From a06cc218bfa18943a46e051d5bbf463e1ddc0b6e Mon Sep 17 00:00:00 2001
From: defanor <defanor@uberspace.net>
Date: Sat, 29 Apr 2017 04:36:01 +0300
Subject: Initial commit

---
 fp2alias.c | 144 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 fp2alias.c

(limited to 'fp2alias.c')

diff --git a/fp2alias.c b/fp2alias.c
new file mode 100644
index 0000000..b1f68d6
--- /dev/null
+++ b/fp2alias.c
@@ -0,0 +1,144 @@
+/*
+  fp2alias, a basic authentication and authorization helper
+
+  This is free and unencumbered software released into the public
+  domain.
+*/
+
+#include <config.h>
+
+#include <syslog.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+
+/* This value is used in format strings as well */
+#define MAX_ALIAS_LEN 32
+
+#define DEFAULT_ALIAS_FILE "/etc/tls/aliases"
+
+/* Get an alias from a file, or from a user */
+int get_alias (const char *filename,
+               const char *fingerprint,
+               char *alias,
+               int add_new)
+{
+  FILE * fd;
+  char hash[65];
+  char login[MAX_ALIAS_LEN + 1];
+  int l;
+
+  /* Try to find the fingerprint */
+  fd = fopen(filename, "r");
+  if (!fd) {
+    syslog(LOG_ERR, "Can't open %s for reading: %s (errno=%d)",
+           filename, strerror(errno), errno);
+    return -1;
+  }
+  do {
+    l = fscanf(fd, "%64[a-f0-9] %32[a-z0-9]\n", hash, login);
+    if (! strncmp(hash, fingerprint, 64)) {
+      fclose(fd);
+      strncpy(alias, login, MAX_ALIAS_LEN + 1);
+      return 0;
+    }
+  } while (l != EOF);
+
+  /* In read-only mode, that's all */
+  if (! add_new) {
+    fclose(fd);
+    puts("I don't recognize you.");
+    return -1;
+  }
+
+  /* Ask for an alias to add */
+  puts("Enter your alias, please.");
+  fflush(stdout);
+  l = scanf("%32[a-z0-9]", alias);
+  if (l == EOF || strlen(alias) < 2) {
+    fclose(fd);
+    return -1;
+  }
+
+  /* Check that the alias is not taken */
+  fd = freopen(filename, "a+", fd);
+  if (!fd) {
+    syslog(LOG_ERR, "Can't reopen %s for writing: %s (errno=%d)",
+           filename, strerror(errno), errno);
+    return -1;
+  }
+  do {
+    l = fscanf(fd, "%64[a-f0-9] %32[a-z0-9]\n", hash, login);
+    if (! strncmp(alias, login, MAX_ALIAS_LEN)) {
+      fclose(fd);
+      printf("The '%s' alias is taken already.", alias);
+      return -1;
+    }
+  } while (l != EOF);
+
+  /* Everything appears to be fine; add it */
+  fprintf(fd, "%s %s\n", fingerprint, alias);
+  fclose(fd);
+  return 0;
+}
+
+void print_help (const char *name)
+{
+  printf("Usage: %s [option ...] [--] [<command> [argument ...]]\n", name);
+  puts("Options:");
+  puts(" -f <file>     a file with \"<fingerprint> <alias>\" entries");
+  puts(" -a            add new aliases");
+  puts(" -i <ident>    syslog ident to use");
+  puts(" -e            print messages into stderr, in addition to syslog");
+  puts(" -h            print this help message and exit");
+}
+
+int main (int argc,
+          char **argv)
+{
+  int c;
+  int syslog_options = 0;
+  char *ident = "fp2alias";
+  char *alias_file = DEFAULT_ALIAS_FILE;
+  char *sha256;
+  char alias[MAX_ALIAS_LEN + 1];
+  int add_new = 0;
+
+  ident = argv[0];
+
+  while ((c = getopt (argc, argv, "f:ai:eh")) != -1)
+    switch (c)
+      {
+      case 'f': alias_file = optarg;           break;
+      case 'a': add_new = 1;                   break;
+      case 'i': ident = optarg;                break;
+      case 'e': syslog_options |= LOG_PERROR;  break;
+      case 'h': print_help(argv[0]);           return 0;
+      default:  print_help(argv[0]);           return 1;
+      }
+
+  openlog(ident, syslog_options, LOG_USER);
+
+  sha256 = getenv("SHA256");
+  if (! sha256) {
+    syslog(LOG_ERR, "The SHA256 environment variable is not defined");
+    closelog();
+    return 1;
+  }
+
+  if (get_alias(alias_file, sha256, alias, add_new) < 0) {
+    closelog();
+    return 1;
+  }
+  syslog(LOG_INFO, "Identified %s as %s", sha256, alias);
+  closelog();
+
+  /* Run a program if one is specified */
+  if (argc > optind) {
+    setenv("ALIAS", alias, 1);
+    return execvp(argv[optind], &argv[optind]);
+  }
+  return 0;
+}
-- 
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