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From 87c22d3bb794118d25bc138108fd5bdd607365ef Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 1 Jun 2020 17:16:46 +0200
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Subject: [PATCH] user-util: be stricter in parse_uid()
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Let's refuse "+" and "-" prefixed UIDs. Let's refuse whitespace-prefixed
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UIDS, Let's refuse zero-prefixed UIDs. Let's be safe than sorry.
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(cherry picked from commit f5979b63cc305ba217dfd174b1bf0583bcf75a73)
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Related: #1848373
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---
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 src/basic/user-util.c     | 10 +++++++++-
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 src/test/test-user-util.c | 26 +++++++++++++++++++++++---
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 2 files changed, 32 insertions(+), 4 deletions(-)
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diff --git a/src/basic/user-util.c b/src/basic/user-util.c
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index 10eeb256cd..40f4e45db6 100644
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--- a/src/basic/user-util.c
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+++ b/src/basic/user-util.c
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@@ -49,7 +49,15 @@ int parse_uid(const char *s, uid_t *ret) {
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         assert(s);
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         assert_cc(sizeof(uid_t) == sizeof(uint32_t));
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-        r = safe_atou32_full(s, 10, &uid);
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+
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+        /* We are very strict when parsing UIDs, and prohibit +/- as prefix, leading zero as prefix, and
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+         * whitespace. We do this, since this call is often used in a context where we parse things as UID
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+         * first, and if that doesn't work we fall back to NSS. Thus we really want to make sure that UIDs
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+         * are parsed as UIDs only if they really really look like UIDs. */
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+        r = safe_atou32_full(s, 10
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+                             | SAFE_ATO_REFUSE_PLUS_MINUS
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+                             | SAFE_ATO_REFUSE_LEADING_ZERO
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+                             | SAFE_ATO_REFUSE_LEADING_WHITESPACE, &uid);
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         if (r < 0)
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                 return r;
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diff --git a/src/test/test-user-util.c b/src/test/test-user-util.c
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index 8bf3dcd567..99203f7e48 100644
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--- a/src/test/test-user-util.c
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+++ b/src/test/test-user-util.c
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@@ -52,13 +52,33 @@ static void test_parse_uid(void) {
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         assert_se(r == -EINVAL);
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         assert_se(uid == 100);
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+        r = parse_uid("+1234", &uid);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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+
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+        r = parse_uid("-1234", &uid);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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+
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+        r = parse_uid(" 1234", &uid);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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+
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         r = parse_uid("01234", &uid);
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-        assert_se(r == 0);
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-        assert_se(uid == 1234);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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+
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+        r = parse_uid("-0", &uid);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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+
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+        r = parse_uid("+0", &uid);
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+        assert_se(r == -EINVAL);
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+        assert_se(uid == 100);
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         r = parse_uid("asdsdas", &uid);
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         assert_se(r == -EINVAL);
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-        assert_se(uid == 1234);
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+        assert_se(uid == 100);
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 }
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 static void test_uid_ptr(void) {