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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:16:13 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:16:13 +0000 |
commit | e90fcc54809db2591dc083f43ef54c6ec8c60847 (patch) | |
tree | f20bc206c3c2d5d59d37c46c5cf5d53a20642556 /src/exim_lock.c | |
parent | Initial commit. (diff) | |
download | exim4-e90fcc54809db2591dc083f43ef54c6ec8c60847.tar.xz exim4-e90fcc54809db2591dc083f43ef54c6ec8c60847.zip |
Adding upstream version 4.96.upstream/4.96upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/exim_lock.c | 663 |
1 files changed, 663 insertions, 0 deletions
diff --git a/src/exim_lock.c b/src/exim_lock.c new file mode 100644 index 0000000..427d22c --- /dev/null +++ b/src/exim_lock.c @@ -0,0 +1,663 @@ +/* A program to lock a file exactly as Exim would, for investigation of +interlocking problems. + +Options: -fcntl use fcntl() lock + -flock use flock() lock + -lockfile use lock file + -mbx use mbx locking rules, with either fcntl() or flock() + +Default is -fcntl -lockfile. + +Argument: the name of the lock file + +Copyright (c) The Exim Maintainers 2016 - 2021 +*/ + +#include "os.h" + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <signal.h> +#include <errno.h> +#include <time.h> +#include <netdb.h> +#include <fcntl.h> +#include <unistd.h> +#include <utime.h> +#include <sys/utsname.h> +#include <sys/stat.h> +#include <sys/file.h> +#include <pwd.h> + +/* Not all systems have flock() available. Those that do must define LOCK_SH +in sys/file.h. */ + +#ifndef LOCK_SH +#define NO_FLOCK +#endif + + +typedef unsigned BOOL; +#define FALSE 0 +#define TRUE 1 + + +/* Flag for timeout signal handler */ + +static int sigalrm_seen = FALSE; + + +/* We need to pull in strerror() and os_non_restarting_signal() from the +os.c source, if they are required for this OS. However, we don't need any of +the other stuff in os.c, so force the other macros to omit it. */ + +#ifndef OS_RESTARTING_SIGNAL + #define OS_RESTARTING_SIGNAL +#endif + +#ifndef OS_STRSIGNAL + #define OS_STRSIGNAL +#endif + +#ifndef OS_STREXIT + #define OS_STREXIT +#endif + +#ifndef OS_LOAD_AVERAGE + #define OS_LOAD_AVERAGE +#endif + +#ifndef FIND_RUNNING_INTERFACES + #define FIND_RUNNING_INTERFACES +#endif + +#ifndef OS_GET_DNS_RESOLVER_RES + #define OS_GET_DNS_RESOLVER_RES +#endif + +#include "../src/os.c" + + + +/************************************************* +* Timeout handler * +*************************************************/ + +static void +sigalrm_handler(int sig) +{ +sigalrm_seen = TRUE; +} + + + +/************************************************* +* Give usage and die * +*************************************************/ + +static void +usage(void) +{ +printf("usage: exim_lock [-v] [-q] [-lockfile] [-fcntl] [-flock] [-mbx]\n" + " [-retries <n>] [-interval <n>] [-timeout <n>] [-restore-times]\n" + " <file name> [command]\n"); +exit(1); +} + + + +/************************************************* +* Apply a lock to a file descriptor * +*************************************************/ + +static int +apply_lock(int fd, int fcntltype, BOOL dofcntl, int fcntltime, BOOL doflock, + int flocktime) +{ +int yield = 0; +int save_errno; +struct flock lock_data; +lock_data.l_type = fcntltype; +lock_data.l_whence = lock_data.l_start = lock_data.l_len = 0; + +sigalrm_seen = FALSE; + +if (dofcntl) + { + if (fcntltime > 0) + { + os_non_restarting_signal(SIGALRM, sigalrm_handler); + alarm(fcntltime); + yield = fcntl(fd, F_SETLKW, &lock_data); + save_errno = errno; + alarm(0); + errno = save_errno; + } + else yield = fcntl(fd, F_SETLK, &lock_data); + if (yield < 0) printf("exim_lock: fcntl() failed: %s\n", strerror(errno)); + } + +#ifndef NO_FLOCK +if (doflock && (yield >= 0)) + { + int flocktype = (fcntltype == F_WRLCK)? LOCK_EX : LOCK_SH; + if (flocktime > 0) + { + os_non_restarting_signal(SIGALRM, sigalrm_handler); + alarm(flocktime); + yield = flock(fd, flocktype); + save_errno = errno; + alarm(0); + errno = save_errno; + } + else yield = flock(fd, flocktype | LOCK_NB); + if (yield < 0) printf("exim_lock: flock() failed: %s\n", strerror(errno)); + } +#endif + +return yield; +} + + + +/************************************************* +* The exim_lock program * +*************************************************/ + +int main(int argc, char **argv) +{ +int lock_retries = 10; +int lock_interval = 3; +int lock_fcntl_timeout = 0; +int lock_flock_timeout = 0; +int i, j, len; +int fd = -1; +int hd = -1; +int md = -1; +int yield = 0; +time_t now = time(NULL); +BOOL use_lockfile = FALSE; +BOOL use_fcntl = FALSE; +BOOL use_flock = FALSE; +BOOL use_mbx = FALSE; +BOOL verbose = FALSE; +BOOL quiet = FALSE; +BOOL restore_times = FALSE; +char *filename; +char *lockname = NULL, *hitchname = NULL; +char *primary_hostname; +const char *command; +struct utsname s; +char buffer[256]; +char tempname[256]; + +/* Decode options */ + +for (i = 1; i < argc; i++) + { + char *arg = argv[i]; + if (*arg != '-') break; + if (strcmp(arg, "-fcntl") == 0) use_fcntl = TRUE; + else if (strcmp(arg, "-flock") == 0) use_flock = TRUE; + else if (strcmp(arg, "-lockfile") == 0) use_lockfile = TRUE; + else if (strcmp(arg, "-mbx") == 0) use_mbx = TRUE; + else if (strcmp(arg, "-v") == 0) verbose = TRUE; + else if (strcmp(arg, "-q") == 0) quiet = TRUE; + else if (strcmp(arg, "-restore-times") == 0) restore_times = TRUE; + else if (++i < argc) + { + int value = atoi(argv[i]); + if (strcmp(arg, "-retries") == 0) lock_retries = value; + else if (strcmp(arg, "-interval") == 0) lock_interval = value; + else if (strcmp(arg, "-timeout") == 0) + lock_fcntl_timeout = lock_flock_timeout = value; + else usage(); + } + else usage(); + } + +if (quiet) verbose = FALSE; + +/* Can't use flock() if the OS doesn't provide it */ + +#ifdef NO_FLOCK +if (use_flock) + { + printf("exim_lock: can't use flock() because it was not available in the\n" + " operating system when exim_lock was compiled\n"); + exit(1); + } +#endif + +/* Default is to use lockfiles and fcntl(). */ + +if (!use_lockfile && !use_fcntl && !use_flock && !use_mbx) + use_lockfile = use_fcntl = TRUE; + +/* Default fcntl() for use with mbx */ + +if (use_mbx && !use_fcntl && !use_flock) use_fcntl = TRUE; + +/* Unset unused timeouts */ + +if (!use_fcntl) lock_fcntl_timeout = 0; +if (!use_flock) lock_flock_timeout = 0; + +/* A file name is required */ + +if (i >= argc) usage(); + +filename = argv[i++]; + +/* Expand file names starting with ~ */ + +if (*filename == '~') + { + struct passwd *pw; + + if (*(++filename) == '/') + pw = getpwuid(getuid()); + else + { + char *s = buffer; + while (*filename != 0 && *filename != '/') + *s++ = *filename++; + *s = 0; + pw = getpwnam(buffer); + } + + if (pw == NULL) + { + printf("exim_lock: unable to expand file name %s\n", argv[i-1]); + exit(1); + } + + if ((int)strlen(pw->pw_dir) + (int)strlen(filename) + 1 > sizeof(buffer)) + { + printf("exim_lock: expanded file name %s%s is too long", pw->pw_dir, + filename); + exit(1); + } + + strcpy(buffer, pw->pw_dir); + strcat(buffer, filename); + filename = buffer; + } + +/* If using a lock file, prepare by creating the lock file name and +the hitching post name. */ + +if (use_lockfile) + { + if (uname(&s) < 0) + { + printf("exim_lock: failed to find host name using uname()\n"); + exit(1); + } + primary_hostname = s.nodename; + + len = (int)strlen(filename); + lockname = malloc(len + 8); + sprintf(lockname, "%s.lock", filename); + hitchname = malloc(len + 32 + (int)strlen(primary_hostname)); + + /* Presumably, this must match appendfile.c */ + sprintf(hitchname, "%s.%s.%08x.%08x", lockname, primary_hostname, + (unsigned int)now, (unsigned int)getpid()); + + if (verbose) + printf("exim_lock: lockname = %s\n hitchname = %s\n", lockname, + hitchname); + } + +/* Locking retry loop */ + +for (j = 0; j < lock_retries; j++) + { + int sleep_before_retry = TRUE; + struct stat statbuf, ostatbuf, lstatbuf, statbuf2; + int mbx_tmp_oflags; + + /* Try to build a lock file if so configured */ + + if (use_lockfile) + { + int rc, rc2; + if (verbose) printf("exim_lock: creating lock file\n"); + hd = open(hitchname, O_WRONLY | O_CREAT | O_EXCL, 0440); + if (hd < 0) + { + printf("exim_lock: failed to create hitching post %s: %s\n", hitchname, + strerror(errno)); + exit(1); + } + + /* Apply hitching post algorithm. */ + + if ((rc = link(hitchname, lockname)) != 0) + rc2 = fstat(hd, &statbuf); + (void)close(hd); + unlink(hitchname); + + if (rc != 0 && (rc2 != 0 || statbuf.st_nlink != 2)) + { + printf("exim_lock: failed to link hitching post to lock file\n"); + hd = -1; + goto RETRY; + } + + if (!quiet) printf("exim_lock: lock file successfully created\n"); + } + + /* We are done if no other locking required. */ + + if (!use_fcntl && !use_flock && !use_mbx) break; + + /* Open the file for writing. */ + + if ((fd = open(filename, O_RDWR + O_APPEND)) < 0) + { + printf("exim_lock: failed to open %s for writing: %s\n", filename, + strerror(errno)); + yield = 1; + goto CLEAN_UP; + } + + /* If there is a timeout, implying blocked locking, we don't want to + sleep before any retries after this. */ + + if (lock_fcntl_timeout > 0 || lock_flock_timeout > 0) + sleep_before_retry = FALSE; + + /* Lock using fcntl. There are pros and cons to using a blocking call vs + a non-blocking call and retries. Exim is non-blocking by default, but setting + a timeout changes it to blocking. */ + + if (!use_mbx && (use_fcntl || use_flock)) + if (apply_lock(fd, F_WRLCK, use_fcntl, lock_fcntl_timeout, use_flock, + lock_flock_timeout) >= 0) + { + if (!quiet) + { + if (use_fcntl) printf("exim_lock: fcntl() lock successfully applied\n"); + if (use_flock) printf("exim_lock: flock() lock successfully applied\n"); + } + break; + } + else + goto RETRY; /* Message already output */ + + /* Lock using MBX rules. This is complicated and is documented with the + source of the c-client library that goes with Pine and IMAP. What has to + be done to interwork correctly is to take out a shared lock on the mailbox, + and an exclusive lock on a /tmp file. */ + + else + { + if (apply_lock(fd, F_RDLCK, use_fcntl, lock_fcntl_timeout, use_flock, + lock_flock_timeout) >= 0) + { + if (!quiet) + { + if (use_fcntl) + printf("exim_lock: fcntl() read lock successfully applied\n"); + if (use_flock) + printf("exim_lock: fcntl() read lock successfully applied\n"); + } + } + else goto RETRY; /* Message already output */ + + if (fstat(fd, &statbuf) < 0) + { + printf("exim_lock: fstat() of %s failed: %s\n", filename, + strerror(errno)); + yield = 1; + goto CLEAN_UP; + } + + /* Set up file in /tmp and check its state if already existing. */ + + sprintf(tempname, "/tmp/.%lx.%lx", (long)statbuf.st_dev, + (long)statbuf.st_ino); + + if (lstat(tempname, &statbuf) >= 0) + { + if ((statbuf.st_mode & S_IFMT) == S_IFLNK) + { + printf("exim_lock: symbolic link on lock name %s\n", tempname); + yield = 1; + goto CLEAN_UP; + } + if (statbuf.st_nlink > 1) + { + printf("exim_lock: hard link to lock name %s\n", tempname); + yield = 1; + goto CLEAN_UP; + } + } + + mbx_tmp_oflags = O_RDWR | O_CREAT; +#ifdef O_NOFOLLOW + mbx_tmp_oflags |= O_NOFOLLOW; +#endif + md = open(tempname, mbx_tmp_oflags, 0600); + if (md < 0) + { + printf("exim_lock: failed to create mbx lock file %s: %s\n", + tempname, strerror(errno)); + goto CLEAN_UP; + } + + /* security fixes from 2010-05 */ + if (lstat(tempname, &lstatbuf) < 0) + { + printf("exim_lock: failed to lstat(%s) after opening it: %s\n", + tempname, strerror(errno)); + goto CLEAN_UP; + } + if (fstat(md, &statbuf2) < 0) + { + printf("exim_lock: failed to fstat() open fd of \"%s\": %s\n", + tempname, strerror(errno)); + goto CLEAN_UP; + } + if ((statbuf2.st_nlink > 1) || + (lstatbuf.st_nlink > 1) || + (!S_ISREG(lstatbuf.st_mode)) || + (lstatbuf.st_dev != statbuf2.st_dev) || + (lstatbuf.st_ino != statbuf2.st_ino)) + { + printf("exim_lock: race condition exploited against us when " + "locking \"%s\"\n", tempname); + goto CLEAN_UP; + } + + (void)chmod(tempname, 0600); + + if (apply_lock(md, F_WRLCK, use_fcntl, lock_fcntl_timeout, use_flock, + lock_flock_timeout) >= 0) + { + if (!quiet) + { + if (use_fcntl) + printf("exim_lock: fcntl() lock successfully applied to mbx " + "lock file %s\n", tempname); + if (use_flock) + printf("exim_lock: flock() lock successfully applied to mbx " + "lock file %s\n", tempname); + } + + /* This test checks for a race condition */ + + if (lstat(tempname, &statbuf) != 0 || + fstat(md, &ostatbuf) != 0 || + statbuf.st_dev != ostatbuf.st_dev || + statbuf.st_ino != ostatbuf.st_ino) + { + if (!quiet) printf("exim_lock: mbx lock file %s changed between " + "creation and locking\n", tempname); + goto RETRY; + } + else break; + } + else goto RETRY; /* Message already output */ + } + + /* Clean up before retrying */ + + RETRY: + + if (md >= 0) + { + if (close(md) < 0) + printf("exim_lock: close %s failed: %s\n", tempname, strerror(errno)); + else + if (!quiet) printf("exim_lock: %s closed\n", tempname); + md = -1; + } + + if (fd >= 0) + { + if (close(fd) < 0) + printf("exim_lock: close failed: %s\n", strerror(errno)); + else + if (!quiet) printf("exim_lock: file closed\n"); + fd = -1; + } + + if (hd >= 0) + { + if (unlink(lockname) < 0) + printf("exim_lock: unlink of %s failed: %s\n", lockname, strerror(errno)); + else + if (!quiet) printf("exim_lock: lock file removed\n"); + hd = -1; + } + + /* If a blocking call timed out, break the retry loop if the total time + so far is not less than than retries * interval. */ + + if (sigalrm_seen && + (j + 1) * ((lock_fcntl_timeout > lock_flock_timeout)? + lock_fcntl_timeout : lock_flock_timeout) >= + lock_retries * lock_interval) + j = lock_retries; + + /* Wait a bit before retrying, except when it was a blocked fcntl() that + caused the problem. */ + + if (j < lock_retries && sleep_before_retry) + { + printf(" ... waiting\n"); + sleep(lock_interval); + } + } + +if (j >= lock_retries) + { + printf("exim_lock: locking failed too many times\n"); + yield = 1; + goto CLEAN_UP; + } + +if (!quiet) printf("exim_lock: locking %s succeeded: ", filename); + +/* If there are no further arguments, run the user's shell; otherwise +the next argument is a command to run. */ + +if (i >= argc) + { + command = getenv("SHELL"); + if (command == NULL || *command == 0) command = "/bin/sh"; + if (!quiet) printf("running %s ...\n", command); + } +else + { + command = argv[i]; + if (!quiet) printf("running the command ...\n"); + } + +/* Run the command, saving and restoring the times if required. */ + +if (restore_times) + { + struct stat strestore; +#ifdef EXIM_HAVE_FUTIMENS + int fd = open(filename, O_RDWR); /* use fd for both get & restore */ + struct timespec tt[2]; + + if (fd < 0) + { + printf("open '%s': %s\n", filename, strerror(errno)); + yield = 1; + goto CLEAN_UP; + } + if (fstat(fd, &strestore) != 0) + { + printf("fstat '%s': %s\n", filename, strerror(errno)); + yield = 1; + close(fd); + goto CLEAN_UP; + } + i = system(command); + tt[0] = strestore.st_atim; + tt[1] = strestore.st_mtim; + (void) futimens(fd, tt); + (void) close(fd); +#else + struct utimbuf ut; + + stat(filename, &strestore); + i = system(command); + ut.actime = strestore.st_atime; + ut.modtime = strestore.st_mtime; + utime(filename, &ut); +#endif + } +else i = system(command); + +if(i && !quiet) printf("warning: nonzero status %d\n", i); + +/* Remove the locks and exit. Unlink the /tmp file if we can get an exclusive +lock on the mailbox. This should be a non-blocking lock call, as there is no +point in waiting. */ + +CLEAN_UP: + +if (md >= 0) + { + if (apply_lock(fd, F_WRLCK, use_fcntl, 0, use_flock, 0) >= 0) + { + if (!quiet) printf("exim_lock: %s unlinked - no sharers\n", tempname); + unlink(tempname); + } + else if (!quiet) + printf("exim_lock: %s not unlinked - unable to get exclusive mailbox lock\n", + tempname); + if (close(md) < 0) + printf("exim_lock: close %s failed: %s\n", tempname, strerror(errno)); + else + if (!quiet) printf("exim_lock: %s closed\n", tempname); + } + +if (fd >= 0) + { + if (close(fd) < 0) + printf("exim_lock: close %s failed: %s\n", filename, strerror(errno)); + else + if (!quiet) printf("exim_lock: %s closed\n", filename); + } + +if (hd >= 0) + { + if (unlink(lockname) < 0) + printf("exim_lock: unlink %s failed: %s\n", lockname, strerror(errno)); + else + if (!quiet) printf("exim_lock: lock file removed\n"); + } + +return yield; +} + +/* End */ |