Add random string generator

TODO.txt

@@ -12,7 +12,7 @@ Milestone: v0.1.1
 -----------------
 
 [x] DbDelete()
-[ ] UtilRandomString()
+[x] UtilRandomString()
 [ ] Database version file
 [ ] User registration
 

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.

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:

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
         {

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;
+}

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 */