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-rw-r--r--src/global/mypwd.c369
1 files changed, 369 insertions, 0 deletions
diff --git a/src/global/mypwd.c b/src/global/mypwd.c
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+/*++
+/* NAME
+/* mypwd 3
+/* SUMMARY
+/* caching getpwnam_r()/getpwuid_r()
+/* SYNOPSIS
+/* #include <mypwd.h>
+/*
+/* int mypwuid_err(uid, pwd)
+/* uid_t uid;
+/* struct mypasswd **pwd;
+/*
+/* int mypwnam_err(name, pwd)
+/* const char *name;
+/* struct mypasswd **pwd;
+/*
+/* void mypwfree(pwd)
+/* struct mypasswd *pwd;
+/* BACKWARDS COMPATIBILITY
+/* struct mypasswd *mypwuid(uid)
+/* uid_t uid;
+/*
+/* struct mypasswd *mypwnam(name)
+/* const char *name;
+/* DESCRIPTION
+/* This module maintains a reference-counted cache of password
+/* database lookup results. The idea is to avoid making repeated
+/* getpw*() calls for the same information.
+/*
+/* mypwnam_err() and mypwuid_err() are wrappers that cache a
+/* private copy of results from the getpwnam_r() and getpwuid_r()
+/* library routines (on legacy systems: from getpwnam() and
+/* getpwuid(). Note: cache updates are not protected by mutex.
+/*
+/* Results are shared between calls with the same \fIname\fR
+/* or \fIuid\fR argument, so changing results is verboten.
+/*
+/* mypwnam() and mypwuid() are binary-compatibility wrappers
+/* for legacy applications.
+/*
+/* mypwfree() cleans up the result of mypwnam*() and mypwuid*().
+/* BUGS
+/* This module is security sensitive and complex at the same
+/* time, which is bad.
+/* DIAGNOSTICS
+/* mypwnam_err() and mypwuid_err() return a non-zero system
+/* error code when the lookup could not be performed. They
+/* return zero, plus a null struct mypasswd pointer, when the
+/* requested information was not found.
+/*
+/* Fatal error: out of memory.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <unistd.h>
+#include <string.h>
+#ifdef USE_PATHS_H
+#include <paths.h>
+#endif
+#include <errno.h>
+
+/* Utility library. */
+
+#include <mymalloc.h>
+#include <htable.h>
+#include <binhash.h>
+#include <msg.h>
+
+/* Global library. */
+
+#include "mypwd.h"
+
+ /*
+ * Workaround: Solaris >= 2.5.1 provides two getpwnam_r() and getpwuid_r()
+ * implementations. The default variant is compatible with historical
+ * Solaris implementations. The non-default variant is POSIX-compliant.
+ *
+ * To get the POSIX-compliant variant, we include the file <pwd.h> after
+ * defining _POSIX_PTHREAD_SEMANTICS. We do this after all other includes,
+ * so that we won't unexpectedly affect any other APIs.
+ *
+ * This happens to work because nothing above this includes <pwd.h>, and
+ * because of the specific way that Solaris redefines getpwnam_r() and
+ * getpwuid_r() for POSIX compliance. We know the latter from peeking under
+ * the hood. What we do is only marginally better than directly invoking
+ * __posix_getpwnam_r() and __posix_getpwuid_r().
+ */
+#ifdef GETPW_R_NEEDS_POSIX_PTHREAD_SEMANTICS
+#define _POSIX_PTHREAD_SEMANTICS
+#endif
+#include <pwd.h>
+
+ /*
+ * The private cache. One for lookups by name, one for lookups by uid, and
+ * one for the last looked up result. There is a minor problem: multiple
+ * cache entries may have the same uid value, but the cache that is indexed
+ * by uid can store only one entry per uid value.
+ */
+static HTABLE *mypwcache_name = 0;
+static BINHASH *mypwcache_uid = 0;
+static struct mypasswd *last_pwd;
+
+ /*
+ * XXX Solaris promises that we can determine the getpw*_r() buffer size by
+ * calling sysconf(_SC_GETPW_R_SIZE_MAX). Many systems promise that they
+ * will return an ERANGE error when the buffer is too small. However, not
+ * all systems make such promises. Therefore, we settle for the dumbest
+ * option: a large buffer. This is acceptable because the buffer is used
+ * only for short-term storage.
+ */
+#ifdef HAVE_POSIX_GETPW_R
+#define GETPW_R_BUFSIZ 1024
+#endif
+#define MYPWD_ERROR_DELAY (30)
+
+/* mypwenter - enter password info into cache */
+
+static struct mypasswd *mypwenter(const struct passwd * pwd)
+{
+ struct mypasswd *mypwd;
+
+ /*
+ * Initialize on the fly.
+ */
+ if (mypwcache_name == 0) {
+ mypwcache_name = htable_create(0);
+ mypwcache_uid = binhash_create(0);
+ }
+ mypwd = (struct mypasswd *) mymalloc(sizeof(*mypwd));
+ mypwd->refcount = 0;
+ mypwd->pw_name = mystrdup(pwd->pw_name);
+ mypwd->pw_passwd = mystrdup(pwd->pw_passwd);
+ mypwd->pw_uid = pwd->pw_uid;
+ mypwd->pw_gid = pwd->pw_gid;
+ mypwd->pw_gecos = mystrdup(pwd->pw_gecos);
+ mypwd->pw_dir = mystrdup(pwd->pw_dir);
+ mypwd->pw_shell = mystrdup(*pwd->pw_shell ? pwd->pw_shell : _PATH_BSHELL);
+
+ /*
+ * Avoid mypwcache_uid memory leak when multiple names have the same UID.
+ * This makes the lookup result dependent on program history. But, it was
+ * already history-dependent before we added this extra check.
+ */
+ htable_enter(mypwcache_name, mypwd->pw_name, (void *) mypwd);
+ if (binhash_locate(mypwcache_uid, (void *) &mypwd->pw_uid,
+ sizeof(mypwd->pw_uid)) == 0)
+ binhash_enter(mypwcache_uid, (void *) &mypwd->pw_uid,
+ sizeof(mypwd->pw_uid), (void *) mypwd);
+ return (mypwd);
+}
+
+/* mypwuid - caching getpwuid() */
+
+struct mypasswd *mypwuid(uid_t uid)
+{
+ struct mypasswd *mypwd;
+
+ while ((errno = mypwuid_err(uid, &mypwd)) != 0) {
+ msg_warn("getpwuid_r: %m");
+ sleep(MYPWD_ERROR_DELAY);
+ }
+ return (mypwd);
+}
+
+/* mypwuid_err - caching getpwuid_r(), minus thread safety */
+
+int mypwuid_err(uid_t uid, struct mypasswd ** result)
+{
+ struct passwd *pwd;
+ struct mypasswd *mypwd;
+
+ /*
+ * See if this is the same user as last time.
+ */
+ if (last_pwd != 0) {
+ if (last_pwd->pw_uid != uid) {
+ mypwfree(last_pwd);
+ last_pwd = 0;
+ } else {
+ *result = mypwd = last_pwd;
+ mypwd->refcount++;
+ return (0);
+ }
+ }
+
+ /*
+ * Find the info in the cache or in the password database.
+ */
+ if ((mypwd = (struct mypasswd *)
+ binhash_find(mypwcache_uid, (void *) &uid, sizeof(uid))) == 0) {
+#ifdef HAVE_POSIX_GETPW_R
+ char pwstore[GETPW_R_BUFSIZ];
+ struct passwd pwbuf;
+ int err;
+
+ err = getpwuid_r(uid, &pwbuf, pwstore, sizeof(pwstore), &pwd);
+ if (err != 0)
+ return (err);
+ if (pwd == 0) {
+ *result = 0;
+ return (0);
+ }
+#else
+ if ((pwd = getpwuid(uid)) == 0) {
+ *result = 0;
+ return (0);
+ }
+#endif
+ mypwd = mypwenter(pwd);
+ }
+ *result = last_pwd = mypwd;
+ mypwd->refcount += 2;
+ return (0);
+}
+
+/* mypwnam - caching getpwnam() */
+
+struct mypasswd *mypwnam(const char *name)
+{
+ struct mypasswd *mypwd;
+
+ while ((errno = mypwnam_err(name, &mypwd)) != 0) {
+ msg_warn("getpwnam_r: %m");
+ sleep(MYPWD_ERROR_DELAY);
+ }
+ return (mypwd);
+}
+
+/* mypwnam_err - caching getpwnam_r(), minus thread safety */
+
+int mypwnam_err(const char *name, struct mypasswd ** result)
+{
+ struct passwd *pwd;
+ struct mypasswd *mypwd;
+
+ /*
+ * See if this is the same user as last time.
+ */
+ if (last_pwd != 0) {
+ if (strcmp(last_pwd->pw_name, name) != 0) {
+ mypwfree(last_pwd);
+ last_pwd = 0;
+ } else {
+ *result = mypwd = last_pwd;
+ mypwd->refcount++;
+ return (0);
+ }
+ }
+
+ /*
+ * Find the info in the cache or in the password database.
+ */
+ if ((mypwd = (struct mypasswd *) htable_find(mypwcache_name, name)) == 0) {
+#ifdef HAVE_POSIX_GETPW_R
+ char pwstore[GETPW_R_BUFSIZ];
+ struct passwd pwbuf;
+ int err;
+
+ err = getpwnam_r(name, &pwbuf, pwstore, sizeof(pwstore), &pwd);
+ if (err != 0)
+ return (err);
+ if (pwd == 0) {
+ *result = 0;
+ return (0);
+ }
+#else
+ if ((pwd = getpwnam(name)) == 0) {
+ *result = 0;
+ return (0);
+ }
+#endif
+ mypwd = mypwenter(pwd);
+ }
+ *result = last_pwd = mypwd;
+ mypwd->refcount += 2;
+ return (0);
+}
+
+/* mypwfree - destroy password info */
+
+void mypwfree(struct mypasswd * mypwd)
+{
+ if (mypwd->refcount < 1)
+ msg_panic("mypwfree: refcount %d", mypwd->refcount);
+
+ /*
+ * See mypwenter() for the reason behind the binhash_locate() test.
+ */
+ if (--mypwd->refcount == 0) {
+ htable_delete(mypwcache_name, mypwd->pw_name, (void (*) (void *)) 0);
+ if (binhash_locate(mypwcache_uid, (void *) &mypwd->pw_uid,
+ sizeof(mypwd->pw_uid)))
+ binhash_delete(mypwcache_uid, (void *) &mypwd->pw_uid,
+ sizeof(mypwd->pw_uid), (void (*) (void *)) 0);
+ myfree(mypwd->pw_name);
+ myfree(mypwd->pw_passwd);
+ myfree(mypwd->pw_gecos);
+ myfree(mypwd->pw_dir);
+ myfree(mypwd->pw_shell);
+ myfree((void *) mypwd);
+ }
+}
+
+#ifdef TEST
+
+ /*
+ * Test program. Look up a couple users and/or uid values and see if the
+ * results will be properly free()d.
+ */
+#include <stdlib.h>
+#include <ctype.h>
+#include <vstream.h>
+#include <msg_vstream.h>
+
+int main(int argc, char **argv)
+{
+ struct mypasswd **mypwd;
+ int i;
+
+ msg_vstream_init(argv[0], VSTREAM_ERR);
+ if (argc == 1)
+ msg_fatal("usage: %s name or uid ...", argv[0]);
+
+ mypwd = (struct mypasswd **) mymalloc((argc + 2) * sizeof(*mypwd));
+
+ /*
+ * Do a sequence of lookups.
+ */
+ for (i = 1; i < argc; i++) {
+ if (ISDIGIT(argv[i][0]))
+ mypwd[i] = mypwuid(atoi(argv[i]));
+ else
+ mypwd[i] = mypwnam(argv[i]);
+ if (mypwd[i] == 0)
+ msg_fatal("%s: not found", argv[i]);
+ msg_info("lookup %s %s/%d refcount=%d name_cache=%d uid_cache=%d",
+ argv[i], mypwd[i]->pw_name, mypwd[i]->pw_uid,
+ mypwd[i]->refcount, mypwcache_name->used, mypwcache_uid->used);
+ }
+ mypwd[argc] = last_pwd;
+
+ /*
+ * The following should free all entries.
+ */
+ for (i = 1; i < argc + 1; i++) {
+ msg_info("free %s/%d refcount=%d name_cache=%d uid_cache=%d",
+ mypwd[i]->pw_name, mypwd[i]->pw_uid, mypwd[i]->refcount,
+ mypwcache_name->used, mypwcache_uid->used);
+ mypwfree(mypwd[i]);
+ }
+ msg_info("name_cache=%d uid_cache=%d",
+ mypwcache_name->used, mypwcache_uid->used);
+
+ myfree((void *) mypwd);
+ return (0);
+}
+
+#endif
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