journal: Move more pattern matching logic into pcre2-util

To avoid having "#if HAVE_PCRE2" all throughout the code, let's
confine the pcre2 header specific stuff to pcre2-util.c. Instead of
exposing all the individual symbols from pcre2, let's only expose
three high level functions that do all we need:

- pcre2_pattern_compile(): Compile the regex
- pcre2_pattern_matches(): Check if the compiled regex matches a message
- pcre2_pattern_free(): Free the compiled regex

We expose the compiled pcre2 pattern (which is of type pcre2_code *) as
a void pointer to avoid having to include pcre2.h in all code where we
work with compiled pcre2 patterns. For readability, we typedef void
to pcre2_pattern and use that as the type specifier for compiled pcre2
patterns.

1 files changed, 116 insertions, 3 deletions

diff --git a/src/shared/pcre2-util.c b/src/shared/pcre2-util.c
index 80f6cec342..998dab0491 100644
--- a/src/shared/pcre2-util.c
+++ b/src/shared/pcre2-util.c
@@ -14,8 +14,10 @@ pcre2_code* (*sym_pcre2_compile)(PCRE2_SPTR, PCRE2_SIZE, uint32_t, int *, PCRE2_
 int (*sym_pcre2_get_error_message)(int, PCRE2_UCHAR *, PCRE2_SIZE);
 int (*sym_pcre2_match)(const pcre2_code *, PCRE2_SPTR, PCRE2_SIZE, PCRE2_SIZE, uint32_t, pcre2_match_data *, pcre2_match_context *);
 PCRE2_SIZE* (*sym_pcre2_get_ovector_pointer)(pcre2_match_data *);
+#endif
 
 int dlopen_pcre2(void) {
+#if HAVE_PCRE2
         /* So here's something weird: PCRE2 actually renames the symbols exported by the library via C
          * macros, so that the exported symbols carry a suffix "_8" but when used from C the suffix is
          * gone. In the argument list below we ignore this mangling. Surprisingly (at least to me), we
@@ -33,12 +35,123 @@ int dlopen_pcre2(void) {
                         DLSYM_ARG(pcre2_get_error_message),
                         DLSYM_ARG(pcre2_match),
                         DLSYM_ARG(pcre2_get_ovector_pointer));
+#else
+        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "PCRE2 support is not compiled in.");
+#endif
 }
 
+int pattern_compile_and_log(const char *pattern, PatternCompileCase case_, pcre2_code **ret) {
+#if HAVE_PCRE2
+        PCRE2_SIZE erroroffset;
+        pcre2_code *p;
+        unsigned flags = 0;
+        int errorcode, r;
+
+        assert(pattern);
+
+        r = dlopen_pcre2();
+        if (r < 0)
+                return r;
+
+        if (case_ == PATTERN_COMPILE_CASE_INSENSITIVE)
+                flags = PCRE2_CASELESS;
+        else if (case_ == PATTERN_COMPILE_CASE_AUTO) {
+                _cleanup_(sym_pcre2_match_data_freep) pcre2_match_data *md = NULL;
+                bool has_case;
+                _cleanup_(sym_pcre2_code_freep) pcre2_code *cs = NULL;
+
+                md = sym_pcre2_match_data_create(1, NULL);
+                if (!md)
+                        return log_oom();
+
+                r = pattern_compile_and_log("[[:upper:]]", PATTERN_COMPILE_CASE_SENSITIVE, &cs);
+                if (r < 0)
+                        return r;
+
+                r = sym_pcre2_match(cs, (PCRE2_SPTR8) pattern, PCRE2_ZERO_TERMINATED, 0, 0, md, NULL);
+                has_case = r >= 0;
+
+                flags = !has_case * PCRE2_CASELESS;
+        }
+
+        log_debug("Doing case %s matching based on %s",
+                  flags & PCRE2_CASELESS ? "insensitive" : "sensitive",
+                  case_ != PATTERN_COMPILE_CASE_AUTO ? "request" : "pattern casing");
+
+        p = sym_pcre2_compile((PCRE2_SPTR8) pattern,
+                              PCRE2_ZERO_TERMINATED, flags, &errorcode, &erroroffset, NULL);
+        if (!p) {
+                unsigned char buf[LINE_MAX];
+
+                r = sym_pcre2_get_error_message(errorcode, buf, sizeof buf);
+
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Bad pattern \"%s\": %s", pattern,
+                                       r < 0 ? "unknown error" : (char *)buf);
+        }
+
+        if (ret)
+                *ret = p;
+
+        return 0;
 #else
+        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "PCRE2 support is not compiled in.");
+#endif
+}
 
-int dlopen_pcre2(void) {
-        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
-                               "PCRE2 support is not compiled in.");
+int pattern_matches_and_log(pcre2_code *compiled_pattern, const char *message, size_t size, size_t *ret_ovec) {
+#if HAVE_PCRE2
+        _cleanup_(sym_pcre2_match_data_freep) pcre2_match_data *md = NULL;
+        int r;
+
+        assert(compiled_pattern);
+        assert(message);
+        /* pattern_compile_and_log() must be called before this function is called and that function already
+         * dlopens pcre2 so we can assert on it being available here. */
+        assert(pcre2_dl);
+
+        md = sym_pcre2_match_data_create(1, NULL);
+        if (!md)
+                return log_oom();
+
+        r = sym_pcre2_match(compiled_pattern,
+                            (const unsigned char *)message,
+                            size,
+                            0,      /* start at offset 0 in the subject */
+                            0,      /* default options */
+                            md,
+                            NULL);
+        if (r == PCRE2_ERROR_NOMATCH)
+                return false;
+        if (r < 0) {
+                unsigned char buf[LINE_MAX];
+
+                r = sym_pcre2_get_error_message(r, buf, sizeof(buf));
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Pattern matching failed: %s",
+                                       r < 0 ? "unknown error" : (char*) buf);
+        }
+
+        if (ret_ovec) {
+                ret_ovec[0] = sym_pcre2_get_ovector_pointer(md)[0];
+                ret_ovec[1] = sym_pcre2_get_ovector_pointer(md)[1];
+        }
+
+        return true;
+#else
+        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "PCRE2 support is not compiled in.");
+#endif
 }
+
+void *pattern_free(pcre2_code *p) {
+#if HAVE_PCRE2
+        if (!p)
+                return NULL;
+
+        assert(pcre2_dl);
+        sym_pcre2_code_free(p);
+        return NULL;
+#else
+        assert(p == NULL);
+        return NULL;
 #endif
+}