From 81dc898df9b4b4035534a927f3234a3839b698bf Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:25 +0100 Subject: [PATCH 02/12] pretty: fix out-of-bounds write caused by integer overflow When using a padding specifier in the pretty format passed to git-log(1) we need to calculate the string length in several places. These string lengths are stored in `int`s though, which means that these can easily overflow when the input lengths exceeds 2GB. This can ultimately lead to an out-of-bounds write when these are used in a call to memcpy(3P): ==8340==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f1ec62f97fe at pc 0x7f2127e5f427 bp 0x7ffd3bd63de0 sp 0x7ffd3bd63588 WRITE of size 1 at 0x7f1ec62f97fe thread T0 #0 0x7f2127e5f426 in __interceptor_memcpy /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 #1 0x5628e96aa605 in format_and_pad_commit pretty.c:1762 #2 0x5628e96aa7f4 in format_commit_item pretty.c:1801 #3 0x5628e97cdb24 in strbuf_expand strbuf.c:429 #4 0x5628e96ab060 in repo_format_commit_message pretty.c:1869 #5 0x5628e96acd0f in pretty_print_commit pretty.c:2161 #6 0x5628e95a44c8 in show_log log-tree.c:781 #7 0x5628e95a76ba in log_tree_commit log-tree.c:1117 #8 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508 #9 0x5628e922c35b in cmd_log_walk builtin/log.c:549 #10 0x5628e922f1a2 in cmd_log builtin/log.c:883 #11 0x5628e9106993 in run_builtin git.c:466 #12 0x5628e9107397 in handle_builtin git.c:721 #13 0x5628e9107b07 in run_argv git.c:788 #14 0x5628e91088a7 in cmd_main git.c:923 #15 0x5628e939d682 in main common-main.c:57 #16 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f) #17 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #18 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115 0x7f1ec62f97fe is located 2 bytes to the left of 4831838265-byte region [0x7f1ec62f9800,0x7f1fe62f9839) allocated by thread T0 here: #0 0x7f2127ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85 #1 0x5628e98774d4 in xrealloc wrapper.c:136 #2 0x5628e97cb01c in strbuf_grow strbuf.c:99 #3 0x5628e97ccd42 in strbuf_addchars strbuf.c:327 #4 0x5628e96aa55c in format_and_pad_commit pretty.c:1761 #5 0x5628e96aa7f4 in format_commit_item pretty.c:1801 #6 0x5628e97cdb24 in strbuf_expand strbuf.c:429 #7 0x5628e96ab060 in repo_format_commit_message pretty.c:1869 #8 0x5628e96acd0f in pretty_print_commit pretty.c:2161 #9 0x5628e95a44c8 in show_log log-tree.c:781 #10 0x5628e95a76ba in log_tree_commit log-tree.c:1117 #11 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508 #12 0x5628e922c35b in cmd_log_walk builtin/log.c:549 #13 0x5628e922f1a2 in cmd_log builtin/log.c:883 #14 0x5628e9106993 in run_builtin git.c:466 #15 0x5628e9107397 in handle_builtin git.c:721 #16 0x5628e9107b07 in run_argv git.c:788 #17 0x5628e91088a7 in cmd_main git.c:923 #18 0x5628e939d682 in main common-main.c:57 #19 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f) #20 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #21 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115 SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 in __interceptor_memcpy Shadow bytes around the buggy address: 0x0fe458c572a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa =>0x0fe458c572f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa] 0x0fe458c57300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==8340==ABORTING The pretty format can also be used in `git archive` operations via the `export-subst` attribute. So this is what in our opinion makes this a critical issue in the context of Git forges which allow to download an archive of user supplied Git repositories. Fix this vulnerability by using `size_t` instead of `int` to track the string lengths. Add tests which detect this vulnerability when Git is compiled with the address sanitizer. Reported-by: Joern Schneeweisz Original-patch-by: Joern Schneeweisz Modified-by: Taylor Blau Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano Upstream-Status: Backport [https://github.com/git/git/commit/81dc898df9b4b4035534a927f3234a3839b698bf] CVE: CVE-2022-41903 Signed-off-by: Vijay Anusuri --- pretty.c | 11 ++++++----- t/t4205-log-pretty-formats.sh | 17 +++++++++++++++++ 2 files changed, 23 insertions(+), 5 deletions(-) diff --git a/pretty.c b/pretty.c index b32f036..637e344 100644 --- a/pretty.c +++ b/pretty.c @@ -1427,7 +1427,9 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ struct format_commit_context *c) { struct strbuf local_sb = STRBUF_INIT; - int total_consumed = 0, len, padding = c->padding; + size_t total_consumed = 0; + int len, padding = c->padding; + if (padding < 0) { const char *start = strrchr(sb->buf, '\n'); int occupied; @@ -1439,7 +1441,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ } while (1) { int modifier = *placeholder == 'C'; - int consumed = format_commit_one(&local_sb, placeholder, c); + size_t consumed = format_commit_one(&local_sb, placeholder, c); total_consumed += consumed; if (!modifier) @@ -1505,7 +1507,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ } strbuf_addbuf(sb, &local_sb); } else { - int sb_len = sb->len, offset = 0; + size_t sb_len = sb->len, offset = 0; if (c->flush_type == flush_left) offset = padding - len; else if (c->flush_type == flush_both) @@ -1528,8 +1530,7 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */ const char *placeholder, void *context) { - int consumed; - size_t orig_len; + size_t consumed, orig_len; enum { NO_MAGIC, ADD_LF_BEFORE_NON_EMPTY, diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index f42a69f..a2acee1 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -788,4 +788,21 @@ test_expect_success '%S in git log --format works with other placeholders (part test_cmp expect actual ' +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' + # We only assert that this command does not crash. This needs to be + # executed with the address sanitizer to demonstrate failure. + git log -1 --pretty="format:%>(2147483646)%x41%41%>(2147483646)%x41" >/dev/null +' + +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'set up huge commit' ' + test-tool genzeros 2147483649 | tr "\000" "1" >expect && + huge_commit=$(git commit-tree -F expect HEAD^{tree}) +' + +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' + git log -1 --format="%B%<(1)%x30" $huge_commit >actual && + echo 0 >>expect && + test_cmp expect actual +' + test_done -- 2.25.1