From b69aba74578adf58f48de0f21dceddc2d9f1c4b1 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 11 Jan 2022 09:55:16 +0900
Subject: [PATCH] Improve error handling of cryptohash computations
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The existing cryptohash facility was causing problems in some code paths
related to MD5 (frontend and backend) that relied on the fact that the
only type of error that could happen would be an OOM, as the MD5
implementation used in PostgreSQL ~13 (the in-core implementation is
used when compiling with or without OpenSSL in those older versions),
could fail only under this circumstance.

The new cryptohash facilities can fail for reasons other than OOMs, like
attempting MD5 when FIPS is enabled (upstream OpenSSL allows that up to
1.0.2, Fedora and Photon patch OpenSSL 1.1.1 to allow that), so this
would cause incorrect reports to show up.

This commit extends the cryptohash APIs so as callers of those routines
can fetch more context when an error happens, by using a new routine
called pg_cryptohash_error().  The error states are stored within each
implementation's internal context data, so as it is possible to extend
the logic depending on what's suited for an implementation.  The default
implementation requires few error states, but OpenSSL could report
various issues depending on its internal state so more is needed in
cryptohash_openssl.c, and the code is shaped so as we are always able to
grab the necessary information.

The core code is changed to adapt to the new error routine, painting
more "const" across the call stack where the static errors are stored,
particularly in authentication code paths on variables that provide
log details.  This way, any future changes would warn if attempting to
free these strings.  The MD5 authentication code was also a bit blurry
about the handling of "logdetail" (LOG sent to the postmaster), so
improve the comments related that, while on it.

The origin of the problem is 87ae969, that introduced the centralized
cryptohash facility.  Extra changes are done for pgcrypto in v14 for the
non-OpenSSL code path to cope with the improvements done by this
commit.

Reported-by: Michael Mühlbeyer
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/89B7F072-5BBE-4C92-903E-D83E865D9367@trivadis.com
Backpatch-through: 14
---
 contrib/passwordcheck/passwordcheck.c     |  2 +-
 contrib/uuid-ossp/uuid-ossp.c             | 18 +++--
 src/backend/commands/user.c               |  4 +-
 src/backend/libpq/auth-sasl.c             |  2 +-
 src/backend/libpq/auth-scram.c            |  5 +-
 src/backend/libpq/auth.c                  | 33 ++++----
 src/backend/libpq/crypt.c                 | 38 +++++----
 src/backend/replication/backup_manifest.c | 11 ++-
 src/backend/utils/adt/cryptohashfuncs.c   | 25 +++---
 src/common/cryptohash.c                   | 57 +++++++++++++-
 src/common/cryptohash_openssl.c           | 93 +++++++++++++++++++++++
 src/common/md5_common.c                   | 20 +++--
 src/include/common/cryptohash.h           |  1 +
 src/include/common/md5.h                  |  9 ++-
 src/include/libpq/crypt.h                 |  7 +-
 src/include/libpq/sasl.h                  |  4 +-
 src/interfaces/libpq/fe-auth.c            | 22 +++++-
 src/tools/pgindent/typedefs.list          |  1 +
 18 files changed, 275 insertions(+), 77 deletions(-)

diff --git a/contrib/passwordcheck/passwordcheck.c b/contrib/passwordcheck/passwordcheck.c
index 1da323c0aa..074836336d 100644
--- a/contrib/passwordcheck/passwordcheck.c
+++ b/contrib/passwordcheck/passwordcheck.c
@@ -74,7 +74,7 @@ check_password(const char *username,
 		 *
 		 * We only check for username = password.
 		 */
-		char	   *logdetail;
+		const char *logdetail = NULL;
 
 		if (plain_crypt_verify(username, shadow_pass, username, &logdetail) == STATUS_OK)
 			ereport(ERROR,
diff --git a/contrib/uuid-ossp/uuid-ossp.c b/contrib/uuid-ossp/uuid-ossp.c
index 4859bd1933..7c0fb812fd 100644
--- a/contrib/uuid-ossp/uuid-ossp.c
+++ b/contrib/uuid-ossp/uuid-ossp.c
@@ -319,14 +319,17 @@ uuid_generate_internal(int v, unsigned char *ns, const char *ptr, int len)
 					pg_cryptohash_ctx *ctx = pg_cryptohash_create(PG_MD5);
 
 					if (pg_cryptohash_init(ctx) < 0)
-						elog(ERROR, "could not initialize %s context", "MD5");
+						elog(ERROR, "could not initialize %s context: %s", "MD5",
+							 pg_cryptohash_error(ctx));
 					if (pg_cryptohash_update(ctx, ns, sizeof(uu)) < 0 ||
 						pg_cryptohash_update(ctx, (unsigned char *) ptr, len) < 0)
-						elog(ERROR, "could not update %s context", "MD5");
+						elog(ERROR, "could not update %s context: %s", "MD5",
+							 pg_cryptohash_error(ctx));
 					/* we assume sizeof MD5 result is 16, same as UUID size */
 					if (pg_cryptohash_final(ctx, (unsigned char *) &uu,
 											sizeof(uu)) < 0)
-						elog(ERROR, "could not finalize %s context", "MD5");
+						elog(ERROR, "could not finalize %s context: %s", "MD5",
+							 pg_cryptohash_error(ctx));
 					pg_cryptohash_free(ctx);
 				}
 				else
@@ -335,12 +338,15 @@ uuid_generate_internal(int v, unsigned char *ns, const char *ptr, int len)
 					unsigned char sha1result[SHA1_DIGEST_LENGTH];
 
 					if (pg_cryptohash_init(ctx) < 0)
-						elog(ERROR, "could not initialize %s context", "SHA1");
+						elog(ERROR, "could not initialize %s context: %s", "SHA1",
+							 pg_cryptohash_error(ctx));
 					if (pg_cryptohash_update(ctx, ns, sizeof(uu)) < 0 ||
 						pg_cryptohash_update(ctx, (unsigned char *) ptr, len) < 0)
-						elog(ERROR, "could not update %s context", "SHA1");
+						elog(ERROR, "could not update %s context: %s", "SHA1",
+							 pg_cryptohash_error(ctx));
 					if (pg_cryptohash_final(ctx, sha1result, sizeof(sha1result)) < 0)
-						elog(ERROR, "could not finalize %s context", "SHA1");
+						elog(ERROR, "could not finalize %s context: %s", "SHA1",
+							 pg_cryptohash_error(ctx));
 					pg_cryptohash_free(ctx);
 
 					memcpy(&uu, sha1result, sizeof(uu));
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index c79c8d247f..3b512a84b3 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -355,7 +355,7 @@ CreateRole(ParseState *pstate, CreateRoleStmt *stmt)
 	if (password)
 	{
 		char	   *shadow_pass;
-		char	   *logdetail;
+		const char *logdetail = NULL;
 
 		/*
 		 * Don't allow an empty password. Libpq treats an empty password the
@@ -775,7 +775,7 @@ AlterRole(ParseState *pstate, AlterRoleStmt *stmt)
 	if (password)
 	{
 		char	   *shadow_pass;
-		char	   *logdetail;
+		const char *logdetail = NULL;
 
 		/* Like in CREATE USER, don't allow an empty password. */
 		if (password[0] == '\0' ||
diff --git a/src/backend/libpq/auth-sasl.c b/src/backend/libpq/auth-sasl.c
index 6cc776edeb..a1d7dbb6d5 100644
--- a/src/backend/libpq/auth-sasl.c
+++ b/src/backend/libpq/auth-sasl.c
@@ -50,7 +50,7 @@
  */
 int
 CheckSASLAuth(const pg_be_sasl_mech *mech, Port *port, char *shadow_pass,
-			  char **logdetail)
+			  const char **logdetail)
 {
 	StringInfoData sasl_mechs;
 	int			mtype;
diff --git a/src/backend/libpq/auth-scram.c b/src/backend/libpq/auth-scram.c
index fdfc3d5067..7c9dee70ce 100644
--- a/src/backend/libpq/auth-scram.c
+++ b/src/backend/libpq/auth-scram.c
@@ -111,7 +111,8 @@ static void scram_get_mechanisms(Port *port, StringInfo buf);
 static void *scram_init(Port *port, const char *selected_mech,
 						const char *shadow_pass);
 static int	scram_exchange(void *opaq, const char *input, int inputlen,
-						   char **output, int *outputlen, char **logdetail);
+						   char **output, int *outputlen,
+						   const char **logdetail);
 
 /* Mechanism declaration */
 const pg_be_sasl_mech pg_be_scram_mech = {
@@ -335,7 +336,7 @@ scram_init(Port *port, const char *selected_mech, const char *shadow_pass)
  */
 static int
 scram_exchange(void *opaq, const char *input, int inputlen,
-			   char **output, int *outputlen, char **logdetail)
+			   char **output, int *outputlen, const char **logdetail)
 {
 	scram_state *state = (scram_state *) opaq;
 	int			result;
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index b0d6988aff..9a266beb5d 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -45,7 +45,7 @@
  * Global authentication functions
  *----------------------------------------------------------------
  */
-static void auth_failed(Port *port, int status, char *logdetail);
+static void auth_failed(Port *port, int status, const char *logdetail);
 static char *recv_password_packet(Port *port);
 static void set_authn_id(Port *port, const char *id);
 
@@ -54,10 +54,11 @@ static void set_authn_id(Port *port, const char *id);
  * Password-based authentication methods (password, md5, and scram-sha-256)
  *----------------------------------------------------------------
  */
-static int	CheckPasswordAuth(Port *port, char **logdetail);
-static int	CheckPWChallengeAuth(Port *port, char **logdetail);
+static int	CheckPasswordAuth(Port *port, const char **logdetail);
+static int	CheckPWChallengeAuth(Port *port, const char **logdetail);
 
-static int	CheckMD5Auth(Port *port, char *shadow_pass, char **logdetail);
+static int	CheckMD5Auth(Port *port, char *shadow_pass,
+						 const char **logdetail);
 
 
 /*----------------------------------------------------------------
@@ -247,7 +248,7 @@ ClientAuthentication_hook_type ClientAuthentication_hook = NULL;
  * particular, if logdetail isn't NULL, we send that string to the log.
  */
 static void
-auth_failed(Port *port, int status, char *logdetail)
+auth_failed(Port *port, int status, const char *logdetail)
 {
 	const char *errstr;
 	char	   *cdetail;
@@ -383,7 +384,7 @@ void
 ClientAuthentication(Port *port)
 {
 	int			status = STATUS_ERROR;
-	char	   *logdetail = NULL;
+	const char *logdetail = NULL;
 
 	/*
 	 * Get the authentication method to use for this frontend/database
@@ -769,7 +770,7 @@ recv_password_packet(Port *port)
  * Plaintext password authentication.
  */
 static int
-CheckPasswordAuth(Port *port, char **logdetail)
+CheckPasswordAuth(Port *port, const char **logdetail)
 {
 	char	   *passwd;
 	int			result;
@@ -804,7 +805,7 @@ CheckPasswordAuth(Port *port, char **logdetail)
  * MD5 and SCRAM authentication.
  */
 static int
-CheckPWChallengeAuth(Port *port, char **logdetail)
+CheckPWChallengeAuth(Port *port, const char **logdetail)
 {
 	int			auth_result;
 	char	   *shadow_pass;
@@ -866,7 +867,7 @@ CheckPWChallengeAuth(Port *port, char **logdetail)
 }
 
 static int
-CheckMD5Auth(Port *port, char *shadow_pass, char **logdetail)
+CheckMD5Auth(Port *port, char *shadow_pass, const char **logdetail)
 {
 	char		md5Salt[4];		/* Password salt */
 	char	   *passwd;
@@ -3085,6 +3086,8 @@ PerformRadiusTransaction(const char *server, const char *secret, const char *por
 	md5trailer = packet->vector;
 	for (i = 0; i < encryptedpasswordlen; i += RADIUS_VECTOR_LENGTH)
 	{
+		const char *errstr = NULL;
+
 		memcpy(cryptvector + strlen(secret), md5trailer, RADIUS_VECTOR_LENGTH);
 
 		/*
@@ -3093,10 +3096,12 @@ PerformRadiusTransaction(const char *server, const char *secret, const char *por
 		 */
 		md5trailer = encryptedpassword + i;
 
-		if (!pg_md5_binary(cryptvector, strlen(secret) + RADIUS_VECTOR_LENGTH, encryptedpassword + i))
+		if (!pg_md5_binary(cryptvector, strlen(secret) + RADIUS_VECTOR_LENGTH,
+						   encryptedpassword + i, &errstr))
 		{
 			ereport(LOG,
-					(errmsg("could not perform MD5 encryption of password")));
+					(errmsg("could not perform MD5 encryption of password: %s",
+							errstr)));
 			pfree(cryptvector);
 			pg_freeaddrinfo_all(hint.ai_family, serveraddrs);
 			return STATUS_ERROR;
@@ -3181,6 +3186,7 @@ PerformRadiusTransaction(const char *server, const char *secret, const char *por
 		struct timeval timeout;
 		struct timeval now;
 		int64		timeoutval;
+		const char *errstr = NULL;
 
 		gettimeofday(&now, NULL);
 		timeoutval = (endtime.tv_sec * 1000000 + endtime.tv_usec) - (now.tv_sec * 1000000 + now.tv_usec);
@@ -3299,10 +3305,11 @@ PerformRadiusTransaction(const char *server, const char *secret, const char *por
 
 		if (!pg_md5_binary(cryptvector,
 						   packetlength + strlen(secret),
-						   encryptedpassword))
+						   encryptedpassword, &errstr))
 		{
 			ereport(LOG,
-					(errmsg("could not perform MD5 encryption of received packet")));
+					(errmsg("could not perform MD5 encryption of received packet: %s",
+							errstr)));
 			pfree(cryptvector);
 			continue;
 		}
diff --git a/src/backend/libpq/crypt.c b/src/backend/libpq/crypt.c
index 7ebcdd7123..1ff8b0507d 100644
--- a/src/backend/libpq/crypt.c
+++ b/src/backend/libpq/crypt.c
@@ -34,7 +34,7 @@
  * sent to the client, to avoid giving away user information!
  */
 char *
-get_role_password(const char *role, char **logdetail)
+get_role_password(const char *role, const char **logdetail)
 {
 	TimestampTz vuntil = 0;
 	HeapTuple	roleTup;
@@ -116,6 +116,7 @@ encrypt_password(PasswordType target_type, const char *role,
 {
 	PasswordType guessed_type = get_password_type(password);
 	char	   *encrypted_password;
+	const char *errstr = NULL;
 
 	if (guessed_type != PASSWORD_TYPE_PLAINTEXT)
 	{
@@ -132,8 +133,8 @@ encrypt_password(PasswordType target_type, const char *role,
 			encrypted_password = palloc(MD5_PASSWD_LEN + 1);
 
 			if (!pg_md5_encrypt(password, role, strlen(role),
-								encrypted_password))
-				elog(ERROR, "password encryption failed");
+								encrypted_password, &errstr))
+				elog(ERROR, "password encryption failed: %s", errstr);
 			return encrypted_password;
 
 		case PASSWORD_TYPE_SCRAM_SHA_256:
@@ -159,17 +160,18 @@ encrypt_password(PasswordType target_type, const char *role,
  * 'client_pass' is the response given by the remote user to the MD5 challenge.
  * 'md5_salt' is the salt used in the MD5 authentication challenge.
  *
- * In the error case, optionally store a palloc'd string at *logdetail
- * that will be sent to the postmaster log (but not the client).
+ * In the error case, save a string at *logdetail that will be sent to the
+ * postmaster log (but not the client).
  */
 int
 md5_crypt_verify(const char *role, const char *shadow_pass,
 				 const char *client_pass,
 				 const char *md5_salt, int md5_salt_len,
-				 char **logdetail)
+				 const char **logdetail)
 {
 	int			retval;
 	char		crypt_pwd[MD5_PASSWD_LEN + 1];
+	const char *errstr = NULL;
 
 	Assert(md5_salt_len > 0);
 
@@ -183,16 +185,13 @@ md5_crypt_verify(const char *role, const char *shadow_pass,
 
 	/*
 	 * Compute the correct answer for the MD5 challenge.
-	 *
-	 * We do not bother setting logdetail for any pg_md5_encrypt failure
-	 * below: the only possible error is out-of-memory, which is unlikely, and
-	 * if it did happen adding a psprintf call would only make things worse.
 	 */
 	/* stored password already encrypted, only do salt */
 	if (!pg_md5_encrypt(shadow_pass + strlen("md5"),
 						md5_salt, md5_salt_len,
-						crypt_pwd))
+						crypt_pwd, &errstr))
 	{
+		*logdetail = errstr;
 		return STATUS_ERROR;
 	}
 
@@ -215,15 +214,16 @@ md5_crypt_verify(const char *role, const char *shadow_pass,
  * pg_authid.rolpassword.
  * 'client_pass' is the password given by the remote user.
  *
- * In the error case, optionally store a palloc'd string at *logdetail
- * that will be sent to the postmaster log (but not the client).
+ * In the error case, store a string at *logdetail that will be sent to the
+ * postmaster log (but not the client).
  */
 int
 plain_crypt_verify(const char *role, const char *shadow_pass,
 				   const char *client_pass,
-				   char **logdetail)
+				   const char **logdetail)
 {
 	char		crypt_client_pass[MD5_PASSWD_LEN + 1];
+	const char *errstr = NULL;
 
 	/*
 	 * Client sent password in plaintext.  If we have an MD5 hash stored, hash
@@ -251,14 +251,10 @@ plain_crypt_verify(const char *role, const char *shadow_pass,
 			if (!pg_md5_encrypt(client_pass,
 								role,
 								strlen(role),
-								crypt_client_pass))
+								crypt_client_pass,
+								&errstr))
 			{
-				/*
-				 * We do not bother setting logdetail for pg_md5_encrypt
-				 * failure: the only possible error is out-of-memory, which is
-				 * unlikely, and if it did happen adding a psprintf call would
-				 * only make things worse.
-				 */
+				*logdetail = errstr;
 				return STATUS_ERROR;
 			}
 			if (strcmp(crypt_client_pass, shadow_pass) == 0)
diff --git a/src/backend/replication/backup_manifest.c b/src/backend/replication/backup_manifest.c
index 1678b89266..7e22f9e48c 100644
--- a/src/backend/replication/backup_manifest.c
+++ b/src/backend/replication/backup_manifest.c
@@ -68,7 +68,8 @@ InitializeBackupManifest(backup_manifest_info *manifest,
 		manifest->buffile = BufFileCreateTemp(false);
 		manifest->manifest_ctx = pg_cryptohash_create(PG_SHA256);
 		if (pg_cryptohash_init(manifest->manifest_ctx) < 0)
-			elog(ERROR, "failed to initialize checksum of backup manifest");
+			elog(ERROR, "failed to initialize checksum of backup manifest: %s",
+				 pg_cryptohash_error(manifest->manifest_ctx));
 	}
 
 	manifest->manifest_size = UINT64CONST(0);
@@ -311,7 +312,7 @@ AddWALInfoToBackupManifest(backup_manifest_info *manifest, XLogRecPtr startptr,
  * Finalize the backup manifest, and send it to the client.
  */
 void
-SendBackupManifest(backup_manifest_info *manifest, bbsink *sink)
+SendBackupManifest(backup_manifest_info *manifest, bbsink * sink)
 {
 	uint8		checksumbuf[PG_SHA256_DIGEST_LENGTH];
 	char		checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH];
@@ -334,7 +335,8 @@ SendBackupManifest(backup_manifest_info *manifest, bbsink *sink)
 	manifest->still_checksumming = false;
 	if (pg_cryptohash_final(manifest->manifest_ctx, checksumbuf,
 							sizeof(checksumbuf)) < 0)
-		elog(ERROR, "failed to finalize checksum of backup manifest");
+		elog(ERROR, "failed to finalize checksum of backup manifest: %s",
+			 pg_cryptohash_error(manifest->manifest_ctx));
 	AppendStringToManifest(manifest, "\"Manifest-Checksum\": \"");
 
 	hex_encode((char *) checksumbuf, sizeof checksumbuf, checksumstringbuf);
@@ -391,7 +393,8 @@ AppendStringToManifest(backup_manifest_info *manifest, char *s)
 	if (manifest->still_checksumming)
 	{
 		if (pg_cryptohash_update(manifest->manifest_ctx, (uint8 *) s, len) < 0)
-			elog(ERROR, "failed to update checksum of backup manifest");
+			elog(ERROR, "failed to update checksum of backup manifest: %s",
+				 pg_cryptohash_error(manifest->manifest_ctx));
 	}
 	BufFileWrite(manifest->buffile, s, len);
 	manifest->manifest_size += len;
diff --git a/src/backend/utils/adt/cryptohashfuncs.c b/src/backend/utils/adt/cryptohashfuncs.c
index 7e43c0e01d..03d84ea217 100644
--- a/src/backend/utils/adt/cryptohashfuncs.c
+++ b/src/backend/utils/adt/cryptohashfuncs.c
@@ -35,15 +35,17 @@ md5_text(PG_FUNCTION_ARGS)
 	text	   *in_text = PG_GETARG_TEXT_PP(0);
 	size_t		len;
 	char		hexsum[MD5_HASH_LEN + 1];
+	const char *errstr = NULL;
 
 	/* Calculate the length of the buffer using varlena metadata */
 	len = VARSIZE_ANY_EXHDR(in_text);
 
 	/* get the hash result */
-	if (pg_md5_hash(VARDATA_ANY(in_text), len, hexsum) == false)
+	if (pg_md5_hash(VARDATA_ANY(in_text), len, hexsum, &errstr) == false)
 		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
+				(errcode(ERRCODE_INTERNAL_ERROR),
+				 errmsg("could not compute %s hash: %s", "MD5",
+						errstr)));
 
 	/* convert to text and return it */
 	PG_RETURN_TEXT_P(cstring_to_text(hexsum));
@@ -58,12 +60,14 @@ md5_bytea(PG_FUNCTION_ARGS)
 	bytea	   *in = PG_GETARG_BYTEA_PP(0);
 	size_t		len;
 	char		hexsum[MD5_HASH_LEN + 1];
+	const char *errstr = NULL;
 
 	len = VARSIZE_ANY_EXHDR(in);
-	if (pg_md5_hash(VARDATA_ANY(in), len, hexsum) == false)
+	if (pg_md5_hash(VARDATA_ANY(in), len, hexsum, &errstr) == false)
 		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
+				(errcode(ERRCODE_INTERNAL_ERROR),
+				 errmsg("could not compute %s hash: %s", "MD5",
+						errstr)));
 
 	PG_RETURN_TEXT_P(cstring_to_text(hexsum));
 }
@@ -111,12 +115,15 @@ cryptohash_internal(pg_cryptohash_type type, bytea *input)
 
 	ctx = pg_cryptohash_create(type);
 	if (pg_cryptohash_init(ctx) < 0)
-		elog(ERROR, "could not initialize %s context", typestr);
+		elog(ERROR, "could not initialize %s context: %s", typestr,
+			 pg_cryptohash_error(ctx));
 	if (pg_cryptohash_update(ctx, data, len) < 0)
-		elog(ERROR, "could not update %s context", typestr);
+		elog(ERROR, "could not update %s context: %s", typestr,
+			 pg_cryptohash_error(ctx));
 	if (pg_cryptohash_final(ctx, (unsigned char *) VARDATA(result),
 							digest_len) < 0)
-		elog(ERROR, "could not finalize %s context", typestr);
+		elog(ERROR, "could not finalize %s context: %s", typestr,
+			 pg_cryptohash_error(ctx));
 	pg_cryptohash_free(ctx);
 
 	SET_VARSIZE(result, digest_len + VARHDRSZ);
diff --git a/src/common/cryptohash.c b/src/common/cryptohash.c
index b13815dd98..ddf35d28b2 100644
--- a/src/common/cryptohash.c
+++ b/src/common/cryptohash.c
@@ -40,10 +40,18 @@
 #define FREE(ptr) free(ptr)
 #endif
 
+/* Set of error states */
+typedef enum pg_cryptohash_errno
+{
+	PG_CRYPTOHASH_ERROR_NONE = 0,
+	PG_CRYPTOHASH_ERROR_DEST_LEN
+} pg_cryptohash_errno;
+
 /* Internal pg_cryptohash_ctx structure */
 struct pg_cryptohash_ctx
 {
 	pg_cryptohash_type type;
+	pg_cryptohash_errno error;
 
 	union
 	{
@@ -76,9 +84,10 @@ pg_cryptohash_create(pg_cryptohash_type type)
 	ctx = ALLOC(sizeof(pg_cryptohash_ctx));
 	if (ctx == NULL)
 		return NULL;
+
 	memset(ctx, 0, sizeof(pg_cryptohash_ctx));
 	ctx->type = type;
-
+	ctx->error = PG_CRYPTOHASH_ERROR_NONE;
 	return ctx;
 }
 
@@ -174,32 +183,50 @@ pg_cryptohash_final(pg_cryptohash_ctx *ctx, uint8 *dest, size_t len)
 	{
 		case PG_MD5:
 			if (len < MD5_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_md5_final(&ctx->data.md5, dest);
 			break;
 		case PG_SHA1:
 			if (len < SHA1_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_sha1_final(&ctx->data.sha1, dest);
 			break;
 		case PG_SHA224:
 			if (len < PG_SHA224_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_sha224_final(&ctx->data.sha224, dest);
 			break;
 		case PG_SHA256:
 			if (len < PG_SHA256_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_sha256_final(&ctx->data.sha256, dest);
 			break;
 		case PG_SHA384:
 			if (len < PG_SHA384_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_sha384_final(&ctx->data.sha384, dest);
 			break;
 		case PG_SHA512:
 			if (len < PG_SHA512_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			pg_sha512_final(&ctx->data.sha512, dest);
 			break;
 	}
@@ -221,3 +248,31 @@ pg_cryptohash_free(pg_cryptohash_ctx *ctx)
 	explicit_bzero(ctx, sizeof(pg_cryptohash_ctx));
 	FREE(ctx);
 }
+
+/*
+ * pg_cryptohash_error
+ *
+ * Returns a static string providing errors about an error that
+ * happened during a computation.
+ */
+const char *
+pg_cryptohash_error(pg_cryptohash_ctx *ctx)
+{
+	/*
+	 * This implementation would never fail because of an out-of-memory error,
+	 * except when creating the context.
+	 */
+	if (ctx == NULL)
+		return _("out of memory");
+
+	switch (ctx->error)
+	{
+		case PG_CRYPTOHASH_ERROR_NONE:
+			return _("success");
+		case PG_CRYPTOHASH_ERROR_DEST_LEN:
+			return _("destination buffer too small");
+	}
+
+	Assert(false);
+	return _("success");
+}
diff --git a/src/common/cryptohash_openssl.c b/src/common/cryptohash_openssl.c
index f7b390ed54..2e835b066b 100644
--- a/src/common/cryptohash_openssl.c
+++ b/src/common/cryptohash_openssl.c
@@ -21,6 +21,7 @@
 #include "postgres_fe.h"
 #endif
 
+#include <openssl/err.h>
 #include <openssl/evp.h>
 
 #include "common/cryptohash.h"
@@ -46,6 +47,14 @@
 #define FREE(ptr) free(ptr)
 #endif
 
+/* Set of error states */
+typedef enum pg_cryptohash_errno
+{
+	PG_CRYPTOHASH_ERROR_NONE = 0,
+	PG_CRYPTOHASH_ERROR_DEST_LEN,
+	PG_CRYPTOHASH_ERROR_OPENSSL
+} pg_cryptohash_errno;
+
 /*
  * Internal pg_cryptohash_ctx structure.
  *
@@ -55,6 +64,8 @@
 struct pg_cryptohash_ctx
 {
 	pg_cryptohash_type type;
+	pg_cryptohash_errno error;
+	const char *errreason;
 
 	EVP_MD_CTX *evpctx;
 
@@ -63,6 +74,19 @@ struct pg_cryptohash_ctx
 #endif
 };
 
+static const char *
+SSLerrmessage(unsigned long ecode)
+{
+	if (ecode == 0)
+		return NULL;
+
+	/*
+	 * This may return NULL, but we would fall back to a default error path if
+	 * that were the case.
+	 */
+	return ERR_reason_error_string(ecode);
+}
+
 /*
  * pg_cryptohash_create
  *
@@ -88,6 +112,8 @@ pg_cryptohash_create(pg_cryptohash_type type)
 		return NULL;
 	memset(ctx, 0, sizeof(pg_cryptohash_ctx));
 	ctx->type = type;
+	ctx->error = PG_CRYPTOHASH_ERROR_NONE;
+	ctx->errreason = NULL;
 
 	/*
 	 * Initialization takes care of assigning the correct type for OpenSSL.
@@ -153,7 +179,11 @@ pg_cryptohash_init(pg_cryptohash_ctx *ctx)
 
 	/* OpenSSL internals return 1 on success, 0 on failure */
 	if (status <= 0)
+	{
+		ctx->errreason = SSLerrmessage(ERR_get_error());
+		ctx->error = PG_CRYPTOHASH_ERROR_OPENSSL;
 		return -1;
+	}
 	return 0;
 }
 
@@ -174,7 +204,11 @@ pg_cryptohash_update(pg_cryptohash_ctx *ctx, const uint8 *data, size_t len)
 
 	/* OpenSSL internals return 1 on success, 0 on failure */
 	if (status <= 0)
+	{
+		ctx->errreason = SSLerrmessage(ERR_get_error());
+		ctx->error = PG_CRYPTOHASH_ERROR_OPENSSL;
 		return -1;
+	}
 	return 0;
 }
 
@@ -195,27 +229,45 @@ pg_cryptohash_final(pg_cryptohash_ctx *ctx, uint8 *dest, size_t len)
 	{
 		case PG_MD5:
 			if (len < MD5_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 		case PG_SHA1:
 			if (len < SHA1_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 		case PG_SHA224:
 			if (len < PG_SHA224_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 		case PG_SHA256:
 			if (len < PG_SHA256_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 		case PG_SHA384:
 			if (len < PG_SHA384_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 		case PG_SHA512:
 			if (len < PG_SHA512_DIGEST_LENGTH)
+			{
+				ctx->error = PG_CRYPTOHASH_ERROR_DEST_LEN;
 				return -1;
+			}
 			break;
 	}
 
@@ -223,7 +275,11 @@ pg_cryptohash_final(pg_cryptohash_ctx *ctx, uint8 *dest, size_t len)
 
 	/* OpenSSL internals return 1 on success, 0 on failure */
 	if (status <= 0)
+	{
+		ctx->errreason = SSLerrmessage(ERR_get_error());
+		ctx->error = PG_CRYPTOHASH_ERROR_OPENSSL;
 		return -1;
+	}
 	return 0;
 }
 
@@ -248,3 +304,40 @@ pg_cryptohash_free(pg_cryptohash_ctx *ctx)
 	explicit_bzero(ctx, sizeof(pg_cryptohash_ctx));
 	FREE(ctx);
 }
+
+/*
+ * pg_cryptohash_error
+ *
+ * Returns a static string providing errors about an error that
+ * happened during a computation.
+ */
+const char *
+pg_cryptohash_error(pg_cryptohash_ctx *ctx)
+{
+	/*
+	 * This implementation would never fail because of an out-of-memory error,
+	 * except when creating the context.
+	 */
+	if (ctx == NULL)
+		return _("out of memory");
+
+	/*
+	 * If a reason is provided, rely on it, else fallback to any error code
+	 * set.
+	 */
+	if (ctx->errreason)
+		return ctx->errreason;
+
+	switch (ctx->error)
+	{
+		case PG_CRYPTOHASH_ERROR_NONE:
+			return _("success");
+		case PG_CRYPTOHASH_ERROR_DEST_LEN:
+			return _("destination buffer too small");
+		case PG_CRYPTOHASH_ERROR_OPENSSL:
+			return _("OpenSSL failure");
+	}
+
+	Assert(false);				/* cannot be reached */
+	return _("success");
+}
diff --git a/src/common/md5_common.c b/src/common/md5_common.c
index 65b0be4b66..edc935eeb8 100644
--- a/src/common/md5_common.c
+++ b/src/common/md5_common.c
@@ -67,7 +67,7 @@ bytesToHex(uint8 b[16], char *s)
  */
 
 bool
-pg_md5_hash(const void *buff, size_t len, char *hexsum)
+pg_md5_hash(const void *buff, size_t len, char *hexsum, const char **errstr)
 {
 	uint8		sum[MD5_DIGEST_LENGTH];
 	pg_cryptohash_ctx *ctx;
@@ -80,6 +80,7 @@ pg_md5_hash(const void *buff, size_t len, char *hexsum)
 		pg_cryptohash_update(ctx, buff, len) < 0 ||
 		pg_cryptohash_final(ctx, sum, sizeof(sum)) < 0)
 	{
+		*errstr = pg_cryptohash_error(ctx);
 		pg_cryptohash_free(ctx);
 		return false;
 	}
@@ -90,18 +91,23 @@ pg_md5_hash(const void *buff, size_t len, char *hexsum)
 }
 
 bool
-pg_md5_binary(const void *buff, size_t len, void *outbuf)
+pg_md5_binary(const void *buff, size_t len, void *outbuf, const char **errstr)
 {
 	pg_cryptohash_ctx *ctx;
 
+	*errstr = NULL;
 	ctx = pg_cryptohash_create(PG_MD5);
 	if (ctx == NULL)
+	{
+		*errstr = pg_cryptohash_error(NULL);	/* returns OOM */
 		return false;
+	}
 
 	if (pg_cryptohash_init(ctx) < 0 ||
 		pg_cryptohash_update(ctx, buff, len) < 0 ||
 		pg_cryptohash_final(ctx, outbuf, MD5_DIGEST_LENGTH) < 0)
 	{
+		*errstr = pg_cryptohash_error(ctx);
 		pg_cryptohash_free(ctx);
 		return false;
 	}
@@ -118,11 +124,12 @@ pg_md5_binary(const void *buff, size_t len, void *outbuf)
  * Output format is "md5" followed by a 32-hex-digit MD5 checksum.
  * Hence, the output buffer "buf" must be at least 36 bytes long.
  *
- * Returns true if okay, false on error (out of memory).
+ * Returns true if okay, false on error with *errstr providing some
+ * error context.
  */
 bool
 pg_md5_encrypt(const char *passwd, const char *salt, size_t salt_len,
-			   char *buf)
+			   char *buf, const char **errstr)
 {
 	size_t		passwd_len = strlen(passwd);
 
@@ -131,7 +138,10 @@ pg_md5_encrypt(const char *passwd, const char *salt, size_t salt_len,
 	bool		ret;
 
 	if (!crypt_buf)
+	{
+		*errstr = _("out of memory");
 		return false;
+	}
 
 	/*
 	 * Place salt at the end because it may be known by users trying to crack
@@ -141,7 +151,7 @@ pg_md5_encrypt(const char *passwd, const char *salt, size_t salt_len,
 	memcpy(crypt_buf + passwd_len, salt, salt_len);
 
 	strcpy(buf, "md5");
-	ret = pg_md5_hash(crypt_buf, passwd_len + salt_len, buf + 3);
+	ret = pg_md5_hash(crypt_buf, passwd_len + salt_len, buf + 3, errstr);
 
 	free(crypt_buf);
 
diff --git a/src/include/common/cryptohash.h b/src/include/common/cryptohash.h
index ea1300d5d4..8e339c83ad 100644
--- a/src/include/common/cryptohash.h
+++ b/src/include/common/cryptohash.h
@@ -34,5 +34,6 @@ extern int	pg_cryptohash_init(pg_cryptohash_ctx *ctx);
 extern int	pg_cryptohash_update(pg_cryptohash_ctx *ctx, const uint8 *data, size_t len);
 extern int	pg_cryptohash_final(pg_cryptohash_ctx *ctx, uint8 *dest, size_t len);
 extern void pg_cryptohash_free(pg_cryptohash_ctx *ctx);
+extern const char *pg_cryptohash_error(pg_cryptohash_ctx *ctx);
 
 #endif							/* PG_CRYPTOHASH_H */
diff --git a/src/include/common/md5.h b/src/include/common/md5.h
index bbd2ec0165..942ca4242c 100644
--- a/src/include/common/md5.h
+++ b/src/include/common/md5.h
@@ -26,9 +26,12 @@
 #define MD5_PASSWD_LEN	35
 
 /* Utilities common to all the MD5 implementations, as of md5_common.c */
-extern bool pg_md5_hash(const void *buff, size_t len, char *hexsum);
-extern bool pg_md5_binary(const void *buff, size_t len, void *outbuf);
+extern bool pg_md5_hash(const void *buff, size_t len, char *hexsum,
+						const char **errstr);
+extern bool pg_md5_binary(const void *buff, size_t len, void *outbuf,
+						  const char **errstr);
 extern bool pg_md5_encrypt(const char *passwd, const char *salt,
-						   size_t salt_len, char *buf);
+						   size_t salt_len, char *buf,
+						   const char **errstr);
 
 #endif							/* PG_MD5_H */
diff --git a/src/include/libpq/crypt.h b/src/include/libpq/crypt.h
index ee60772e94..3238cf66d3 100644
--- a/src/include/libpq/crypt.h
+++ b/src/include/libpq/crypt.h
@@ -35,12 +35,13 @@ extern PasswordType get_password_type(const char *shadow_pass);
 extern char *encrypt_password(PasswordType target_type, const char *role,
 							  const char *password);
 
-extern char *get_role_password(const char *role, char **logdetail);
+extern char *get_role_password(const char *role, const char **logdetail);
 
 extern int	md5_crypt_verify(const char *role, const char *shadow_pass,
 							 const char *client_pass, const char *md5_salt,
-							 int md5_salt_len, char **logdetail);
+							 int md5_salt_len, const char **logdetail);
 extern int	plain_crypt_verify(const char *role, const char *shadow_pass,
-							   const char *client_pass, char **logdetail);
+							   const char *client_pass,
+							   const char **logdetail);
 
 #endif
diff --git a/src/include/libpq/sasl.h b/src/include/libpq/sasl.h
index 7ba3f5f5bc..71cc0dc251 100644
--- a/src/include/libpq/sasl.h
+++ b/src/include/libpq/sasl.h
@@ -126,11 +126,11 @@ typedef struct pg_be_sasl_mech
 	int			(*exchange) (void *state,
 							 const char *input, int inputlen,
 							 char **output, int *outputlen,
-							 char **logdetail);
+							 const char **logdetail);
 } pg_be_sasl_mech;
 
 /* Common implementation for auth.c */
 extern int	CheckSASLAuth(const pg_be_sasl_mech *mech, Port *port,
-						  char *shadow_pass, char **logdetail);
+						  char *shadow_pass, const char **logdetail);
 
 #endif							/* PG_SASL_H */
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 8d2e4e5db4..2e6b2e8f04 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -790,6 +790,7 @@ pg_password_sendauth(PGconn *conn, const char *password, AuthRequest areq)
 		case AUTH_REQ_MD5:
 			{
 				char	   *crypt_pwd2;
+				const char *errstr = NULL;
 
 				/* Allocate enough space for two MD5 hashes */
 				crypt_pwd = malloc(2 * (MD5_PASSWD_LEN + 1));
@@ -802,14 +803,21 @@ pg_password_sendauth(PGconn *conn, const char *password, AuthRequest areq)
 
 				crypt_pwd2 = crypt_pwd + MD5_PASSWD_LEN + 1;
 				if (!pg_md5_encrypt(password, conn->pguser,
-									strlen(conn->pguser), crypt_pwd2))
+									strlen(conn->pguser), crypt_pwd2,
+									&errstr))
 				{
+					appendPQExpBuffer(&conn->errorMessage,
+									  libpq_gettext("could not encrypt password: %s\n"),
+									  errstr);
 					free(crypt_pwd);
 					return STATUS_ERROR;
 				}
 				if (!pg_md5_encrypt(crypt_pwd2 + strlen("md5"), md5Salt,
-									4, crypt_pwd))
+									4, crypt_pwd, &errstr))
 				{
+					appendPQExpBuffer(&conn->errorMessage,
+									  libpq_gettext("could not encrypt password: %s\n"),
+									  errstr);
 					free(crypt_pwd);
 					return STATUS_ERROR;
 				}
@@ -1175,12 +1183,13 @@ char *
 PQencryptPassword(const char *passwd, const char *user)
 {
 	char	   *crypt_pwd;
+	const char *errstr = NULL;
 
 	crypt_pwd = malloc(MD5_PASSWD_LEN + 1);
 	if (!crypt_pwd)
 		return NULL;
 
-	if (!pg_md5_encrypt(passwd, user, strlen(user), crypt_pwd))
+	if (!pg_md5_encrypt(passwd, user, strlen(user), crypt_pwd, &errstr))
 	{
 		free(crypt_pwd);
 		return NULL;
@@ -1287,8 +1296,13 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 		crypt_pwd = malloc(MD5_PASSWD_LEN + 1);
 		if (crypt_pwd)
 		{
-			if (!pg_md5_encrypt(passwd, user, strlen(user), crypt_pwd))
+			const char *errstr = NULL;
+
+			if (!pg_md5_encrypt(passwd, user, strlen(user), crypt_pwd, &errstr))
 			{
+				appendPQExpBuffer(&conn->errorMessage,
+								  libpq_gettext("could not encrypt password: %s\n"),
+								  errstr);
 				free(crypt_pwd);
 				crypt_pwd = NULL;
 			}
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index f093605472..5015fa7db0 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -3350,6 +3350,7 @@ pg_conv_map
 pg_crc32
 pg_crc32c
 pg_cryptohash_ctx
+pg_cryptohash_errno
 pg_cryptohash_type
 pg_ctype_cache
 pg_enc