From 14570dc67d2a500dfb9f33a7445bdbd6133af4ac Mon Sep 17 00:00:00 2001 From: "brian m. carlson" Date: Mon, 25 May 2020 19:58:50 +0000 Subject: [PATCH] wrapper: add function to compare strings with different NUL termination When parsing capabilities for the pack protocol, there are times we'll want to compare the value of a capability to a NUL-terminated string. Since the data we're reading will be space-terminated, not NUL-terminated, we need a function that compares the two strings, but also checks that they're the same length. Otherwise, if we used strncmp to compare these strings, we might accidentally accept a parameter that was a prefix of the expected value. Add a function, xstrncmpz, that takes a NUL-terminated string and a non-NUL-terminated string, plus a length, and compares them, ensuring that they are the same length. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano --- git-compat-util.h | 6 ++++++ wrapper.c | 8 ++++++++ 2 files changed, 14 insertions(+) diff --git a/git-compat-util.h b/git-compat-util.h index 8ba576e81e..a3dcfc8613 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -869,6 +869,12 @@ FILE *fopen_for_writing(const char *path); FILE *fopen_or_warn(const char *path, const char *mode); /* + * Like strncmp, but only return zero if s is NUL-terminated and exactly len + * characters long. If it is not, consider it greater than t. + */ +int xstrncmpz(const char *s, const char *t, size_t len); + +/* * FREE_AND_NULL(ptr) is like free(ptr) followed by ptr = NULL. Note * that ptr is used twice, so don't pass e.g. ptr++. */ diff --git a/wrapper.c b/wrapper.c index 3a1c0e0526..4ff4a9c3db 100644 --- a/wrapper.c +++ b/wrapper.c @@ -105,6 +105,14 @@ char *xstrndup(const char *str, size_t len) return xmemdupz(str, p ? p - str : len); } +int xstrncmpz(const char *s, const char *t, size_t len) +{ + int res = strncmp(s, t, len); + if (res) + return res; + return s[len] == '\0' ? 0 : 1; +} + void *xrealloc(void *ptr, size_t size) { void *ret; -- 2.11.4.GIT