Avoid using unsafe C functions (#10932)

replace use of:
sprintf --> snprintf
strcpy/strncpy  --> redis_strlcpy
strcat/strncat  --> redis_strlcat

**why are we making this change?**
Much of the code uses some unsafe variants or deprecated buffer handling
functions.
While most cases are probably not presenting any issue on the known path
programming errors and unterminated strings might lead to potential
buffer overflows which are not covered by tests.

**As part of this PR we change**
1. added implementation for redis_strlcpy and redis_strlcat based on the strl implementation: https://linux.die.net/man/3/strl
2. change all occurrences of use of sprintf with use of snprintf
3. change occurrences of use of  strcpy/strncpy with redis_strlcpy
4. change occurrences of use of strcat/strncat with redis_strlcat
5. change the behavior of ll2string/ull2string/ld2string so that it will always place null
  termination ('\0') on the output buffer in the first index. this was done in order to make
  the use of these functions more safe in cases were the user will not check the output
  returned by them (for example in rdbRemoveTempFile)
6. we added a compiler directive to issue a deprecation error in case a use of
  sprintf/strcpy/strcat is found during compilation which will result in error during compile time.
  However keep in mind that since the deprecation attribute is not supported on all compilers,
  this is expected to fail during push workflows.


**NOTE:** while this is only an initial milestone. We might also consider
using the *_s implementation provided by the C11 Extensions (however not
yet widly supported). I would also suggest to start
looking at static code analyzers to track unsafe use cases.
For example LLVM clang checker supports security.insecureAPI.DeprecatedOrUnsafeBufferHandling
which can help locate unsafe function usage.
https://clang.llvm.org/docs/analyzer/checkers.html#security-insecureapi-deprecatedorunsafebufferhandling-c
The main reason not to onboard it at this stage is that the alternative
excepted by clang is to use the C11 extensions which are not always
supported by stdlib.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/anet.c b/src/anet.c
index 4ea201df5..753f2fe42 100644
--- a/src/anet.c
+++ b/src/anet.c
@@ -48,6 +48,7 @@
 
 #include "anet.h"
 #include "config.h"
+#include "util.h"
 
 #define UNUSED(x) (void)(x)
 
@@ -388,7 +389,7 @@ int anetUnixGenericConnect(char *err, const char *path, int flags)
         return ANET_ERR;
 
     sa.sun_family = AF_LOCAL;
-    strncpy(sa.sun_path,path,sizeof(sa.sun_path)-1);
+    redis_strlcpy(sa.sun_path,path,sizeof(sa.sun_path));
     if (flags & ANET_CONNECT_NONBLOCK) {
         if (anetNonBlock(err,s) != ANET_OK) {
             close(s);
@@ -497,7 +498,7 @@ int anetUnixServer(char *err, char *path, mode_t perm, int backlog)
 
     memset(&sa,0,sizeof(sa));
     sa.sun_family = AF_LOCAL;
-    strncpy(sa.sun_path,path,sizeof(sa.sun_path)-1);
+    redis_strlcpy(sa.sun_path,path,sizeof(sa.sun_path));
     if (anetListen(err,s,(struct sockaddr*)&sa,sizeof(sa),backlog) == ANET_ERR)
         return ANET_ERR;
     if (perm)