd_tuple != NULL) { + warnx("%s: fd_tuple != NULL", __func__); + errno = EACCES; + return (-1); + } + + if ((fd_tuple = calloc(1, sizeof(*fd_tuple))) == NULL) { + warn("%s: calloc", __func__); + errno = ENOMEM; + return (-1); + } + + fd_tuple->snoop_in = -1; + fd_tuple->snoop_out = -1; + fd_tuple->real_dev = -1; + + if ((fd_tuple->snoop_in = get_fd(path, "in")) < 0 || + (fd_tuple->snoop_out = get_fd(path, "out")) < 0 || + (fd_tuple->real_dev = open_f(path, flags, mode)) < 0) { + warn("%s: get_fd/open", __func__); + goto fail; + } + + return (fd_tuple->real_dev); +fail: + if (fd_tuple->snoop_in != -1) + close(fd_tuple->snoop_in); + if (fd_tuple->snoop_out != -1) + close(fd_tuple->snoop_out); + if (fd_tuple->real_dev != -1) + close(fd_tuple->real_dev); + + free(fd_tuple); + fd_tuple = NULL; + + errno = EACCES; + + return (-1); +} + +int +close(int fd) +{ + if (close_f == NULL) { + close_f = dlsym(RTLD_NEXT, "close"); + if (close_f == NULL) { + warnx("%s: dlsym", __func__); + errno = EBADF; + return (-1); + } + } + + if (fd_tuple == NULL || fd_tuple->real_dev != fd) + return (close_f(fd)); + + close_f(fd_tuple->snoop_in); + close_f(fd_tuple->snoop_out); + close_f(fd_tuple->real_dev); + + free(fd_tuple); + fd_tuple = NULL; + + return (0); +} + +ssize_t +read(int fd, void *buf, size_t nbytes) +{ + ssize_t n; + + if (read_f == NULL) { + read_f = dlsym(RTLD_NEXT, "read"); + if (read_f == NULL) { + warnx("%s: dlsym", __func__); + errno = EBADF; + return (-1); + } + } + + if (write_f == NULL) { + write_f = dlsym(RTLD_NEXT, "write"); + if (write_f == NULL) { + warnx("%s: dlsym", __func__); + errno = EBADF; + return (-1); + } + } + + if (fd_tuple == NULL || fd_tuple->real_dev != fd) + return (read_f(fd, buf, nbytes)); + + if ((n = read_f(fd, buf, nbytes)) < 0 || + write_f(fd_tuple->snoop_in, buf, n) != n) + return (-1); + + return (n); +} + +ssize_t +write(int fd, const void *buf, size_t nbytes) +{ + ssize_t n; + + if (write_f == NULL) { + write_f = dlsym(RTLD_NEXT, "write"); + if (write_f == NULL) { + warnx("%s: dlsym", __func__); + errno = EBADF; + return (-1); + } + } + + if (fd_tuple == NULL || fd_tuple->real_dev != fd) + return (write_f(fd, buf, nbytes)); + + if ((n = write_f(fd, buf, nbytes)) < 0 || + write_f(fd_tuple->snoop_out, buf, n) != n) + return (-1); + + return (n); +} |