Support environment variable expansion in logging.ini

The syntax is a stripped-down subset of what is available for variable
expansion in bootstrap ini-files:  It only supports "${name}", to be replaced
with the contents of an environment variable of that name (which itself is not
expanded further).  If no such environment variable exists, it is replaced with
the empty string.  If the name contains a NUL character, or if there is a syntax
error (i.e., missing opening or closing curly brace), the corresponding text is
left unchanged.

Also, backslash quoting is supported to allow for verbatim, uninterpreted
"${name}" content.  But logging.ini is typically used to specify Windows-style

LogFilePath=C:\log.txt

pathnames containing backslashes, so restrict backslash quoting to just "\$"
(replaced with "$") and "\\" (replaced with "\"), and leave all other
backslashes alone.

(It is not possible to reuse the bootstrap macro expansion code here, as that
would cause recursive dependencies.  Therefore, this only implements this
stripped-down subset.)

Change-Id: I8c949a1637a7f14e0672a9cc1c79014edfa336bd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/164759
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@allotropia.de>

1 files changed, 37 insertions, 1 deletions

diff --git a/sal/osl/all/log.cxx b/sal/osl/all/log.cxx
index a8b86e3e7e79..3f92e9a62ec9 100644
--- a/sal/osl/all/log.cxx
+++ b/sal/osl/all/log.cxx
@@ -113,7 +113,43 @@ char const* setEnvFromLoggingIniFile(const char* env, const char* key)
             std::string_view aKey(sLine.data(), n);
             if (aKey != sWantedKey)
                 continue;
-            _putenv_s(env, sLine.substr(n+1, sLine.length()).c_str());
+            std::string value(sLine, n+1, sLine.length());
+            for (std::size_t i = 0;;) {
+                i = value.find_first_of("\\$", i);
+                if (i == std::string::npos) {
+                    break;
+                }
+                if (value[i] == '\\') {
+                    if (i == value.size() - 1 || (value[i + 1] != '\\' && value[i + 1] != '$')) {
+                        ++i;
+                        continue;
+                    }
+                    value.erase(i, 1);
+                    ++i;
+                } else {
+                    if (i == value.size() - 1 || value[i + 1] != '{') {
+                        ++i;
+                        continue;
+                    }
+                    std::size_t i2 = value.find('}', i + 2);
+                    if (i2 == std::string::npos) {
+                        break;
+                    }
+                    std::string name(value, i + 2, i2 - (i + 2));
+                    if (name.find('\0') != std::string::npos) {
+                        i = i2 + 1;
+                        continue;
+                    }
+                    char const * p = std::getenv(name.c_str());
+                    if (p == nullptr) {
+                        value.erase(i, i2 + 1 - i);
+                    } else {
+                        value.replace(i, i2 + 1 - i, p);
+                        i += std::strlen(p);
+                    }
+                }
+            }
+            _putenv_s(env, value.c_str());
             sResult = std::getenv(env);
             break;
         }