Merge pull request #22759 from msekletar/issue-18077-long-sysfs-paths-hashing

Create "hashed" unit names from long paths

src/basic/string-util.h

@@ -10,17 +10,18 @@
 #include "string-util-fundamental.h"
 
 /* What is interpreted as whitespace? */
-#define WHITESPACE        " \t\n\r"
-#define NEWLINE           "\n\r"
-#define QUOTES            "\"\'"
-#define COMMENTS          "#;"
-#define GLOB_CHARS        "*?["
-#define DIGITS            "0123456789"
-#define LOWERCASE_LETTERS "abcdefghijklmnopqrstuvwxyz"
-#define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-#define LETTERS           LOWERCASE_LETTERS UPPERCASE_LETTERS
-#define ALPHANUMERICAL    LETTERS DIGITS
-#define HEXDIGITS         DIGITS "abcdefABCDEF"
+#define WHITESPACE          " \t\n\r"
+#define NEWLINE             "\n\r"
+#define QUOTES              "\"\'"
+#define COMMENTS            "#;"
+#define GLOB_CHARS          "*?["
+#define DIGITS              "0123456789"
+#define LOWERCASE_LETTERS   "abcdefghijklmnopqrstuvwxyz"
+#define UPPERCASE_LETTERS   "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+#define LETTERS             LOWERCASE_LETTERS UPPERCASE_LETTERS
+#define ALPHANUMERICAL      LETTERS DIGITS
+#define HEXDIGITS           DIGITS "abcdefABCDEF"
+#define LOWERCASE_HEXDIGITS DIGITS "abcdef"
 
 static inline char* strstr_ptr(const char *haystack, const char *needle) {
         if (!haystack || !needle)

src/basic/unit-name.c

@@ -5,12 +5,17 @@
 #include <stdint.h>
 #include <stdlib.h>
 
+#include "sd-id128.h"
+
 #include "alloc-util.h"
 #include "glob-util.h"
 #include "hexdecoct.h"
 #include "memory-util.h"
 #include "path-util.h"
+#include "random-util.h"
+#include "sparse-endian.h"
 #include "special.h"
+#include "stdio-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "unit-name.h"
@@ -31,6 +36,9 @@
         VALID_CHARS_WITH_AT                     \
         "[]!-*?"
 
+#define LONG_UNIT_NAME_HASH_KEY SD_ID128_MAKE(ec,f2,37,fb,58,32,4a,32,84,9f,06,9b,0d,21,eb,9a)
+#define UNIT_NAME_HASH_LENGTH_CHARS 16
+
 bool unit_name_is_valid(const char *n, UnitNameFlags flags) {
         const char *e, *i, *at;
 
@@ -507,6 +515,68 @@ int unit_name_template(const char *f, char **ret) {
         return 0;
 }
 
+bool unit_name_is_hashed(const char *name) {
+        char *s;
+
+        if (!unit_name_is_valid(name, UNIT_NAME_PLAIN))
+                return false;
+
+        assert_se(s = strrchr(name, '.'));
+
+        if (s - name < UNIT_NAME_HASH_LENGTH_CHARS + 1)
+                return false;
+
+        s -= UNIT_NAME_HASH_LENGTH_CHARS;
+        if (s[-1] != '_')
+                return false;
+
+        for (size_t i = 0; i < UNIT_NAME_HASH_LENGTH_CHARS; i++)
+                if (!strchr(LOWERCASE_HEXDIGITS, s[i]))
+                        return false;
+
+        return true;
+}
+
+int unit_name_hash_long(const char *name, char **ret) {
+        _cleanup_free_ char *n = NULL, *hash = NULL;
+        char *suffix;
+        le64_t h;
+        size_t len;
+
+        if (strlen(name) < UNIT_NAME_MAX)
+                return -EMSGSIZE;
+
+        suffix = strrchr(name, '.');
+        if (!suffix)
+                return -EINVAL;
+
+        if (unit_type_from_string(suffix+1) < 0)
+                return -EINVAL;
+
+        h = htole64(siphash24_string(name, LONG_UNIT_NAME_HASH_KEY.bytes));
+
+        hash = hexmem(&h, sizeof(h));
+        if (!hash)
+                return -ENOMEM;
+
+        assert_se(strlen(hash) == UNIT_NAME_HASH_LENGTH_CHARS);
+
+        len = UNIT_NAME_MAX - 1 - strlen(suffix+1) - UNIT_NAME_HASH_LENGTH_CHARS - 2;
+        assert(len > 0 && len < UNIT_NAME_MAX);
+
+        n = strndup(name, len);
+        if (!n)
+                return -ENOMEM;
+
+        if (!strextend(&n, "_", hash, suffix))
+                return -ENOMEM;
+        assert_se(unit_name_is_valid(n, UNIT_NAME_PLAIN));
+
+        *ret = TAKE_PTR(n);
+
+        return 0;
+}
+
 int unit_name_from_path(const char *path, const char *suffix, char **ret) {
         _cleanup_free_ char *p = NULL, *s = NULL;
         int r;
@@ -526,8 +596,17 @@ int unit_name_from_path(const char *path, const char *suffix, char **ret) {
         if (!s)
                 return -ENOMEM;
 
-        if (strlen(s) >= UNIT_NAME_MAX) /* Return a slightly more descriptive error for this specific condition */
-                return -ENAMETOOLONG;
+        if (strlen(s) >= UNIT_NAME_MAX) {
+                _cleanup_free_ char *n = NULL;
+
+                log_debug("Unit name \"%s\" too long, falling back to hashed unit name.", s);
+
+                r = unit_name_hash_long(s, &n);
+                if (r < 0)
+                        return r;
+
+                free_and_replace(s, n);
+        }
 
         /* Refuse if this for some other reason didn't result in a valid name */
         if (!unit_name_is_valid(s, UNIT_NAME_PLAIN))
@@ -581,6 +660,9 @@ int unit_name_to_path(const char *name, char **ret) {
         if (r < 0)
                 return r;
 
+        if (unit_name_is_hashed(name))
+                return -ENAMETOOLONG;
+
         return unit_name_path_unescape(prefix, ret);
 }
 

src/basic/unit-name.h

@@ -44,6 +44,9 @@ int unit_name_replace_instance(const char *f, const char *i, char **ret);
 
 int unit_name_template(const char *f, char **ret);
 
+int unit_name_hash_long(const char *name, char **ret);
+bool unit_name_is_hashed(const char *name);
+
 int unit_name_from_path(const char *path, const char *suffix, char **ret);
 int unit_name_from_path_instance(const char *prefix, const char *path, const char *suffix, char **ret);
 int unit_name_to_path(const char *name, char **ret);