diff options
Diffstat (limited to 'libpam')
| -rw-r--r-- | libpam/Makefile.am | 2 | ||||
| -rw-r--r-- | libpam/include/security/pam_modutil.h | 13 | ||||
| -rw-r--r-- | libpam/libpam.map | 5 | ||||
| -rw-r--r-- | libpam/pam_modutil_sanitize.c | 175 |
4 files changed, 194 insertions, 1 deletions
diff --git a/libpam/Makefile.am b/libpam/Makefile.am index 417ca779..685a797d 100644 --- a/libpam/Makefile.am +++ b/libpam/Makefile.am @@ -43,4 +43,4 @@ libpam_la_SOURCES = pam_account.c pam_auth.c pam_data.c pam_delay.c \ pam_modutil_cleanup.c pam_modutil_getpwnam.c pam_modutil_ioloop.c \ pam_modutil_getgrgid.c pam_modutil_getpwuid.c pam_modutil_getgrnam.c \ pam_modutil_getspnam.c pam_modutil_getlogin.c pam_modutil_ingroup.c \ - pam_modutil_priv.c + pam_modutil_priv.c pam_modutil_sanitize.c diff --git a/libpam/include/security/pam_modutil.h b/libpam/include/security/pam_modutil.h index 8087ba15..4ce8c552 100644 --- a/libpam/include/security/pam_modutil.h +++ b/libpam/include/security/pam_modutil.h @@ -129,6 +129,19 @@ extern int PAM_NONNULL((1,2)) pam_modutil_regain_priv(pam_handle_t *pamh, struct pam_modutil_privs *p); +enum pam_modutil_redirect_fd { + PAM_MODUTIL_IGNORE_FD, /* do not redirect */ + PAM_MODUTIL_PIPE_FD, /* redirect to a pipe */ + PAM_MODUTIL_NULL_FD, /* redirect to /dev/null */ +}; + +/* redirect standard descriptors, close all other descriptors. */ +extern int PAM_NONNULL((1)) +pam_modutil_sanitize_helper_fds(pam_handle_t *pamh, + enum pam_modutil_redirect_fd redirect_stdin, + enum pam_modutil_redirect_fd redirect_stdout, + enum pam_modutil_redirect_fd redirect_stderr); + #ifdef __cplusplus } #endif diff --git a/libpam/libpam.map b/libpam/libpam.map index b0885d65..d6835b47 100644 --- a/libpam/libpam.map +++ b/libpam/libpam.map @@ -67,3 +67,8 @@ LIBPAM_MODUTIL_1.1.3 { pam_modutil_drop_priv; pam_modutil_regain_priv; } LIBPAM_MODUTIL_1.1; + +LIBPAM_MODUTIL_1.1.9 { + global: + pam_modutil_sanitize_helper_fds; +} LIBPAM_MODUTIL_1.1.3; diff --git a/libpam/pam_modutil_sanitize.c b/libpam/pam_modutil_sanitize.c new file mode 100644 index 00000000..65f85d01 --- /dev/null +++ b/libpam/pam_modutil_sanitize.c @@ -0,0 +1,175 @@ +/* + * This file implements the following functions: + * pam_modutil_sanitize_helper_fds: + * redirects standard descriptors, closes all other descriptors. + */ + +#include "pam_modutil_private.h" +#include <security/pam_ext.h> +#include <unistd.h> +#include <fcntl.h> +#include <syslog.h> +#include <sys/resource.h> + +/* + * Creates a pipe, closes its write end, redirects fd to its read end. + * Returns fd on success, -1 otherwise. + */ +static int +redirect_in_pipe(pam_handle_t *pamh, int fd, const char *name) +{ + int in[2]; + + if (pipe(in) < 0) { + pam_syslog(pamh, LOG_ERR, "Could not create pipe: %m"); + return -1; + } + + close(in[1]); + + if (in[0] == fd) + return fd; + + if (dup2(in[0], fd) != fd) { + pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name); + fd = -1; + } + + close(in[0]); + return fd; +} + +/* + * Creates a pipe, closes its read end, redirects fd to its write end. + * Returns fd on success, -1 otherwise. + */ +static int +redirect_out_pipe(pam_handle_t *pamh, int fd, const char *name) +{ + int out[2]; + + if (pipe(out) < 0) { + pam_syslog(pamh, LOG_ERR, "Could not create pipe: %m"); + return -1; + } + + close(out[0]); + + if (out[1] == fd) + return fd; + + if (dup2(out[1], fd) != fd) { + pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name); + fd = -1; + } + + close(out[1]); + return fd; +} + +/* + * Opens /dev/null for writing, redirects fd there. + * Returns fd on success, -1 otherwise. + */ +static int +redirect_out_null(pam_handle_t *pamh, int fd, const char *name) +{ + int null = open("/dev/null", O_WRONLY); + + if (null < 0) { + pam_syslog(pamh, LOG_ERR, "open of %s failed: %m", "/dev/null"); + return -1; + } + + if (null == fd) + return fd; + + if (dup2(null, fd) != fd) { + pam_syslog(pamh, LOG_ERR, "dup2 of %s failed: %m", name); + fd = -1; + } + + close(null); + return fd; +} + +static int +redirect_out(pam_handle_t *pamh, enum pam_modutil_redirect_fd mode, + int fd, const char *name) +{ + switch (mode) { + case PAM_MODUTIL_PIPE_FD: + if (redirect_out_pipe(pamh, fd, name) < 0) + return -1; + break; + case PAM_MODUTIL_NULL_FD: + if (redirect_out_null(pamh, fd, name) < 0) + return -1; + break; + case PAM_MODUTIL_IGNORE_FD: + break; + } + return fd; +} + +/* Closes all descriptors after stderr. */ +static void +close_fds(void) +{ + /* + * An arbitrary upper limit for the maximum file descriptor number + * returned by RLIMIT_NOFILE. + */ + const int MAX_FD_NO = 65535; + + /* The lower limit is the same as for _POSIX_OPEN_MAX. */ + const int MIN_FD_NO = 20; + + int fd; + struct rlimit rlim; + + if (getrlimit(RLIMIT_NOFILE, &rlim) || rlim.rlim_max > MAX_FD_NO) + fd = MAX_FD_NO; + else if (rlim.rlim_max < MIN_FD_NO) + fd = MIN_FD_NO; + else + fd = rlim.rlim_max - 1; + + for (; fd > STDERR_FILENO; --fd) + close(fd); +} + +int +pam_modutil_sanitize_helper_fds(pam_handle_t *pamh, + enum pam_modutil_redirect_fd stdin_mode, + enum pam_modutil_redirect_fd stdout_mode, + enum pam_modutil_redirect_fd stderr_mode) +{ + if (stdin_mode != PAM_MODUTIL_IGNORE_FD && + redirect_in_pipe(pamh, STDIN_FILENO, "stdin") < 0) { + return -1; + } + + if (redirect_out(pamh, stdout_mode, STDOUT_FILENO, "stdout") < 0) + return -1; + + /* + * If stderr should not be ignored and + * redirect mode for stdout and stderr are the same, + * optimize by redirecting stderr to stdout. + */ + if (stderr_mode != PAM_MODUTIL_IGNORE_FD && + stdout_mode == stderr_mode) { + if (dup2(STDOUT_FILENO, STDERR_FILENO) != STDERR_FILENO) { + pam_syslog(pamh, LOG_ERR, + "dup2 of %s failed: %m", "stderr"); + return -1; + } + } else { + if (redirect_out(pamh, stderr_mode, STDERR_FILENO, "stderr") < 0) + return -1; + } + + close_fds(); + return 0; +} |