1 files changed, 21 insertions, 3 deletions

diff --git a/shell/math.c b/shell/math.c
index 0c806ad39..af1ab55c0 100644
--- a/shell/math.c
+++ b/shell/math.c
@@ -540,11 +540,29 @@ static arith_t strto_arith_t(const char *nptr, char **endptr)
         /* bash allows "N#" (empty "nnnn" part) */
         for (;;) {
                 unsigned digit = (unsigned)*nptr - '0';
-                if (digit >= 10 || digit >= base) {
+                if (digit >= 10) {
+                        /* *nptr is not 0..9 */
+                        if (*nptr > 'z')
+                                break; /* this rejects e.g. $((64#~)) */
+                        /* in bases up to 36, case does not matter for a-z */
                         digit = (unsigned)(*nptr | 0x20) - ('a' - 10);
-                        if (digit >= base)
-                                break;
+                        if (base > 36 && *nptr <= '_') {
+                                /* otherwise, A-Z,@,_ are 36..61,62,63 */
+                                if (*nptr == '@')
+                                        digit = 62;
+                                else if (*nptr == '_')
+                                        digit = 63;
+                                else if (digit < 36) /* A-Z */
+                                        digit += 36 - 10;
+                                else
+                                        break; /* error, such as [ or \ */
+                        }
+                        //bb_error_msg("ch:'%c'%d digit:%u", *nptr, *nptr, digit);
+                        //if (digit < 10) - example where we need this?
+                        //      break;
                 }
+                if (digit >= base)
+                        break;
                 /* bash does not check for overflows */
                 n = n * base + digit;
                 nptr++;