sd-id128: split UUID file read/write code into new id128-util.[ch]

We currently have code to read and write files containing UUIDs at various
places. Unify this in id128-util.[ch], and move some other stuff there too.

The new files are located in src/libsystemd/sd-id128/ (instead of src/shared/),
because they are actually the backend of sd_id128_get_machine() and
sd_id128_get_boot().

In follow-up patches we can use this reduce the code in nspawn and
machine-id-setup by adopted the common implementation.

3 files changed, 241 insertions, 89 deletions

diff --git a/src/libsystemd/sd-id128/id128-util.c b/src/libsystemd/sd-id128/id128-util.c
new file mode 100644
index 0000000000..c1742cab0e
--- /dev/null
+++ b/src/libsystemd/sd-id128/id128-util.c
@@ -0,0 +1,171 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <fcntl.h>
+
+#include "fd-util.h"
+#include "hexdecoct.h"
+#include "id128-util.h"
+#include "io-util.h"
+#include "stdio-util.h"
+
+char *id128_to_uuid_string(sd_id128_t id, char s[37]) {
+        unsigned n, k = 0;
+
+        assert(s);
+
+        /* Similar to sd_id128_to_string() but formats the result as UUID instead of plain hex chars */
+
+        for (n = 0; n < 16; n++) {
+
+                if (IN_SET(n, 4, 6, 8, 10))
+                        s[k++] = '-';
+
+                s[k++] = hexchar(id.bytes[n] >> 4);
+                s[k++] = hexchar(id.bytes[n] & 0xF);
+        }
+
+        assert(k == 36);
+
+        s[k] = 0;
+
+        return s;
+}
+
+bool id128_is_valid(const char *s) {
+        size_t i, l;
+
+        assert(s);
+
+        l = strlen(s);
+        if (l == 32) {
+
+                /* Plain formatted 128bit hex string */
+
+                for (i = 0; i < l; i++) {
+                        char c = s[i];
+
+                        if (!(c >= '0' && c <= '9') &&
+                            !(c >= 'a' && c <= 'z') &&
+                            !(c >= 'A' && c <= 'Z'))
+                                return false;
+                }
+
+        } else if (l == 36) {
+
+                /* Formatted UUID */
+
+                for (i = 0; i < l; i++) {
+                        char c = s[i];
+
+                        if ((i == 8 || i == 13 || i == 18 || i == 23)) {
+                                if (c != '-')
+                                        return false;
+                        } else {
+                                if (!(c >= '0' && c <= '9') &&
+                                    !(c >= 'a' && c <= 'z') &&
+                                    !(c >= 'A' && c <= 'Z'))
+                                        return false;
+                        }
+                }
+
+        } else
+                return false;
+
+        return true;
+}
+
+int id128_read_fd(int fd, Id128Format f, sd_id128_t *ret) {
+        char buffer[36 + 2];
+        ssize_t l;
+
+        assert(fd >= 0);
+        assert(f < _ID128_FORMAT_MAX);
+
+        /* Reads an 128bit ID from a file, which may either be in plain format (32 hex digits), or in UUID format, both
+         * followed by a newline and nothing else. */
+
+        l = loop_read(fd, buffer, sizeof(buffer), false); /* we expect a short read of either 33 or 37 chars */
+        if (l < 0)
+                return (int) l;
+        if (l == 0) /* empty? */
+                return -ENOMEDIUM;
+
+        if (l == 33) {
+                if (f == ID128_UUID)
+                        return -EINVAL;
+
+                if (buffer[32] != '\n')
+                        return -EINVAL;
+
+                buffer[32] = 0;
+
+        } else if (l == 37) {
+                if (f == ID128_PLAIN)
+                        return -EINVAL;
+
+                if (buffer[36] != '\n')
+                        return -EINVAL;
+
+                buffer[36] = 0;
+        } else
+                return -EINVAL;
+
+        return sd_id128_from_string(buffer, ret);
+}
+
+int id128_read(const char *p, Id128Format f, sd_id128_t *ret) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open(p, O_RDONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return -errno;
+
+        return id128_read_fd(fd, f, ret);
+}
+
+int id128_write_fd(int fd, Id128Format f, sd_id128_t id) {
+        char buffer[36 + 2];
+        size_t sz;
+
+        assert(fd >= 0);
+        assert(f < _ID128_FORMAT_MAX);
+
+        if (f != ID128_UUID) {
+                sd_id128_to_string(id, buffer);
+                buffer[32] = '\n';
+                sz = 33;
+        } else {
+                id128_to_uuid_string(id, buffer);
+                buffer[36] = '\n';
+                sz = 37;
+        }
+
+        return loop_write(fd, buffer, sz, false);
+}
+
+int id128_write(const char *p, Id128Format f, sd_id128_t id) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open(p, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
+        if (fd < 0)
+                return -errno;
+
+        return id128_write_fd(fd, f, id);
+}
diff --git a/src/libsystemd/sd-id128/id128-util.h b/src/libsystemd/sd-id128/id128-util.h
new file mode 100644
index 0000000000..73e4c710c4
--- /dev/null
+++ b/src/libsystemd/sd-id128/id128-util.h
@@ -0,0 +1,45 @@
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdbool.h>
+
+#include "sd-id128.h"
+#include "macro.h"
+
+char *id128_to_uuid_string(sd_id128_t id, char s[37]);
+
+/* Like SD_ID128_FORMAT_STR, but formats as UUID, not in plain format */
+#define ID128_UUID_FORMAT_STR "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x"
+
+bool id128_is_valid(const char *s) _pure_;
+
+typedef enum Id128Format {
+        ID128_ANY,
+        ID128_PLAIN,  /* formatted as 32 hex chars as-is */
+        ID128_UUID,   /* formatted as 36 character uuid string */
+        _ID128_FORMAT_MAX,
+} Id128Format;
+
+int id128_read_fd(int fd, Id128Format f, sd_id128_t *ret);
+int id128_read(const char *p, Id128Format f, sd_id128_t *ret);
+
+int id128_write_fd(int fd, Id128Format f, sd_id128_t id);
+int id128_write(const char *p, Id128Format f, sd_id128_t id);
diff --git a/src/libsystemd/sd-id128/sd-id128.c b/src/libsystemd/sd-id128/sd-id128.c
index d9c0116f60..1470e4c01a 100644
--- a/src/libsystemd/sd-id128/sd-id128.c
+++ b/src/libsystemd/sd-id128/sd-id128.c
@@ -25,6 +25,7 @@
 
 #include "fd-util.h"
 #include "hexdecoct.h"
+#include "id128-util.h"
 #include "io-util.h"
 #include "macro.h"
 #include "random-util.h"
@@ -93,117 +94,52 @@ _public_ int sd_id128_from_string(const char s[], sd_id128_t *ret) {
         return 0;
 }
 
-static sd_id128_t make_v4_uuid(sd_id128_t id) {
-        /* Stolen from generate_random_uuid() of drivers/char/random.c
-         * in the kernel sources */
-
-        /* Set UUID version to 4 --- truly random generation */
-        id.bytes[6] = (id.bytes[6] & 0x0F) | 0x40;
-
-        /* Set the UUID variant to DCE */
-        id.bytes[8] = (id.bytes[8] & 0x3F) | 0x80;
-
-        return id;
-}
-
 _public_ int sd_id128_get_machine(sd_id128_t *ret) {
-        static thread_local sd_id128_t saved_machine_id;
-        static thread_local bool saved_machine_id_valid = false;
-        _cleanup_close_ int fd = -1;
-        char buf[33];
-        unsigned j;
-        sd_id128_t t;
+        static thread_local sd_id128_t saved_machine_id = {};
         int r;
 
         assert_return(ret, -EINVAL);
 
-        if (saved_machine_id_valid) {
-                *ret = saved_machine_id;
-                return 0;
-        }
-
-        fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
-        if (fd < 0)
-                return -errno;
-
-        r = loop_read_exact(fd, buf, 33, false);
-        if (r < 0)
-                return r;
-        if (buf[32] !='\n')
-                return -EIO;
-
-        for (j = 0; j < 16; j++) {
-                int a, b;
-
-                a = unhexchar(buf[j*2]);
-                b = unhexchar(buf[j*2+1]);
+        if (sd_id128_is_null(saved_machine_id)) {
+                r = id128_read("/etc/machine-id", ID128_PLAIN, &saved_machine_id);
+                if (r < 0)
+                        return r;
 
-                if (a < 0 || b < 0)
-                        return -EIO;
-
-                t.bytes[j] = a << 4 | b;
+                if (sd_id128_is_null(saved_machine_id))
+                        return -EINVAL;
         }
 
-        saved_machine_id = t;
-        saved_machine_id_valid = true;
-
-        *ret = t;
+        *ret = saved_machine_id;
         return 0;
 }
 
 _public_ int sd_id128_get_boot(sd_id128_t *ret) {
-        static thread_local sd_id128_t saved_boot_id;
-        static thread_local bool saved_boot_id_valid = false;
-        _cleanup_close_ int fd = -1;
-        char buf[36];
-        unsigned j;
-        sd_id128_t t;
-        char *p;
+        static thread_local sd_id128_t saved_boot_id = {};
         int r;
 
         assert_return(ret, -EINVAL);
 
-        if (saved_boot_id_valid) {
-                *ret = saved_boot_id;
-                return 0;
+        if (sd_id128_is_null(saved_boot_id)) {
+                r = id128_read("/proc/sys/kernel/random/boot_id", ID128_UUID, &saved_boot_id);
+                if (r < 0)
+                        return r;
         }
 
-        fd = open("/proc/sys/kernel/random/boot_id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
-        if (fd < 0)
-                return -errno;
-
-        r = loop_read_exact(fd, buf, 36, false);
-        if (r < 0)
-                return r;
-
-        for (j = 0, p = buf; j < 16; j++) {
-                int a, b;
-
-                if (p >= buf + 35)
-                        return -EIO;
-
-                if (*p == '-') {
-                        p++;
-                        if (p >= buf + 35)
-                                return -EIO;
-                }
-
-                a = unhexchar(p[0]);
-                b = unhexchar(p[1]);
-
-                if (a < 0 || b < 0)
-                        return -EIO;
+        *ret = saved_boot_id;
+        return 0;
+}
 
-                t.bytes[j] = a << 4 | b;
+static sd_id128_t make_v4_uuid(sd_id128_t id) {
+        /* Stolen from generate_random_uuid() of drivers/char/random.c
+         * in the kernel sources */
 
-                p += 2;
-        }
+        /* Set UUID version to 4 --- truly random generation */
+        id.bytes[6] = (id.bytes[6] & 0x0F) | 0x40;
 
-        saved_boot_id = t;
-        saved_boot_id_valid = true;
+        /* Set the UUID variant to DCE */
+        id.bytes[8] = (id.bytes[8] & 0x3F) | 0x80;
 
-        *ret = t;
-        return 0;
+        return id;
 }
 
 _public_ int sd_id128_randomize(sd_id128_t *ret) {