dropbear for android error fstatat64(AT_FDCWD, "//.ssh

[TianRandai111]

My computer environment：

$  uname -a                                                                                                                                                        
Linux localhost 4.9.113 #1 SMP PREEMPT Wed Dec 15 12:08:54 CST 2021 armv7l

$ echo $SHELL                                                                                                                                                 
/system/bin/sh

$ echo $USER                                                                                                                                                      
root

$ echo $HOME                                                                                                                                                      
/data

error:
strace -f /data/local/tmp/usr/local/sbin/dropbear -F -E -p 2222 -r /data/.ssh/id_dropbear

[pid  1677] openat(AT_FDCWD, "/data/.ssh/shells", O_RDONLY|O_LARGEFILE) = 5
[pid  1677] fstat64(5, {st_mode=S_IFREG|0644, st_size=115, ...}) = 0
[pid  1677] fstat64(5, {st_mode=S_IFREG|0644, st_size=115, ...}) = 0
[pid  1677] read(5, "# /etc/shells: valid login shell"..., 4096) = 115
[pid  1677] read(5, "", 4096)           = 0
[pid  1677] close(5)                    = 0
[pid  1677] madvise(0xb0f17000, 4096, MADV_DONTNEED) = 0
[pid  1677] madvise(0xb0f2e000, 20480, MADV_DONTNEED) = 0
[pid  1677] getuid32()                  = 0
[pid  1677] getgid32()                  = 0
[pid  1677] setresgid32(-1, 0, -1)      = 0
[pid  1677] setresuid32(-1, 0, -1)      = 0
[pid  1677] fstatat64(AT_FDCWD, "/", {st_mode=S_IFDIR|0755, st_size=0, ...}, 0) = 0
[pid  1677] fstatat64(AT_FDCWD, "//.ssh", 0xbbd56538, 0) = -1 ENOENT (No such file or directory)
[pid  1677] setresuid32(-1, 0, -1)      = 0
[pid  1677] setresgid32(-1, 0, -1)      = 0
[pid  1677] madvise(0xb0f33000, 20480, MADV_DONTNEED) = 0
[pid  1677] writev(0, [{iov_base="bE\350\256a>d\220\350\20\21\226<{\220\356W\333\204\375_\226\36\314!+\214\33\20\370\207v"..., iov_len=44}], 1) = 44
[pid  1677] madvise(0xb0f2e000, 12288, MADV_DONTNEED) = 0
[pid  1677] pselect6(5, [0 3], [], NULL, {tv_sec=301, tv_nsec=0}, NULL) = 1 (in [0], left {tv_sec=300, tv_nsec=998957500})
[pid  1677] read(0, "", 8)              = 0
[pid  1677] close(0)                    = 0
[pid  1677] openat(AT_FDCWD, "/dev/__properties__/u:object_r:exported_system_prop:s0", O_RDONLY|O_LARGEFILE|O_NOFOLLOW|O_CLOEXEC) = 0
[pid  1677] fstat64(0, {st_mode=S_IFREG|0444, st_size=131072, ...}) = 0
[pid  1677] mmap2(NULL, 131072, PROT_READ, MAP_SHARED, 0, 0) = 0xb1104000
[pid  1677] close(0)                    = 0
[pid  1677] openat(AT_FDCWD, "/data/misc/zoneinfo/current/tzdata", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 0
[pid  1677] read(0, "tzdata2018e\0\0\0\0\30\0\0x$\0\7\\x", 24) = 24
[pid  1677] lseek(0, 24, SEEK_SET)      = 24
[pid  1677] read(0, "Africa/Abidjan\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 30732) = 30732
[pid  1677] madvise(0xb0f47000, 36864, MADV_DONTNEED) = 0
[pid  1677] lseek(0, 295759, SEEK_SET)  = 295759
[pid  1677] read(0, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\2\0\0\0\2\0\0\0\0"..., 388) = 388
[pid  1677] close(0)                    = 0
[pid  1677] openat(AT_FDCWD, "/data/misc/zoneinfo/current/tzdata", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 0
[pid  1677] read(0, "tzdata2018e\0\0\0\0\30\0\0x$\0\7\\x", 24) = 24
[pid  1677] lseek(0, 24, SEEK_SET)      = 24
[pid  1677] read(0, "Africa/Abidjan\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 30732) = 30732
[pid  1677] madvise(0xb0f56000, 36864, MADV_DONTNEED) = 0
[pid  1677] close(0)                    = 0
[pid  1677] openat(AT_FDCWD, "/system/usr/share/zoneinfo/tzdata", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 0
[pid  1677] read(0, "tzdata2018e\0\0\0\0\30\0\0x$\0\7\\x", 24) = 24
[pid  1677] lseek(0, 24, SEEK_SET)      = 24
[pid  1677] read(0, "Africa/Abidjan\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 30732) = 30732
[pid  1677] madvise(0xb0f56000, 36864, MADV_DONTNEED) = 0
[pid  1677] close(0)                    = 0
[pid  1677] madvise(0xb0f47000, 61440, MADV_DONTNEED) = 0
[pid  1677] madvise(0xb0f38000, 61440, MADV_DONTNEED) = 0
[pid  1677] write(2, "[1677] Sep 12 16:46:56 Exit befo"..., 108[1677] Sep 12 16:46:56 Exit before auth from <192.168.6.202:40262>: (user 'root', 0 fails): Exited normally
) = 108

[pid  1677] fstatat64(AT_FDCWD, "/", {st_mode=S_IFDIR|0755, st_size=0, ...}, 0) = 0
[pid  1677] fstatat64(AT_FDCWD, "//.ssh", 0xbbd56538, 0) = -1 ENOENT (No such file or directory)

dropbear read path //.ssh, but my environment no has //.ssh, Where should I modify the C code file

[mkj]

I think that fstatat64 is from

dropbear/src/svr-authpubkey.c

Line 559 in 9925b00

if (checkfileperm(filename) != DROPBEAR_SUCCESS) {

The home directory gets filled out by getpwnam(), you could update pw_dir in fill_passwd() I guess.

dropbear/src/common-session.c

Line 648 in 9925b00

ses.authstate.pw_dir = m_strdup(pw->pw_dir);