wg: stricter key file reading

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/config.c b/src/config.c
index a1290889a5b74e9f7e9b080b313ea585b4172a51..7007b880d76d91edaa036adbc3c634c760a67ff5 100644 (file)
--- a/src/config.c
+++ b/src/config.c
@@ -424,32 +424,48 @@ err:
        return false;
 }
 
-static int read_line(char **dst, const char *path)
+static int read_keyfile(char dst[WG_KEY_LEN_BASE64], const char *path)
 {
        FILE *f;
-       size_t n = 0;
-
-       *dst = NULL;
+       int ret = -1, c;
 
        f = fopen(path, "r");
        if (!f) {
                perror("fopen");
                return -1;
        }
-       if (getline(dst, &n, f) < 0 && errno) {
-               perror("getline");
-               fclose(f);
-               return -1;
+
+       if (fread(dst, WG_KEY_LEN_BASE64 - 1, 1, f) != 1) {
+               if (errno) {
+                       perror("fread");
+                       goto out;
+               }
+               /* If we're at the end and we didn't read anything, we're /dev/null. */
+               if (!ferror(f) && feof(f) && !ftell(f)) {
+                       ret = 1;
+                       goto out;
+               }
+
+               fprintf(stderr, "Invalid length key in key file\n");
+               goto out;
        }
-       fclose(f);
-       n = strlen(*dst);
-       if (!n)
-               return 1;
-       while (--n) {
-               if (isspace((*dst)[n]))
-                       (*dst)[n] = '\0';
+       dst[WG_KEY_LEN_BASE64 - 1] = '\0';
+
+       while ((c = getc(f)) != EOF) {
+               if (!isspace(c)) {
+                       fprintf(stderr, "Found trailing character in key file: `%c`\n", c);
+                       goto out;
+               }
        }
-       return 0;
+       if (ferror(f) && errno) {
+               perror("getc");
+               goto out;
+       }
+       ret = 0;
+
+out:
+       fclose(f);
+       return ret;
 }
 
 static char *strip_spaces(const char *in)
@@ -492,14 +508,11 @@ bool config_read_cmd(struct wgdevice **device, char *argv[], int argc)
                        argv += 2;
                        argc -= 2;
                } else if (!strcmp(argv[0], "private-key") && argc >= 2 && !buf.dev->num_peers) {
-                       char *line;
-                       int ret = read_line(&line, argv[1]);
+                       char key_line[WG_KEY_LEN_BASE64];
+                       int ret = read_keyfile(key_line, argv[1]);
                        if (ret == 0) {
-                               if (!parse_key(buf.dev->private_key, line)) {
-                                       free(line);
+                               if (!parse_key(buf.dev->private_key, key_line))
                                        goto error;
-                               }
-                               free(line);
                        } else if (ret == 1)
                                buf.dev->flags |= WGDEVICE_REMOVE_PRIVATE_KEY;
                        else
@@ -544,18 +557,14 @@ bool config_read_cmd(struct wgdevice **device, char *argv[], int argc)
                        argv += 2;
                        argc -= 2;
                } else if (!strcmp(argv[0], "preshared-key") && argc >= 2 && buf.dev->num_peers) {
-                       char *line;
-                       int ret = read_line(&line, argv[1]);
+                       char key_line[WG_KEY_LEN_BASE64];
+                       int ret = read_keyfile(key_line, argv[1]);
                        if (ret == 0) {
-                               if (!parse_key(peer_from_offset(buf.dev, peer_offset)->preshared_key, line)) {
-                                       free(line);
+                               if (!parse_key(peer_from_offset(buf.dev, peer_offset)->preshared_key, key_line))
                                        goto error;
-                               }
-                               free(line);
-                       } else if (ret == 1) {
-                               free(line);
+                       } else if (ret == 1)
                                buf.dev->flags |= WGPEER_REMOVE_PRESHARED_KEY;
-                       } else
+                       else
                                goto error;
                        argv += 2;
                        argc -= 2;