Properly handle read() and write() throughout the SSSD

We need to guarantee at all times that reads and writes complete
successfully. This means that they must be checked for returning
EINTR and EAGAIN, and all writes must be wrapped in a loop to
ensure that they do not truncate their output.

9 files changed, 131 insertions, 42 deletions

diff --git a/src/krb5_plugin/sssd_krb5_locator_plugin.c b/src/krb5_plugin/sssd_krb5_locator_plugin.c
index dfc9c197..70479efd 100644
--- a/src/krb5_plugin/sssd_krb5_locator_plugin.c
+++ b/src/krb5_plugin/sssd_krb5_locator_plugin.c
@@ -133,7 +133,7 @@ static int get_krb5info(const char *realm, struct sssd_ctx *ctx,
     memset(buf, 0, BUFSIZE+1);
     while (len != 0 && (ret = read(fd, p, len)) != 0) {
         if (ret == -1) {
-            if (errno == EINTR) continue;
+            if (errno == EINTR || errno == EAGAIN) continue;
             PLUGIN_DEBUG(("read failed [%d][%s].\n", errno, strerror(errno)));
             close(fd);
             goto done;
diff --git a/src/monitor/monitor.c b/src/monitor/monitor.c
index 8820d695..e52d7934 100644
--- a/src/monitor/monitor.c
+++ b/src/monitor/monitor.c
@@ -1372,7 +1372,7 @@ static void process_config_file(struct tevent_context *ev,
         len = read(file_ctx->mt_ctx->inotify_fd, buf+total_len,
                    event_size-total_len);
         if (len == -1) {
-            if (errno == EINTR) continue;
+            if (errno == EINTR || errno == EAGAIN) continue;
             DEBUG(0, ("Critical error reading inotify file descriptor.\n"));
             goto done;
         }
@@ -1393,7 +1393,7 @@ static void process_config_file(struct tevent_context *ev,
         while (total_len < in_event->len) {
             len = read(file_ctx->mt_ctx->inotify_fd, &name, in_event->len);
             if (len == -1) {
-                if (errno == EINTR) continue;
+                if (errno == EINTR || errno == EAGAIN) continue;
                 DEBUG(0, ("Critical error reading inotify file descriptor.\n"));
                 goto done;
             }
diff --git a/src/providers/krb5/krb5_common.c b/src/providers/krb5/krb5_common.c
index c78f0e60..fbc30889 100644
--- a/src/providers/krb5/krb5_common.c
+++ b/src/providers/krb5/krb5_common.c
@@ -158,6 +158,7 @@ errno_t write_krb5info_file(const char *realm, const char *server,
     TALLOC_CTX *tmp_ctx = NULL;
     const char *name_tmpl = NULL;
     int server_len;
+    ssize_t written;
 
     if (realm == NULL || *realm == '\0' || server == NULL || *server == '\0' ||
         service == NULL || service == '\0') {
@@ -203,14 +204,24 @@ errno_t write_krb5info_file(const char *realm, const char *server,
         goto done;
     }
 
-    ret = write(fd, server, server_len);
-    if (ret == -1) {
-        DEBUG(1, ("write failed [%d][%s].\n", errno, strerror(errno)));
-        goto done;
+    written = 0;
+    while (written < server_len) {
+        ret = write(fd, server+written, server_len-written);
+        if (ret == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("write failed [%d][%s].\n", errno, strerror(errno)));
+            goto done;
+        }
+        else {
+            written += ret;
+        }
     }
-    if (ret != server_len) {
-        DEBUG(1, ("Partial write occured, this should never happen.\n"));
-        ret = EINTR;
+
+    if (written != server_len) {
+        DEBUG(1, ("Write error, wrote [%d] bytes, expected [%d]\n",
+                   written, server_len));
         goto done;
     }
 
diff --git a/src/sss_client/common.c b/src/sss_client/common.c
index 237b90ab..a4856e08 100644
--- a/src/sss_client/common.c
+++ b/src/sss_client/common.c
@@ -123,6 +123,7 @@ static enum nss_status sss_nss_send_req(enum sss_cli_command cmd,
             return NSS_STATUS_UNAVAIL;
         }
 
+        errno = 0;
         if (datasent < SSS_NSS_HEADER_SIZE) {
             res = write(sss_cli_sd,
                         (char *)header + datasent,
@@ -133,8 +134,15 @@ static enum nss_status sss_nss_send_req(enum sss_cli_command cmd,
                         (const char *)rd->data + rdsent,
                         rd->len - rdsent);
         }
+        error = errno;
 
         if ((res == -1) || (res == 0)) {
+            if ((error == EINTR) || error == EAGAIN) {
+                /* If the write was interrupted, go back through
+                 * the loop and try again
+                 */
+                continue;
+            }
 
             /* Write failed */
             sss_cli_close_socket();
@@ -217,6 +225,7 @@ static enum nss_status sss_nss_recv_rep(enum sss_cli_command cmd,
             return NSS_STATUS_UNAVAIL;
         }
 
+        errno = 0;
         if (datarecv < SSS_NSS_HEADER_SIZE) {
             res = read(sss_cli_sd,
                        (char *)header + datarecv,
@@ -227,8 +236,15 @@ static enum nss_status sss_nss_recv_rep(enum sss_cli_command cmd,
                        (char *)(*buf) + bufrecv,
                        header[0] - datarecv);
         }
+        error = errno;
 
         if ((res == -1) || (res == 0)) {
+            if ((error == EINTR) || error == EAGAIN) {
+                /* If the read was interrupted, go back through
+                 * the loop and try again
+                 */
+                continue;
+            }
 
             /* Read failed.  I think the only useful thing
              * we can do here is just return -1 and fail
diff --git a/src/sss_client/pam_sss.c b/src/sss_client/pam_sss.c
index 2faa3ad2..644073f5 100644
--- a/src/sss_client/pam_sss.c
+++ b/src/sss_client/pam_sss.c
@@ -489,7 +489,7 @@ static errno_t display_pw_reset_message(pam_handle_t *pamh,
     while (total_len < stat_buf.st_size) {
         ret = read(fd, msg_buf + total_len, stat_buf.st_size - total_len);
         if (ret == -1) {
-            if (errno == EINTR) continue;
+            if (errno == EINTR || errno == EAGAIN) continue;
             ret = errno;
             D(("read failed [%d][%s].", ret, strerror(ret)));
             goto done;
diff --git a/src/tools/files.c b/src/tools/files.c
index b3b516ea..27ebf72d 100644
--- a/src/tools/files.c
+++ b/src/tools/files.c
@@ -402,7 +402,7 @@ static int copy_file(const char *src,
     int ifd = -1;
     int ofd = -1;
     char buf[1024];
-    ssize_t cnt, written, offset;
+    ssize_t cnt, written, res;
     struct stat fstatbuf;
 
     ifd = open(src, O_RDONLY);
@@ -454,27 +454,44 @@ static int copy_file(const char *src,
         goto fail;
     }
 
-    while ((cnt = read(ifd, buf, sizeof(buf))) > 0) {
-        offset = 0;
-        while (cnt > 0) {
-            written = write(ofd, buf+offset, (size_t)cnt);
-            if (written == -1) {
-                ret = errno;
-                DEBUG(1, ("Cannot write() to source file '%s': [%d][%s].\n",
-                            dst, ret, strerror(ret)));
-                goto fail;
+    while ((cnt = read(ifd, buf, sizeof(buf))) != 0) {
+        if (cnt == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
             }
-            offset += written;
-            cnt -= written;
+
+            DEBUG(1, ("Cannot read() from source file '%s': [%d][%s].\n",
+                        src, ret, strerror(ret)));
+            goto fail;
+        }
+        else if (cnt > 0) {
+            /* Copy the buffer to the new file */
+            written = 0;
+            while (written < cnt) {
+                res = write(ofd, buf+written, (size_t)cnt-written);
+                if (res == -1) {
+                    ret = errno;
+                    if (ret == EINTR || ret == EAGAIN) {
+                        /* retry the write */
+                        continue;
+                    }
+                    DEBUG(1, ("Cannot write() to destination file '%s': [%d][%s].\n",
+                                dst, ret, strerror(ret)));
+                    goto fail;
+                }
+                else if (res <= 0) {
+                    DEBUG(1, ("Unexpected result from write(): [%d]\n", res));
+                    goto fail;
+                }
+
+                written += res;
+            }
+        }
+        else {
+            DEBUG(1, ("Unexpected return code of read [%d]\n", cnt));
+            goto fail;
         }
     }
-    if (cnt == -1) {
-        ret = errno;
-        DEBUG(1, ("Cannot read() from source file '%s': [%d][%s].\n",
-                    dst, ret, strerror(ret)));
-        goto fail;
-    }
-
 
     ret = close(ifd);
     ifd = -1;
diff --git a/src/util/backup_file.c b/src/util/backup_file.c
index cf9ddf30..99079327 100644
--- a/src/util/backup_file.c
+++ b/src/util/backup_file.c
@@ -86,7 +86,7 @@ int backup_file(const char *src_file, int dbglvl)
     while (1) {
         num = read(src_fd, buf, BUFFER_SIZE);
         if (num < 0) {
-            if (errno == EINTR) continue;
+            if (errno == EINTR || errno == EAGAIN) continue;
             ret = errno;
             DEBUG(dbglvl, ("Error (%d [%s]) reading from source %s\n",
                            ret, strerror(ret), src_file));
@@ -101,7 +101,7 @@ int backup_file(const char *src_file, int dbglvl)
             errno = 0;
             num = write(dst_fd, &buf[pos], count);
             if (num < 0) {
-                if (errno == EINTR) continue;
+                if (errno == EINTR || errno == EAGAIN) continue;
                 ret = errno;
                 DEBUG(dbglvl, ("Error (%d [%s]) writing to destination %s\n",
                                ret, strerror(ret), dst_file));
diff --git a/src/util/find_uid.c b/src/util/find_uid.c
index 965966ef..952aeea4 100644
--- a/src/util/find_uid.c
+++ b/src/util/find_uid.c
@@ -100,10 +100,15 @@ static errno_t get_uid_from_pid(const pid_t pid, uid_t *uid)
         DEBUG(1, ("open failed [%d][%s].\n", errno, strerror(errno)));
         return errno;
     }
-    ret = read(fd, buf, BUFSIZE);
-    if (ret == -1) {
-        DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
-        return errno;
+
+    while ((ret = read(fd, buf, BUFSIZE)) != 0) {
+        if (ret == -1) {
+            if (errno == EINTR || errno == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
+            return errno;
+        }
     }
 
     ret = close(fd);
diff --git a/src/util/server.c b/src/util/server.c
index 007b3624..8f5b4414 100644
--- a/src/util/server.c
+++ b/src/util/server.c
@@ -104,6 +104,10 @@ int pidfile(const char *path, const char *name)
     char *file;
     int fd;
     int ret, err;
+    ssize_t len;
+    ssize_t size;
+    ssize_t written;
+    ssize_t pidlen = sizeof(pid_str - 1);
 
     file = talloc_asprintf(NULL, "%s/%s.pid", path, name);
     if (!file) {
@@ -114,9 +118,30 @@ int pidfile(const char *path, const char *name)
     err = errno;
     if (fd != -1) {
 
-        pid_str[sizeof(pid_str) -1] = '\0';
-        ret = read(fd, pid_str, sizeof(pid_str) -1);
-        if (ret > 0) {
+        pid_str[pidlen] = '\0';
+
+
+        while ((ret = read(fd, pid_str + len, pidlen - len)) != 0) {
+            if (ret == -1) {
+                if (errno == EINTR || errno == EAGAIN) {
+                    continue;
+                }
+                DEBUG(1, ("read failed [%d][%s].\n", errno, strerror(errno)));
+                break;
+            } else if (ret > 0) {
+                len += ret;
+                if (len > pidlen) {
+                    DEBUG(1, ("read too much, this should never happen.\n"));
+                    break;
+                }
+                continue;
+            } else {
+                DEBUG(1, ("unexpected return code of read [%d].\n", ret));
+                break;
+            }
+        }
+
+        if (ret == 0) {
             /* let's check the pid */
 
             pid = (pid_t)atoi(pid_str);
@@ -159,10 +184,25 @@ int pidfile(const char *path, const char *name)
 
     memset(pid_str, 0, sizeof(pid_str));
     snprintf(pid_str, sizeof(pid_str) -1, "%u\n", (unsigned int) getpid());
+    size = strlen(pid_str);
+
+    written = 0;
+    while (written < size) {
+        ret = write(fd, pid_str+written, size-written);
+        if (ret == -1) {
+            err = errno;
+            if (err == EINTR || err == EAGAIN) {
+                continue;
+            }
+            DEBUG(1, ("write failed [%d][%s]\n", err, strerror(err)));
+            break;
+        }
+        else {
+            written += ret;
+        }
+    }
 
-    ret = write(fd, pid_str, strlen(pid_str));
-    err = errno;
-    if (ret != strlen(pid_str)) {
+    if (written != size) {
         close(fd);
         return err;
     }