| Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 1 | /* |
| 2 | |
| 3 | uidswap.c |
| 4 | |
| 5 | Author: Tatu Ylonen <ylo@cs.hut.fi> |
| 6 | |
| 7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 8 | All rights reserved |
| 9 | |
| 10 | Created: Sat Sep 9 01:56:14 1995 ylo |
| 11 | |
| 12 | Code for uid-swapping. |
| 13 | |
| 14 | */ |
| 15 | |
| 16 | #include "includes.h" |
| 17 | RCSID("$Id: uidswap.c,v 1.1 1999/10/27 03:42:46 damien Exp $"); |
| 18 | |
| 19 | #include "ssh.h" |
| 20 | #include "uidswap.h" |
| 21 | |
| 22 | /* Note: all these functions must work in all of the following cases: |
| 23 | |
| 24 | 1. euid=0, ruid=0 |
| 25 | 2. euid=0, ruid!=0 |
| 26 | 3. euid!=0, ruid!=0 |
| 27 | |
| 28 | Additionally, they must work regardless of whether the system has |
| 29 | POSIX saved uids or not. */ |
| 30 | |
| 31 | #ifdef _POSIX_SAVED_IDS |
| 32 | /* Lets assume that posix saved ids also work with seteuid, even though that |
| 33 | is not part of the posix specification. */ |
| 34 | #define SAVED_IDS_WORK_WITH_SETEUID |
| 35 | #endif /* _POSIX_SAVED_IDS */ |
| 36 | |
| 37 | /* Saved effective uid. */ |
| 38 | static uid_t saved_euid = 0; |
| 39 | |
| 40 | /* Temporarily changes to the given uid. If the effective user id is not |
| 41 | root, this does nothing. This call cannot be nested. */ |
| 42 | |
| 43 | void temporarily_use_uid(uid_t uid) |
| 44 | { |
| 45 | #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| 46 | |
| 47 | /* Save the current euid. */ |
| 48 | saved_euid = geteuid(); |
| 49 | |
| 50 | /* Set the effective uid to the given (unprivileged) uid. */ |
| 51 | if (seteuid(uid) == -1) |
| 52 | debug("seteuid %d: %.100s", (int)uid, strerror(errno)); |
| 53 | |
| 54 | #else /* SAVED_IDS_WORK_WITH_SETUID */ |
| 55 | |
| 56 | /* Propagate the privileged uid to all of our uids. */ |
| 57 | if (setuid(geteuid()) < 0) |
| 58 | debug("setuid %d: %.100s", (int)geteuid(), strerror(errno)); |
| 59 | |
| 60 | /* Set the effective uid to the given (unprivileged) uid. */ |
| 61 | if (seteuid(uid) == -1) |
| 62 | debug("seteuid %d: %.100s", (int)uid, strerror(errno)); |
| 63 | |
| 64 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 65 | |
| 66 | } |
| 67 | |
| 68 | /* Restores to the original uid. */ |
| 69 | |
| 70 | void restore_uid() |
| 71 | { |
| 72 | #ifdef SAVED_IDS_WORK_WITH_SETEUID |
| 73 | |
| 74 | /* Set the effective uid back to the saved uid. */ |
| 75 | if (seteuid(saved_euid) < 0) |
| 76 | debug("seteuid %d: %.100s", (int)saved_euid, strerror(errno)); |
| 77 | |
| 78 | #else /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 79 | |
| 80 | /* We are unable to restore the real uid to its unprivileged value. */ |
| 81 | /* Propagate the real uid (usually more privileged) to effective uid |
| 82 | as well. */ |
| 83 | setuid(getuid()); |
| 84 | |
| 85 | #endif /* SAVED_IDS_WORK_WITH_SETEUID */ |
| 86 | } |
| 87 | |
| 88 | /* Permanently sets all uids to the given uid. This cannot be called while |
| 89 | temporarily_use_uid is effective. */ |
| 90 | |
| 91 | void permanently_set_uid(uid_t uid) |
| 92 | { |
| 93 | if (setuid(uid) < 0) |
| 94 | debug("setuid %d: %.100s", (int)uid, strerror(errno)); |
| 95 | } |