opendoas

my fork of doas with custom prompt
git clone git://git.kocotian.pl/opendoas.git
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commit 331dda05d1d06fcb12763be9c34c82b5e280b3bc
parent bf8b7becf2167e13a5b43d8f61b7e16913de2ead
Author: Duncaen <mail@duncano.de>
Date:   Wed, 30 Jan 2019 22:31:47 +0100

timestamp: rename and simplify

Diffstat:
Mconfigure | 4++--
Mdoas.c | 8+++++---
Mincludes.h | 8++++----
Dpersist_timestamp.c | 362-------------------------------------------------------------------------------
Atimestamp.c | 399+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 410 insertions(+), 371 deletions(-)

diff --git a/configure b/configure @@ -185,8 +185,8 @@ int main(void) { persistmethod() { [ -z "$WITHOUT_TIMESTAMP" ] && { - printf 'CFLAGS += -DPERSIST_TIMESTAMP\n' >>$CONFIG_MK - printf 'SRCS += persist_timestamp.c\n' >>$CONFIG_MK + printf 'CPPFLAGS += -DUSE_TIMESTAMP\n' >>$CONFIG_MK + printf 'SRCS += timestamp.c\n' >>$CONFIG_MK printf 'timestamp\n' return 0 } diff --git a/doas.c b/doas.c @@ -298,13 +298,15 @@ main(int argc, char **argv) confpath = optarg; break; case 'L': -#ifdef TIOCCLRVERAUTH +#if defined(USE_BSD_AUTH) i = open("/dev/tty", O_RDWR); if (i != -1) ioctl(i, TIOCCLRVERAUTH); exit(i == -1); -#elif PERSIST_TIMESTAMP - exit(persist_clear() != 0); +#elif defined(USE_TIMESTAMP) + exit(timestamp_clear() == -1); +#else + exit(0); #endif case 'u': if (parseuid(optarg, &target) != 0) diff --git a/includes.h b/includes.h @@ -24,10 +24,10 @@ int pamauth(const char *, const char *, int, int); void shadowauth(const char *, int); #endif -#ifdef PERSIST_TIMESTAMP -int persist_open(int *, int); -int persist_set(int, int); -int persist_clear(); +#ifdef USE_TIMESTAMP +int timestamp_open(int *, int); +int timestamp_set(int, int); +int timestamp_clear(void); #endif #endif /* INCLUDES_H */ diff --git a/persist_timestamp.c b/persist_timestamp.c @@ -1,362 +0,0 @@ -/* - * 1) Timestamp files and directories - * - * Timestamp files MUST NOT be accessible to users other than root, - * this includes the name, metadata and the content of timestamp files - * and directories. - * - * Symlinks can be used to create, manipulate or delete wrong files - * and directories. The Implementation MUST reject any symlinks for - * timestamp files or directories. - * - * To avoid race conditions the implementation MUST use the same - * file descriptor for permission checks and do read or write - * write operations after the permission checks. - * - * The timestamp files MUST be opened with openat(2) using the - * timestamp directory file descriptor. Permissions of the directory - * MUST be checked before opening the timestamp file descriptor. - * - * 2) Clock sources for timestamps - * - * Timestamp files MUST NOT rely on only one clock source, using the - * wall clock would allow to reset the clock to an earlier point in - * time to reuse a timestamp. - * - * The timestamp MUST consist of multiple clocks and MUST reject the - * timestamp if there is a change to any clock because there is no way - * to differentiate between malicious and legitimate clock changes. - * - * 3) Timestamp lifetime - * - * The implementation MUST NOT use the user controlled stdin, stdout - * and stderr file descriptors to determine the controlling terminal. - * On linux the /proc/$pid/stat file MUST be used to get the terminal - * number. - * - * There is no reliable way to determine the lifetime of a tty/pty. - * The start time of the session leader MUST be used as part of the - * timestamp to determine if the tty is still the same. - * If the start time of the session leader changed the timestamp MUST - * be rejected. - * - */ - -#include <sys/ioctl.h> -#include <sys/stat.h> -#include <sys/vfs.h> - -#if !defined(timespecisset) || \ - !defined(timespeccmp) || \ - !defined(timespecadd) -# include "sys-time.h" -#endif - -#include <ctype.h> -#include <err.h> -#include <errno.h> -#include <fcntl.h> -#include <limits.h> -#include <stdio.h> -#include <stdlib.h> -#include <string.h> -#include <time.h> -#include <unistd.h> - -#include "includes.h" - -#ifndef TIMESTAMP_DIR -# define TIMESTAMP_DIR "/tmp/doas" -#endif - -#if defined(TIMESTAMP_TMPFS) && defined(__linux__) -# ifndef TMPFS_MAGIC -# define TMPFS_MAGIC 0x01021994 -# endif -#endif - -#ifdef __linux__ -/* Use tty_nr from /proc/self/stat instead of using - * ttyname(3), stdin, stdout and stderr are user - * controllable and would allow to reuse timestamps - * from another writable terminal. - * See https://www.sudo.ws/alerts/tty_tickets.html - */ -static int -proc_info(pid_t pid, int *ttynr, unsigned long long *starttime) -{ - char path[128]; - char buf[1024]; - char *p, *saveptr, *ep; - const char *errstr; - int fd, n; - - p = buf; - - if (snprintf(path, sizeof path, "/proc/%d/stat", pid) == -1) - return -1; - - if ((fd = open(path, O_RDONLY)) == -1) - return -1; - - while ((n = read(fd, p, buf + sizeof buf - p)) != 0) { - if (n == -1) { - if (errno == EAGAIN || errno == EINTR) - continue; - break; - } - p += n; - if (p >= buf + sizeof buf) - break; - } - close(fd); - - /* error if it contains NULL bytes */ - if (n != 0 || memchr(buf, '\0', p - buf)) - return -1; - - /* Get the 7th field, 5 fields after the last ')', - * (2th field) because the 5th field 'comm' can include - * spaces and closing paranthesis too. - * See https://www.sudo.ws/alerts/linux_tty.html - */ - if ((p = strrchr(buf, ')')) == NULL) - return -1; - - n = 2; - for ((p = strtok_r(p, " ", &saveptr)); p; - (p = strtok_r(NULL, " ", &saveptr))) { - switch (n++) { - case 7: - *ttynr = strtonum(p, INT_MIN, INT_MAX, &errstr); - if (errstr) - return -1; - break; - case 22: - errno = 0; - *starttime = strtoull(p, &ep, 10); - if (p == ep || - (errno == ERANGE && *starttime == ULLONG_MAX)) - return -1; - break; - } - if (n == 23) - break; - } - - return 0; -} -#else -#error "proc_info not implemented" -#endif - -static const char * -tsname() -{ - static char buf[128]; - int tty, fd; - unsigned long long starttime; - pid_t ppid, sid, leader; - if ((fd = open("/dev/tty", O_RDONLY)) == -1) - err(1, "open: /dev/tty"); - if (ioctl(fd, TIOCGSID, &leader) == -1) - err(1, "ioctl: failed to get session leader"); - close(fd); - if (proc_info(leader, &tty, &starttime) == -1) - errx(1, "failed to get tty number"); - ppid = getppid(); - if ((sid = getsid(0)) == -1) - err(1, "getsid"); - if (snprintf(buf, sizeof buf, ".%d_%d_%llu_%d_%d", - tty, leader, starttime, ppid, sid) == -1) - return NULL; - return buf; -} - -static int -checktsdir(int fd) -{ - struct stat st; - - if (fstat(fd, &st) == -1) - err(1, "fstatat"); - - if ((st.st_mode & S_IFMT) != S_IFDIR) - errx(0, "timestamp directory is not a directory"); - if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0) - errx(1, "timestamp directory permissions wrong"); - if (st.st_uid != 0 || st.st_gid != 0) - errx(1, "timestamp directory is not owned by root"); - -#if defined(TIMESTAMP_TMPFS) && defined(__linux__) - struct statfs sf; - if (fstatfs(fd, &sf) == -1) - err(1, "statfs"); - - if (sf.f_type != TMPFS_MAGIC) - errx(1, "timestamp directory not on tmpfs"); -#endif - - return 0; -} - -static int -opentsdir() -{ - gid_t gid; - int fd; - -reopen: - if ((fd = open(TIMESTAMP_DIR, O_RDONLY | O_DIRECTORY)) == -1) { - if (errno == ENOENT) { - gid = getegid(); - if (setegid(0) != 0) - err(1, "setegid"); - if (mkdir(TIMESTAMP_DIR, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0) - err(1, "mkdir"); - if (setegid(gid) != 0) - err(1, "setegid"); - goto reopen; - } else { - err(1, "failed to open timestamp directory: %s", TIMESTAMP_DIR); - } - } - - if (checktsdir(fd) != 0) - return -1; - - return fd; -} - -static int -checktsfile(int fd, size_t *tssize) -{ - struct stat st; - gid_t gid; - - if (fstat(fd, &st) == -1) - err(1, "stat"); - if ((st.st_mode & S_IFMT) != S_IFREG) - errx(1, "timestamp is not a regular file"); - if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0) - errx(1, "timestamp has wrong permissions"); - - gid = getegid(); - if (st.st_uid != 0 || st.st_gid != gid) - errx(1, "timestamp has wrong owner"); - - *tssize = st.st_size; - - return 0; -} - -static int -validts(int fd, int secs) -{ - struct timespec mono, real, ts_mono, ts_real, timeout; - - if (read(fd, &ts_mono, sizeof ts_mono) != sizeof ts_mono || - read(fd, &ts_real, sizeof ts_real) != sizeof ts_real) - err(1, "read"); - if (!timespecisset(&ts_mono) || !timespecisset(&ts_real)) - errx(1, "timespecisset"); - - if (clock_gettime(CLOCK_MONOTONIC_RAW, &mono) == -1 || - clock_gettime(CLOCK_REALTIME, &real) == -1) - err(1, "clock_gettime"); - - if (timespeccmp(&mono, &ts_mono, >) || - timespeccmp(&real, &ts_real, >)) - return -1; - - memset(&timeout, 0, sizeof timeout); - timeout.tv_sec = secs; - timespecadd(&timeout, &mono, &mono); - timespecadd(&timeout, &real, &real); - - if (timespeccmp(&mono, &ts_mono, <) || - timespeccmp(&real, &ts_real, <)) - errx(1, "timestamp is too far in the future"); - - return 0; -} - -int -persist_set(int fd, int secs) -{ - struct timespec mono, real, ts_mono, ts_real, timeout; - - if (clock_gettime(CLOCK_MONOTONIC_RAW, &mono) == -1 || - clock_gettime(CLOCK_REALTIME, &real) == -1) - err(1, "clock_gettime"); - - memset(&timeout, 0, sizeof timeout); - timeout.tv_sec = secs; - timespecadd(&timeout, &mono, &ts_mono); - timespecadd(&timeout, &real, &ts_real); - - if (lseek(fd, 0, SEEK_SET) == -1) - err(1, "lseek"); - if (write(fd, (void *)&ts_mono, sizeof ts_mono) != sizeof ts_mono || - write(fd, (void *)&ts_real, sizeof ts_real) != sizeof ts_real) - err(1, "write"); - - return 0; -} - -int -persist_open(int *valid, int secs) -{ - int dirfd, fd; - const char *name; - - *valid = 0; - - if ((name = tsname()) == NULL) - errx(1, "failed to get timestamp name"); - if ((dirfd = opentsdir()) == -1) - errx(1, "opentsdir"); - - if ((fd = openat(dirfd, name, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1) - if (errno != ENOENT) - err(1, "open timestamp file"); - - if (fd == -1) { - if ((fd = openat(dirfd, name, (O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW), - (S_IRUSR|S_IWUSR))) == -1) - err(1, "open timestamp file"); - } - - size_t tssize; - if (checktsfile(fd, &tssize) == -1) - err(1, "checktsfile"); - - /* The timestamp size is 0 if its a new file or a - * timestamp that was never set, its not valid but - * can be used to write the new timestamp. - * If the size does not match the expected size it - * is incomplete and should never be used - */ - if (tssize == sizeof(struct timespec) * 2) - *valid = validts(fd, secs) == 0; - else if (tssize != 0) - errx(1, "corrupt timestamp file"); - - close(dirfd); - return fd; -} - -int -persist_clear() -{ - const char *name; - int dirfd; - if ((name = tsname()) == NULL) - errx(1, "failed to get timestamp name"); - if ((dirfd = opentsdir()) == -1) - errx(1, "opentsdir"); - if (unlinkat(dirfd, name, 0) == -1 && errno != ENOENT) - return -1; - close(dirfd); - return 0; -} diff --git a/timestamp.c b/timestamp.c @@ -0,0 +1,399 @@ +/* + * 1) Timestamp files and directories + * + * Timestamp files MUST NOT be accessible to users other than root, + * this includes the name, metadata and the content of timestamp files + * and directories. + * + * Symlinks can be used to create, manipulate or delete wrong files + * and directories. The Implementation MUST reject any symlinks for + * timestamp files or directories. + * + * To avoid race conditions the implementation MUST use the same + * file descriptor for permission checks and do read or write + * write operations after the permission checks. + * + * The timestamp files MUST be opened with openat(2) using the + * timestamp directory file descriptor. Permissions of the directory + * MUST be checked before opening the timestamp file descriptor. + * + * 2) Clock sources for timestamps + * + * Timestamp files MUST NOT rely on only one clock source, using the + * wall clock would allow to reset the clock to an earlier point in + * time to reuse a timestamp. + * + * The timestamp MUST consist of multiple clocks and MUST reject the + * timestamp if there is a change to any clock because there is no way + * to differentiate between malicious and legitimate clock changes. + * + * 3) Timestamp lifetime + * + * The implementation MUST NOT use the user controlled stdin, stdout + * and stderr file descriptors to determine the controlling terminal. + * On linux the /proc/$pid/stat file MUST be used to get the terminal + * number. + * + * There is no reliable way to determine the lifetime of a tty/pty. + * The start time of the session leader MUST be used as part of the + * timestamp to determine if the tty is still the same. + * If the start time of the session leader changed the timestamp MUST + * be rejected. + * + */ + +#include <sys/ioctl.h> +#include <sys/stat.h> +#include <sys/vfs.h> + +#if !defined(timespecisset) || \ + !defined(timespeccmp) || \ + !defined(timespecadd) +# include "sys-time.h" +#endif + +#include <ctype.h> +#include <dirent.h> +#include <err.h> +#include <errno.h> +#include <fcntl.h> +#include <limits.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> +#include <unistd.h> + +#include "includes.h" + +#ifndef TIMESTAMP_DIR +# define TIMESTAMP_DIR "/run/doas" +#endif + +#if defined(TIMESTAMP_TMPFS) && defined(__linux__) +# ifndef TMPFS_MAGIC +# define TMPFS_MAGIC 0x01021994 +# endif +#endif + +#ifdef __linux__ +/* Use tty_nr from /proc/self/stat instead of using + * ttyname(3), stdin, stdout and stderr are user + * controllable and would allow to reuse timestamps + * from another writable terminal. + * See https://www.sudo.ws/alerts/tty_tickets.html + */ +static int +proc_info(pid_t pid, int *ttynr, unsigned long long *starttime) +{ + char path[128]; + char buf[1024]; + char *p, *saveptr, *ep; + const char *errstr; + int fd, n; + + p = buf; + + if (snprintf(path, sizeof path, "/proc/%d/stat", pid) == -1) + return -1; + + if ((fd = open(path, O_RDONLY)) == -1) + return -1; + + while ((n = read(fd, p, buf + sizeof buf - p)) != 0) { + if (n == -1) { + if (errno == EAGAIN || errno == EINTR) + continue; + close(fd); + return -1; + } + p += n; + if (p >= buf + sizeof buf) + break; + } + close(fd); + + /* error if it contains NULL bytes */ + if (n != 0 || memchr(buf, '\0', p - buf)) + return -1; + + /* Get the 7th field, 5 fields after the last ')', + * (2th field) because the 5th field 'comm' can include + * spaces and closing paranthesis too. + * See https://www.sudo.ws/alerts/linux_tty.html + */ + if ((p = strrchr(buf, ')')) == NULL) + return -1; + + n = 2; + for ((p = strtok_r(p, " ", &saveptr)); p; + (p = strtok_r(NULL, " ", &saveptr))) { + switch (n++) { + case 7: + *ttynr = strtonum(p, INT_MIN, INT_MAX, &errstr); + if (errstr) + return -1; + break; + case 22: + errno = 0; + *starttime = strtoull(p, &ep, 10); + if (p == ep || + (errno == ERANGE && *starttime == ULLONG_MAX)) + return -1; + break; + } + if (n == 23) + break; + } + + return 0; +} +#else +#error "proc_info not implemented" +#endif + +/* The session prefix is the tty number, the pid + * of the session leader and the start time of the + * session leader. + */ +static const char * +session_prefix() +{ + static char prefix[128]; + int tty, fd; + unsigned long long starttime; + pid_t leader; + + if ((fd = open("/dev/tty", O_RDONLY)) == -1) + err(1, "open: /dev/tty"); + if (ioctl(fd, TIOCGSID, &leader) == -1) + err(1, "ioctl: failed to get session leader"); + close(fd); + + if (proc_info(leader, &tty, &starttime) == -1) + errx(1, "failed to get tty number"); + if (snprintf(prefix, sizeof prefix, ".%d_%d_%llu_", + tty, leader, starttime) == -1) + return NULL; + return prefix; +} + +static const char * +timestamp_name() +{ + static char name[128]; + pid_t ppid, sid; + const char *prefix; + + ppid = getppid(); + if ((sid = getsid(0)) == -1) + err(1, "getsid"); + if ((prefix = session_prefix()) == NULL) + return NULL; + if (snprintf(name, sizeof name, "%s_%d_%d", prefix, ppid, sid) == -1) + return NULL; + return name; +} + +static int +opentsdir() +{ + struct stat st; + int fd; + int isnew; + + fd = -1; + isnew = 0; + +reopen: + if ((fd = open(TIMESTAMP_DIR, O_RDONLY | O_DIRECTORY)) == -1) { + if (errno == ENOENT && isnew == 0) { + if (mkdir(TIMESTAMP_DIR, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0) + err(1, "mkdir"); + isnew = 1; + goto reopen; + } else { + err(1, "failed to open timestamp directory: %s", TIMESTAMP_DIR); + } + } + +recheck: + if (fstat(fd, &st) == -1) + err(1, "fstatat"); + + if ((st.st_mode & S_IFMT) != S_IFDIR) + errx(1, "timestamp directory is not a directory"); + if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0) + errx(1, "timestamp directory has wrong permissions"); + + if (isnew == 1) { + if (fchown(fd, 0, 0) == -1) + err(1, "fchown"); + isnew = 0; + goto recheck; + } else { + if (st.st_uid != 0 || st.st_gid != 0) + errx(1, "timestamp directory has wrong owner or group"); + } + +#if defined(TIMESTAMP_TMPFS) && defined(__linux__) + struct statfs sf; + if (fstatfs(fd, &sf) == -1) + err(1, "statfs"); + + if (sf.f_type != TMPFS_MAGIC) + errx(1, "timestamp directory not on tmpfs"); +#endif + + return fd; +} + +/* + * Returns 1 if the timestamp is valid, 0 if its invalid + */ +static int +timestamp_valid(int fd, int secs) +{ + struct timespec mono, real, ts_mono, ts_real, timeout; + + if (read(fd, &ts_mono, sizeof ts_mono) != sizeof ts_mono || + read(fd, &ts_real, sizeof ts_real) != sizeof ts_real) + err(1, "read"); + if (!timespecisset(&ts_mono) || !timespecisset(&ts_real)) + errx(1, "timespecisset"); + + if (clock_gettime(CLOCK_MONOTONIC_RAW, &mono) == -1 || + clock_gettime(CLOCK_REALTIME, &real) == -1) + err(1, "clock_gettime"); + + if (timespeccmp(&mono, &ts_mono, >) || + timespeccmp(&real, &ts_real, >)) + return 0; + + memset(&timeout, 0, sizeof timeout); + timeout.tv_sec = secs; + timespecadd(&timeout, &mono, &mono); + timespecadd(&timeout, &real, &real); + + if (timespeccmp(&mono, &ts_mono, <) || + timespeccmp(&real, &ts_real, <)) + errx(1, "timestamp is too far in the future"); + + return 1; +} + +int +timestamp_set(int fd, int secs) +{ + struct timespec mono, real, ts_mono, ts_real, timeout; + + if (clock_gettime(CLOCK_MONOTONIC_RAW, &mono) == -1 || + clock_gettime(CLOCK_REALTIME, &real) == -1) + err(1, "clock_gettime"); + + memset(&timeout, 0, sizeof timeout); + timeout.tv_sec = secs; + timespecadd(&timeout, &mono, &ts_mono); + timespecadd(&timeout, &real, &ts_real); + + if (lseek(fd, 0, SEEK_SET) == -1) + err(1, "lseek"); + if (ftruncate(fd, 0) == -1) + err(1, "ftruncate"); + if (write(fd, (void *)&ts_mono, sizeof ts_mono) != sizeof ts_mono || + write(fd, (void *)&ts_real, sizeof ts_real) != sizeof ts_real) + err(1, "write"); + + return 0; +} + +int +timestamp_open(int *valid, int secs) +{ + struct stat st; + int dirfd, fd; + gid_t gid; + const char *name; + + *valid = 0; + + if ((name = timestamp_name()) == NULL) + errx(1, "failed to get timestamp name"); + if ((dirfd = opentsdir()) == -1) + errx(1, "opentsdir"); + + if ((fd = openat(dirfd, name, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1) + if (errno != ENOENT) + err(1, "open timestamp file"); + + if (fd == -1) { + if ((fd = openat(dirfd, name, (O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW), + (S_IRUSR|S_IWUSR))) == -1) + err(1, "open timestamp file"); + } + + if (fstat(fd, &st) == -1) + err(1, "stat"); + if ((st.st_mode & S_IFMT) != S_IFREG) + errx(1, "timestamp is not a regular file"); + if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0) + errx(1, "timestamp file has wrong permissions"); + + gid = getegid(); + if (st.st_uid != 0 || st.st_gid != gid) + errx(1, "timestamp file has wrong owner or group"); + + /* The timestamp size is 0 if its a new file or a + * timestamp that was never set, its not valid but + * can be used to write the new timestamp. + * If the size does not match the expected size it + * is incomplete and should never be used + */ + if (st.st_size == sizeof (struct timespec) * 2) { + *valid = timestamp_valid(fd, secs); + } else if (st.st_size == 0) { + *valid = 0; + } else { + errx(1, "corrupt timestamp file"); + } + + close(dirfd); + return fd; +} + +int +timestamp_clear() +{ + struct dirent *ent; + DIR *dp; + const char *prefix; + int dirfd; + int ret = 0; + size_t plen; + + if ((prefix = session_prefix()) == NULL) + errx(1, "failed to get timestamp session prefix"); + plen = strlen(prefix); + + if ((dirfd = opentsdir()) == -1) + errx(1, "opentsdir"); + if ((dp = fdopendir(dirfd)) == NULL) + err(1, "fopendir"); + + /* + * Delete all files in the timestamp directory + * with the same session prefix. + */ + while ((ent = readdir(dp)) != NULL) { + if (ent->d_type != DT_REG) + continue; + if (strncmp(prefix, ent->d_name, plen) != 0) + continue; + if (unlinkat(dirfd, ent->d_name, 0) == -1) + ret = -1; + } + closedir(dp); + close(dirfd); + + return ret; +}