Dan Willemsen | d279748 | 2017-07-26 13:13:13 -0700 | [diff] [blame^] | 1 | // Copyright 2011 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // +build darwin dragonfly freebsd !android,linux netbsd openbsd solaris |
| 6 | // +build cgo |
| 7 | |
| 8 | package user |
| 9 | |
| 10 | import ( |
| 11 | "fmt" |
| 12 | "strconv" |
| 13 | "strings" |
| 14 | "syscall" |
| 15 | "unsafe" |
| 16 | ) |
| 17 | |
| 18 | /* |
| 19 | #cgo solaris CFLAGS: -D_POSIX_PTHREAD_SEMANTICS |
| 20 | #include <unistd.h> |
| 21 | #include <sys/types.h> |
| 22 | #include <pwd.h> |
| 23 | #include <grp.h> |
| 24 | #include <stdlib.h> |
| 25 | |
| 26 | static int mygetpwuid_r(int uid, struct passwd *pwd, |
| 27 | char *buf, size_t buflen, struct passwd **result) { |
| 28 | return getpwuid_r(uid, pwd, buf, buflen, result); |
| 29 | } |
| 30 | |
| 31 | static int mygetpwnam_r(const char *name, struct passwd *pwd, |
| 32 | char *buf, size_t buflen, struct passwd **result) { |
| 33 | return getpwnam_r(name, pwd, buf, buflen, result); |
| 34 | } |
| 35 | |
| 36 | static int mygetgrgid_r(int gid, struct group *grp, |
| 37 | char *buf, size_t buflen, struct group **result) { |
| 38 | return getgrgid_r(gid, grp, buf, buflen, result); |
| 39 | } |
| 40 | |
| 41 | static int mygetgrnam_r(const char *name, struct group *grp, |
| 42 | char *buf, size_t buflen, struct group **result) { |
| 43 | return getgrnam_r(name, grp, buf, buflen, result); |
| 44 | } |
| 45 | */ |
| 46 | import "C" |
| 47 | |
| 48 | func current() (*User, error) { |
| 49 | return lookupUnixUid(syscall.Getuid()) |
| 50 | } |
| 51 | |
| 52 | func lookupUser(username string) (*User, error) { |
| 53 | var pwd C.struct_passwd |
| 54 | var result *C.struct_passwd |
| 55 | nameC := C.CString(username) |
| 56 | defer C.free(unsafe.Pointer(nameC)) |
| 57 | |
| 58 | buf := alloc(userBuffer) |
| 59 | defer buf.free() |
| 60 | |
| 61 | err := retryWithBuffer(buf, func() syscall.Errno { |
| 62 | // mygetpwnam_r is a wrapper around getpwnam_r to avoid |
| 63 | // passing a size_t to getpwnam_r, because for unknown |
| 64 | // reasons passing a size_t to getpwnam_r doesn't work on |
| 65 | // Solaris. |
| 66 | return syscall.Errno(C.mygetpwnam_r(nameC, |
| 67 | &pwd, |
| 68 | (*C.char)(buf.ptr), |
| 69 | C.size_t(buf.size), |
| 70 | &result)) |
| 71 | }) |
| 72 | if err != nil { |
| 73 | return nil, fmt.Errorf("user: lookup username %s: %v", username, err) |
| 74 | } |
| 75 | if result == nil { |
| 76 | return nil, UnknownUserError(username) |
| 77 | } |
| 78 | return buildUser(&pwd), err |
| 79 | } |
| 80 | |
| 81 | func lookupUserId(uid string) (*User, error) { |
| 82 | i, e := strconv.Atoi(uid) |
| 83 | if e != nil { |
| 84 | return nil, e |
| 85 | } |
| 86 | return lookupUnixUid(i) |
| 87 | } |
| 88 | |
| 89 | func lookupUnixUid(uid int) (*User, error) { |
| 90 | var pwd C.struct_passwd |
| 91 | var result *C.struct_passwd |
| 92 | |
| 93 | buf := alloc(userBuffer) |
| 94 | defer buf.free() |
| 95 | |
| 96 | err := retryWithBuffer(buf, func() syscall.Errno { |
| 97 | // mygetpwuid_r is a wrapper around getpwuid_r to |
| 98 | // to avoid using uid_t because C.uid_t(uid) for |
| 99 | // unknown reasons doesn't work on linux. |
| 100 | return syscall.Errno(C.mygetpwuid_r(C.int(uid), |
| 101 | &pwd, |
| 102 | (*C.char)(buf.ptr), |
| 103 | C.size_t(buf.size), |
| 104 | &result)) |
| 105 | }) |
| 106 | if err != nil { |
| 107 | return nil, fmt.Errorf("user: lookup userid %d: %v", uid, err) |
| 108 | } |
| 109 | if result == nil { |
| 110 | return nil, UnknownUserIdError(uid) |
| 111 | } |
| 112 | return buildUser(&pwd), nil |
| 113 | } |
| 114 | |
| 115 | func buildUser(pwd *C.struct_passwd) *User { |
| 116 | u := &User{ |
| 117 | Uid: strconv.Itoa(int(pwd.pw_uid)), |
| 118 | Gid: strconv.Itoa(int(pwd.pw_gid)), |
| 119 | Username: C.GoString(pwd.pw_name), |
| 120 | Name: C.GoString(pwd.pw_gecos), |
| 121 | HomeDir: C.GoString(pwd.pw_dir), |
| 122 | } |
| 123 | // The pw_gecos field isn't quite standardized. Some docs |
| 124 | // say: "It is expected to be a comma separated list of |
| 125 | // personal data where the first item is the full name of the |
| 126 | // user." |
| 127 | if i := strings.Index(u.Name, ","); i >= 0 { |
| 128 | u.Name = u.Name[:i] |
| 129 | } |
| 130 | return u |
| 131 | } |
| 132 | |
| 133 | func currentGroup() (*Group, error) { |
| 134 | return lookupUnixGid(syscall.Getgid()) |
| 135 | } |
| 136 | |
| 137 | func lookupGroup(groupname string) (*Group, error) { |
| 138 | var grp C.struct_group |
| 139 | var result *C.struct_group |
| 140 | |
| 141 | buf := alloc(groupBuffer) |
| 142 | defer buf.free() |
| 143 | cname := C.CString(groupname) |
| 144 | defer C.free(unsafe.Pointer(cname)) |
| 145 | |
| 146 | err := retryWithBuffer(buf, func() syscall.Errno { |
| 147 | return syscall.Errno(C.mygetgrnam_r(cname, |
| 148 | &grp, |
| 149 | (*C.char)(buf.ptr), |
| 150 | C.size_t(buf.size), |
| 151 | &result)) |
| 152 | }) |
| 153 | if err != nil { |
| 154 | return nil, fmt.Errorf("user: lookup groupname %s: %v", groupname, err) |
| 155 | } |
| 156 | if result == nil { |
| 157 | return nil, UnknownGroupError(groupname) |
| 158 | } |
| 159 | return buildGroup(&grp), nil |
| 160 | } |
| 161 | |
| 162 | func lookupGroupId(gid string) (*Group, error) { |
| 163 | i, e := strconv.Atoi(gid) |
| 164 | if e != nil { |
| 165 | return nil, e |
| 166 | } |
| 167 | return lookupUnixGid(i) |
| 168 | } |
| 169 | |
| 170 | func lookupUnixGid(gid int) (*Group, error) { |
| 171 | var grp C.struct_group |
| 172 | var result *C.struct_group |
| 173 | |
| 174 | buf := alloc(groupBuffer) |
| 175 | defer buf.free() |
| 176 | |
| 177 | err := retryWithBuffer(buf, func() syscall.Errno { |
| 178 | // mygetgrgid_r is a wrapper around getgrgid_r to |
| 179 | // to avoid using gid_t because C.gid_t(gid) for |
| 180 | // unknown reasons doesn't work on linux. |
| 181 | return syscall.Errno(C.mygetgrgid_r(C.int(gid), |
| 182 | &grp, |
| 183 | (*C.char)(buf.ptr), |
| 184 | C.size_t(buf.size), |
| 185 | &result)) |
| 186 | }) |
| 187 | if err != nil { |
| 188 | return nil, fmt.Errorf("user: lookup groupid %d: %v", gid, err) |
| 189 | } |
| 190 | if result == nil { |
| 191 | return nil, UnknownGroupIdError(strconv.Itoa(gid)) |
| 192 | } |
| 193 | return buildGroup(&grp), nil |
| 194 | } |
| 195 | |
| 196 | func buildGroup(grp *C.struct_group) *Group { |
| 197 | g := &Group{ |
| 198 | Gid: strconv.Itoa(int(grp.gr_gid)), |
| 199 | Name: C.GoString(grp.gr_name), |
| 200 | } |
| 201 | return g |
| 202 | } |
| 203 | |
| 204 | type bufferKind C.int |
| 205 | |
| 206 | const ( |
| 207 | userBuffer = bufferKind(C._SC_GETPW_R_SIZE_MAX) |
| 208 | groupBuffer = bufferKind(C._SC_GETGR_R_SIZE_MAX) |
| 209 | ) |
| 210 | |
| 211 | func (k bufferKind) initialSize() C.size_t { |
| 212 | sz := C.sysconf(C.int(k)) |
| 213 | if sz == -1 { |
| 214 | // DragonFly and FreeBSD do not have _SC_GETPW_R_SIZE_MAX. |
| 215 | // Additionally, not all Linux systems have it, either. For |
| 216 | // example, the musl libc returns -1. |
| 217 | return 1024 |
| 218 | } |
| 219 | if !isSizeReasonable(int64(sz)) { |
| 220 | // Truncate. If this truly isn't enough, retryWithBuffer will error on the first run. |
| 221 | return maxBufferSize |
| 222 | } |
| 223 | return C.size_t(sz) |
| 224 | } |
| 225 | |
| 226 | type memBuffer struct { |
| 227 | ptr unsafe.Pointer |
| 228 | size C.size_t |
| 229 | } |
| 230 | |
| 231 | func alloc(kind bufferKind) *memBuffer { |
| 232 | sz := kind.initialSize() |
| 233 | return &memBuffer{ |
| 234 | ptr: C.malloc(sz), |
| 235 | size: sz, |
| 236 | } |
| 237 | } |
| 238 | |
| 239 | func (mb *memBuffer) resize(newSize C.size_t) { |
| 240 | mb.ptr = C.realloc(mb.ptr, newSize) |
| 241 | mb.size = newSize |
| 242 | } |
| 243 | |
| 244 | func (mb *memBuffer) free() { |
| 245 | C.free(mb.ptr) |
| 246 | } |
| 247 | |
| 248 | // retryWithBuffer repeatedly calls f(), increasing the size of the |
| 249 | // buffer each time, until f succeeds, fails with a non-ERANGE error, |
| 250 | // or the buffer exceeds a reasonable limit. |
| 251 | func retryWithBuffer(buf *memBuffer, f func() syscall.Errno) error { |
| 252 | for { |
| 253 | errno := f() |
| 254 | if errno == 0 { |
| 255 | return nil |
| 256 | } else if errno != syscall.ERANGE { |
| 257 | return errno |
| 258 | } |
| 259 | newSize := buf.size * 2 |
| 260 | if !isSizeReasonable(int64(newSize)) { |
| 261 | return fmt.Errorf("internal buffer exceeds %d bytes", maxBufferSize) |
| 262 | } |
| 263 | buf.resize(newSize) |
| 264 | } |
| 265 | } |
| 266 | |
| 267 | const maxBufferSize = 1 << 20 |
| 268 | |
| 269 | func isSizeReasonable(sz int64) bool { |
| 270 | return sz > 0 && sz <= maxBufferSize |
| 271 | } |