From 4f2f7cd9662fad74a0da79c51cb011fa034a8ca4 Mon Sep 17 00:00:00 2001
From: Jordan Bancino <jordan@bancino.net>
Date: Thu, 15 Dec 2022 03:41:59 +0000
Subject: [PATCH] Add random string generator

---
 TODO.txt                         |  2 +-
 man/man3/Util.3                  | 14 +++++++++++++-
 man/man7/telodendria-changelog.7 |  6 ++++++
 src/Routes/RouteRegister.c       |  1 +
 src/Util.c                       | 32 ++++++++++++++++++++++++++++++++
 src/include/Util.h               |  3 +++
 6 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/TODO.txt b/TODO.txt
index ecce73a..7aa951c 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -12,7 +12,7 @@ Milestone: v0.1.1
 -----------------
 
 [x] DbDelete()
-[ ] UtilRandomString()
+[x] UtilRandomString()
 [ ] Database version file
 [ ] User registration
 
diff --git a/man/man3/Util.3 b/man/man3/Util.3
index f69df98..8f55715 100644
--- a/man/man3/Util.3
+++ b/man/man3/Util.3
@@ -1,4 +1,4 @@
-.Dd $Mdocdate: November 26 2022 $
+.Dd $Mdocdate: December 15 2022 $
 .Dt UTIL 3
 .Os Telodendria Project
 .Sh NAME
@@ -26,6 +26,8 @@
 .Fn UtilGetDelim "char **" "size_t *" "int" "FILE *"
 .Ft ssize_t
 .Fn UtilGetLine "char **" "size_t *" "FILE *"
+.Ft char *
+.Fn UtilRandomString "size_t"
 .Sh DESCRIPTION
 .Pp
 This header holds a number of random functions related to strings,
@@ -98,6 +100,12 @@ work identically to the POSIX equivalents, documented in
 .Xr getdelim 3 ,
 except it assumes pointers were allocated using the Memory API, and it
 uses the Memory API itself to reallocate necessary pointers.
+.Pp
+.Fn UtilRandomString
+generates a random string of the given length. At the moment, it only
+selects from uppercase and lowercase numbers, but the character set may
+be expanded in the future, or a function may be added to specify an
+arbitrary character set.
 .Sh RETURN VALUES
 .Pp
 .Fn UtilServerTs
@@ -131,3 +139,7 @@ and
 .Fn UtilGetLine
 return the same value as their POSIX equivalents, documented in
 .Xr getdelim 3 .
+.Pp
+.Fn UtilRandomString
+returns a string, allocated on the heap, of the given length, or NULL if there
+was an error allocating memory.
diff --git a/man/man7/telodendria-changelog.7 b/man/man7/telodendria-changelog.7
index cadae6f..e33cb8c 100644
--- a/man/man7/telodendria-changelog.7
+++ b/man/man7/telodendria-changelog.7
@@ -43,6 +43,12 @@ While the database is for persistent storage, there may
 be some ephemeral data that lives there only for a short
 while, so it will be necessary to remove that data when
 necessary.
+.It
+Added a thread-safe random string generator, which will
+be used extensively for generating session tokens, device
+IDs, access tokens, and more. This generator is seeded by
+the current timestamp and the thread ID, so it should be
+fairly random.
 .El
 .Pp
 Bug fixes:
diff --git a/src/Routes/RouteRegister.c b/src/Routes/RouteRegister.c
index c479173..43673d0 100644
--- a/src/Routes/RouteRegister.c
+++ b/src/Routes/RouteRegister.c
@@ -75,6 +75,7 @@ ROUTE_IMPL(RouteRegister, args)
 
             HashMapSet(response, "flows", JsonValueArray(flows));
             HashMapSet(response, "params", JsonValueObject(HashMapCreate()));
+            HashMapSet(response, "session", JsonValueString(UtilRandomString(24)));
         }
         else
         {
diff --git a/src/Util.c b/src/Util.c
index dcb75af..2c1d733 100644
--- a/src/Util.c
+++ b/src/Util.c
@@ -36,6 +36,7 @@
 #include <sys/time.h>
 #include <sys/stat.h>
 #include <limits.h>
+#include <pthread.h>
 
 #ifndef PATH_MAX
 #define PATH_MAX 256
@@ -394,3 +395,34 @@ UtilGetLine(char **linePtr, size_t * n, FILE * stream)
 {
     return UtilGetDelim(linePtr, n, '\n', stream);
 }
+
+char *
+UtilRandomString(size_t len)
+{
+    static const char charset[] =
+        "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    char *str;
+    size_t i;
+
+    unsigned int seed = UtilServerTs() * (unsigned long) pthread_self();
+
+    if (!len)
+    {
+        return NULL;
+    }
+
+    str = Malloc(len + 1);
+    if (!str)
+    {
+        return NULL;
+    }
+
+    for (i = 0; i < len; i++)
+    {
+        str[i] = charset[rand_r(&seed) % (sizeof(charset) - 1)];
+    }
+
+    str[len] = '\0';
+    return str;
+}
diff --git a/src/include/Util.h b/src/include/Util.h
index 4484991..e492afd 100644
--- a/src/include/Util.h
+++ b/src/include/Util.h
@@ -59,4 +59,7 @@ extern ssize_t
 extern ssize_t
  UtilGetLine(char **, size_t *, FILE *);
 
+extern char *
+ UtilRandomString(size_t);
+
 #endif                             /* TELODENDRIA_UTIL_H */