Interceptor: add support for Command execution

That is necessary to execute modified commands. Otherwise the function
would return and fall back to the original execve. This change itself
does make sense together with a later change that actually modifies the
command.

Bug: 205577427
Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: I6a9d7e31256063f3fe2883975fdc4cf486566b24

1 files changed, 19 insertions, 0 deletions

diff --git a/interceptor/interceptor.cc b/interceptor/interceptor.cc
index de3b2f3..71f67a2 100644
--- a/interceptor/interceptor.cc
+++ b/interceptor/interceptor.cc
@@ -44,6 +44,9 @@ static void process_command(const char* filename, char* const argv[], char* cons
 // log command if logging is enabled
 static void log(const interceptor::Command&, const std::string& prefix);
 
+// execute potentially modified command
+static void exec(const interceptor::Command&);
+
 // OVERLOADS for LD_PRELOAD USE
 
 // Intercept execve calls, for that capture the original execve call
@@ -134,6 +137,9 @@ static void process_command(const char* filename, char* const argv[], char* cons
 
   interceptor::Command command(filename, argv, envp);
   log(command, "");
+
+  // pass down the transformed command to execve
+  exec(command);
 }
 
 static void log(const interceptor::Command& command, const std::string& prefix) {
@@ -147,3 +153,16 @@ static void log(const interceptor::Command& command, const std::string& prefix)
     }
   }
 }
+
+static void exec(const interceptor::Command& command) {
+  std::vector<const char*> c_args;
+  c_args.reserve(command.args().size() + 1);
+  c_args[command.args().size()] = nullptr;
+  for (const auto& arg : command.args()) {
+    c_args.push_back(arg.data());
+  }
+  // TODO: at this point, we could free some memory that is held in Command.
+  //       While the args vector is reused for args, we could free the EnvMap
+  //       and the original args.
+  old_execve(command.program().c_str(), const_cast<char**>(c_args.data()), command.envp());
+}