Enable the use of the kernel __realpath() system call in the libc wrapper.

For now, this also still uses the existing realpath implmentation
and emits a syslog if we see differening results. Once we have run
with that for a little while we will remove the old code

ok deraadt@

1 files changed, 136 insertions, 3 deletions

diff --git a/src/lib/libc/stdlib/realpath.c b/src/lib/libc/stdlib/realpath.c
index 5d226d9abc..76f88562fb 100644
--- a/src/lib/libc/stdlib/realpath.c
+++ b/src/lib/libc/stdlib/realpath.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: realpath.c,v 1.22 2017/12/24 01:50:50 millert Exp $ */
+/*      $OpenBSD: realpath.c,v 1.23 2019/05/28 13:08:56 beck Exp $ */
 /*
  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
  *
@@ -32,6 +32,8 @@
 #include <string.h>
 #include <unistd.h>
 #include <limits.h>
+#include <syslog.h>
+#include <stdarg.h>
 
 /* A slightly modified copy of this file exists in libexec/ld.so */
 
@@ -42,8 +44,8 @@
  * components.  Returns (resolved) on success, or (NULL) on failure,
  * in which case the path which caused trouble is left in (resolved).
  */
-char *
-realpath(const char *path, char *resolved)
+static char *
+urealpath(const char *path, char *resolved)
 {
         const char *p;
         char *q;
@@ -51,6 +53,7 @@ realpath(const char *path, char *resolved)
         unsigned symlinks;
         int serrno, mem_allocated;
         ssize_t slen;
+        int trailingslash = 0;
         char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
 
         if (path == NULL) {
@@ -231,3 +234,133 @@ err:
                 free(resolved);
         return (NULL);
 }
+
+/*
+ * Copyright (c) 2019 Bob Beck <beck@openbsd.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+int __realpath(const char *pathname, char *resolved);
+PROTO_NORMAL(__realpath);
+
+/*
+ * wrapper for kernel __realpath
+ */
+
+char *
+realpath(const char *path, char *resolved)
+{
+        char pbuf[PATH_MAX], rbuf[PATH_MAX], expected[PATH_MAX];
+        struct syslog_data sdata = SYSLOG_DATA_INIT;
+        int usererrno = 0, kernelerrno = 0, trailingslash = 0, save_errno;
+        int kernelonly = (getenv("USE_KERNEL_REALPATH") != NULL);
+        ssize_t i;
+
+        rbuf[0] = pbuf[0] = expected[0] = '\0';
+
+        if (!kernelonly) {
+                memset(expected, 0, sizeof(expected));
+                if (urealpath(path, expected) == NULL) {
+                        usererrno = errno;
+                        expected[0] = '\0';
+                }
+        }
+
+        if (path == NULL) {
+                kernelerrno = EINVAL;
+                goto out;
+        }
+        if (path[0] == '\0') {
+                kernelerrno = ENOENT;
+                goto out;
+        }
+        if (strlcat(pbuf, path, sizeof(pbuf)) >= sizeof(pbuf)) {
+                kernelerrno = ENAMETOOLONG;
+                goto out;
+        }
+
+        if (pbuf[strlen(pbuf) - 1] == '/')
+                trailingslash = 1;
+
+        if (__realpath(pbuf, rbuf) == -1)
+                kernelerrno = errno;
+
+        /*
+         * XXX XXX XXX
+         *
+         * The old userland implementation strips trailing slashes.
+         * According to Dr. POSIX, realpathing "/bsd" should be fine,
+         * realpathing "/bsd/" should return ENOTDIR.
+         *
+         * Similar, but *different* to the above, The old userland
+         * implementation allows for realpathing "/nonexistent" but
+         * not "/nonexistent/", Both those should return ENOENT
+         * according to POSIX.
+         *
+         * This hack should go away once we decide to match POSIX.
+         * which we should as soon as is convenient.
+         */
+        if (kernelerrno == ENOTDIR) {
+                /* Try again without the trailing slash. */
+                kernelerrno = 0;
+                for (i = strlen(pbuf); i > 1 && pbuf[i - 1] == '/'; i--)
+                        pbuf[i - 1] = '\0';
+                rbuf[0] = '\0';
+                if (__realpath(pbuf, rbuf) == -1)
+                        kernelerrno = errno;
+        }
+
+out:
+        if (!kernelonly) {
+                /* syslog if kernel and userland are different */
+                save_errno = errno;
+                if (strcmp(rbuf, expected) != 0 || (usererrno == 0 &&
+                    kernelerrno != 0))
+                        syslog_r(LOG_CRIT | LOG_CONS, &sdata,
+                            "realpath '%s' -> '%s' errno %d, "
+                            "expected '%s' errno %d", path, rbuf,
+                            kernelerrno, expected, usererrno);
+                errno = save_errno;
+
+                /* use userland result */
+                if (usererrno) {
+                        errno = usererrno;
+                        return NULL;
+                }
+                else
+                        errno = 0;
+                if (resolved == NULL)
+                        resolved = strdup(expected);
+                else if (strlcpy(resolved, expected, PATH_MAX) >= PATH_MAX) {
+                        errno = ENAMETOOLONG;
+                        return NULL;
+                }
+
+        } else {
+                /* use kernel result */
+                if (kernelerrno) {
+                        errno = kernelerrno;
+                        return NULL;
+                }
+                else
+                        errno = 0;
+                if (resolved == NULL)
+                        resolved = strdup(rbuf);
+                else if (strlcpy(resolved, rbuf, PATH_MAX) >= PATH_MAX) {
+                        errno = ENAMETOOLONG;
+                        return NULL;
+                }
+        }
+        return (resolved);
+}